Abstract:
The subject matter discloses a wireless communication system comprising: at least one active phased array antenna unit for transmission and reception of electronic radiation and a phased array circuit for driving and controlling said at least one phased array antenna unit, wherein said at least one phased array antenna unit comprises at least four one dimensional arrays of radiations. The subject matter also discloses a method for utilizing the described system.

Description:
RELATED APPLICATIONS 
       [0001]    Patent applications serial number PCT/IL2006/001144 filed on Oct. 3, 2006 and titled PHASE SHIFTED OSCILLATOR AND ANTENNA and PCT/IL2006/001039 filed on Sep. 6, 2006 and titled APPARATUS AND METHODS FOR RADAR IMAGING BASED ON INJECTED PUSH PUSH OSCILLATORS the disclosures of which is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the field of broadband access and more particularly to a wireless communication method and system using an active phase array antenna to be used in systems like WIMAX, WIFI, WPAN, cellular communication and the like 
       BACKGROUND OF THE INVENTION 
       [0003]    There is an increasing demand for broadband wireless access solutions. The term WI-MAX was defined as Worldwide Interoperability for Microwave Access by the WI-MAX forum that was acting to promote conformance and interoperability of the IEEE 802.16 standard. 
         [0004]    Several methods and technologies were adopted in order to enable broadband access compliant with IEEE 802.16 and similar standards, the most common technology that support this standard is known as MIMO—Multiple In Multiple Out, a technology that is based on deployment of several antennas. 
         [0005]    However, the MIMO technology suffers from some prominent drawbacks mainly due to its relative high cost. Furthermore, MIMO as other technologies being in use for WIMAX, WIFI, WPAN and cellular communications does not offer a system and method to cope with dynamic changes of required bandwidth and does not offer an efficient method to enable precise directional transmission and receiving. 
         [0006]    While the foregoing introduction referred to WIMAX, very similar problems are associated with WI-FI standard (IEEE 802.11), WPAN (IEEE802.153C), common cellular communication protocols and other methods and protocols as well. The present invention is designed to solve similar problems for such and other like now known or later developed communications methods and protocols. 
       SUMMARY OF THE INVENTION 
       [0007]    An aspect of an embodiment of the invention, relates to a system and method for performing wireless communication between objects spaced a distance from a few meters to a number of kilometers by transmitting and receiving electronic signals via active phased array antenna systems. For example communication between a cellular station and plurality of cellular phone devices, WIMAX, WIFI, WPAN, cell phone communication between a control station and a car control unit, HDTV transmission from a TV Set Top Box (STB) to HDTV Receivers, and the like. 
         [0008]    In an exemplary embodiment of the invention, an antenna unit consisting four one-dimensional phased arrays of radiators enables communication (transmitting and receiving) with a plurality of devices, wherein the antenna unit is switching among plurality of radiation modes for enabling efficient transmission (or receiving) to specific devices that are located in a wide angel around the antenna unit. 
         [0009]    It is further an object of the invention to provide low cost systems for enabling high rate communication among a plurality of receiving/transmitting objects. 
         [0010]    It is further an object of the invention to provide a system and method for high throughput communication for outdoor as well as indoor applications. 
         [0011]    There is thus provided in accordance with an exemplary embodiment of the invention a wireless communication system comprising one or more phased array antenna units for transmission and reception of a radiation, a phased array circuit for driving and controlling the one or more phased array antenna units, wherein the one or more phased array antenna units comprise four or more dimensional arrays of radiators. 
         [0012]    In some embodiments of the invention, the phased array antenna unit can be active. 
         [0013]    In some embodiments of the invention, the dimensional arrays of radiators are linear. 
         [0014]    In some embodiments of the invention, the phased array antenna unit is positioned in a vertical orientation. 
         [0015]    In some embodiments of the invention, the dimensional arrays of radiators are symmetric. 
         [0016]    In some embodiments of the invention, the dimensional arrays of radiators are linear and symmetric. 
         [0017]    In some embodiments of the invention, the even dimensional arrays of radiators are shifted with reference to the odd one dimensional arrays of radiators by about half of the distance between two adjacent radiators. 
         [0018]    In some embodiments of the invention, the one or more phased array antenna units comprise four or more radiators, wherein one of two or more groups of radiators is defined as a reference group and two or more of the four or. more groups of radiators are controlled by the phased array circuit to transmit and receive with a programmable phase shift relative to said reference group 
         [0019]    In some embodiments of the invention, each group of radiators comprises at least one dimensional array of radiators. 
         [0020]    In some embodiments of the invention, the programmable phase shift is +180 or −180 degrees. 
         [0021]    In some embodiments of the invention, the system is selectively switching between three or more radiation modes, where a radiation mode is defined according to the number of groups of radiators that transmit and receive each in a different phase shift and according to the programmable phase shift that is associated with each group of radiators. 
         [0022]    In some embodiments of the invention, the selectively switching between the three or more radiation modes enables communication with objects over a substantially wide horizontal angle. 
         [0023]    In some embodiments of the invention, the wide horizontal angle is greater than 90 degrees. 
         [0024]    In some embodiments of the invention, the selectively switching between the three Or more radiation modes depends on signal level received in the three or more radiation modes. 
         [0025]    In some embodiments of the invention, the phased array circuit controls the phased array antenna unit to radiate in a vertical beam aperture. 
         [0026]    In some embodiments of the invention, the narrow vertical beam aperture is steered vertically according to a programmable pattern. 
         [0027]    In some embodiments of the invention, the phased array circuit includes two level of PSIPPO; and the narrow vertical beam aperture is steered vertically according to a programmable pattern by providing control signals to the two level of PSIPPO. 
         [0028]    In some embodiments of the invention, the communication system is used for outdoor communication. 
         [0029]    In some embodiments of the invention, the communication system is used for indoor communication. 
         [0030]    In some embodiments of the invention, the one or more phased array antenna units for transmission and reception of radiated electronic signals transmits or receives various now known or later developed communications protocols and methods. Such can include, for example, WIMAX or WIFI or HDTV or cellular communication compliant data signals, or any combination thereof. 
         [0031]    In some embodiments of the invention, the system comprises four phased array antennas, positioned in a substantially rectangle structure to cover a 360 degrees of the area surrounding the antennas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings. Identical structures, elements or parts, which appear in more than one figure, are generally labeled with a same or similar number in all the figures in which they appear, wherein: 
           [0033]      FIG. 1A  is a schematic illustration of a phased array antenna unit according to an exemplary embodiment of the invention; 
           [0034]      FIG. 1B  is a schematic view of a phased array antenna system including four phased array antenna units, located on a vertical pole according to an exemplary embodiment of the invention. 
           [0035]      FIG. 2A  is a graphic description of the radiation pattern of a phased array antenna unit in a first mode of operation, (polar and Cartesian), according to an exemplary embodiment of the invention; 
           [0036]      FIG. 2B  is a graphic description of the radiation pattern of a phased array antenna unit in a second mode of operation, (polar and Cartesian), according to an exemplary embodiment of the invention; 
           [0037]      FIG. 2C  is a graphic description of the radiation pattern of a phased array antenna unit at a third mode of operation, (polar and Cartesian), according to an exemplary embodiment of the invention; 
           [0038]      FIG. 2D  is a graphic description of the radiation pattern of a phased array antenna unit summarizing three modes of operation, (polar and Cartesian), where each mode is operated at different times, accordingly with the service needs according to an exemplary embodiment of the invention; 
           [0039]      FIG. 2E  is a polar graphic description of the radiation pattern of phased array antenna units summarizing three modes of operation of four phased array antenna units that are located on four sides of a single pole, according to an exemplary embodiment of the invention; 
           [0040]      FIG. 3A  is a schematic illustration of the base of a circuit for implementing a phased array antenna circuit that supports a combination of three modes of operation according to an exemplary embodiment of the invention; 
           [0041]      FIG. 3B  is a schematic illustration of the front end of the transceiver, connected to the high frequency ports of the mixers of  FIG. 3A  to implement a phased array antenna circuit that supports a combination of three modes of operation according to an exemplary embodiment of the invention; 
           [0042]      FIG. 4  is an illustration of a 360 degree phased array antenna system communicating with three transmitting/receiving end points according to an exemplary embodiment of the present invention; 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]    In PCT/IL2006/001144 filed on Oct. 3, 2006 and in PCT/IL2006/001039 filed on Sep. 6, 2006 the disclosures of which are incorporated herein by reference there are described elements and circuit designs for providing low cost and light weight distributed active phased array antennas. The applications describe circuits, which can be implemented as low cost and small sized circuits or manufactured as integrated chips to generate and control the signals transmitted and detected by phase array antennas. The current application implements the concepts described in the above applications to provide suitable active phase array antennas for implementing the current invention as further described below. 
         [0044]      FIG. 1A  shows a radiating part of an active phased array antenna (APAA) (referred to as “antenna unit”)  100  that includes four or more one-dimensional arrays of radiators (referred to as “radiators”)  110 ,  115 ,  120 ,  125 , which can be implemented using microstrip technology, located on a rectangular casing  105 , consisting on a dielectric substrate with the related base plate. The entire antenna array specifically described in  FIG. 1A  consists of 64 radiators marked as A 1  to A 16 , B 1  to B 16 , C 1  to C 16  and D 1  to D 16 . However, different numbers of radiators may be used depending on the required power output and precision. Each radiator is shaped as a hexagonal patch, for example radiator A 1 ,  130 . Each radiator has a feeder (an I/O port that conveys the electromagnetic wave to and from the radiator)  135 ,  145 ,  155 ,  165  either at the upper vertex of the radiator (e.g. A 1  to A 16 , C 1  to C 16 ), or at the lower vertex of the radiator (e.g. B 1  to B 16 , D 1  to D 16 ). The hexagonal shape of the radiator has been shown by simulation to provide better results than a square radiator or a circular radiator, in terms of transmission gain and/or receiving gain and also by providing relatively good isolation between adjacent radiators. However, different geometrical shapes may be selected. 
         [0045]    It should be noted that while the one dimensional array of radiators that is shown in  FIG. 1A  is linear (radiators are located along a straight line) and symmetric (equal distances between radiators), in another exemplary embodiments according to the invention the one dimensional array of radiators may be non linear or not symmetric. 
         [0046]    In an exemplary embodiment of the present invention, the positioning of the radiator&#39;s feeder forms a symmetric structure, in the first and third one-dimensional array of radiators the radiator&#39;s feeders are located at the upper vertex of the hexagonal patch, while at the second and fourth one-dimensional array of radiators the radiator&#39;s feeders are located at the lower vertex of the patch. It should be noted that this symmetric positioning of the radiator&#39;s feeder optionally contributes to achieving a symmetrical radiation pattern. 
         [0047]    In an exemplary embodiment of the invention the even one dimensional arrays of radiators are shifted with reference to the odd one dimensional arrays of radiators by about half of the distance between two adjacent radiators, thus radiator B 1   140  is not shown under radiator A 1   130  but between radiator A 1  and A 2 . This deployment of radiators enables to optimize the density of radiators at a given area which results with improved beam formation. 
         [0048]    While  FIG. 1A  shows the antenna casing  105  in horizontal orientation, for practical use in an APAA system—the antenna will be positioned vertically, i.e. radiators A 1 , B 1 , C 1 , and D 1  will be located at the upper end of the antenna and radiators A 16 , B 16 , C 16  and D 16  will be positioned at the lower end of the antenna. As shown in  FIG. 1B . 
         [0049]    The antenna dimensions depend on the wave&#39;s frequency and the dielectric constant of the substrate. However, for use in some applications, such as for example, WI-MAX application, the radiators dimensions will typically not exceed a few centimeters. 
         [0050]    In an exemplary embodiment of the invention, to achieve wider azimuth angle coverage with still high power density for communicating with devices in the area of coverage of antenna  100  three different radiation patterns (referred to as “radiation modes”) are generated with the same physical array of radiators. 
         [0051]    Optionally, production of the multiple radiation modes by antenna  100  is defined by the relative phase shift to a signal among the four one-dimensional arrays of radiators  110 ,  115 ,  120 ,  125 . 
         [0052]    In an exemplary embodiment of the present invention, a first radiation mode is defined by providing the following phase shift pattern to the four one-dimensional arrays of radiators  110 ,  115 ,  120 ,  125 . Optionally, the first one-dimensional array of radiators  110  gets a 0 degree phase shift—this array serves as a reference array. The second one-dimensional array of radiators  115  gets the same phase shift of 0 degrees as the first array. The third one-dimensional array of radiators  120  gets a phase shift of 180 degrees with reference to the first one-dimensional array of radiators  110  (i.e. for each 1&lt;=i&lt;=16 radiator Ci is phase shifted 180 degrees with reference to the corresponding radiator Ai in first one-dimensional array of radiators  110 . The same applies for the fourth one-dimensional array which is also shifted 180 degrees with reference to the first one-dimensional array of radiators. 
         [0053]    It should be noted that it is possible to both transmit and receive via the same radiators and it is typically the more efficient architecture. However in an exemplary embodiment of the invention, the transmission and receiving is split between transmitting radiators and receiving radiators. Deployment of different radiators for transmission and receiving may be carried out in various topologies, such as separating the functions to two different phased array units or alternatively define sub groups of the radiators in a phased array unit for transmission while the complementary sub group is used for receiving. 
         [0054]      FIG. 2A  shows a schematic view of the polar  205 , and Cartesian representation  210  of the radiation pattern attire first radiation mode indicating on the azimuth coverage of the antenna, according to an exemplary embodiment of the invention. The azimuth angle that is covered by beam  205  (for transmission and reception) is a substantially planar shaped beam, which has a vertical dimension of about 5 degrees of aperture. This narrow aperture angle depends on the number of radiators in a single one dimensional array. 
         [0055]      FIG. 2A  further shows a Cartesian graph  210  which describes the antenna gain (dB) versus azimuth. 
         [0056]    As will be further explained below the system is able to conduct a vertical steering of the radiation pattern, giving the phase 0 or 180 degrees to the radiators Ak, Bk, Ck Dk; and adding phases equally linearly distributed to the radiators of each one dimensional array. This way the proper elevation angle will be covered. Azimuth coverage by three antenna radiation modes, together with elevation by electronic steering of the phased array antenna, will enable the system to cover a wide solid angle, with high power density of the transmitted signal. 
         [0057]      FIG. 2A  shows that the first radiation mode creates two main lobes that cover an angle of about 100 degrees. However, this first radiation mode provides best coverage at two maximum points (forming the two lobes) and weaker coverage at the mid section—between the two main lobes. Optionally, as described below other radiation modes will be used to enhance coverage in the areas where the beam  205  of the first radiation mode is not at its best. 
         [0058]    Optionally, the first radiation mode is achieved by providing the following phase shifts to the four one-dimensional arrays of radiators  110 ,  115 ,  120 ,  125 . Optionally, the first one-dimensional array of radiators  110 , which serves as a reference gets a 0 degrees phase shift, the second one-dimensional array of radiators  115  gets the same phase shift (i.e. 0 degrees) with reference to the first one-dimensional array of radiators  110 . The third one-dimensional array of radiators  120  gets a 180 degrees shift with reference to the first one-dimensional array of radiators  110 . The fourth one-dimensional array of radiators  125  also gets a 180 degrees shift with reference to the first one-dimensional array of radiators  110  (i.e. same phase shift as the third one-dimensional array of radiators). 
         [0059]      FIG. 2B  shows the polar  230 , and Cartesian  235  representation of the radiation pattern of the second radiation mode, so that the azimuth coverage of the second radiation mode can be appreciated, according to an exemplary embodiment of the invention. Optionally, the second radiation mode is achieved by providing the following phase shifts to the four one-dimensional arrays of radiators  110 ,  115 ,  120 ,  125 . Optionally, the first one-dimensional array of radiators  110 , which serves as a reference gets a 0 degrees phase shift, the second one-dimensional array of radiators  115  gets a 180 degrees phase shift with reference to the first one-dimensional array of radiators. The third one-dimensional array of radiators  120  gets a 0 degrees shift, i.e. the same phase that is provided to the first one-dimensional array of radiators  110 . The fourth one-dimensional array of radiators  125  gets a phase shift of 180 degrees with reference to the first one-dimensional array  110 . 
         [0060]      FIG. 2B  further shows a Cartesian graph  235  which describes the antenna gain (dB) versus azimuth. 
         [0061]      FIG. 2B  shows that the second radiation mode provides transmission and reception coverage in one main lobe. As mentioned for the first mode, the vertical beam angle of the second radiation mode has the same narrow aperture of about 5 degrees. 
         [0062]      FIG. 2C  shows the polar  260 , and Cartesian representation  265  of the radiation pattern of the third radiation mode, indicating on the azimuth coverage of the third radiation mode, according to an exemplary embodiment of the invention. The third radiation mode is achieved by providing the following phase shifts to the four one-dimensional arrays of radiators: The first one-dimensional array of radiators  110 , which serves as a reference gets a 0 degrees phase shift, the second one-dimensional array of radiators  115  gets a 180 degrees phase shift with reference to the first one-dimensional array of radiators. The third one-dimensional array  120  gets a 180 degrees shift. The fourth one-dimensional array of radiators  125  gets a phase shift of 0 degrees with reference to the first one-dimensional array of radiators  110 , i.e. the same phase that is provided to the first one-dimensional array of radiators  110 . 
         [0063]      FIG. 2C  further shows a Cartesian graph  265  which describes the antenna gain (dB) versus azimuth 
         [0064]      FIG. 2C  shows that the third radiation mode provides transmission and reception coverage in two main lobes which provide optimal coverage of the gap between the area covered by the first and second radiation modes. As mentioned for the first radiation mode, the vertical beam angle of the third radiation mode has the same narrow aperture of about 5 degrees. 
         [0065]      FIG. 2D  shows the coverage that is provided by the summation of all the three modes. It shows that the summation of the three modes, polar view  280 , and Cartesian view  285  provides a good coverage of a section that is greater than 90 degrees wide. 
         [0066]    In some embodiments of the invention, the APAA system will switch between less than three modes or more than three modes. 
         [0067]    In some embodiments of the invention, the APAA system may provide a phase shift that is greater or smaller than 180 degrees to the one-dimensional arrays of radiators 
         [0068]    In some embodiments of the invention, the APAA system may include more or less than four one-dimensional arrays of radiators. 
         [0069]    In some embodiments of the invention, the APAA system may include various combinations of radiators other than one-dimensional arrays of radiators, where any sub-group (referred to as group) of the radiators will be associated with a programmable phase shift with reference to any reference sub-group. For example the antenna unit may include eight one-dimensional arrays of radiators, wherein the first and second one-dimensional arrays of radiator will consist a first group of radiators, the third and fourth one-dimensional arrays of radiator will consist a second group of radiators, the fifth and sixth one-dimensional arrays of radiator will consist a third group of radiators, the seventh and eighth one-dimensional arrays of radiator will consist a fourth group of radiators. 
         [0070]    In a more general case the antenna unit may consist of N (integer practically greater than eight) radiators located at any possible geometry, where the system is selectively switching between radiation modes, wherein a radiation mode is defined by the number of groups and the phase shift that is associated with each group. 
         [0071]    While operating the APAA system according to an exemplary embodiment of the present invention, the system switches among the three radiation modes. The switching may be a periodic switching pattern or any desired pattern. In an exemplary embodiment of the invention, the system is able to alter the switching pattern to accommodate dynamic situations, for example when receiving or transmitting sources join or leave the area that is covered by the system, or when different needs and priorities are required. Optionally, alteration of the switching pattern provides priority in coverage of one area over another, for example to increase the bandwidth to a specific client device. 
         [0072]    The use of radiation modes where the phase shift between the one-dimensional arrays of radiators is either zero degrees or 180° enables to simplify the electronic circuits that support the transmission and receiving in the APAA system as shown in  FIG. 3A  and  FIG. 3B . 
         [0073]      FIG. 3A  is an exemplary illustration of the base of a circuit for providing a radiation signal to an array of radiators, according to an exemplary embodiment of the invention. 
         [0074]    As described in details in PCT/IL2006/001144, the circuit uses an oscillator unit  305  whose output splits to eight branches through the splitting elements  306 - 312 , called “manifold”. The signals then arrive to a first level of PSIPPO (phase shift push-push oscillator)  320 - 327 . Persons skilled in the art will readily appreciate that the phase shift that is determined at this level of PSIPPO serves to steer the beam in elevation. It can be anticipated that, applying a zero degree phase shift at the first and second level of PSIPPO, the radiation pattern, (beam), will be a flat kind of “fan” as described in  FIGS. 2A   2 B and  2 C and referenced by the numerals  205 ,  230 , and  260  respectively, which has its symmetry axis perpendicular to the antenna surface. 
         [0075]    The signals exiting the first level of PSIPPO are split by another level of splitting elements  330 - 337  and proceeds to a second level of PSIPPO  340 - 355  which contributes in steering the beam in elevation.  FIG. 3A  shows the components of the system, starting from the Master Oscillator  305  at very low frequency, then the power splitters of the manifolds  306 - 312 , the PSIPPO of the two levels  320 - 327  and  340 - 355 , till the mixers  361   a - 361   p  that are behaving as Up-Converters or Down-Converters, depending on the position of the switches  380   a - 380   d  and  383   a - 383   d  located near the radiators and depicted in  FIG. 3B . 
         [0076]    The same system behavior can be secured, in principle, by a circuit structure without the switched lines shown in  FIG. 3B . However this solution involves much higher number of components, and provides lower commercial benefit. 
         [0077]    In the general case, transmitting or receiving by a 16X4 radiators antenna would require the use of four circuits as shown in  FIG. 3A . However, using the schematic of  FIG. 3B  the system becomes less expensive and more effective. In fact  FIG. 3B , with the two levels of switched lines of the upper and lower paths, is able to deliver to the radiators Ak, Bk, Ck, Dk signals with phases of 0 degrees or phased by 180 degrees. That means: only one subsystem of  FIG. 3A  will be sufficient to feed all the signals required by the three antenna modes. 
         [0078]    With reference to  FIG. 3A , the signals coming from the second level of PSIPPO  340 - 355  are the pump signals able to Up-Convert, (or Down-Convert), the base band signals entering the mixers through the IF port, (or the RF signal coming from the radiators, entering the mixers through the RF port). The fact that the same signals, with the same phases, are used for transmitting and receiving operations, secures the same direction of the beam in transmission and reception. 
         [0079]    The high frequency port of the sixteen mixers will be each one connected to a block of  FIG. 3B . Every high frequency port of the mixers will deliver, (or receive), signal to, (from), the set of four radiators Ak, Bk, Ck, Dk, with 1&lt;=k&lt;=16. 
         [0080]      FIG. 3B  shows a low cost, simple circuit that enables to provide a phase shifted signal to four one dimensional arrays of four radiators, each one belonging to one of the 4 different linear arrays, each containing 16 elements, at the same position in the array. The circuit that is shown in  FIG. 3B  is duplicated sixteen times, corresponding to the 16 positions of the patches in a single array, and is connected to each of the mixers  361   a - 361   p.    FIG. 3B  includes three identical switch paths the first includes a delay element  373  and two switches  372  and  374 . The second switch path includes a delay element  378   b  and two switches  377   b  and  379   b  and the third switch path includes a delay element  378   d  and two switches  377   d  and  379   d.  The circuit further includes four direction sub circuits each including the switches  380   383  and the amplifiers  381   382  wherein the index a-d indicates the sub circuit respectively. 
         [0081]    Returning now to FIG.  2 A—in order to operate in the first radiation mode, a phase shift of 180 degrees should be provided to both the third and fourth one-dimensional arrays of radiators, while a phase shift of 0 degrees should be provided to both the first and second one-dimensional arrays of radiators. This is implemented by selecting the following paths in  FIG. 3B : 
         [0082]    Radiator Ak will radiate the signal that follow the path through  390   a , with reference phase 0 degrees. 
         [0083]    Radiator Bk will radiate the signal that follows the path through  1001 / 1000 / 401 / 500 , with phase 0 degrees. 
         [0084]    Radiator Ck will radiate the signal that follows the path through  390   c , with phase 180 degrees, as far as the signal is routed through delay element  373  that shifts the signal by 180 degrees. 
         [0085]    Radiator Dk will radiate the signal that follows the path through  390   d , with phase 180 degrees, as far as path the signal is routed through delay element  373  that shifts the signal by 180 degrees. 
         [0086]    In order to drive the signal to all 16X4 radiators similar, (or identical: depending on the beam steering), operation is performed by the signals exiting all the “k” mixers, where 1&lt;=k&lt;=16. 
         [0087]    It should be noted that the delay elements  373 ,  378   b  and  378   d  are simple and low cost transmission lines, and paths  391   a,    390   a,    390   b,    390  and  390   d  are also simple transmission lines. The electrical difference between the first and the second group of lines is 180 degrees. The usage of electronic switches and transmission lines, instead of using multiple subsystem of  FIG. 3A , reduces both cost and size of the entire system. 
         [0088]      FIG. 4  shows an APAA system  400  according to an exemplary embodiment of the present invention. The system consists of four phased array antenna units  410 ,  415 ,  420  and  425  each located on a different side of a pole  405 . 
         [0089]    In an exemplary embodiment of the invention, each of the four phased array antenna units covers more than 90 degrees in azimuth in a way that all the four phased array antenna units cover 360 degrees. Each phased array antenna unit switches among the three radiating modes as described with reference to  FIG. 2A-2C . Simultaneously each of the four phased array antenna units also steers the elevation of the beam. Steering the beam vertically is controlled by the two arrays of PSIPPO  320 - 327  and  350 - 355  ( FIG. 3A ). 
         [0090]    Optionally all four phased array units are controlled by a single phased array circuit. In another exemplary embodiment of the invention each of, or part of the four phased array units is controlled and driven by a separate phased array circuit. 
         [0091]    While transmitting and receiving data, the system may detect a PC device  430  that transmits data to the phased array antenna unit  415 , and a car control device  435  that also transmits data to the same phased array antenna unit  415 .  FIG. 4  further shows an antenna of a repeater device  440  and a cell phone device  445  which are transmitting data that is received by the phased array antenna unit  410 . Since the system is switching between the three radiation modes, each device transmission is intercepted at a different intensity at each of the three radiation modes. In an exemplary embodiment of the present invention, the system identifies for each device the best receiving mode among the three modes, when the received signal is maximal and allocates priority in transmitting and receiving to the device in the best receiving mode. Thus, assuming that the best receiving mode for the PC device  430  is the first radiation mode and the best receiving mode for the car control device is the third radiation mode, the system may reduce the time allocated for transmission and receiving in the second radiation mode and increase the time allocated to the first and third radiation modes. In an exemplary embodiment of the invention the system allocates transmission and reception time slots also according to bandwidth requirements that are imposed by the transmitting devices. In an exemplary embodiment of the invention the system allocates time slots for varying elevations considering the elevation where transmitting devices were best received. 
         [0092]    In an exemplary embodiment of the invention there is a separate control circuit for each of the four phased array antenna units  410 ,  415 ,  420  and  425  thus enabling to optimize bandwidth needs separately for each of the four phased array antennas. 
         [0093]    While the foregoing description referred to an APAA system, it will be appreciated by persons skilled in the art that the present invention is not limited to active communication but is applicable for any suitable communication protocol or methods, to include for example, WIMAX, WI-FI, WPAN, as well as for HDTV (high definition T.V.) or cellular communication standards and protocols. 
         [0094]    It should be appreciated that the above described methods and systems may be varied in many ways, including omitting or adding steps, changing the order of steps and the type of devices used. It should be appreciated that different features may be combined in different ways. In particular, not all the features shown above in a particular embodiment are necessary in every embodiment of the invention. Further combinations of the above features are also considered to be within the scope of some embodiments of the invention. For example The system, as described above, can work with 4 linear arrays of antennas, each one containing whatever number of radiators. 
         [0095]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims, which follow.