Patent Publication Number: US-10320087-B2

Title: Overlapping linear sub-array for phased array antennas

Description:
TECHNICAL FIELD 
     The current disclosure relates to phased array antennas for use in communication systems and in particular to an overlapping linear sub-array for feeding phased array antennas. 
     BACKGROUND 
     Phase array antenna can be used in a variety of different wireless communication networks, and they can be used to enable steering of the transmission and/or reception in both the azimuth and elevation planes. Steering transmission and reception allows for an antenna array to direct the transmission or reception resources towards a particular location, which can increase the system capacity, that is networks designed to provide service to mobile devices, there is increased interest in beam steering as it allows for better concentration of connectivity resources to the locations that need them. A relatively large array is required in order to achieve desirable directivity. In conventional phased array design there is one phase shifter, delay line and/or amplitude control per array element. This increases both the cost and complexity of manufacture of the array. In order to reduce system complexity there is a need to reduce the amount of control circuitry. Sub-array antenna designs are used to group a small amount of array elements together and use only one phase shifter or delay line to drive the group of array elements. However using sub-arrays can result in grating lobes as well as reduce the array&#39;s steerability. 
     It is desirable to have an additional, alternative and/or improved phased array antenna design for communication systems. 
     SUMMARY 
     In accordance with the present disclosure there is provided an antenna array comprising: a plurality of array elements arranged in a grid; a first feed network in a first substrate layer comprising a plurality of column signal feeds each column signal feed connected to array elements of a respective one of a plurality of columns of the grid; and a second feed network in a second substrate layer comprising a plurality of row signal feeds each row signal feed connected to array elements of a respective one of a plurality of rows of the grid. 
     In a further embodiment of the antenna array, the plurality of column signal feeds are provided by microstrips within the first substrate layer. 
     In a further embodiment of the antenna array, the plurality of column signal feeds are provided by substrate integrated waveguides (SIWs) within the first substrate layer. 
     In a further embodiment of the antenna array, the plurality of row signal feeds are provided by microstrips within the first substrate layer. 
     In a further embodiment of the antenna array, the plurality of row signal feeds are provided by substrate integrated waveguides (SIWs) within the first substrate layer. 
     In a further embodiment of the antenna array, the plurality of array elements are provided by isotropic array elements. 
     In a further embodiment of the antenna array, the plurality of array elements are provided by patch array elements. 
     In a further embodiment, the antenna array further comprises a plurality of phase shifters each of the phase shifters associated with a respective one of the plurality of column signal feeds and the plurality of row signal feeds. 
     In a further embodiment of the antenna array, the grid comprises N columns and M rows, and wherein the antenna array comprises N+M phase shifters. 
     In a further embodiment of the antenna array, wherein N=M. 
     In a further embodiment of the antenna array, a column phase progression is 2β x  and a row phase progression is 2β y , where: 
             {               β   x     =         -   k     ·     d   x       ⁢   sin   ⁢           ⁢     θ   o     ⁢   cos   ⁢           ⁢     φ   o                     β   y     =         -   k     ·     d   y       ⁢   sin   ⁢           ⁢     θ   o     ⁢   sin   ⁢           ⁢     ϑ   o               ;           
k is a phase number defined by
 
               k   =       2   ·   π     λ       ;         
and ϑ o  and φ o  are beam steering directions.
 
     In a further embodiment, the antenna array further comprises a plurality of secondary array elements arranged in a secondary grid having a spacing between secondary array elements greater than a spacing between array elements of the grid, a third feed network in the first substrate layer comprising a plurality of secondary column signal feeds each secondary column signal feed coupled to secondary array elements of a respective one of the plurality of columns of the secondary grid; and a fourth feed network in the second substrate layer comprising a plurality of secondary row signal feeds each secondary row signal feed coupled to secondary array elements of a respective one of the plurality of rows of the secondary grid. 
     In accordance with the present disclosure there is provided a phased array system comprising: an antenna array comprising: a plurality of array elements arranged in a grid; a first feed network in a first substrate layer comprising a plurality of column signal feeds each column signal feed connected to array elements of a respective one of a plurality of columns of the grid; and a second feed network in a second substrate layer comprising a plurality of row signal feeds each row signal feed connected to array elements of a respective one of a plurality of rows of the grid; and a controller for determining a first phase shift to apply between adjacent columns of the plurality of columns and a second phase shift to apply between adjacent rows of the plurality of rows in order to control a desired steering angle of a main beam of the phased array system. 
     In a further embodiment of the phased array system, the phased array system comprises a dual-band phased array system, wherein the antenna array comprises a subset of the plurality of array elements arranged in a plurality of rows and a plurality of columns, each of the array elements of the subset having a greater spacing between array elements than a spacing between the plurality of array elements, each array element of the subset comprising: a primary array element coupled to the first and second feed networks; and a secondary array element, the antenna array further comprising: a third feed network in the first substrate layer comprising a plurality of secondary column signal feeds each secondary column signal feed coupled to secondary array elements of a respective one of the plurality of columns of the subset of array elements; and a fourth feed network in the second substrate layer comprising a plurality of secondary row signal feeds each secondary row signal feed coupled to secondary array elements of a respective one of the plurality of rows of the subset of array elements. 
     In a further embodiment of the phased array system, the plurality of column signal feeds are provided by one of: microstrips within the first substrate layer; and substrate integrated waveguides (SIWs) within the first substrate layer. 
     In a further embodiment of the phased array system, the plurality of row signal feeds are provided by one of: microstrips within the first substrate layer; and substrate integrated waveguides (SIWs) within the first substrate layer. 
     In a further embodiment, the phased array system further comprises a plurality of phase shifters each of the phase shifters associated with a respective one of the plurality of column signal feeds and the a plurality of row signal feeds. 
     In a further embodiment of the phased array system, the plurality of phase shifters are part of the controller. 
     In a further embodiment of the phased array system, the grid comprises N columns and M rows, and wherein the antenna array comprises N+M phase shifters. 
     In a further embodiment of the phased array system, a column phase progression is 2β x  and a row phase progression is 2β y , where: 
             {               β   x     =         -   k     ·     d   x       ⁢   sin   ⁢           ⁢     θ   o     ⁢   cos   ⁢           ⁢     φ   o                     β   y     =         -   k     ·     d   y       ⁢   sin   ⁢           ⁢     θ   o     ⁢   sin   ⁢           ⁢     ϑ   o               ,           
κ is a phase number defined by
 
               k   =       2   ·   π     λ       ;         
and ϑ o  and φ o  are beam steering directions.
 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are described herein with reference to the appended drawings, in which: 
         FIG. 1  depicts a simplified wireless communication system; 
         FIG. 2  depicts schematically an antenna array comprising individual phase shifters for each antenna element; 
         FIG. 3  is a 3D plot of the radiation pattern of a phased array antenna having individual phase shifters for each antenna element with its main beam steered away from its boresight; 
         FIG. 4  is a plot of a slice through the 3D plot of  FIG. 3  for φ=15° while sweeping over theta ϑ. 
         FIG. 5  depicts a schematic of an overlapping linear sub-array; 
         FIG. 6  depicts a vector plot of feed signals of a radiating element in a time domain; 
         FIG. 7  depicts a schematic of feed signals of a radiating element in a frequency domain; 
         FIG. 8  depicts a schematic of a feed network for an overlapping linear sub-array; 
         FIG. 9  depicts a further schematic of a feed network for an overlapping linear sub-array; 
         FIG. 10  depicts a schematic of a feed network for a overlapping linear sub-array; 
         FIG. 11  depicts a phased array system; 
         FIG. 12  depicts the simulated radiating pattern for a 16×16 antenna array having patch elements and steered to 30 degrees in elevation; 
         FIG. 13  depicts the simulated radiating pattern for a 16×16 antenna array having patch elements and steered to 40 degrees in elevation; and 
         FIG. 14  depicts the simulated radiating pattern for a 16×16 antenna array having patch elements and steered to 70 degrees in elevation. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a simplified wireless communication system. As depicted a number of base-stations or transceivers  102   a ,  102   b ,  102   c  (referred to collectively as transceivers  102 ) are connected to network  104 . Network  104  is a mobile network that can provide services to mobile devices and can provide at least one of data and voice service. By connecting to network  104  through access points such as transceivers  102 , a mobile device can be connected to other networks including the Internet. The transceivers  102  may each communicate with one or more mobile devices, which are depicted as mobile devices  106   a ,  106   b ,  106   c , and  106   d  (referred to collectively as mobile devices  106 ) over a wireless connection. Both the mobile devices  106  and transceivers  102  each include one or more radio antennas for transmitting and receiving radio frequency (RF) signals. In many networks, when transceivers  102   a ,  102   b ,  102   c  can utilize phased array antennas, it is possible to improve directivity and therefore network efficiency. Those skilled in the art will appreciate that the term mobile device refers to devices that can connect to mobile networks, and should not be interpreted as a requirement that the device itself is capable of mobility. A machine-to-machine device, such as a sensor, is considered a mobile device although it may not necessarily be mobile. Transceivers  102  may connect to network  104  through fixed links, and these links may themselves be wireless links that make use of phased array antennae at one or both ends of the wireless link. Although transceivers  102  are illustrated in  FIG. 1  as connected to network  104 , it should be understood that an access point may connect to network  104  through a wireless connection to another access point that is itself connected to network  104 . As such, phased arrays may be used to provide backhaul communication links as well as inter-access point communication links as well as between base-stations. 
     Although phased arrays can be used in many different network implementations, including in third and fourth generation (3G/4G) mobile networks, such as those supporting the Long Term Evolution (LTE) networking standards defined by the Third Generation Partnership Project (3GPP), the following discussion will be directed to the application of phase array in next generation wireless networks, such as fifth generation wireless networks (5G). This should not be viewed as limiting the scope of applicability of phase array antennas. 
     In order to provide the performance desired for next generation wireless networks such as 5G, networks may include phased array antennas in transmitters and receivers to allow transmission beams to steered and to allow receivers to be directed in both an azimuth plane as well as an elevation plane. Although the specific field of view (FOV) that can be scanned by the phased array will vary depending upon the particular requirements, generally, the design objective is to allow a main beam to be steered over +/−70° or greater in both the azimuth and elevation plane. 
       FIG. 2  depicts schematically an antenna array that may be used in a communication network. The antenna array  200  comprises a grid  202  of regularly spaced individual array elements  204 , which may also be referred to as antenna elements. Each antenna element  204  is capable of transmitting and/or receiving signals. It is noted that only a single array element  204  is labeled for clarity of  FIG. 2 . The grid spacing between the individual array elements may vary depending upon design details including the frequency range that the antenna will be used with. The grid spacing may be approximately λ 0 /2, where λ 0  is the wavelength in free space of the signal that is being transmitted or received at a particular carrier frequency The transmission or reception direction of the antenna  200  can be steered by shifting the phase of the transmitted or received signals for the individual array elements. As depicted in  FIG. 2 , the grid array  202  is associated with control circuitry  206 , which includes a phase shifter  208  for each of the individual array elements. Additional components, for example, for switching between transmit and receive circuitry, amplifiers, etc. may be included in the control circuitry  206 . 
       FIG. 3  is a 3D plot of the radiation pattern of a typical phased array antenna with its main beam steered away from its boresight. The phased array antenna modeled for calculating the radiation pattern comprises a 16×16 grid of isotropic array elements with a grid spacing of 
                 λ   0     2     ,       for   ⁢           ⁢     λ   0       =     c     86   ⁢           ⁢   GHz               
where c is speed of light. The antenna radiation pattern steering at a spatial location of ϑ=15° and φ=15° was calculated using Matlab™. As can be seen in  FIG. 3 , the radiation pattern or radiated intensity of the antenna is highly directional. The transmission strength for the peak directivity  302  was 25.72 dBi (decibel relative to isotropic), at an operation frequency of 86 GHz.  FIG. 4  is a plot of a slice through the 3D plot of  FIG. 3  for φ=15° while sweeping along theta ϑ. As depicted a main beam  402  occurs at ϑ=15°, φ=15°. Additionally, the levels of the side lobes  404  are all 13 dBc (decibel relative to a carrier) lower than the main beam.
 
     In order to reduce the number of control circuits required for operating a phased array, individual array elements can be grouped together and each group may be driven by a phase shifter. The phased array described further below overlaps groups of array elements so that each array element is a member of two groups. As described, each array element may be part of a vertical grouping of array elements and a horizontal grouping of array elements. Accordingly, each individual array element is a member of two overlapping groups and as such each individual array element is controlled by two phase shifters. The overlapping vertical and horizontal sub-array arrangement described herein allows a reduction in the number of control circuits required for the phased array antenna since each one of vertical and horizontal sub-array groupings of multiple array elements has a control circuit rather than each individual array element having a dedicated control circuit. As an example, the number of phase shifters for an N×N phased array may be reduced from N 2  to 2N, which for a 16×16 phased array antenna would reduce the number of phase shifters by over 85%. The reduction in the control circuitry as well as the relatively simple sub-array architecture may provide a cost reduction, simplify a design process and/or simplify the manufacture of the antenna. 
       FIG. 5  depicts a schematic of an overlapping linear sub-array. The sub-array  500  comprises a grid of array elements  502 . It is noted that only a single array element is labeled for clarity of the figure. The array elements  502  are arranged into a plurality of columns and a plurality of rows. As depicted, the array elements  502  in each column of the grid are grouped together into individual linear groups  504 - 1 - 504 -N. Similarly, the array elements  502  in each row of the grid are grouped together into individual linear groups  508 - 1 - 508 -N. Each column group of array elements  504 - 1 - 504 -N are controlled by respective phase shifter  506 - 1 - 506 -N, with each of the array elements in a respective column group associated with the same phase shifter, and as such have the same phase shift. 
     As depicted, the linear array of vertical column groups  504 - 1 - 504 -N and their associated phase shifters  506 - 1 - 506 -N provide phase shifts of 0, β x , 2β x , 3β x , . . . , (N−1)β x  resulting in the desired steering angle in an azimuth direction. Similarly, the linear array of horizontal row groups  508 - 1 - 508 -N and their associated phase shifters  510 - 1 - 510 -N provide phase shifts of 0, β y , 2β y , 3β y , . . . , (N−1)β y  resulting in the desired steering angle in the elevation angle. Each of the array elements  502  are in overlapping row and column groups and as such are associated with two phase shifters. A phase matrix  512  is shown in  FIG. 5  depicting the ideal phase feed values for each array element. As depicted, each of the array elements is fed by a sum of the associated phase shifts. Accordingly, by properly selecting the phase shift values of both phase shifters of rows and columns, it is possible to steer the main beam of the antenna array in both the azimuth and elevation directions with only 2N phase shifters as opposed to N 2  phase shifters. However, it is necessary to adjust the steering angles used to determine the required phase shift to account for the combination of the two phase shifts at each array element. 
       FIG. 6  depicts a schematic of feed signals of a radiating element in a time domain. As depicted two sinusoidal signals  602 ,  604  combine linearly to produce a resultant combined signal  606 . 
       FIG. 7  depicts a schematic of feed signals combining at a radiating element in a frequency domain. As depicted two feed signals A  702  and B  704  may combine linearly to produce signal C  706 . The individual signals may be described by:
 
 {right arrow over (A)}= ½ e   jα   (1)
 
 {right arrow over (B)}= ½ e   jβ   (2)
 
 {right arrow over (C)}={right arrow over (A)}+{right arrow over (B)}   (3)
 
     The combined signal C is described by: 
     
       
         
           
             
               
                 
                   
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     Accordingly, if each sub array is fed with double the original phase shift required to provide the desired phase shift assuming the column and rows were fed independently, it will be possible to deliver the ideal phase shift values to each of the array elements. That is, if α=2β x  and β=2β y  then the combination of the two phase shifts at each array element will be β x +β y . By providing each column group and row group with twice the phase shift required by the column or row group individually, the combination will result in the ideal phase shift value being provided to the array elements. β x  and β y  are the phase progressions required in both x and y direction of an un-overlapping rectangular phased array. β x  and β y  are defined by: 
     
       
         
           
             
               
                 
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     Where: 
     κ is a phase number defined by 
               k   =       2   ·   π     λ       ;         
and
 
     ϑ o  and φ o  are the beam steering directions. 
     As described above, if each array element is fed by two phase shift values, it is possible to provide ideal phase shift values to each array element in order to steer the array&#39;s main beam in both the azimuth and elevation directions. Providing the ideal phase shift values, or values that are close to a approaching the ideal phase shift values, prevents, or at least reduces grating lobes that traditionally result from grouping a plurality of array elements together for control by a reduced number of phase shifters resulting large inter-subarray spacing in both the x and y direction. In order to provide the two individual phase shift values to the same array element, two separate feed networks are required. According to equation 4, it may be necessary to scale input signals so that the magnitude of array signals are uniform. Further, where α−β approaches π, it may be preferable to introduce a deviation into one or both of α and β rather than require large scaling. As described with reference to  FIGS. 8 to 10  below, the feed network for feeding the column groups of array elements may be formed in a layer above, or below, a second layer in which the feed network for feeding the row groups of array elements is formed. 
       FIG. 8  depicts a schematic of a feed network for overlapping linear sub-arrays of an antenna array structure. The antenna array structure  800  comprises the array elements  802   a ,  802   b ,  802   c ,  802   d  (only one row of array elements are labeled for clarity o the figure and referred to collectively as array elements  802 ) printed on a substrate. The array elements  802  are depicted as circles, however the actual radiating elements may be provided by various physical radiating element designs, such as isotropic radiating elements, patch radiating elements as well as other designs depending upon application requirements. The array elements  802  are arranged in a grid pattern of a plurality of vertical columns and horizontal rows. Each of the plurality of columns and rows comprise a plurality of array elements  802 , with each array element being associated with a single particular column and row. The plurality of columns array elements  802  are fed by a first feed network comprising a plurality column signal feeds  806   a ,  806   b ,  806   c ,  806   d  (referred to collectively as column signal feeds  806 ), each feeding a respective column grouping of array elements. The column signal feeds  806  are formed in a first substrate layer  804 . The column signal feeds  806  may be formed as substrate-integrated waveguide (SIW) or microstrips as depicted within the first substrate layer  804 . 
     Each individual column signal feed is associated with a respective control component, depicted as a phase shifter  810   a ,  810   b ,  810   c ,  810   d  for feeding all array elements with the same phase shift. That is, each of array elements in the first vertical column group are fed by a common column signal feed  806   a  associated with a single phase shifter  810   a . A second row grouping of array elements  802  is overlapped with the column grouping so that individual array elements are part of both a column grouping and a row grouping. Individual array elements  802  in a particular column grouping are overlapped with different row groupings, and similarly, individual array elements  802  in a row grouping overlap with different column groupings. 
     Each row grouping of array elements is fed by second feed network of respective row signal feeds  812   a ,  812   b ,  812   c ,  812   d  (referred to collectively as row signal feeds  812 ) that are formed in a second substrate layer  808  separate from the first layer. As with the column signal feeds  806 , the row signal feeds  812  may be formed as SIW or microstrips, which are depicted in  FIG. 8 , within the second substrate layer  808 . The phase of individual row subarrays are controlled by phase shifters  814   a ,  814   b,    814   c  and  814   d . Forming the first and second feed networks in separate layers allows the individual signal feeds to be properly routed to the individual array elements without crossing other signal feeds. Accordingly each array element can be fed by two different phase shifts obtaining sum of the phases. It is noted that although the column signal feeds  806  and row signal feeds  812  are depicted as being of different widths, the actual dimensions of the signal feeds may be the same as required by the particular design. The different thickness of lines of  FIG. 8  is intended to provide a distinction between column signal feeds  806  and row signal feeds  812 . 
     Although  FIG. 8  depicts the column signal feeds  806  of the first feed network being formed in the first substrate layer  804 , and the row signal feeds  812  of the second feed network being formed in the second substrate layer  808 , it is possible for the layers to be reversed with the row signal feeds being formed in the first layer  804  and the column signal feeds being formed in the second layer  808 . The array elements  802  are depicted as being formed on a top surface of the of the first substrate  802  with the column signal feeds  806  and row signal feeds  812  coupling to the array elements  802  at an interface of the array elements  802  and first layer  804 . It is possible for the array elements  802  to extend into the first layer  804  or extend completely through the first layer and contact, or extend into, the second substrate layer  808 , which may eliminate the need for signal feeds formed in the lower second substrate layer to pass fully through the upper first substrate layer in order to couple to the array elements  802 . 
       FIG. 9  depicts a further schematic of a feed network for an overlapping linear sub-array of an antenna array structure. The antenna array structure  900  is similar to the antenna array structure  800 . In particular, the antenna array structure  900  comprises a plurality of radiating array elements  902  arranged in a grid pattern of a plurality of columns and rows. The antenna array structure  900  comprises a first feed network arranged in a first substrate layer (not depicted in  FIG. 9 ) and a second feed network arranged in a second substrate layer (not depicted in  FIG. 9 ). As described above with reference to  FIG. 8 , the first feed network comprises a plurality of column signal feeds  906   a ,  906   b ,  906   c ,  906   d  (referred to collectively as column signal feeds  906 ), each associated with a respective control component such as a phase shifter (not depicted in  FIG. 9 ). Each of the column signal feeds  906  provides a feed signal to a plurality of array elements that are arranged within the same column of the grid. Similarly, the second feed network comprises a plurality of row signal feeds  912   a ,  912   b,    912   c ,  912   d  (referred to collectively as row signal feeds  912 ), each associated with a respective control component such as a phase shifter (not depicted in  FIG. 9 ). Each of the row signal feeds  906  provides a feed signal to a plurality of array elements that are arranged within the same row of the grid. Accordingly, as described above, each array element is fed by two signals, a column signal feed and row signal feed, which are combined at the array elements. In contrast to  FIG. 8 , which depicted the feed networks as being provided by microstrips, the feed networks of the column signal feeds  906  and row signal feeds  912  are provided as substrate integrated waveguides (SIWs). 
       FIGS. 8 and 9  have described the column and row signal feeds as being provided in the same manner. That is,  FIG. 8  depicts the column and row signal feeds as both being provided by microstrips while  FIG. 9  depicts the column and row signal feeds as both being provided by SIWs. It is possible for a combination of the two techniques to be used in a single antenna array. As an example, the column signal feeds may be provided by microstrips in a first substrate layer and the row signal feeds may be provided by SIWs in a second substrate layer. 
       FIG. 10  depicts a schematic of a feed network for an overlapping linear sub-array of a dual antenna array structure. The dual antenna array structure  1000  comprises overlapping array element groups as described above. In contrast to the antenna array structures  800 ,  900  described above, which provided a single band antenna, the antenna array structure  1000  may provide a dual band antenna. The antenna structure  1000  comprises a first or primary set of array elements  1002 ,  1002   a,    1002   b ,  1002   c ,  1002   d  (referred to collectively as primary array elements  1002 ), which are arranged in a grid pattern of columns and rows as described above with reference to the antenna array structures described above with reference to  FIGS. 8 and 8 . A subset of the primary array elements are broken into two separate radiating elements, namely the primary radiating elements  1002   a ,  1002   b ,  1002   c ,  1002   d  and secondary radiating elements  1012   a ,  1012   b ,  1012   c ,  1012   d  (referred to collectively as secondary array elements  1012 ). As with the primary array elements  1002 , the secondary array elements  1012  are also arranged in a grid pattern of a plurality of columns and rows. As depicted, the spacing between the primary array elements  1002  is smaller than that of the element spacing between secondary array elements  1012 . Accordingly, the primary array elements may be used in the transmission and/or reception of signals at a first frequency while the secondary array elements may be used in the transmission and/or reception of signals at a second frequency that is lower than the first frequency. As described further below, both the primary array elements  1002  and the secondary array elements may each be associated with overlapping column and row groups, which allow both main lobe of the primary frequency as well as the main lobe of the secondary frequency to be independently steered. 
     As depicted in  FIG. 10 , the primary array elements  1002  are fed by a first feed network of column signal feeds  1006   a ,  1006   b ,  1006   c ,  1006   d  and a second feed network of row signal feeds  1012   a ,  1012   b ,  1012   c ,  1012   d . The column signal feeds  1006  of the first feed network are depicted as waveguides integrated in a first substrate layer and the row signal feeds  1012  of the second feed network are depicted as waveguides integrated in a second substrate layer. Secondary feed networks for providing column signal feeds and row signal feeds to the secondary array elements  1012  may be provided within the first and second feed networks. The secondary feed networks are depicted as microstrips within the waveguides of the first and second feed networks. In particular, a first column signal feed  1016   a  for feeding the first column of the secondary array elements, namely secondary array elements  1012   a ,  1012   c , is located with the first column signal feed SIW  1006   a  that feeds the first column of primary array elements  1002 . The first column signal feed  1016   a  may be provided as a microstrip within the SIW  1006   a . A second column signal feed  1016   b  for feeding the second column of the secondary array elements, namely secondary array elements  1012   b ,  1012   d , is located with the associated column signal feed SIW, which in the embodiment depicted in  FIG. 10  is the fourth column signal feed waveguide  1012   d,  that feeds the respective column of primary array elements  1002 . The second column signal feed  1016   b  may be provided as a microstrip within the SIW  1006   b . Similarly, row groupings of the secondary array elements  1012  are fed by microstrips  1018   a ,  1018   b  located within corresponding row signal feed SIWs  1012   a ,  1012   d  of the feed networks of the primary array elements. 
     The dual-mode antenna array structure  1000  described above allows the main beam of the primary array elements  1002  to be steered in both the azimuth and elevation angles simultaneously. The main beam of the secondary array elements  1012  can also be steered in both the azimuth and elevation angles simultaneously. The primary and secondary main beams may be steered independent from each other. 
       FIG. 11  depicts a phased array system. The phased array system  1100  comprises an antenna array structure  1102  that has overlapped sub-arrays, such as one of the antenna arrays  800 ,  900  described above. The array structure  1102  comprises a number of column signal feeds  1106  and a number of row signal feeds  1108  that provide the signals with appropriate phase shifts in order to provide the desired steering angle. The system  1100  further comprises an antenna array drive controller  1104 . The drive controller  1104  receives indications of desired steering angles for both the elevation  1110  and azimuth  1112  and determines the required phase shifts for the column signal feeds  1106  and the row signal feeds  1108 . The controller may be provided by, for example, a programmable microcontroller, field programmable gate array (FPGA), application specific integrated circuit (ASIC). 
     The controller  1104  may determine the required phase shift of the column groupings in order to provide the desired steering angle ϑ 0  and φ o assuming the column groupings of array elements are not overlapped, as well as the phase shift of the row groupings in order to provide the desired elevation steering angle assuming the row groupings of array elements are not overlapped. As described above, the required phase shifts for non-overlapping sub-arrays are then doubled for feeding the overlapping sub-arrays of the antenna array  1102 . The antenna array drive controller  1104  may receive a main lobe signal  1114  to be transmitted by the antenna array. The main lobe signal  1114  is phase shifted according to the determined values and phase shifted signals are provided to column and row signal feeds  1106 ,  1108 . The phase shifters may form part of the controller, in which case, the phase shifted signals are provided to the antenna array. Alternatively, the phase shifters may be separate from the controller  11004  and the controller can provide signals to the phase shifters in order to provide the required phase shift to the main lobe signal  1114 . 
     It is possible to apply additional techniques to improve desired characteristics of the signal. For example, amplitude tapering may be applied in order to further reduce side lobe levels. The system  1100  provides an antenna that can be steered in both azimuth and elevation directions over a large field of view while reducing grating lobe effects. 
     The system  1100  is described above with regard to a single band antenna such as provided by the antenna arrays  800 ,  900 . The system  1100  may include a dual band antenna array, such as antenna array  1000 . In the case of a dual band antenna, the controller may receive separate steering angles for the secondary beam, or the same steering angles may be used for both the primary and secondary bands of the antenna. 
     The above has described antenna arrays and systems with a primary focus on transmitting signals. One of ordinary skill in the art will readily appreciate that the same antenna array structures  800 ,  900 ,  1000  may also be used in receiving signals. 
     A 16×16 antenna array was simulated with both isotropic and patch radiating elements. The results of the simulation are depicted in Table 1 below.  FIG. 12  depicts the simulated radiating pattern for a 16×16 antenna array having patch elements and steered to 30 degrees in elevation.  FIG. 13  depicts the simulated radiating pattern for a 16×16 antenna array having patch elements and steered to 40 degrees in elevation.  FIG. 14  depicts the simulated radiating pattern for a 16×16 antenna array having patch elements and steered to 70 degrees in elevation. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Main lobe and side lobe levels for different 
               
               
                 array elements and steering angles 
               
            
           
           
               
               
               
               
            
               
                 Array element 
                 Steering Angle 
                 Main lobe (dBi) 
                 Side lobe level (dB) 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Isotropic 
                 15 
                 24.60 
                 10 
               
               
                 Isotropic 
                 30 
                 23.67 
                 10 
               
               
                 Isotropic 
                 40 
                 23.17 
                 10 
               
               
                 Isotropic 
                 70 
                 20.64 
                 6 
               
               
                 Patch 
                 15 
                 27.87 
                 10 
               
               
                 Patch 
                 30 
                 27.34 
                 10 
               
               
                 Patch 
                 40 
                 26.85 
                 10 
               
               
                 Patch 
                 70 
                 24.06 
                 6 
               
               
                   
               
            
           
         
       
     
     Although the above describes an electronically steerable antenna array, it is possible to use the antenna array structure of overlapping sub-arrays to provide an antenna that is pointed in a fixed direction by determining the required phase shifts and fixing the phase shifts, rather than providing variable phase shift control components. Further, although described with reference to N×N arrays, arrays of N×M radiating elements are considered. 
     The above description provides various specific implementations for a phased array antenna. The specific embodiments have been simulated for reception and transmission in the approximately 71 GHz-86 GHz frequency range intended for use in possible 5G communication networks. It will be appreciated that the same technique of tiling rectangular sub-array groupings of individual array elements may be applied to phased array for communication networks operated at other frequency ranges. 
     The present disclosure provided, for the purposes of explanation, numerous specific embodiments, implementations, examples and details in order to provide a thorough understanding of the invention. It is apparent, however, that the embodiments may be practiced without all of the specific details or with an equivalent arrangement. In other instances, some well-known structures and devices are shown in block diagram form, or omitted, in order to avoid unnecessarily obscuring the embodiments of the invention. The description should in no way be limited to the illustrative implementations, drawings, and techniques illustrated, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents. 
     While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and components might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.