Variable slot antenna and method for driving same

The present invention relates to variable directivity of an antenna having wideband characteristics suitable for transmitting and receiving analog high-frequency signals such as microwave bands and millimeter-wave bands, or digital signals.

For two reasons, there is a need for wireless devices that can operate in a much wider band than before. The first reason is to support communication systems for short-range radios that are licensed to use a vast frequency band, and the second reason is that a single communication system has multiple communication systems that are scattered using different frequencies. This is because the terminal supports it.

For example, the frequency band of 3.1 GHz to 10.6 GHz approved for high-speed communication systems for short distances corresponds to a vast value of 109.5% as the ratio band standardized by the central frequency f0 in the band, which is basic. It is extremely difficult to cover the entire band with the specific band characteristics of less than 5% of the patch antenna known as a simple antenna and about 10% of the half-wavewidth slot antenna. Taking the frequency band currently used for wireless communication in the world as an example, in order to cover the 1.8 GHz band to 2.4 GHz band with the same antenna, a specific band of about 30% is required, and from the 800 MHz band. In order to cover up to the 2.4GHz band at the same time, a specific band of 100% or more is required. As the number of systems handled by the same terminal at the same time increases and the frequency band to be covered increases, the realization of a wideband antenna is desired as a solution for a simple terminal configuration. In addition, as the speed of signals has increased, it has become more necessary to suppress reflected interfering waves, so it is strongly desired to realize an antenna that has not only wideband characteristics but also variable directivity characteristics in a compact shape. Become. In addition, in the case of a wireless system that collectively uses wideband signals, it is necessary to realize a compact antenna that satisfies all of the wideband characteristics, variable directivity characteristics, and maintenance of the main beam direction within the wideband operating band. become.

The quarter-wavelength slot antenna shown in FIG. 25 is one of the most basic planar antennas, and it is known that a value of about 15% can be obtained in a specific band. FIG. 25 (a) shows a schematic perspective view from the upper surface side, FIG. 25 (b) shows a schematic cross-sectional view cut along a straight line AB, and FIG. 25 (c) shows a schematic view of the back surface seen from the upper surface side.

As shown in these figures, there is a feeding line 115 on the upper surface of the dielectric substrate 103, a notch is formed in the depth direction from the edge 105 of the finite ground conductor 101 on the back surface side, and one end 111 is opened. Functions as slot 109. The slot 109 is a circuit obtained by completely removing the conductor in the thickness direction in a part of the ground conductor 101, and the lowest-order resonance near a frequency in which the slot length Ls corresponds to a quarter effective wavelength. Shows the phenomenon. The power supply line 115 partially faces and intersects the slot 109, and excites the slot 109. It is connected to the external circuit via the input terminal 201. In general, the distance t3 from the open end point 125 of the feeding line 115 to the slot 109 is set to a length of about a quarter effective wavelength at the center frequency f0 in order to achieve input matching.

Patent Document 1 discloses a structure for operating a quarter-wavelength slot antenna at a plurality of resonance frequencies. FIG. 26 (a) shows a schematic structure diagram. The quarter wavelength slot 109 formed by cutting out a part of the ground conductor 101 on the back surface of the dielectric substrate 103 is excited at the feeding point 113 to obtain normal antenna operation. Normally, the resonance frequency of the slot antenna is defined by the loop length of the slot 109, but the capacitive element 16 set between the points 16a and 16b of Patent Document 1 is a signal having a frequency higher than the original resonance frequency of the slot 109. Since it is set to pass through, it is possible to change the resonator length Ls of the slot depending on the frequency. That is, as shown in FIG. 26 (b), at low frequencies, the resonator length of the slot is determined by the physical length of the notched structure as usual, whereas it is shown in FIG. 26 (c). As described above, at high frequencies, the resonator length Ls2 of the slot operates at a high frequency so as to be shorter than the physical resonator length Ls. Therefore, it is said that the double resonance operation can be realized by one slot resonator structure.

Non-Patent Document 1 discloses a method for operating a half-wavelength slot antenna in a wide band. As described above, as an input matching method for the slot antenna shown in FIG. 25, the slot resonator 109 is excited at a point where the effective wavelength is a quarter at the center frequency f0 from the tip open end point 125 of the feeding line 115. The method has traditionally been adopted.

However, in Non-Patent Document 2, as shown in the top perspective schematic diagram in FIG. 27, it corresponds to the distance from the tip open end point 125 of the feeding line 115 to the quarter effective wavelength at f0 on the input terminal 201 side. The line width of the feeding line 115 in the region is reduced to form a resonator, which is coupled to the slot 109 near the center of the formed inductive resonator region 127.

With the introduction of the inductive resonator region 127, the number of resonators operating in the vicinity of the operating band is increased to two in the circuit, and the resonators are strongly coupled to each other, so that a double resonance operation can be obtained. Fig.2 (b) of Non-Patent Document 2 uses a substrate having a dielectric constant of 2.94 and a height of 0.75 mm, assuming a slot length (Ls) of 24 mm and a design frequency of 5 GHz, and covers the inductive resonator region of the feed line 115. The line length (t1 + t2 + Ws) of the quarter wavelength line is 9.8 mm, the line width W2 is 0.5 mm, and the offset distance (Lo) between the power supply line 115 and the slot center is changed from 9.8 mm to 10.2 mm. Corresponds to the frequency dependence of the reflection intensity characteristic in the case of. Under any offset distance condition, good reflection intensity characteristics of -10 dB or less are obtained in a specific band of 32% (from around 4.1 GHz to around 5.7 GHz). This band characteristic is far superior to the specific band of 9% of a normal slot antenna manufactured under the same substrate conditions, as compared in the measured characteristics of fig.4 of Non-Patent Document 2.

On the other hand, various methods have been proposed for a long time in order to change the directivity of the antenna and scan the radiated beam. For example, there is a method of equivalently realizing beam scanning by processing signals received by a plurality of antennas in a digital signal section such as an adaptive array, or arranging a plurality of antennas in different directions in advance like a sector antenna. However, there is also a method of switching the main beam direction by switching the route on the feeding line side. There is also a method of tilting the main beam direction by arranging a reflector or a director which is a non-feeding element around the antenna.

Patent Document 2 discloses, as a sector antenna using a slot antenna, a sector antenna configuration in which a plurality of slot antennas are arranged radially and the main beam direction is switched by switching the route on the feeder line side. .. In Patent Document 2, by using a Vivaldi antenna known to have an ultra-wideband antenna characteristic as an antenna, it is possible to collectively switch the main beam direction of a radiated electromagnetic wave having an ultra-wideband frequency component.

Further, Patent Document 3 discloses an example of a variable antenna that inclines the direction of the main beam radiated from the radiation slot element by using a non-feeding parasitic element. In the variable antenna shown in FIG. 28, the half effective wavelength slot resonator excited by the feeding line 115 is the radiator (slot) 109, and the non-feeding slot resonator is the parasitic elements 109x and 109y. It is placed on 101. By adjusting the slot lengths of the parasitic elements 109x and 109y, the function of the parasitic element with respect to the reflector can be switched between a waveguide and a reflector, and the direction of the radiated beam from the radiator can be changed. To make the parasitic elements 109x, 109y function as a waveguide, the slot length of the parasitic element may be adjusted to be shorter than the slot length of the radiator, and to make the parasitic elements 109x, 109y function as a reflector, Adjust the slot length of the parasitic element to be longer than the slot length of the radiator. To adjust the slot length, set the slot length on the circuit board to be long in advance, and in the state where it functions as a slot circuit with a short slot length, the switch element straddles the slot in the width direction in the middle of the slot length. Selectively conduct between the ground conductors at 205a and 205b. Patent Document 3 cites the use of a MEMS switch as an example of a method for realizing the switch elements 205a and 205b.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2004-336328</text></patcit><patcit num="2"><text>Special Table 2003-527018 Gazette</text></patcit><patcit num="3"><text>Japanese Patent Application Laid-Open No. 2005-210520</text></patcit><patcit num="4"><text>Special Table 2005-514844</text></patcit><nplcit num="1"><text>A Novel Broadband Microstrip-Fed Wide Slot Antenna With Double Rejection Zeros IEEE Antennas and Wireless Propagation Letters, vol.2, 2003, pp. 194-196</text></nplcit>

<p> With conventional slot antennas, it is impossible to simultaneously satisfy all of the functions of ensuring wide bandwidth, maintaining the main beam orientation direction within the operating band, and dramatically switching the main beam orientation direction all at once with a small structure. there were.</p><p> First, in the case of a normal slot antenna having only a single resonator structure in the structure, the operating band is limited by the band of the resonance phenomenon, and the frequency band in which good reflection intensity characteristics can be obtained is from 10%. It was limited to a specific band of about 15%.</p><p> On the other hand, in Patent Document 1, although wideband operation is realized by introducing a capacitive reactance element into the slot, a dramatic directivity switching function is not disclosed at all. In addition, it was easily imagined that additional components such as chip capacitors would be required as the capacitive reactance element, and that the antenna characteristics would vary due to the variation in the characteristics of the newly introduced additional components. Further, Patent Document 1 does not disclose a directivity variable function that collectively switches the main beam direction of an antenna having a wide band characteristic.</p><p> Further, as shown in the example of Non-Patent Document 1, even if the band characteristics are improved by coupling between the resonators by introducing a plurality of resonators into the structure, the specific band characteristics are limited to about 35%. Further improvement was needed. Further, the top perspective schematic view of FIG. 27, which imitates Non-Patent Document 1, draws the slot width Ws narrowly as in fig.1 in Non-Patent Document, but under the condition that the above-mentioned broadband characteristics are obtained, 4 Ws is set to a value of 5 mm, which corresponds to the length of more than half of the 1 / wavelength region of 9.8 mm. If it becomes necessary to arrange slots within a limited occupied area for the purpose of miniaturization, it is necessary to take measures such as bending linear slots, and wideband characteristics cannot be obtained unless Ws is large. The structure is difficult to miniaturize. Further, Non-Patent Document 1 does not disclose any directivity variable function for collectively switching the main beam direction of an antenna having a wide band characteristic.</p><p> The antenna disclosed in Patent Document 2 is mainly a driving method in which four slot antennas that do not share most of the components are arranged and introduced radially in the structure, and the feeding circuit to each slot antenna is switched. Although the beam direction switching function is realized, the antenna structure is extremely large, and there is a problem in realizing a small communication terminal.</p><p> Even in the antenna disclosed in Patent Document 3, since slot antennas that do not share components are arranged in parallel, a problem arises from the viewpoint of miniaturization. Further, since the frequency band in which the slot antenna used as a parasitic element functions as a director or a reflector is limited, there is a problem that the main beam direction of the antenna may change in a different direction within the operating frequency band. Therefore, the antenna disclosed in Patent Document 3 cannot satisfy the condition of maintaining the main beam orientation direction within the band.</p><p> The present invention solves the above-mentioned conventional problems, and dramatically switches the main beam directions collectively while maintaining the same main beam direction over the entire wide band operating band while maintaining a compact circuit configuration. An object of the present invention is to provide a variable slot antenna that realizes a function and a method for driving the variable slot antenna.</p>

<p> In the variable slot antenna of the present invention, the dielectric substrate, the ground conductor having a finite area, and the slot region in which the ground conductor is completely divided into two finite ground conductor regions and both ends are open are the dielectric. A power supply line arranged on the back surface of the body substrate and intersecting a region near the center in the length direction of the slot region was arranged on the surface of the dielectric substrate and separated by crossing the slot region in the width direction. Selective conduction paths that can be selected whether or not to connect between the finite ground conductor regions are arranged one by one in a direction facing the open points at both ends of the slot region from the intersection of the power supply line and the slot region. In the variable slot antenna structure, the feeding line intersecting the slot region at the feeding portion near the center in the longitudinal direction of the slot region is arranged on the surface of the dielectric substrate, and at the first point near the feeding portion. The power feeding line is once branched into a branch line group including at least two or more branch lines, and at least one set of branch line pairs in the branch line group is reconnected at a second point near the slot. Form a loop wiring in the power supply line, The maximum value of the loop length of all the loop wirings included in the structure is set to a length less than one effective wavelength at the upper limit frequency of the operating band, and in the first state, among the selective conduction path groups, the said At least one or more first selective conduction paths arranged on the first direction side facing the first open end side of the slot region from the feeding point are all selected in the open state, and the selective conduction is performed. At least one of at least one or more second selective conduction paths arranged on the second direction side of the path group facing the second open end side of the slot region from the feeding point. The above second selective conduction path is selected as the conduction state to radiate the main beam in the first direction, and in the second state, at least one or more of the first selective conduction paths are in the conduction state. The main beam is radiated in the second direction by selecting the above and selecting all the second selective conduction paths in the open state.</p>

<p> According to the variable slot antenna of the present invention, a wide band can be realized with a small structure, which was difficult to realize with a conventional slot antenna. In addition, the maintenance of the main beam orientation direction within the operating band and the function of dramatically switching the main beam direction at once can be satisfied at the same time, so the use of ultra-wideband high-speed communication in mobile terminals whose transmission and reception conditions change from moment to moment. It is possible to realize a functional multi-band terminal.</p>

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment) In FIGS. 1 (a) and 1 (b), the structure of the variable slot antenna of the present embodiment will be described with reference to a schematic top perspective view, and the directional characteristics of the variable slot antenna obtained in two driving states will be described. The variability is schematically shown. In addition, FIGS. 2 (a) and 2 (b) show schematic cross-sectional views obtained by cutting the structure along the straight lines A1-A2 and B1-B2 in FIG. 1, respectively. For the sake of simplification of the discussion, first, as an embodiment having high symmetry, an embodiment of a driving method for switching the main beam direction to the left and right will be described by taking a symmetrical variable slot antenna structure as an example.

A grounding conductor 101 having a finite area is formed on the back surface of the dielectric substrate 103, and a slot region 109 is formed by cutting out from the outer edge portion 105 of the side surface of the grounding conductor 101 in the depth direction 107 and opening both ends. That is, the finite ground conductor 101 is divided into a first ground conductor 101a and a second ground conductor 101b by the slot region 109. As a result, both ends of the slot region 109 become the first open end 111a and the second open end 111b, respectively. At the central feeding point 113 of the slot region 109, the slot region 109 intersects the feeding line 115 formed on the surface of the dielectric substrate 103. The direction facing the first open end 111a from the feeding point 113 is the first direction 117a, and at least one or more first selective conduction paths 119 are formed on the first direction side from the feeding point 113. Similarly, the direction facing the second open end 111b from the feeding point 113 is the second direction 117b, and at least one or more second selective conduction paths 121 are formed on the second direction side from the feeding point 113. Has been done. For the sake of simplification of the discussion, the case where the number of the first selective conduction path 119 and the number of the second selective conduction path 121 are one will be described first. That is, as shown in FIG. 1, one selective conduction path 119 and one 121 are arranged on the left side and the right side from the feeding point 113, respectively. The first selective conduction path 119 and the second selective conduction path 121 are both the first ground conductor 101a and the second ground conductor 101b divided by the slot region 109 based on the control signal given from the outside. It serves to selectively conduct between. In FIG. 1 (a), it is assumed that the first selective conduction path 119 is conducted and the second selective conduction path 121 is controlled in the open state. The selective conduction path 119 is opened, and the second selective conduction path 121 is shown as controlling the conduction state. By controlling the first and second selective conduction paths, the direction of arrow 123a in the state of FIG. 1 (a) and the direction of arrow 123b in the state of FIG. 1 (b).

(Outline of Feeding Structure) In the variable slot antenna of the present embodiment, the feeding line 115 is branched into at least two or more branch wirings 115a, 115b, ... At the first branching point 223 near the feeding point 113. To. Then, at the second branch point 221 the pair of branch wirings 115a and 115b are reconnected to form the loop wiring 209. Further, some of the branch wirings may form a short open stub structure without forming a loop wiring, but the stub length is set to less than one-fourth of the effective wavelength at the upper limit frequency fH of the operating band. To. Further, the loop length of the loop wiring 209 is set to less than 1 times the effective wavelength at fH. As shown in FIG. 1, the loop wiring is preferably arranged at two locations so as to intersect the two boundary lines of the slot region 109 and the ground conductors 101a and 101b, respectively.

(Normal Matching Conditions-Broadband) The variable slot antenna of the present invention can have two types of feeding line structures as shown in the top perspective schematic diagram in FIGS. 3 (a) and 3 (b). In the structure shown in the perspective diagram from the top surface in Fig. 3 (a), the distance t3 from the tip open end point 125 of the feeding line 115 to the center of the slot region 109 in the width direction is a quarter effective wavelength at f0. It is set and input matching is obtained in the operating band including f0. The characteristic impedance of the feed line 115 is preferably set to 50Ω.

(Power supply conditions for ultra-wideband characteristics) Further, the variable slot antenna of the present invention may have a feeding line structure as shown in FIG. 1 and a schematic top perspective view in FIG. 3 (b). That is, the inductive resonator region 127 is composed of a transmission line having a characteristic impedance higher than 50Ω at a position corresponding to the distance (t1 + Ws + t2) from the tip open end point 125 of the feeding line 115 toward the input terminal side. It is a power supply structure that is set to. Here, it is preferable that the impedance Z of the general external circuit connected to the input terminal 201 and the characteristic impedance of the feeding line 115 match, and if the impedance of the external circuit is not 50Ω, the characteristic impedance of the inductive resonator region 127 is It is set to a higher value. In the form shown in FIG. 3, the region length of the inductive resonator region 127 is set to about a quarter effective wavelength at f0. The slot width Ws is preferably set to be about the same as the sum of t1 and t2. The structure shown in FIG. 3 (a) is effective for obtaining wideband characteristics under the condition that the slot width Ws must be set narrowly, and the structure shown in FIG. 3 (b) is used for setting the slot width Ws. It is effective when you want to obtain ultra-wideband characteristics under conditions with few restrictions.

(Function of Loop Wiring 209) The loop wiring 209 in the variable slot antenna of the present invention simultaneously fulfills two functions of increasing the number of excitation points of the slot resonator to a plurality of excitation points and adjusting the electrical length of the input matching circuit, and operates the antenna. Achieves an ultra-wide band. The functions performed by the loop wiring will be described in detail below.

First, the high frequency characteristics when the loop wiring structure is adopted in a general high frequency circuit assuming an infinite area ground conductor on the back surface will be described. FIG. 4 (a) shows a schematic circuit diagram in which the loop wiring 209 including the first path 115a and the second path 115b is connected between the input terminal 201 and the output terminal 203. The loop wiring becomes a resonance condition under the condition that the sum of the path lengths Lp1 and Lp2 of the first path 115a and the second path 115b corresponds to 1 times the effective wavelength for the transmission signal, and can be used as a ring resonator. is there. However, when Lp1 and Lp2 are shorter than the effective wavelength of the transmission signal, the loop wiring 209 does not need to be positively used in a normal high-frequency circuit because it does not show a steep frequency response. In a general high-frequency circuit having a uniform ground conductor, even if the local high-frequency current distribution fluctuates due to the introduction of loop wiring, the fluctuation is averaged as a macro high-frequency characteristic between the two terminals 201 and 203. Will be done. That is, the high-frequency characteristics of the loop wiring in the non-resonant state are not so different from the high-frequency characteristics of the transmission line when the characteristics of the two paths are averaged and replaced with one path.

On the other hand, as shown in the top perspective schematic diagram in FIG. 5, the introduction of the loop wiring 209 in the variable slot antenna of the present invention provides a unique effect that cannot be obtained by the above-mentioned general high-frequency circuit. That is, if the linear feeding line 115 is replaced with the loop wiring 209 in the vicinity of the location where the slot region 109 exists in the ground conductor 101, the local high-frequency current distribution around the slot region 109 is changed, and the slot antenna It is possible to change the resonance characteristics. The high frequency current on the ground conductor is guided in the direction of 233 along the first path 115a branched by the first branch point 221 and also toward the side of 235 along the second path 115b. Can be done. As a result, different paths of 233 and 235 can be created in the flow of high frequency current on the ground conductor, and the slot antenna can be excited at multiple locations. Local changes in the high frequency current distribution near the slot on this ground conductor dramatically expand the operating band of the slot antenna.

Generally, the high-frequency current distribution during signal transmission differs between the signal conductor side and the ground conductor side of the transmission line. FIG. 6 shows a schematic diagram of the cross-sectional structure of the transmission line, and explains how the intensity distribution of the high-frequency current on the signal conductor side and the ground conductor side fluctuates due to the branching of the signal conductor. In the transmission line of FIG. 6 (a), the signal conductor is not branched, and it is the edge portions 403 and 405 of the signal conductor 401 that concentrate the high frequency current on the signal conductor side, and the high frequency current on the ground conductor 101 side. Concentration occurs in the region 407 facing the central portion of the signal conductor 401. Therefore, for example, even if the width of the feeding line 115 is increased in the conventional slot antenna, the distribution of the high-frequency current cannot be significantly changed on the ground conductor side, and the effect of widening the bandwidth is equal to that of the variable slot antenna of the present invention. Is difficult to obtain. However, as shown in FIG. 6 (b) as a schematic diagram of the transmission line cross-sectional structure when the signal conductor 401 is branched into the two signal conductors 409 and 411, the introduction of the branch structure is the introduction of the branch wirings 409 and 411, respectively. For the first time, a high-frequency current distribution is generated in different ground conductor regions 413 and 415 that face each other.

Further, the loop wiring newly introduced in the variable slot antenna of the present invention not only fulfills the function of increasing the number of excitation points of the slot antenna, but also has the function of adjusting the electric length of the feeding line 115. There is. The fluctuation of the electric length of the feeding line due to the introduction of the loop wiring changes the resonance condition of the feeding line 115 to the double resonance condition, further enhancing the effect of expanding the operating band of the present invention.

More specifically, as described in FIG. 25 and FIG. 27 as the prior art, the distance t3 from the tip open end point to the point where the slot and a part intersect, or (t2 + Ws ÷ 2). Was closely related to the effective wavelength at f0. The feeding structure of the variable slot antenna of the present invention shown in FIGS. 1 and 3 not only inherits the design principle of the feeding line in each slot antenna shown in FIGS. 25 and 27, but also expands its operating band. To do.

In the general slot antenna shown in FIG. 25, in order to satisfy the input matching condition at the resonance frequency of the slot, the slot length is designed according to the operating frequency f0, and t3 is set to a quarter effective wavelength at f0. If the loop structure of the present invention is introduced in the vicinity of the slot in such a power feeding line 115 structure, a path having a short electric length and a path having a long electric length among the two paths constituting the loop wiring are used. In this case, the resonance frequencies of the feeding line 115 are separated, and the double resonance operation is guided.

Further, in the slot antenna shown in FIG. 27, the slot width Ws is set large, t1 + t2 + Ws is set to the quarter effective wavelength at f0, and the transmission line in the region of the quarter effective wavelength has high impedance. Is set to, and t1 and t2 are operated under almost equal conditions. By introducing a resonator structure that is newly coupled to the slot resonator in the equivalent circuit, input matching was established at two resonant frequencies, and wideband operation of the slot antenna was realized. Even in such a power supply line 115 structure, if the loop wiring of the present invention is introduced in the vicinity of the slot, a path having a short electric length and a path having a long electric length among the two paths constituting the loop wiring can be obtained. The difference in the electrical length through the wiring causes a resonance phenomenon that couples with the slot resonator at a plurality of frequencies of two or more, further widening the wide band matching condition that has already been obtained.

Summarizing the above description, the variable of the present invention is achieved by combining the first function of double-resonating the resonance phenomenon of the slot itself and the second function of double-resonating the resonance phenomenon of the feeding line coupled to the slot. In each operating state, the slot antenna can operate in a wider band than the conventional slot antenna.

(Limitation of Loop Wiring) However, in order to maintain wideband matching characteristics, the loop wiring in the variable slot antenna of the present invention must be used under the condition that the loop wiring alone does not cause unnecessary resonance. Taking the loop wiring 209 shown in Fig. 4 (a) as an example, the loop length Lp, which is the sum of the path lengths Lp1 and Lp2, is larger than the effective wavelength of the upper limit frequency fH of the operating band even for the loop wiring having the largest structure. Must be set short.

On the other hand, there is an open stub shown in Fig. 4 (b) as a structure adopted in a general high-frequency circuit more frequently than loop wiring. If the open stub 115s of length Lp3 is branched and connected to the transmission line 211, the resonance condition is satisfied at a frequency at which Lp3 becomes a quarter effective wavelength, and for signal transmission between the input terminal 201 and the output terminal 203. This is an unfavorable function for the variable slot antenna of the present invention because the band blocking filter function is exhibited. Therefore, among the wirings branched from the feeding structure of the variable slot antenna of the present invention, those that do not form a loop wiring can have a stub configuration, but even if the stub length is the maximum, the fH is 4 minutes. Must be set to less than one effective wavelength of.

An extreme example of the loop wiring shown in FIG. 4 (c) will be compared with the open stub structure of FIG. 4 (b), and the advantages of the loop wiring will be explained. When Lp2 is made extremely small in the loop wiring 209, the loop wiring apparently approaches the open stub structure as much as possible. However, when Lp2 approaches 0, the resonance frequency of the loop wiring is the frequency at which Lp1 corresponds to one effective wavelength, and the resonance frequency of the open stub is the frequency at which Lp3 corresponds to a quarter effective wavelength. If the lowest-order resonance frequencies of the two structures are compared under the condition that Lp1 is twice as large as Lp3, the resonance frequency of the loop wiring is twice the resonance frequency of the stub wiring. From the above explanation, as a feeding line structure for avoiding an unnecessary resonance phenomenon in a wide operating band, the loop wiring is quantified and compared in the frequency band rather than the open stub, and is twice as effective. In addition, at the open end point 115t of the open stub shown in Fig. 4 (b), the circuit is open, so high-frequency current does not flow, and even if the open end point 115t is placed near the slot, it is difficult to excite the slot. Become. On the other hand, the point 115u of the loop wiring 209 in Fig. 4 (c) is never open in terms of the circuit, so a high-frequency current always flows, and if it is placed near the slot, the slot can be easily excited. However, in order to obtain the effect of the present invention, the adoption of loop wiring is more advantageous than the adoption of open stubs.

From the above description, in the feeding line 115 of the variable slot antenna of the present invention, by introducing a loop wiring instead of a line having a wide line width or an open stub, the limitation of the operating band is successfully avoided and the bandwidth is widened. It became clear that this is effectively realized. Note that FIG. 7 shows a schematic top perspective view of the embodiment when the number of branches of the branch line portion of the power supply line 115 is 3. The number of branch lines that branch the power supply line 115 may be set to a value of three or more, but a dramatic expansion of the operating band cannot be expected compared to the characteristics when the power supply line 115 is branched into two lines. Among the group of branched lines that are branched into a plurality of branches, the ones with the highest distribution intensity of high-frequency current are the path 115a that passes through the location closest to the open end side of the slot and the route that passes through the location farthest from the open end side of the slot. This is because it is only 115b, and the intensity of the high-frequency current flowing in the path 115c wired between the two is not strong. However, when the number of branches is 2, the loop length of the loop wiring formed by the path 115a and the path 115b becomes unintentionally long, which causes a decrease in the resonance frequency of the loop wiring and operates the variable slot antenna of the present invention. There is a limit to the improvement of the upper limit frequency fH of the band. If the route 115c is added, the loop wiring will be divided, which is effective in alleviating the above limitation.

As for the arrangement relationship between the loop wiring and the slot area, as shown in the top perspective schematic diagram in FIG. 5, the first path 115a and the second path 115b constituting the loop wiring are both the slot area 109 and the ground conductor 101. It is preferable to intersect with at least one of the boundary lines 237 and 239.

The loop wiring 209 may be designed to intersect both the boundaries 237 and 239, respectively, as FIG. 8 shows another form of top-view schematic. As is clear from the figure in which the loop wiring 209 is shown in the trapezoidal shape, there are no restrictions on the shape of the loop wiring. A plurality of loop wirings 209 may be formed. When a plurality of loop wirings 209 are provided, the plurality of loop wirings 209 may be connected in series as already shown in FIG. 1 or may be connected in parallel as already shown in FIG. 7. The two loop wirings may be directly connected or indirectly connected via a transmission line having an arbitrary shape. As shown in FIG. 9 as a schematic perspective view of the upper surface of yet another form, two loop wirings 209a and 209b that individually intersect the boundary lines 237 and 239 may be arranged in series. Further, as shown in the top perspective schematic diagram in FIG. 10, parallel loop wirings 209c and 209d that individually intersect the boundary line 237 and parallel loop wirings 209e and 209f that intersect the boundary line 239, respectively, are arranged in series. The configuration may be used.

It is also possible to bring the frequency at which the ground conductor 101 of the finite area constituting the variable slot antenna of the present invention resonates close to the operating band of the variable slot antenna of the present invention to obtain further wide bandwidth and multi-band characteristics. is there. That is, if the frequency at which the ground conductor itself can resonate like a patch antenna, a monopole antenna, or a dipole antenna to obtain radiation characteristics is set to a frequency slightly lower than the resonance band of the variable slot antenna of the present invention, further The input matching band can be expanded.

The line width of the loop wiring 209 is selected so that the same conditions as the characteristic impedance of the feeding line 115 connected to the input side or the open end end side or a high impedance condition are equivalently satisfied. Is preferable. That is, when the power feeding line 115 is branched into two, it is preferable that the loop wiring is composed of branch wiring having a line width of half or less of the original power feeding line 115. As is clear from Non-Patent Document 1, since the slot antenna itself tends to be easily matched to the resistance value of 50Ω of the input terminal by coupling with the high impedance line, the vicinity of the slot area 109 is introduced by introducing the loop wiring portion. This is because it is effective to increase the characteristic impedance of the feeding line 115 in the above to realize further low reflection characteristics.

With the above configuration, it is possible to expand the operating band of the antenna using the 1/4 effective wavelength slot resonator. The main beam direction of the electromagnetic wave radiated from the quarter effective wavelength slot antenna is the direction facing the open end side of the slot region 109 from the feeding point 113, and the main beam direction is maintained within the expanded operating band. Next, the manifestation of the function of dramatically switching the main beam direction at once will be described.

(Characteristics of Drive Method) In the variable slot antenna of the present invention, in order to dramatically switch the main beam direction, either the first selective conduction path 119 or the second selective conduction path 121 is selected. Is conducted, and the other selective conduction path is always selected to be open. In this case, it is possible to orient the main beam in the direction facing the selective conduction path side opened from the feeding point 113, and if the selective conduction path for conduction and the selective conduction path for opening are switched, the main beam direction can be changed. You can switch in different directions.

For example, when it is desired to direct the main beam to the right direction 123a (FIG. 1 (a)), the second selective conduction path 121 arranged on the right side with respect to the feeding point 113 is opened, and the feeding point 113 is provided. The first selective conduction path 119 arranged on the left side on the opposite side may be short-circuited. On the contrary, as shown in FIG. 1 (b), when it is desired to direct the main beam to the left direction 123b, the first selective conduction path 119 arranged on the left side with respect to the feeding point 113 is opened to supply power. The second selective conduction path 121 located on the right side of the location 113 may be short-circuited. Table 1 summarizes the states in which each selective conduction path should be controlled in this drive method when the main beam is directed to the left and right.

<tables num="1"><img file="JP4131985B2_D0001.tif" /></tables>

In the variable slot antenna of the present invention, the conducted selective conduction path locally connects between the divided ground conductors 101a and 101b, and one side is open and one side is short-circuited in the structure. A slot resonator having a wavelength can be made to appear at a high frequency in each driving state. Figures 11 (a) and 11 (b) schematically show the structures realized at high frequencies in the variable slot antennas driven in the states shown in FIGS. 1 (a) and 1 (b). As described above, in the slot region of the variable slot antenna of the present invention, both ends are set to open ends in advance, but in each drive state, one end can be treated as if it is short-circuited at a high frequency. For example, in FIG. 11 (a), the open end 111a shown in FIG. 1 (a) is not shown. This is due to the continuity control of the first selective conduction path 119 arranged in the direction facing the open end 111a from the feeding point 113 so that the open end 111a can be ignored in terms of high frequency when facing from the feeding point 113. This is to become. Further, if the second selective conduction path 121 is set to the open state at a high frequency, the influence of the specific shape of the second selective conduction path 121 on the radiation characteristics becomes extremely limited. 1 (a) can be approximated in terms of high frequency as shown in Fig. 11 (a). Similarly, the variable slot antenna in the drive state of FIG. 1 (b) can be approximated as shown in FIG. 11 (b) in terms of high frequency. Since the main beam direction when the quarter effective wavelength slot resonator is fed is the direction from the feeding point to the open end side, the direction from the feeding point to the open end can be switched depending on the driving state. In the variable slot antenna, dramatic switching of the main beam direction can be realized. The figures shown in FIGS. 5 and 7 to 10 above also schematically show the structure realized at high frequencies in the variable slot antenna in an arbitrary one-drive state, and the selective conduction path is omitted. It was done.

Based on the above principle, as shown in FIGS. 12 and 13, the variable slot antenna driven by the driving method of the present invention is not single but single from the feeding point 113 toward the open ends 111a and 111b of the slot area 109, respectively. When a plurality of selective conduction paths are arranged, the driving method is limited. First, as shown in FIG. 12, when it is desired to direct the main beam to the right side (direction of arrow 123a), a plurality of second selective conduction paths 121-1 in the direction 117b facing the open end 111b from the feeding point 113, When 121-2, ... 121-N are arranged, all the second selective conduction path groups 121-1, 121-2, ... 121-N are set to the open state. Further, as shown in FIG. 13, when it is desired to direct the main beam to the right side (direction of arrow 123a), a plurality of first selective conduction path groups 119-1 in the direction 117a facing the open end 111b from the feeding point 113, When 119-2, ... 119-N is arranged, at least one of the first selective conduction path groups 119-1, 119-2, ... 119-N is selected as the conduction state. It should be done. FIG. 13 shows a state in which only the second selective conduction path 119-2 is conduction controlled. It is possible to adjust the resonator length of the formed slot cavity by selecting a selective conduction path to conduct. It is also possible to adjust the feed impedance to the slot resonator by selecting a selective conduction path that conducts. Of course, all the selective conduction paths may be conducted.

(About selective conduction path) The conduction between the first ground conductor 101a and the second ground conductor 101b obtained by the first and second selective conduction paths does not have to be DC signal conduction, and the pass band is located near the operating frequency. It may be a limited high frequency conduction. Specifically, in order to realize the selective conduction path of the present invention, any switch element such as a diode switch, a high frequency transistor, a high frequency switch, or a MEMS switch that can obtain low loss and high resolution characteristics in the antenna operating band is used. Both can be used. If a diode switch is used, the configuration of the power feeding circuit can be simplified. That is, if the polarities of the diode switches inserted in the first selective conduction path and the second selective conduction path are opposite to each other, either the ground conductor 101a or 101b is grounded in a direct current manner, and the other is grounded. By controlling the voltage applied to the conductor, the first drive state and the second drive state can be easily switched. 14 (a) and 14 (b) show the lower surface structure near the peripheral portion of the implementation example of the selective conduction path used in the present invention, particularly when the width of the slot region 109 is wider than the size of the switch element. The enlarged schematic diagram of each is shown. As shown in FIG. 14 (a), the selective conduction path 191 consists of a switch element 191a capable of switching between conduction and opening of a high frequency signal, and protruding conductors 193a and 193b provided on both sides of the switch element 191a. It may be configured. The conductors 193a and 193b have a shape protruding from the ground conductors 101a and 101b into the slot region 109, respectively. One of the conductors 193a and 193b may be subtracted from the structure and the switch element 191a may be directly connected to any of the ground conductors 101a and 101b. Further, as shown in FIG. 14B, the conductor wires 193c and 193d are used instead of the conductors 193a and 193b to realize the connection between the ground conductor 101a and the switch element 191a and the ground conductor 101b and the switch element 191a. It doesn't matter. Also, selective when the size of the switch element 191a is larger than the width of the slot area 109. An example of realization of the conduction path 191 is shown in FIG. 15 as an enlarged view of only the periphery of the selective conduction path. In any case, the selective conduction path is formed across the slot region to connect the ground conductors 101a and 101b, and a switch element capable of controlling two states of high-frequency conduction and open is always connected in series in the path. It is an inserted structure. The selective conduction path functions as a high-frequency open state when the switch element in the path is opened, and functions as a high-frequency conduction state when the switch element in the path is conduction-controlled. Since the switch element used in the high frequency band has a parasitic circuit component depending on the structure, it is strictly impossible to realize a completely open state or a completely conductive state, but the parasitic circuit component is preliminarily used. If the circuit is designed in consideration, the object of the present invention can be easily achieved. For example, the commercially available gallium arsenide PIN diode switch used in the examples of the present invention has a parasitic capacitance in series of 0.05 pF and is about 25 dB in the 5 GHz band when opened, which is sufficient separation characteristics for the purpose of the present invention. It is possible to obtain. Even if the variable slot antenna of the present invention is designed without considering this value, the characteristics do not change significantly. Further, the above-mentioned commercially available diode switch has a parasitic resistance in series of 4Ω, and a loss at the time of conduction of about 0.3 dB can be obtained in the 5 GHz band, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique. A value of about 3 dB can be obtained, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique. A value of about 3 dB can be obtained, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique. A value of about 3 dB can be obtained, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique. A value of about 3 dB can be obtained, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique. A value of about 3 dB can be obtained, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique. A value of about 3 dB can be obtained, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique. It is 05pF, and when it is open, it is possible to obtain a separation characteristic of about 25 dB in the 5 GHz band, which is sufficient for the purpose of the present invention. Even if the variable slot antenna of the present invention is designed without considering this value, the characteristics do not change significantly. Further, the above-mentioned commercially available diode switch has a parasitic resistance in series of 4Ω, and a loss at the time of conduction of about 0.3 dB can be obtained in the 5 GHz band, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique. It is 05pF, and when it is open, it is possible to obtain a separation characteristic of about 25 dB in the 5 GHz band, which is sufficient for the purpose of the present invention. Even if the variable slot antenna of the present invention is designed without considering this value, the characteristics do not change significantly. Further, the above-mentioned commercially available diode switch has a parasitic resistance in series of 4Ω, and a loss at the time of conduction of about 0.3 dB can be obtained in the 5 GHz band, and a sufficiently low loss characteristic can be obtained for the purpose of the present invention. Therefore, even if the variable slot antenna of the present invention is driven assuming that this value is ignored and an ideal switch element is arranged, deterioration of characteristics such as radiation efficiency of the antenna can be ignored. That is, the selective conduction path used in the present invention can be easily realized by a general circuit technique.

(Regarding the orientation of the slot region) The variable slot antenna of the present invention can change the main beam direction depending on the slot formation direction. That is, if the direction facing the open end of the slot from the feeding point is slightly downward, the main beam direction of the radiated electromagnetic wave can also be slightly downward.

(Regarding the symmetry of the configuration) The shape of the variable slot antenna of the present invention does not necessarily have to be mirror-symmetrical. However, it is considered that the provision of an antenna having the same reflection characteristic, the same gain characteristic, and the same polarization characteristic in two states but having the variability that can switch only the main beam direction is particularly high in industrial utility value. .. Therefore, the shape of the slot region 109, the shape of the feeding line 115, the shape of the loop wiring 209, and the shapes of the ground conductors 101a and 101b are preferably mirror-symmetrical.

(About the slot resonator) For the slot resonator that appears on the circuit in each drive state, the slot width Ws (that is, the distance between the first ground conductor 101a and the second ground conductor 101b) is the slot resonator length. When it is negligibly narrower than Ls (generally when Ws is (Ls / 8) or less), the slot length Ls is set to be a quarter effective wavelength near the center frequency f0 of the operating band. .. When the slot width Ws is wide and cannot be ignored compared to the slot cavity length Ls (generally when Ws exceeds (Ls / 8)), the slot length (Ls × 2 + Ws) considering the slot width is set to f0. It may be set so as to correspond to a half effective wavelength.

The slot cavity length Ls is defined as the distance from the conductive selective conduction path (119 or 121) to the opening 111 across the feed line 115 and feed location 113. As shown in FIG. 12, when a plurality of selective conduction paths are arranged instead of a single one, the Ls is, strictly speaking, from the switch 121 closest to the power supply line 115 to the power supply line 115 and the power supply location. It is defined as the distance across 113 to the opening 111.

(Example of a slot having a different shape) In the variable slot antenna of the present invention, the shape of the slot region does not have to be rectangular, and the boundary line with the ground conductor region can be replaced with an arbitrary straight line or curved shape. For example, as shown in FIG. 16, the shape of the slot region may be such that the slot width is tapered in the vicinity of the open end. Since the beam width is determined by the radiation opening surface of the antenna near the upper limit frequency of the operating band, it is easy to realize a high-gain directional beam by widening the slot width near the open end.

Further, as shown in FIG. 17, if a large number of small and short slots are connected in parallel to the main slot region (that is, they face each other on each of the four sides of the substantially rectangular first ground conductor 101a and the second ground conductor 101b). If small continuous irregularities are provided on one side), the effect of adding series inductance to the main slot region can be obtained, and the practically preferable effect of effectively shortening the slot length and further reducing the size of the circuit can be obtained. Further, even in a variable slot antenna structure in which the slot width of the main slot region is narrowed and bent into a meander shape or the like to reduce the size, the effect of switching the main beam direction can be obtained by the driving method of the present invention.

(Treatment at the open end of the feed line and double resonance structure) It is also possible to obtain wideband matching characteristics by grounding the end point 125 of the feed line 115 via a resistance element. It is also possible to gradually widen the line width of the feeding line 115 near the end point 125 and make the shape of the end point radial to obtain wideband matching characteristics.

Further, for example, it is possible to load an additional dielectric 129 on the open ends 111a and 111b to change the radiation characteristics of the slot antenna. Specifically, it is possible to control the half width characteristic of the main beam during wideband operation.

(Form in a multilayer structure) In the present specification, as shown in the cross-sectional view in FIG. 18A, the power feeding line 115 is arranged on the outermost surface of the dielectric substrate 103, and the back surface of the dielectric substrate 103 is arranged. Although the structure in which the grounding conductor 101 is arranged is described in FIG. 18B, as shown in FIG. 18B, a cross-sectional view of another form is shown. Either or both of them may be arranged on the inner layer surface of the dielectric substrate 103. Further, as shown in FIG. 18C as a cross-sectional view of another form, the conductor wiring surface that functions as the grounding conductor 101 with respect to the feeding line 115 does not have to be limited to one in the structure, and the feeding line does not need to be limited to one. The structure may be such that the ground conductors 101 facing each other across the layer on which 115 is formed are arranged. That is, the method for driving the variable slot antenna of the present invention can obtain the same effect not only with the variable slot antenna having a microstrip line structure but also with the variable slot antenna having a strip line structure.

(Example) The variable slot antenna of Example 1 was produced as shown in FIG. 19 as a schematic perspective view from the upper surface. As the dielectric substrate 103, an FR4 substrate having a total thickness of 0.5 mm was used. On the front and back surfaces of the substrate, a power supply line pattern with a thickness of 20 microns and a ground conductor pattern were formed by copper wiring, respectively. Each wiring pattern was formed by removing a metal layer in a part of the area by wet etching, and the surface was plated with gold having a thickness of 1 micron. The wiring margin is set so that the outer edge portion 105 of the ground conductor 101 is 0.1 mm inside from the end face even when it is closest to the end face of the dielectric substrate 103. In the figure, the ground conductor pattern is shown by the dotted line, and the pattern of the feeding line is shown by the solid line. A high-frequency connector was connected to the input terminal portion 109, and the manufactured antenna and the measurement system were connected via a feeding line 115 having a characteristic impedance of 50 Ω. As shown in the figure, the loop wiring 209 was introduced at the point where the power supply line 115 intersects the slot area 109. The loop wiring 209 is a square loop wiring having a side a2 and a line width W2. Further, a variable slot antenna having a power feeding configuration that intersects the slot region 109 without introducing the loop wiring 209 and with the line width W1 having a characteristic impedance of 50Ω is used as Comparative Example 1. The ground conductor 101 was separated at the center to form a slot region 109 sandwiched between the finite ground conductor regions 101a and 101b, and two selective conduction paths 119 and 121 straddling the slot region 109 were set. A commercially available gallium arsenide PIN diode was used as the high-frequency switch element in the selective conduction path. The PIN diode used has an insertion loss of 0 at 5 GHz when conducting. The separation degree at 3 dB and open was 25 dB at 5 GHz, which was a value that was not a problem in practical use. A bias circuit was connected to the ground conductor region 101b via a 1 kΩ resistor element to realize bias feeding to the diode. By setting the polarities of the diodes 119 and 121 to be opposite to each other and arranging them, the setting to drive one of the selective conduction paths 119 and 121 so that the other operates in the open operation when the conduction operation is completed is completed. The structural parameters of Example 1 shown in FIG. 19 are summarized in Table 2 as a comparison with the structural parameters of Comparative Example 1.

<tables num="2"><img file="JP4131985B2_D0002.tif" /></tables>

In the first driving state, by conducting the selective conduction path 119 and opening the selective conduction path 121, radiation in the plus X direction in the coordinate system in the figure was obtained in a wide frequency band. FIG. 19 corresponds to a schematic structural diagram in the first driving state. Further, in the second driving state, the selective conduction path 119 is opened by applying a reverse bias to the ground conductor region, and the selective conduction path 121 is conducted to emit radiation in the minus X direction. Obtained in a wide frequency band. The reflection characteristics in the first driving state are shown in FIG. 20, and compared with the reflection characteristics in the same first driving state of Comparative Example 1. The frequency band in which a good reflection characteristic value of -10 dB or less could be obtained is 2.7 GHz to 4.3 GHz in Comparative Example 1, while it is 2.3 GHz to 4.7 GHz in Example 1, which is also high on the low frequency side. The region side was also greatly improved. In the comparison of specific bands, Comparative Example 1 was 45%, whereas Example 1 was able to improve to 68.6%. Further, even in the second driving state, the same reflection characteristics could be obtained in almost the same frequency band. The radiation characteristics at 2.5 GHz and 4.5 GHz in the first drive state and the second drive state are shown in FIGS. 21 (a) and 21 (b), respectively. Illustrated is the radiation directivity in the XZ plane in the coordinate system in FIG. In the figure, s1 is the radiation directivity in the first driving state, and s2 is the radiation directivity in the second driving state. As is clear from FIGS. 20 and 21, the main beam direction is oriented in the same direction in a wide frequency band while obtaining substantially the same and good reflection characteristics in the two states in a wide frequency band, and the main beam direction is set to two. I was able to switch completely in the state.

Next, the variable slot antenna of Example 2 was produced as shown in FIG. 22 as a schematic perspective view from the upper surface. The structural parameters of Example 2 are summarized in Table 3. In the second embodiment, the feeding line 115 having a region length of t4 from the open tip portion 125 was replaced with the inductive resonator region 127, and two square loop wirings 209 were connected in series and introduced therein. In addition, the central portion of the inductive resonator region 127 is made to correspond to the slot feeding point.

<tables num="3"><img file="JP4131985B2_D0003.tif" /></tables>

The reflection characteristics of Example 2 in the first driving state are shown in FIG. In Example 2, a good reflection loss value of -10 dB or less could be obtained in the frequency band from 2.63 GHz to 8.8 GHz. The above band corresponds to a wide band characteristic of 108% when converted to a specific band, and the specific band of 65% achieved in the first drive state of Comparative Example 2 which is a variable slot antenna when no loop wiring is introduced. It was a significantly superior value. Further, even in the second driving state, almost the same reflection characteristics could be obtained. The radiation characteristics at 3 GHz, 6 GHz, and 9 GHz in the first drive state and the second drive state of Example 2 are shown in FIGS. 24 (a), (b), and (c), respectively. Illustrated is the radiation directivity in the XZ plane in the coordinate system in FIG. In the figure, s1 is the radiation directivity in the first driving state, and s2 is the radiation directivity in the second driving state. As is clear from FIGS. 23 and 24, the main beam direction is maintained in the same direction in a wide frequency band while obtaining substantially the same and good reflection characteristics in the two states in a wide frequency band, and the main beam direction is set to two. In the state, it was possible to switch all at once almost completely mirror-symmetrically.

As described above, it has been proved that the variable slot antenna of the present invention can realize a dramatic switching function of the main beam direction at once while maintaining the main beam direction within the operating band while occupying a small circuit area. It was.

The variable slot antenna according to the present invention simultaneously expands the operating band, maintains the identity of the main beam direction within the operating band, and simultaneously dramatically switches the main beam direction without increasing the circuit occupied area. Since it can be realized, it becomes possible to realize a high-performance terminal with a simple configuration, which could not be realized without mounting a plurality of large wideband antennas in the past. The variable slot antenna of the present invention contributes to the realization of a communication system for short-range radio using a frequency band much wider than before. Further, a small antenna having variability can be introduced even in a system that requires an ultra-wideband frequency characteristic such as transmitting and receiving a digital signal wirelessly.

The technical ideas grasped from the above explanation are as follows.

A directional variable slot antenna having a dielectric substrate (103), on the back surface of the dielectric substrate (103), a ground conductor (101) having a finite area and a slot region (109) are formed. The slot region (109) divides the ground conductor (101) into two regions including a first ground conductor (101a) and a second ground conductor (101b), and the slot region (109) is divided into two regions. Open ends (111a, 111b) are formed at both ends, respectively, and on the back surface of the dielectric substrate (103), the first ground conductor (101a) further crosses the slot region (109). Two selective conduction path groups (119,121) connecting the second ground conductor (101b) and the second ground conductor (101b) are arranged, and the surface of the dielectric substrate (103) is in the longitudinal direction of the slot region (109). A feeding line (115) intersecting the slot region (109) is arranged at the feeding point (113) near the center, and the two selective conducting paths (119, 121) are the first selective conducting paths (119, 121). It consists of 119) and a second selective conduction path (121). The first selective conduction path (119) and the second selective conduction path (121) are transmitted in a transmission plane view through the directional variable slot antenna from the normal direction of the dielectric substrate (103). The power supply line (115) is sandwiched between them.

Here, the slot resonator length Ls is the distance between the first selective conduction path (119) and the open end (111b) located at the tip in the -X direction of the slot region (109), and the slot width. When Ws is set as the distance between the first ground conductor (101a) and the second ground conductor (101b), if Ws is (Ls / 8) or less, the Ls is the operating band. It is set to be the same length as the 1/4 effective wavelength with respect to the center frequency f0 of, and if Ws exceeds (Ls / 8), (2Ls + Ws) is the center frequency f0 of the operating band. It is set to have the same length as the effective wavelength of half.

In the first state, the main beam in the -X direction is selected by selecting the first selective conduction path (119) as the conduction state and the second selective conduction path (119) as the open state. In the second state, by selecting the first selective conduction path (119) to the open state and the second selective conduction path (121) to the conduction state. , Radiates the main beam in the X direction (123b).

At the first point (221) near the power feeding point (113), the power feeding line (113) is once branched into a branch line group (115a, 115b) including two or more branch lines, and the branch line group Of these, two or more branch lines (115a, 115b) are reconnected at the second point (223) near the slot (109) to form a loop wiring (209) in the power supply line (115), all of which. The maximum value of the loop length of the loop wiring is set to a length less than one effective wavelength at the upper limit frequency of the operating band.

<figref num="1">It is a perspective schematic diagram of a variable slot antenna driven by the driving method of the present invention, (a) is a perspective schematic diagram when the main beam direction is directed to the right side, and (b) is a perspective diagram when the main beam direction is directed to the left side. It is a perspective schematic diagram.</figref><figref num="2">It is a structural sectional view of the variable slot antenna driven by the driving method of this invention, (a) is the structural sectional view of the straight line A1-A2 of FIG. 1 (a), and (b) is FIG. 1 (a). It is a structural sectional view of the straight line B1-B2.</figref><figref num="3">The perspective diagram of the variable slot antenna of the present invention, (a) is a perspective schematic diagram when the feeding structure does not include the inductive resonator region, and (b) is a perspective diagram when the feeding structure includes the inductive resonator region. It is a schematic diagram.</figref><figref num="4">In a general high-frequency circuit structure having an infinite ground conductor structure on the back surface, it is a schematic diagram of two circuits having a branch portion in the signal wiring, (a) is a schematic diagram in the case of loop wiring, and (b) is a tip. The schematic diagram in the case of open stub wiring, (c) is the case of loop wiring, and in particular, is a schematic diagram in the case where the second path is set extremely short.</figref><figref num="5">It is a perspective schematic diagram explaining the path of the high frequency current in the ground conductor in one form of the variable slot antenna of this invention.</figref><figref num="6">It is a cross-sectional structure diagram for explaining the concentration point of high frequency current in the ground conductor of the transmission line, (a) is the cross-sectional structure diagram in the case of a general transmission line, and (b) is the case of a branched transmission line. It is a cross-sectional structure diagram of.</figref><figref num="7">It is a perspective schematic diagram which shows an example of the feeding structure of the variable slot antenna of this invention.</figref><figref num="8">It is a perspective schematic diagram which shows an example of the feeding structure of the variable slot antenna of this invention.</figref><figref num="9">It is a perspective schematic diagram which shows an example of the feeding structure of the variable slot antenna of this invention.</figref><figref num="10">It is a perspective schematic diagram which shows an example of the feeding structure of the variable slot antenna of this invention.</figref><figref num="11">It is a schematic diagram of the structure realized at high frequency on the variable slot antenna of the present invention, (a) is a schematic diagram under the driving condition of FIG. 1 (a), and (b) is the driving condition of FIG. 1 (b). It is a schematic diagram of time.</figref><figref num="12">It is a perspective schematic diagram of the variable slot antenna of this invention.</figref><figref num="13">It is a perspective schematic diagram of the variable slot antenna of this invention.</figref><figref num="14">(a) and (b) are enlarged views around the selective conduction path of the present invention.</figref><figref num="15">It is an enlarged view around the selective conduction path of this invention.</figref><figref num="16">It is a perspective schematic diagram of the variable slot antenna of this invention.</figref><figref num="17">It is a perspective schematic diagram of the variable slot antenna of this invention.</figref><figref num="18">It is sectional drawing of the variable slot antenna of this invention.</figref><figref num="19">It is a structural drawing of the variable antenna of Example 1.</figref><figref num="20">It is a frequency dependence diagram of the reflection characteristic in the first drive state of the variable antenna of Example 1. FIG.</figref><figref num="21">The radiation characteristic diagram of the variable antenna of Example 1, (a) is a radiation characteristic comparison diagram at 2.5 GHz in the first and second drive states, and (b) is a radiation characteristic diagram in the first and second drive states. It is a radiation characteristic comparison diagram at 4.5 GHz.</figref><figref num="22">It is a structural drawing of the variable antenna of Example 2.</figref><figref num="23">It is a frequency dependence diagram of the reflection characteristic in the first drive state of the variable antenna of Example 2. FIG.</figref><figref num="24">The radiation characteristic diagram of the variable antenna of the second embodiment, (a) is a radiation characteristic comparison diagram at 3 GHz in the first and second drive states, and (b) is a radiation characteristic diagram in the first and second drive states. The radiation characteristic comparison diagram at 6 GHz, (c) is the radiation characteristic comparison diagram at 9 GHz in the first and second drive states.</figref><figref num="25">It is a structural schematic diagram of a general 1/4 wavelength slot antenna, (a) a schematic diagram of a top perspective, (b) a schematic cross-sectional side view, and (c) a schematic diagram of the back surface viewed from the top. is there.</figref><figref num="26">(a) is a schematic structural diagram of a quarter-wavelength slot antenna of Patent Document 1, (b) is a schematic structural diagram of a slot antenna when operating in the low frequency band, and (c) is a schematic structural diagram of the slot antenna when operating in the high frequency band. It is a structural schematic diagram of.</figref><figref num="27">It is a top perspective schematic view of the slot antenna structure described in Non-Patent Document 1.</figref><figref num="28">It is a structural drawing of the variable antenna disclosed in Patent Document 3.</figref>

Code description

101, 101a, 101b Ground conductor, ground conductor area 103 Dielectric substrate 105 Side outer edge of ground conductor 107 Depth direction 109 Slot area 111a, 111b Slot open end 113 Power supply point 115, 16 Power supply line 115a, 115b Configure loop wiring First and second paths 117a, 117b Direction facing each slot open end 111a, 111b from the feeding point 119, 119-1, 2, ... N First selective conduction path 121, 121-1, 2, N Second selective conduction path 123a, 123b Main beam direction in each drive state 125 Termination point 127 Inductive resonator region 201, 203 Input / output terminals 109x, 109y Parasitic element 205a, 205b, 18-1, 2, 3 Switch element 209, 209a, 209b, 209c, 209d, 209e, 209f Loop wiring 211 Transmission line 221, 223 Loop wiring branch point 233, 235 Direction in which high-frequency current flows 237, 239 Boundary line Ls Slot length Ws Slot width t3 Distance from the center of the slot to the open end point of the feed line t4 Inductive resonator region length Lo Offset length from the center of the slot to the coupling point with the feed line 115 Ld2 Offset from the slot end point to the feed line 115 Length t1, t2 Line length of each part constituting the inductive resonator region Feed line in the WL inductive resonator region 115 Width 401 Signal conductor 403,405 Edge of signal conductor 407 On the ground conductor facing the center of the signal conductor Region 409, 411 Branched signal conductor 413, 415 Region where high frequency current is induced in the ground conductor based on the signal conductor branch f0 Central frequency of the operating band fH Upper limit frequency of the operating band Lp1, Lp2 First and second paths Long Lp Loop length Lp3 Open stub length