Indoor antenna

INDOOR ANTENNA

Cross-Reference to Related Applications

This application is a continuation-in-part of U.S. patent applications

Serial No. 09/418,737, filed October 15, 1999, entitled "L-Shaped Indoor

Antenna" and Serial No. 09/483,649, filed January 14, 2000, entitled "RF Switched Beam Planar Antenna." The disclosures of these applications are incorporated herein by reference.

Background of the Invention

In conventional cellular and PCS (personal communications system) wireless systems, signals transmitted from a base station (cell site) to a user (remoter terminal) are usually received via an omnidirectional antenna; often in the form of a stub antenna. These systems often sacrifice bandwidth to obtain better area coverage, stemming from the result of less than desirable signal propagation characteristics. For instance, the bit (binary digit) to Hz ratio of the typical digital Cellular or PCS system is often less than 0.5. Lower binary signal modulation types, such as BPSK (Binary Phase Shift Keying) are used, since the effective SNR (Signal to Noise Ratio) or C/l (Carrier to Interference Ratio) are often as low as 20 dB. In fact for voice based signaling, the threshold C/l (or S/N) ratio for adequate quality reception of the signal is about 17 dB.

For wireless systems directed towards data applications, it is desirable to significantly increase the SNR or C/l in order to employ higher order (binary) modulation techniques, such as QAM-64 (Quadrature Amplitude Modulation, with 64 points in the complex constellation). These higher order modulation schemes require substantially greater C/l (or SNR) thresholds; typically higher than 26 dB. For the case of MMDS (multi-user multipath distribution system) signals, where the carrier frequencies are higher (around 2500 MHz), the propagation characteristics are even worse. There is a need therefore for transmission systems that can both satisfy the coverage (propagation) demands, as well as generate high C/l or SNR levels.

One option is to increase the size of the terminal equipment (TE), or remote, antenna gain. This requires increasing the size. Additionally, it helps to increase the elevation (i.e., vertical height above ground level) of the antenna. The higher you place an antenna, the better the system gain. For a simple planar earth model, the total system path loss (attenuation) is a function of each (transmit and receive) antenna's directive gain (towards one another). However, this path loss is also a function of the height (from ground level) of each antenna. Thus, as you increase the height, from ground, the total system path loss decreases, which is an increase in the overall system link performance, or system gain. The link performance (system) gain increases 6 dB every time you double one of the antenna's height from the ground level. If you double both (i.e., transmitting and receiving) antennas' heights, the total gain (link performance) goes up by

12 dB (6 dB + 6 dB). Therefore, doubling the height from the ground is equivalent to quadrupling the size (area) of the antenna; which produces

4X (or 6 dB) of directive gain. In conventional analog MMDS systems, this (i.e., increase of SNR or C/l) has been traditionally accomplished by installing a large reflector type antenna (with up to 30 dBi of directional gain) on a rooftop, or a pole.

The disadvantages are a complex, difficult, and costly installation; as well as poor aesthetics. The migration of the MMDS frequency spectrum, from an analog video system, to a wireless data and Internet system, demands a more user friendly (easier) installation method, with much lower cost. The difficulty here is designing a system with sufficient directional gain, as to overcome loss with transmission through walls, as well as being easy to install, and orient; by the consumer, or other persons without specialized skills.

Summary of the Invention

In accordance with one aspect of the invention, there is provided an easy to install, high gain, omni-directional "indoor" antenna which provides omni-directional coverage. No installation, "pointing" or orientation is required, and the antenna may be installed in a corner of a room.

In accordance with another aspect of the invention, four antenna elements are formed as a "book," that is, two each, back to back; with the pairs oriented at 90° to each other, such that each separate antenna covers a 90° sector, so that the coverage of the antennas when summed creates a full 360° coverage.

In accordance with another aspect of the invention, an indoor antenna comprises a unitary support structure having a plurality of support surfaces; at least one antenna element mounted to each of the support surfaces; and the support surfaces being configured and oriented to achieve substantially 360° coverage by the antenna elements.

In accordance with another aspect of the invention, a method of transmitting and receiving RF signals comprises coupling a first support member having a first pair of opposed planar support surfaces along a common edge with a second support member having a second pair of opposed planar support surfaces, orienting the first and second support members such that the first pair of planar support surfaces are substantially orthogonal to the second pair of planar support surfaces, mounting at least one antenna element to each of a plurality of support surfaces, and arranging the support surfaces in a unitary support structure with the support surfaces oriented to achieve substantially 360° coverage by the antenna elements.

In accordance with another aspect of the invention, a method of transmitting and receiving RF signals comprises mounting at least one antenna element to each of a plurality of support surfaces, and arranging the support surfaces on a unitary support structure with the support surfaces and antennas oriented to achieve substantially 360° coverage. Brief Description of the Drawings

In the drawings:

FIG. 1 is a perspective view showing an antenna in accordance with the one form of the invention; FIG. 2 is a top plan view of the antenna of FIG. 1 ;

FIG. 3 is a perspective view, showing an antenna in accordance with one embodiment of the invention placed in a typical room;

FIGS. 4 and 5 are views similar to FIG. 1 , showing antennas in accordance with two further embodiments of the invention; FIG. 6 is a schematic showing of a summation/splitting device;

FIG. 7 is a view similar to FIG. 1 showing an antenna in accordance with yet another embodiment of the invention;

FIG. 8 is a schematic view, similar to FIG. 6, further illustrating a summer/splitter; FIG. 9 is a schematic view illustrating use of a 4:1 RF switch with control from a modem;

FIG. 10 is a diagrammatic showing of an antenna in accordance with one form of the_, invention, having an internal RF summer/splitter;

FIG. 11 is a view similar to FIG. 10 showing an RF transceiver or transverter incorporated into the antenna assembly;

FIG. 12 is a view similar to FIGS. 10 and 11 showing both a transceiver and modem incorporated into the antenna assembly;

FIG. 13 is a perspective view, similar to FIG. 1 , showing an antenna in accordance with yet another embodiment of the invention, employing a hinged construction; FIG. 14 shows an antenna similar to the antenna of FIG. 2, but with a different placement of radiating elements;

FIG. 15 shows yet another embodiment of an antenna in accordance with the invention, utilizing three panels; FIG. 16 shows an embodiment similar to the embodiment of FIG. 15 with a different placement of radiating elements, similar to that of FIG. 14;

FIG. 17 shows a triangular or 3-sided antenna structure;

FIG. 18 shows a rectangular or 4-sided antenna structure;

FIG. 19 shows a rectangular structure similar to FIG. 18, utilizing a single row of radiating antenna elements such as dipoles;

FIG. 20 shows a multiple sided (6-sided) configuration of an antenna structure;

FIG. 21 is a top perspective view of a repeater in accordance with another embodiment of the invention; FIG. 22 shows a repeater configured similarly to that of FIG. 21 enclosed within a rectilinear housing;

FIG. 23 is a functional block diagram of a beamsteering circuit which might be utilized with the repeater of FIG. 21 (or other repeaters utilizing multiple antenna elements or an antenna array); FIG. 24 is an approximation of the radiation pattern or beams which may be generated by the antenna of FIG. 21 ;

FIG. 25 is a top and side perspective view showing a repeater configured in accordance with yet another embodiment of the invention; and FIG. 26 is an approximation of a beam pattern, illustrating a beamsteering arrangement which might be utilized with the repeater of FIG. 24.

Detailed Description of the Illustrated Embodiment

Referring initially to FIG. 1 and FIG. 2, there is shown the general structure for a "book" antenna system 20 in accordance with one embodiment of the invention, having two rectangular (shown square in FIG. 1) sections 22, 24 joined along a common edge. The two sections, 22, 24 are joined at a 90 degree angle, thus allowing the antenna 20 to fit squarely into a corner, between two walls, in a room (see FIG. 3), so as to resemble an open "book" in appearance.

Using microstrip (patch) antenna technology allows the thickness of the sections 22, 24 to be well under one inch. Each section 22, 24 is comprised of a front (26, 28) and a back (29, 30), with each face (front and back) containing an antenna element 32, 34, 36, 38 (or multiplicity of elements, in an array, see, e.g., FIGS. 4, 5 and 7). Thus there are four (4) distinct antenna faces, each pointing in opposing or orthogonal directions from one another. FIG. 2 shows a top view of the antenna system, denoting the four distinct faces 26, 28, 29, and 30. Each face contains a microstrip/patch antenna 32, 34, 36, and 38. For this particular example, each patch antenna 32, 34, 36, 38 generates a 90° azimuth beam width. The combination of the four 90 degree beams generates an effective 360 degree coverage; thereby emulating an omni-directional antenna. FIG. 3 shows the placement of the antenna 20 at the corner of two walls 42, 44. For optimal performance the antenna system should be placed as high as possible (i.e. near the ceiling 46) to maximize signal reception and transmission to a base station (not shown). FIGS. 4 and 5 show two different variants of antenna element types, which can be used as or in place of the antenna elements 32, 34, 36, 38 of the preceding embodiments. FIG. 4 shows a vertical array (multiplicity of elements) of patch/microstrip antenna elements 52, 54, on each face 26a, 28a of a "book" antenna 20a. It will be understood that similar arrays are on the rear faces which are not visible in FIG. 4. For the case of a multiplicity of antenna elements (on each face) a parallel or series corporate feed structure (not shown) would be used, designed for correct amplitude and phase matching, to generate the desired elevation beam. FIG. 5 shows the same sort of arrays, however, using dipole antenna elements 62, 64 on faces 26b, 28b of "book" antenna 20b. Similar arrays of dipoles are used on the other two faces which are not visible in FIG. 5.

FIG. 6 shows a summation/splitting mechanism 72, in which the input/output path(s) from the antenna element(s) on each face of the "book" antenna of any of the preceding figures is RF summed to generate a single RF input/output path to/from the antenna system. For each of the four faces, the array corporate feed (or RF transmission line, for the case of a single element) is summed, in phase, with the other faces, to generate a single RF input/output. Up to this point, it has been assumed that the transmit and receive bands of the system are all within the VSWR bandwidth of a single patch/microstrip (or dipole) element. However, for the case where the transmit and receive bands of the system are further apart (say, more than 10% of the carrier frequency), then two different arrays can be used for each face. Shown in FIG. 7 is the case where there is a transmit (Tx) patch/microstrip (or dipole) array (vertical) 82, 86 and a receive (Rx) array

(vertical) 84, 88 on each face 26c, 28c of antenna 20c. The same arrangement of Tx and Rx elements would be used on the faces which are not visible in FIG. 7. Two distinct sum/split circuits of the type shown in FIG. 6 would be used (see e.g., FIG. 8) - one for Tx and one for Rx, generating two distinct, separate RF ports (one for the transmit band, and one for the receive band). The antenna system can therefore output two different RF transmission lines, or cable, or (frequency) diplex them (via a frequency diplexer module 95, see FIG. 8) into a single RF transmission line, or cable 90.

The concept as described thus far generates an omni-directional system, which splits the power (four ways) from the input/output transmission line, to each independent 90 degree sector "face," as indicated in FIG. 8. However this splitting/summing device 72 (72a) has the effect of reducing the overall system directional gain by 6 dB. One method to overcome this is to substitute a 4:1 RF switch 92 as shown in FIG. 9. This can be a combination of PIN diodes (not shown), which are biased/controlled via a control line 94 (or set of control lines) from a modem 96. The modem 96, or an associated controller or "PC" 98 can be programmed to sequentially switch the RF path to each antenna face, measure the RF power, and then select the face with the maximum power.

A suitable RF transceiver/transverter (Tc) 100 is interposed between the

4:1 RF switch 92 and the modem 96. In this case, the system would still have omni-directional capability, yet would increase the overall system

(directive) gain by 6 dB. This additionally reduces the amount of signal scattered throughout the network, and increases the overall network C/l.

This also increases the user friendliness of the system, allowing easier installation by the user, with the antenna "pointing" done by the system itself.

FIG. 10 shows one embodiment of the "book" antenna 20 of the invention at a corner of two walls 42, 44, with an internal (i.e., built into the antenna structure) RF Summer/Splitter or a 4:1 RF switch 110, with control from the modem 96 shown by the dotted line in the case of a 4:1 RF switch. The RF output (coaxial line) 90 from the antenna system can run down the corner of the wall into the RF transceiver 100 (or "transverter," as it is denoted in the MMDS industry). The RF transceiver 100 is interfaced to the modem 96 via an IF cable 102 (coaxial or twisted pair). The RF switch 110 may be physically mounted to the surface of the substrate or backplane (such as a printed circuit board or card) which forms one of the sections 22, 24.

FIG. 11 shows an embodiment where the RF transceiver ("transverter") 100 is also incorporated into the antenna assembly. This can be accomplished via a separate (transceiver) box attached to the unit, or by incorporating the transceiver electronics onto the same PCB material as the microstrip antennas.

FIG. 12 shows incorporation of both the transceiver 100 and modem 96 into the antenna assembly. Here, an Ethernet or USB (Universal Serial Bus) cable 120 is run down the wall corner directly to the

PC 98, or LAN network server.

FIG. 13 shows a generally L-shaped antenna structure similar to that of FIGS. 1 and 2, and designated generally by reference numeral 20a.

The antenna 20a employs flat panels 22a and 24a which have oppositely facing surfaces on which antenna elements (not shown in FIG. 13) may be mounted in similar fashion to FIG. 2, or, in some other configuration as will be more fully discussed hereinbelow. Departing from the embodiment of

FIGS. 1 and 2, the embodiment of FIG. 13 is provided with a hinged connection 125 between the respective panels 22a and 24a. Thus, the two panels 22a and 24a may be pivoted or rotated with respect to each other to fit in either an inside corner of a wall or an outside corner of a wall, with the respective panels being impedance matched to the wall. The structure of FIG. 13 could also be adjusted so that the panels 22a and 24a are at some angle other than right angles with respect to each other if required for a particular application.

Referring next to FIG. 14, a generally L-shaped antenna 20b similar to that of FIGS. 1 and 2 is illustrated. The antenna 20b has respective flat panels 22b, 24b which define oppositely facing generally flat surfaces, each of which mounts at least one antenna or radiating element, 32b, 34b, 36b and 38b. It will be noted that departing from the embodiment of FIG. 2, the respective antenna elements or radiating elements on each oppositely pair of surfaces are offset somewhat. That is, the antenna elements 32b and 36b are located closer to outer edges of the respective panels 22b and 24b than the antenna elements 34b and 38b, which are substantially centered. This placement of the antenna elements 32b and

36b permits their radiating patterns (shown in broken lines) to extend at a somewhat wider angle before encountering respective outer edges of the panels 22b and 24b, to achieve a somewhat wider angle of coverage than if these elements 32b and 36b were located centered or farther in toward the corner with respect to panels 22b and 24b whereby the outer edges of the panels would cut off more of the radiating pattern, reducing the effective angle of coverage somewhat. This would be the case in the embodiment where the panels 22, 22b and 24, 24b are printed circuit boards or other flat panels having conductive surfaces or conductive coating forming a backplane for the respective antenna elements.

Referring next to FIG. 15, a further embodiment of an antenna is designated generally by reference numeral 200. The antenna 200 has respective flat panels 220 and 224 having oppositely facing surfaces, each of which may mount at least one antenna element (not shown). In the embodiment illustrated in FIG. 15, the antenna elements are substantially centered on the respective opposite surfaces of each of the panels 220 and 224 as indicated by the radiation patterns (shown in broken lines). In this case, each of the antenna elements is indicated as having a substantially 60° radiating pattern. The panels 220 and 224 are located at right angles to each other and are joined by a third, or center panel 225 which is substantially centered between the panels 220 and 224. This structure is such that the panels 220 and 224 mount directly or flush against respective wall surfaces, spaced outwardly somewhat from an inner corner of two Wall surfaces indicated generally by broken lines 227, 229 in FIG. 15. Thus, the centered panel 225 generally spans the corner, forming an angle of substantially 45° with respect to each of the two wall surfaces 227 and 229 shown in phantom line in FIG. 15.

The third or center panel 225 also has at least one antenna element mounted substantially centrally on each of its opposite surfaces with respect to plan or overhead view shown in FIG. 15, and also having a substantially 60° radiation pattern as indicated by the broken lines in FIG. 15. Thus, at least one antenna element on each of the panels 220, 224 and 225 covers substantially 60°, resulting in substantially 180° of coverage. Similarly, the (at least) three antennas mounted on the opposite surfaces would cover the remaining 180° to achieve substantially 360° of coverage by the structure shown in FIG. 15. Also, it is noted that with the structure of FIG.15, the antenna elements mounted on the inner surfaces of the panels 220 and 224 will not have their 60° radiation patterns cut off by outer edges of the panels 220 and 224. Rather, these panels are spaced sufficiently far apart from the corner of the walls 227 and 229 by the center panel 225, such that the 60° patterns of the substantially centered antenna elements do not encounter the outer edges of the panels 220 and 224.

Referring briefly to FIG. 16, a substantially similar structure 200a is shown in which respective antenna elements are shown mounted to the respective panels 220, 224 and 225. Here, antenna elements 231 and

233 are located on opposite sides of the center panel 225 and are substantially centered in the top or plan view of FIG. 16. However, respective elements 236 and 238 and 232, 234 are relatively offset, in much the same fashion as described above with reference to FIG. 14.

Referring next to FIGS. 17-20, in accordance with yet another form of the invention, the antenna may have a generally polygonal body having three or more outwardly facing, substantially flat surfaces which mount antenna elements for substantially 360° coverage. FIGS. 17 and 18 illustrate a generally triangular and generally rectangular or square cross- sectional configuration of the antenna body or support structure. Each of these structures have substantially identical sides or radiating faces 326, 330 and 426, 430, etc. each of which mounts respective antenna elements 336, 436, 438, etc. In the embodiments shown in FIGS. 17 and 18, two columns of patch antenna elements are illustrated on each of the antenna faces or surfaces. However, other forms of radiating elements such as dipoles, slots, etc. might be utilized without departing from the invention. Also, as shown for example in FIG. 19, a single column of antenna element may be utilized on each face. In the antenna 500 of FIG. 19, each face 526, 530 mounts a single row of radiating elements 536, 538 which are shown in FIG. 19 as dipoles. Similarly, FIG. 20 shows a polygonal or hexagonal cross-sectional shape of the antenna body or structure which has six faces, of which three faces 626, 630 and 631 are visible in FIG. 20. Each of these faces mounts one or more antenna elements, here illustrated as a single column of dipoles 632, 636 and 638. In all of the embodiments shown herein, one or more antenna elements may be mounted to each face or surface of the antenna structure. The elements may have patches, dipoles, radiating slots, or other radiating elements without departing from the invention. These elements may be mounted individually, or in columns and rows. For example, in the embodiment of FIG. 17, one of the columns of antenna elements on each surface might be designated as receive elements while the other column is designated as transmit elements. These variations in the numbers, arrangement and types of antenna elements may be as previously described and illustrated above, for example, with reference to FIGS. 4, 5 and 7. Also, the additional switching configurations and arrangements including switches, diplexers, transceivers, modems and the like as illustrated in FIGS. 8-12 may be utilized and incorporated in similar fashion in connection with, or on a printed circuit board forming one of the faces of, any of the antenna configurations as illustrated in FIGS. 13-20.

In FIG. 21 , an antenna structure 700 has respective opposed convex or semi-elliptical curved surfaces 702 and 704. Each of these surfaces mounts one or more antenna elements 706 which comprise M x N antenna arrays of M rows and N columns, as illustrated in FIG. 21. The antenna elements 706 on each of the surfaces 702 and 704 may be summed using a Butler matrix, or other means, such as a bank of radio frequency (RF) switches (one for each column), or a microstrip network wherein a transceiver 708 and a modem 710 control operation of a switch 712 via a control circuit 714. The switch 712 may switch between the summing networks or elements for each of the faces 702, 704, such as radio frequency switches or Butler matrixes 718 and 720.

The modem 708, transceiver 710 and control circuit 714 may also select the desired radiating element, or column, via the RF switches, or Butler matrix 718, 720, in accordance with preselected criteria, such as signal strength, or some other measure of signal quality. FIG. 24 indicates generally a number of beam patterns which may be generated by one face of the antenna of FIG. 21 and selected, using one of the above-mentioned ways for summing and/or switching of the antenna elements 706. Referring briefly to FIG. 22, the antenna structure 700 of FIG. 21 may be housed within a rectilinear housing 730, if desired, so as to maintain a rectangular appearance and facilitate mounting to various flat wall or ceiling surfaces, or the like. It will be seen that substantially 360° of coverage may be generated using the curved surfaces or faces 702, 704 and the antenna arrays of the embodiment of FIG. 21.

Referring now to FIGS. 25 and 26, yet another antenna configuration or structure 800 for achieving 360° of coverage, including the opposite edge portions of the field, is illustrated. The antenna structure of FIG. 25 is generally rectilinear in form including opposite flat surfaces or faces 802 and 804 and also relatively narrow opposite edge surfaces 806, 808 which are generally orthogonal to the surfaces 802 and 804. Each of the surfaces 802, 804, 806, and 808 mounts one or more radiating elements 810 which are illustrated as dipoles in FIG. 25. It will be understood with respect to FIGS. 21 and 25 that different types of radiating elements may be utilized in much the same fashion as described above with respect to FIGS. 13-20.

In the embodiment of FIG. 25, as illustrated by FIG. 26, the provision of M x N arrays of radiating elements 810 on the surfaces 802 and 804 may be utilized in connection with some form of beamsteering as discussed hereinabove to select an optimum beam direction for a given transmission. However, a single radiating element or single row of radiating elements is mounted on each of the surfaces 806 and 808, which generally have a fixed beam of substantially 90° beam width for covering the edge parts of the field, that is, those portions of the field which are generally perpendicular to the' surfaces 802 and 804. Thus, the optimum beam may be selected, as indicated by FIG. 26, in the same fashion as discussed hereinabove in the embodiments of FIGS. 21 and 25.

The antenna(s) of the invention may be used in many applications, including without limitation:

MMDS (Wireless Internet)

MMDS (analog video)

Cellular (indoor)

PCS (indoor) 3G systems

While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.