Integrated antenna for mobile telephones

The invention relates to an antenna arrangement (planar antenna array, Plate antenna array patch antenna array) with a ground plane and a radiator in a arranged distance substantially parallel to the ground plane and is connected with an end portion thereof with the conductive , wherein at a first resonant frequency of the antenna assembly at the connection of the radiator to the ground plane a minimum voltage is present and in the field the other end (free end) of the radiator, a first is maximum voltage available.

Known are integrated antennas for mobile phones, the based on the principle of the patch antenna. The external dimensions of such antenna module are in existing Applications for example minimized by a folded structure (for example, C-patch) is used. In addition to the simple resonant version (a single operating frequency band) are also other structures known to the operation of the in two defined frequency bands (such as in the two mobile bands of the GSM900 and GSM1800 of standards) enable. Here are either two separate Radiator used or it will take appropriate measures achieved that at the higher operating frequency, only a certain Radiator portion is used. These procedures involve the drawback that, particularly at the higher frequency not all of the available antenna volume is being used. This results in a low bandwidth of the antenna.

The invention has the object of providing an arrangement of type described above so that they two Frequency ranges is suitable and a broadband construction allowed.

This object is according to the characterizing part of claim 1 is achieved in that in a further, higher A resonance frequency of said ends of the radiator Minimum voltage or a second voltage maximum is present, and that the area of ​​the free end of the Emitter with a different location of the radiator in such a capacitively is coupled, in that the further resonance frequency versus reduced to three times the value of the first resonant frequency is.

An advantage of the invention lies in the fact that in both frequency ranges the entire radiator radiates. This is also at the higher frequency a relatively wide bandwidth possible because a large radiator area is available. Even at the lower frequency is an advantage because here the whole total available for the antenna is area used as spotlights. To feed, a single Point of the radiator can be used.

In one embodiment of the invention, the capacitance value are and the terminal of the capacitive coupling chosen such that the second resonance frequency at least in coarse Approximation corresponds to twice the first resonant frequency. Another advantage is the ability to operate in the bands 900/1800 MHz or 900/1900 MHz.

In one embodiment of the invention, the capacitance value are and the further location selected such that the first Resonant frequency is less strongly reduced than the second Resonant frequency. It is advantageous that the antenna in its Dimensions can be kept small.

In one embodiment of the invention said another point on the radiator, the capacitive coupling with the takes place in the vicinity of the first voltage maximum in the Emitter at the second resonant frequency. It is advantageous a particularly strong reduction of the second resonant frequency at a small reduction in the first resonant frequency.

In one embodiment of the invention said another location about 1/3 the length of the unwound Radiator, measured from the connection to the ground plane. This is in many cases favorable assessment.

In one embodiment of the invention, the radiators at least partially approximated to the shape of a C, under Inclusion of an approximately C-shape having a non-circular, polygonal shape. This has proved to be favorable.

In one embodiment of the invention is the shape of the Radiator chosen such that the free end of the radiator a location of the radiator that the desired other terminal the capacity is, is adjacent. Advantageous are hereby possible short connecting lines for the capacitor.

In one embodiment of the invention is the capacitive Coupling formed by a metal strip, the interposition of of dielectric material part of the length the free end portion and a portion of the radiator at the others provided for the capacitive coupling point covers, in such a way that the capacitive coupling by an Series connection of two capacitors is formed. Advantageous is the simple and space-saving design.

The invention also relates to a hand-held radio device, including of transceivers, for at least one of the purposes: Voice communication, data transmission, video transmission, with an antenna, which is characterized in that the antenna by the antenna arrangement according to one of claims is formed, which are discussed above substantially. From Advantage is that a simple transmitter / receiver circuit possible is. Even a small package for the device is possible.

The invention also relates to a use of an antenna array and an embodiment of a hand radio, as discussed above. In this invention, only the second (higher) resonant frequency of the antenna arrangement in used operation. This storage advantages can arise where only the higher frequency band is needed, however, are dual-band antennas according to the invention available.

Further features and advantages of the invention will be made the following description of embodiments of the Invention based on the drawing, the inventively essential Shows details, and from the claims. The single ones Features may either individually or collectively in arbitrary Combination in one embodiment of the invention be realized. Show it:<dl tsize="7" compact="compact"><dt>Fig. 1</dt><dd>is a schematic perspective view of an embodiment an antenna,</dd><dt>FIG. 2</dt><dd>a graphical representation of the stress distribution over the length of an antenna according to Figure 1, but without Capacitor, wherein two resonance frequencies,</dd><dt>Fig. 3</dt><dd>the location of two resonant frequencies of the antenna according to Figure 1 without the presence of the capacitor of the Figure 1,</dd><dt>Fig. 4</dt><dd>the change in the same frequency scale as in Figure 3 Position of the resonance frequencies compared to Figure 3 in consequence of the presence of the capacitor the figure 1</dd><dt>Fig. 5</dt><dd>a view of a hand-held radio telephone device with antenna, and</dd><dt>Fig. 5a</dt><dd>a detail in Fig. 5 at 20, enlarged.</dd></dl>

In Figure 1, the antenna arrangement 1 a ground plane 2 on. This is the example just. At a distance from the Ground plate 2 is a radiator 3 on most of its Length parallel to the ground plane 2 and by appropriate means not shown at a constant distance from the Ground plate 2 held. These means are in a first Embodiment which has been implemented in FIG. 1, some arranged between the radiator 3 and the ground plane 2 Spacers made of insulating material. In another Embodiment, the said means between an the radiator 3 and the ground plane 2 arranged plate dielectric material. The light source 3 is a whole multiple angled. One end of the parallel to the ground plane 2 extending portion of the radiator 3 through a portion 3a (shorting plate), the perpendicular to the ground plane 2 runs on its entire width conductively connected to the ground plane 2. The section 3a includes itself Section 3b of the radiator 3 at right angles to extend this subscribed to the portion 3b 3c a section to, the rectangular parallel to a longitudinal edge of the example Ground plane 2 runs, to this parallel to the section 3b 3d extend a portion, and to the portion 3d closes at a distance from the portion 3c and parallel Gradient to this one section to 3e. The sections 3b to 3d together form approximately the shape of a Letter C. also is the embodiment of the end of section 3e, near the in the short-circuit plate 3a is arranged a further section 3f, the much denser the portion 3b is as in the section 3d and extends up to the vicinity of the portion 3c. The sections 3b to 3f form a flat, angular, spiral-like Arrangement. The antenna shown is as flat antenna, Plate antenna or patch antenna are referred.

The entire radiator 3 with said sections 3a to 3f is integrally formed in one embodiment of the invention made of a thin metal sheet by stamping and bending. In another embodiment, the radiator is as a metallization on the top and one border surface the above-mentioned insulating plate of dielectric Material applied.

The power of the radiator 3 takes place in the transmission and reception via a feed line 5, which lies at a distance of arranged short-circuit plate 3a and to the radiator 3 (the Example is the portion 3b), wherein the distance is selected so that a desired characteristic impedance results for feeding. As a relatively low impedance generally desired is (magnitude 50 Ohm), the feed line 5 is compared to the total unwound length of the radiator 3 relatively close to the short-circuit plate 3a. At the short plate 3a remote end 6, in the example exactly at the free end the radiator 3, more precisely of its section 3f, on the one hand, and exactly one, in the embodiment from lying, position 7 of the portion 3c on the other hand is a Capacitor 8 connected.

The length of the short-circuit plate 3a corresponding height h, in which the majority of the radiator 3 above the ground plane 2 is, is small compared to a quarter of the Wavelength of the high frequency at which the antenna assembly is to be operated. 1

The above-mentioned low-power of the feedline 5 is symbolized in Figure 1 by a coaxial cable 9, the is introduced from below the ground plane. 2 The outer conductor the coaxial cable 9 is connected to the conductive visible Surface of the ground plate 2 in conjunction, and the Center conductor of the coaxial cable 9 is connected to the feed line 5 in connection.

In practical use, the coaxial cable 9 is often be much shorter than shown, or may possibly the coaxial cable omitted entirely because the with the antenna arrangement 1 to be connected to electronic circuit immediately below, in embodiments of the invention the ground plate 2 is. In further embodiments, the invention is the ground plane 2 by the largely continuous metallization of a printed circuit board formed on the underside of the circuit components a printed circuit located.

For explaining the operation of the antenna arrangement of the 1 Reference is first made to Figure 2, of a Antenna, underlying according to Figure 1 but without capacitor. On the horizontal axis is the distance D from the connecting point short plate to the ground plane to the the free end of the radiator 3 is applied, wherein the other End of the short-circuit plate 3a (ie the compound of Ground plate 2) is d = 0th The vertical axis indicates the basic profile of the voltage or field strength in power the antenna array with high frequency at two different Frequencies.

The curve 10 in Figure 2 shows the voltage curve at Feeding of the antenna arrangement without the capacitor with the first, lowest resonance frequency of the radiator 3, which then is present, when a quarter of the wavelength of the effective Length of the radiator 3, including the short-circuit plate equivalent. For simplicity, the influence of the dielectric constant an insulating material (as a spacer neglected or support of the radiator) in these Notes will. When feeding at the feed line 5 this first resonant frequency, the voltage on the thus free end of the radiator, according to a uncoiled Length 1 a first maximum and at the lower end of the short-circuit plate to 0.

The next highest resonant frequency then sets in, if at the end at 6 at increasing the supply frequency again a maximum occurs. This is the case when the length 1 of the radiator 3 a value of 3/4 of the wavelength of the supplying high frequency. These second-mentioned resonance frequency occurs when compared to the former Resonant frequency by a factor of three higher frequency.

Such an arrangement (without capacitor) is unusable, if it is to be used with a portable electromagnetic Waves working transceivers (Transceiver) to be provided with an antenna array to operate in two frequency ranges, which in itself its Frequency vary widely (but not by a factor of 3) which for example in frequency very roughly by a factor of 2 differ. Such frequency ranges are called for GSM radio telephones usual, at which a lower frequency range (Standard devices GSM 900) very roughly at 900 MHz, and a next higher frequency range (Device Standard GSM 1800) at very roughly 1800 MHz. Said antenna assembly can thus, when according to the properties Figure 2 has not resonated with both said Frequencies are operated.

The embodiment shown in Fig. 1 makes such Dual band operation (dual band) but possible.

In practice, the antenna assemblies are referred to as narrow band, that even in such radio telephones, the only operate according to the GSM 900 standard and where the transmit mode and the receive mode in by a frequency gap separated bands take place, for transmitting and receiving each through an opening provided at the feed point wiring a vote must be made. With this Problem, the present invention is not concerned, and this problem is not necessarily due to the invention solved.

Rather, the invention provides a switching specifically for a Switching between two frequency bands (eg as described unnecessarily between 900 MHz and 1800 MHz) in the range of the antenna. To feed is a single feed line. 5

In the arrangement of Figure 1, the arrangement now being such that the terminal 7 of the capacitor 8 as in an unwound length of one third of the total length of the radiator 3. The other terminal of the capacitor 8 is, as already said, with the free end of the Radiator 3. The capacitor 8 is thus between two points of the radiator 3 is connected, in which in operation at the low resonance frequency, the voltages (Read on the curve 10 of Figure 2) relatively little different, in particular much less than the half of the Voltage at the free end of the radiator 3. This relatively low Voltage drives a capacitive current through the capacitor 8 and influenced in terms of a rate decrease this lower resonant frequency (curve 10) of the antenna array 1 compared to the condition without capacitor 8 relatively few.

In contrast is the operation of the antenna array 1 at the higher resonant frequency of the capacitor 8 without any Now Umschaltmaßnahmen between two points (the same Points 6 and 7 as above), between which a relatively large voltage difference exists, which is far greater than the voltage at the free end of the radiator 3. This results Here the eye readily seen from Fig. 2, that the capacitor 8 is applied a voltage which is twice the the voltage at the free end of the radiator 3. In the higher resonant frequency is thus the effect of the capacitor 8 in terms of a rate decrease or antenna extension much stronger than at the lower resonant frequency.

Since the lower resonance frequency in the sense of something Antenna extension (rate decrease) affected is, it is compared with the case without the capacitor, the length 1 make slightly shorter so that the slight rate decrease the lower resonance frequency then the desired resonant frequency, in the example to the resonant frequency leads in the area of ​​GSM 900th

The higher resonant frequency is, as already said, very much more reduced, so that with a suitable choice of Size of the capacitor 8 this higher resonant frequency to has required for GSM 1800 value.

The general teaching of the terminal of the capacitor 8 is that these are so connected to the emitter is that it affects the higher resonant frequency more (Ie reduced) than the low. is specifically the doctrine that the terminal of the capacitor adapted is that the force acting on him voltage at the higher resonant frequency is higher than at the lower resonant frequency. In the special case of the capacitor 8 is about there connected, where at the second resonant frequency, the two antiphase maxima of the voltage curve lie.

It should be noted that at the time a further GSM-Standard exists, which operates at a still higher frequency, namely at about 1900 MHz (GSM 1900). these Frequency falls within the framework of the outlying, especially very roughly twice the frequency of the first resonant frequency and is also to realize thus by the invention.

The frequency ranges for GSM 900 at about 880-960 MHz for GSM 1800 at about 1710 to 1880 MHz for GSM 1900 at about 1850 to 1990 MHz.

The location of the resonant frequencies without the presence of the capacitor 8 is shown in FIG. 3 S₁₁ is the reflection factor, which is measured at the entry point. At the resonance frequencies f1 and f2 is the reflection factor considerably lower than at other frequencies, because at these Resonance frequencies of the antenna the majority of the injected RF power radiates. The frequency f2 has the three times the value of the frequency f1. Figure 4 shows the state, as ascertained by the capacitor. 8 f'1 the frequency. has decreased only slightly compared to f1 and has therefore about the value f1 which has f'2 higher resonant frequency opposite f2 significantly reduced in FIG. 3

The skilled worker knows that by other influences (the housing Hand radio, particularly a GSM radio telephone, the Effect of the device holding hand and other influences) Lengths, which, owing to a theoretical consideration or using an antenna array, the uninstalled in a State is operated, shown to change significantly. There are therefore explained here in relation to the design rules for the construction may still tweaking required.

Whereas the arrangement provided for in figure 1 five radiator sections 3b to 3f form in the plan view about the Shape of the small letter 'e'. For this arrangement is hence the name e-Patch proposed.

The antenna device 1 is so formed that it has a limited available space with as much RF leading radiator surface fills. To this end, also serves to 3e at the portion communicating section 3f for unwound radiator length 1 (the bit is smaller than the respective longitudinal center line of the individual Sections measured) contributes and for its proximity to Section 3c convenient connections for the Capacitor 8 offers. At the lower resonant frequency, when the radiator 3 is a λ / 4 radiators, acts of Radiator 3 over its entire length as a radiator. This is but also at the higher resonant frequency of the case. Also Here shines the spotlight 3 with all its sections 3a 3f, so not just with a shorter length. This is an important advantage, as this also at the higher Resonant frequency, the antenna assembly a relatively broad band is. By contrast, as mentioned above, quite a switchable Matching of the antenna may be required to the antenna array optimally to the lobby of GSM 1800 on the one hand and to the transmission range of GSM 1800 on the other hand adapt. It is understood that these embodiments are directly be applied even when the antenna instead of GSM 1800 GSM 1900 is dimensioned for, or when other standards, such as AMPS, are applied.

In particular, it should be noted that in the embodiment of FIG. 1 for the connection of the capacitor 8 None lost significant parts of the surface of the radiator 3 go. The capacitor 8 can easily switch between the areas 6 and 7 are turned on.

Preferred is an embodiment of an antenna assembly 1 '(Fig. 5), in which the capacitor 8 by a sheet metal strip 20 formed from about the width of the portion 3f is, and about the gap between the free end at 6 the section 3c with sufficient overlap of the two adjacent sections is placed 3c and 3f and Liner of dielectric material (plastic film 22, see Fig. 5a) connected at a defined distance to these parts is. There are thus formed two capacitors which over a relatively wide and short and hence low-inductance Connecting line in series connected to each other are.

Variable are at the optimum sizing of the antenna in particular, the capacitance value of the capacitor 8 and the Junction 7. For example, it may be useful to to connect the capacitor to a point of the section 3c, for which the value of d 2 is slightly greater than the length of 1/3, because in such an increase in the distance of the ground plane is at the higher resonant frequency at Capacitor effective voltage (because the point d = 1/3 is the maximum of the curve 11) changes only slightly, whereas the corresponding voltage of the curve 10 (Lower frequency range) varies strongly, so that in Thus, the influence of the capacitor to the lower Resonance frequency can still be somewhat reduced.

Figure 5 shows a simple representation of a partially disrupted handheld radio 15, namely, a mobile radio telephone, the antenna as the antenna arrangement described above 1 'contains. In this antenna, the capacitor is through a over the parts 3c and 3f, with the interposition of an insulating layer down sheet metal strip 20 as a series circuit realized two capacities. The short-circuit plate 3a is arranged to the upper end of the housing of the radio telephone through. The transceiver is in the example of the regions GSM 900 and GSM 1800 designed. The antenna array is housed entirely inside the casing of the radiotelephone, It therefore is a built-in antenna.

In a particular embodiment of the antenna assembly according to FIG. 1 for a radio telephone for GSM ranges 900 and GSM 1800 takes the spotlight an area of ​​about 5 cm x 4 cm x 0.5 cm (the latter is the length of the short-circuit board) on.

From a consideration of FIG. 1, it is understood that at Retaining the radiator length and the length subdivision 1/3 to 2/3 by the terminal 7 of the capacitor and the close proximity of the area 6 and the point 7, the Radiator sections are changed considerably in shape can, without leaving the inventive principle.

Short supply lines to the capacitor 8 as described mean little space consumption and relatively low losses. Of the low space requirement allows for dimensioning the widest possible range.

It is also emphasized that the feeding of the antenna assembly for both frequency bands at the same node, Namely, at the connecting point of the feed line 5 to the Radiator 3 takes place.

If one wanted in the arrangement of FIG. 1, the higher resonant frequency thus lowering that there the capacitor 8 is omitted and a capacitor between the free end the radiator 3 and the ground is turned on, so would this is also a considerable reduction of the lower resonant frequency have the result and at the frequency ratio 3: 1 between the higher and the lower resonant frequency would change little, so that such a circuit would not be useful.