Patent Publication Number: US-10784575-B2

Title: Phased antenna array and method of thinning thereof

Description:
FIELD 
     The field of the present disclosure relates generally to phased antenna arrays and, more specifically, to an array thinning method and phased antenna arrays resulting therefrom. 
     BACKGROUND 
     Communications systems, such as satellites, sometimes use multi-beam antennas, such as phased antenna arrays, to perform signal processing operations. Phased antenna arrays typically include multiple radiating elements, element and signal control circuits, a signal distribution network, a power supply, and a mechanical support structure. At least some known phased antenna arrays include active radiating elements and inactive radiating elements, with the inactive radiating elements either being physically present in the array but deactivated, or being physically removed from the array. The signal processing operations are performed only by the active radiating elements, and the locations of the active and inactive radiating elements in the array are selected to improve the performance of the array. For example, one known method of selecting the locations of the active and inactive elements in the array is a discrete optimization technique, which evaluates the performance of the array when different element locations in the array are selected to be either active or inactive locations. However, performing the discrete optimization technique for each element location in the array can be a time-consuming task that requires a large amount of computing power. 
     BRIEF DESCRIPTION 
     In one aspect, a method of thinning a phased antenna array is provided. The method includes defining a performance characteristic for the phased antenna array, partitioning the phased antenna array to define a plurality of sectors that each include an equal number of radiating element locations, wherein each radiating element location is either an active radiating element location or an inactive radiating element location. The method also includes determining a number of active radiating element locations to be included in a first sector of the plurality of sectors, and determining, based on the number of active radiating element locations, at least one arrangement of active and inactive radiating element locations in the first sector configured to achieve the performance characteristic. The method further includes applying the at least one arrangement to each remaining sector of the plurality of sectors such that the phased antenna array has rotational symmetry. 
     In another aspect, a phased antenna array is provided. The array includes a plurality of radiating elements partitioned into a plurality of sectors, wherein each sector includes an equal number of radiating elements, and wherein the plurality of radiating elements are arranged to define a plurality of active radiating element locations and a plurality of inactive radiating element locations. Each sector includes the plurality of active radiating element locations and the plurality of inactive radiating element locations defined in a predetermined arrangement such that the phased antenna array has rotational symmetry. 
     In yet another aspect, a satellite is provided. The satellite includes a beamformer and a phased antenna array in communication with the beamformer. The array includes a plurality of radiating elements partitioned into a plurality of sectors, wherein each sector includes an equal number of radiating elements, and wherein the plurality of radiating elements are arranged to define a plurality of active radiating element locations and a plurality of inactive radiating element locations. Each sector includes the plurality of active radiating element locations and the plurality of inactive radiating element locations defined in a predetermined arrangement such that the phased antenna array has rotational symmetry. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an example communications environment. 
         FIG. 2  is a block diagram illustrating an example satellite that may be used in the communications environment shown in  FIG. 1 . 
         FIG. 3  is an illustration of an example computing device that may be used to design and thin a phased antenna array of the satellite shown in  FIG. 2 . 
         FIG. 4  is an illustration of an example phased antenna array that may be used in the satellite shown in  FIG. 2 . 
         FIG. 5  is an illustration of an example radiation pattern emitted by the phased antenna array shown in  FIG. 4 . 
         FIG. 6  is a flow diagram illustrating an example method of thinning a phased antenna array. 
     
    
    
     DETAILED DESCRIPTION 
     The implementations described herein relate to an array thinning method and phased antenna arrays resulting therefrom. More specifically, a phased antenna array is typically designed to include a predetermined amount of radiating element locations, and each location is either an active radiating element location or an inactive radiating element location. The method described herein facilitates determining how to arrange the active and inactive radiating element locations in a manner that facilitates achieving a performance characteristic for the array. For example, the method includes partitioning the array to define a plurality of sectors that each include an equal number of radiating element locations. A combinatorial optimization analysis is performed on a first sector of the plurality of sectors to determine an arrangement of active and inactive radiating element locations that will facilitate achievement of the performance characteristic. Put another way, the combinatorial optimization analysis is performed on a set of radiating element locations that includes less than a total number of radiating element locations in the array. The arrangement in the first sector is then applied to the remaining sectors in the array such that the array has rotational symmetry. As such, applying rotational symmetry to the phased antenna array design facilitates reducing the problem size for the combinatorial optimization analysis, which facilitates reducing an amount of computing power and time required to design the array, and which results in unique array designs that would not typically be realized by other optimization methods. 
     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “exemplary implementation” or “one implementation” of the present disclosure are not intended to be interpreted as excluding the existence of additional implementations that also incorporate the recited features. 
       FIG. 1  is a block diagram illustrating an example communications environment  100  including a satellite  102 , a first communications source  104 , a second communications source  106 , and a third communications source  108 . Satellite  102  exchanges communication data with first communications source  104  in a first communications beam  110 , with second communications source  106  in a second communications beam  112 , and with third communications source  108  in a third communications beam  114 . First communications source  104 , second communications source  106 , and third communications source  108  may be ground-based, air-based, or space-based devices. 
       FIG. 2  is a block diagram illustrating satellite  102 . In the example implementation, satellite  102  includes a phased antenna array  116 . More specifically, phased antenna array  116  is programmable or adjustable to selectively receive/transmit signals or beams from/to various directions and/or sources. Phased antenna array  116  includes a plurality of radiating elements  118 . Radiating elements  118  receive/transmit electromagnetic radiation transmitted from/to one or more sources, such as first communications source  104 , second communications source  106 , and/or third communications source  108 . A plurality of phase shifters  120  and corresponding attenuators  122  are coupled in communication with each radiating element  118 . For simplicity of illustration, the number of phase shifters  120  and attenuators  122  shown in  FIG. 2  is the same as the number of radiating elements  118 . It should be understood, however, that satellite  102  can include more than one phase shifter  120  per radiating element  118 . A beamformer  124  (sometimes referred to as a beamforming system, a system configured to perform beamforming, or a system) is coupled in communication with phase shifters  120  and attenuators  122 . Beamformer  124  transmits control signals to phase shifters  120  and attenuators  122  to adjust the phase and/or magnitude of received electromagnetic radiation, and forms one or more corresponding beams. Each beam is typically associated with a plurality of radiating elements, a plurality of phase shifters, and a plurality of attenuators. Each beam is received in a corresponding beamport  126 , which is included in or coupled to beamformer  124 . 
       FIG. 3  is an illustration of an example computing device  128  that may be used to design and thin phased antenna array  116  (shown in  FIG. 2 ). In the example implementation, computing device  128  includes a memory  130  and a processor  132 , including hardware and software, coupled to memory  130  for executing programmed instructions. Processor  132  may include one or more processing units (e.g., in a multi-core configuration) and/or include a cryptographic accelerator (not shown). Computing device  128  is programmable to perform one or more operations described herein by programming memory  130  and/or processor  132 . For example, processor  132  may be programmed by encoding an operation as executable instructions and providing the executable instructions in memory  130 . 
     Processor  132  may include, but is not limited to, a general purpose central processing unit (CPU), a microcontroller, a microprocessor, a reduced instruction set computer (RISC) processor, an open media application platform (OMAP), an application specific integrated circuit (ASIC), a programmable logic circuit (PLC), and/or any other circuit or processor capable of executing the functions described herein. The methods described herein may be encoded as executable instructions embodied in a computer-readable medium including, without limitation, a storage device and/or a memory device. Such instructions, when executed by processor  132 , cause processor  132  to perform at least a portion of the functions described herein. The above examples are exemplary only, and thus are not intended to limit in any way the definition and/or meaning of the term processor. 
     Computing device  128  also includes at least one media output component  134  for presenting information to a user  136 . Media output component  134  is any component capable of conveying information to a user  136 . In some implementations, media output component  134  includes an output adapter such as a video adapter and/or an audio adapter. An output adapter is operatively coupled to processor  132  and operatively couplable to an output device such as a display device (e.g., a liquid crystal display (LCD), organic light emitting diode (OLED) display, cathode ray tube (CRT), or “electronic ink” display) or an audio output device (e.g., a speaker or headphones). 
     In some implementations, computing device  128  includes an input device  138  for receiving input from user  136 . Input device  138  may include, for example, a keyboard, a pointing device, a mouse, a stylus, a touch sensitive panel (e.g., a touch pad or a touch screen), a gyroscope, an accelerometer, a position detector, or an audio input device. A single component such as a touch screen may function as both an output device of media output component  134  and input device  138 . 
     Computing device  128  is programmable to perform a method of thinning phased antenna array  116  (shown in  FIG. 2 ). As used herein, “thinning” refers to a process of selectively removing radiating elements from a phased antenna array design such that a resulting phased antenna array includes a number of active radiating elements that is less than a total number of radiating element locations in the array. The removed radiating elements may be either selectively deactivated radiating elements or selectively omitted radiating elements. For example, referring to  FIG. 4 , phased antenna array  116  includes a plurality of radiating elements  118  partitioned into a plurality of sectors  140 . Each sector  140  includes an equal number of radiating elements  118  and radiating element locations. Radiating elements  118  are arranged to define a plurality of active radiating element locations  142  and a plurality of inactive radiating element locations  144 . In one implementation, phased antenna array  116  includes a full complement of radiating elements  118  in the radiating element locations (i.e., the combination of active radiating element locations  142  and inactive radiating element locations  144 ), but radiating elements  118  positioned in inactive radiating element locations  144  are selectively deactivatable during operation of phased antenna array  116 . Alternatively, radiating elements  118  are selectively omitted (i.e., physically removed) from phased antenna array  116  in inactive radiating element locations  144 . 
     In operation, computing device  128  receives at least one input from user  136  via input device  138  (all shown in  FIG. 3 ), and the at least one input is used to determine which radiating elements  118  to selectively remove from phased antenna array  116 . In other words, computing device  128  facilitates determining an arrangement of active and inactive radiating element locations  142  and  144  that will result in achievement of a performance characteristic for phased antenna array  116 , as will be explained in more detail below. In the example implementation, computing device  128  receives inputs such as, but not limited to, a total number of radiating elements locations to be included in phased antenna array  116 , a number of active radiating elements and inactive radiating elements to be included in phased antenna array  116 , a performance characteristic for phased antenna array  116 , and a number of sectors  140  included in, and in which to partition, phased antenna array  116 . 
     The total number of radiating elements locations and the number of active and inactive radiating elements are values that are design parameters instituted at the outset of the design phase of phased antenna array  116 . The values of each design parameter may be dictated as a function of cost to make phased antenna array  116 , for example, and are utilized as constraints for computing device  128  when performing the combinatorial optimization analysis. 
     Phased antenna array  116  may include any number of sectors  140  that enables the systems and methods to function as described herein. The selection of the number of sectors  140  to include in phased antenna array  116  is determined as a function of computing power required to perform the combinatorial optimization analysis for a given number of radiating elements  118  in a sector. For example, the greater the number of radiating elements  118  in a sector, the greater the number of possible solutions to the optimization problem, and the greater amount of computing power required to perform the analysis. Therefore, the number of sectors is selected to bound the computation complexity without over-constraining the optimization due to the imposed symmetry. 
     Referring to  FIG. 5 , phased antenna array  116  (shown in  FIG. 4 ) has a coverage region  146  including a main lobe region  148 , a back lobe region  150 , and a plurality of side lobe regions  152 . In the example implementation, the performance characteristic input by user  136 , and then defined by computing device  128  (both shown in  FIG. 3 ), is a side lobe profile for coverage region  146  of phased antenna array  116 . For example, user  136  may input a side lobe objective (e.g., suppress the side lobe level of radiation in a region, or regions, by a certain amount) into computing device  128 . Thus, the user input may be used to define a side lobe level of radiation to be emitted from each side lobe region  152  of phased antenna array  116  that is less than a threshold. 
     Referring again to  FIGS. 3 and 4 , computing device  128  is capable of determining at least one arrangement of active and inactive radiating element locations  142  and  144  in a first sector  154  of the plurality of sectors  140  once the user inputs are received. First sector  154 , and each sector  140 , includes a fraction of the total number of radiating element locations in phased antenna array  116 . Thus, determining the at least one arrangement for first sector  154  facilitates reducing the problem size to be solved by the combinatorial optimization analysis. For example, once the user inputs are received, computing device  128  determines a number of active radiating element locations  142  to be included in first sector  154 . The number of active radiating element locations  142  is determined by determining a total number of active radiating element locations  142  to be included in phased antenna array  116 , and determining a fraction of the total number of active radiating element locations  142 . The fraction used to determine the number of active radiating element locations  142  to include in first sector  154  is based on, and corresponds to, the number of sectors  140  in phased antenna array  116 . 
     For example, phased antenna array  116  may be constrained to include  720  total radiating element locations, and to include  480  active radiating element locations  142 . In one implementation, phased antenna array  116  includes twelve sectors  140  that each define a 30° segment of phased antenna array  116 . Thus, first sector  154  is designed to include 60 total radiating element locations, 40 active radiating element locations  142 , and 20 inactive radiating element locations  144 , which are each 1/12 th  of the respective radiating element location values. 
     Computing device  128  then determines, based on the number of active radiating element locations  142 , at least one arrangement of active and inactive radiating element locations  142  and  144  in first sector  154  configured to achieve the performance characteristic for phased antenna array  116 . For example, in one implementation, computing device  128  performs the combinatorial optimization analysis to determine an arrangement of active and inactive radiating element locations  142  and  144  that will result in the level of radiation for each side lobe region  152  (shown in  FIG. 5 ) being less than the threshold. The arrangement is then applied to each remaining sector  140  of the plurality of sectors  140  such that phased antenna array  116  has rotational symmetry. That is, the arrangement defines a predetermined pattern of active and inactive radiating element locations  142  and  144 , and the arrangement is applied by configuring the remaining sectors to include the same predetermined pattern. Thus, a phased antenna array design is formed having comparable performance characteristics relative to an array formed by performing a combinatorial optimization analysis on the whole array of radiating elements. 
     In some implementations, computing device  128  determines at least a first arrangement and a second arrangement of active and inactive radiating element locations. The active radiating element locations  142  and the inactive radiating element locations  144  are organized differently in the first arrangement and the second arrangement. Thus, in implementations where radiating elements  118  are selectively deactivated radiating elements, more than one arrangement is available for phased antenna array  116  to be operated. As such, phased antenna array  116  is selectively operable between the first arrangement and the second arrangement in the event one or more radiating elements  118  malfunction, for example. 
       FIG. 6  is a flow diagram illustrating an example method  200  of thinning a phased antenna array. The method  200  includes defining  202  a performance characteristic for the phased antenna array, partitioning  204  the phased antenna array to define a plurality of sectors that each include an equal number of radiating element locations, wherein each radiating element location is either an active radiating element location or an inactive radiating element location, determining  206  a number of active radiating element locations to be included in a first sector of the plurality of sectors, determining  208 , based on the number of active radiating element locations, at least one arrangement of active and inactive radiating element locations in the first sector configured to achieve the performance characteristic, and applying  210  the at least one arrangement to each remaining sector of the plurality of sectors such that the phased antenna array has rotational symmetry. 
     This written description uses examples to disclose various implementations, including the best mode, and also to enable any person skilled in the art to practice the various implementations, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.