Patent Publication Number: US-10763593-B1

Title: Broadband single pol TX, dual pol RX, circular polarization waveguide network

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. § 119 from U.S. Provisional Patent Application 62/757,087 filed Nov. 7, 2018, which is incorporated herein by reference in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FILED OF THE INVENTION 
     The present invention generally relates to antenna technology, and more particularly to a broadband single-polarization transmit (TX), dual-polarization receive (RX), circular polarization waveguide network. 
     BACKGROUND 
     Many space and terrestrial communication systems can communicate over a radio frequency (RF) link such as Ku-band, Ka-band or other suitable type of link. The Ku-band and the Ka-band, for example, are portions of the electromagnetic spectrum in the microwave range of frequencies between 10 GHz and 18 GHz, and 17 GHz and 40 GHz, respectively. Existing Ka-band circular polarization (CP) waveguide networks are generally rather complex and quite expensive to produce and may require a large network size. For example, an existing solution generates broadband CP by using two septum polarizers, one for (receive) RX and one for transmit (TX), that feed to a double quadrature junction (QJ) network coupled to receive-reject filters and transmit-reject filters. This solution may be impossible to fabricate as a simple split block with minimal split planes due to complexity of the employed QJs, RX filters, TX filters and septum polarizers. 
     SUMMARY 
     According to various aspects of the subject technology, methods and configuration are disclosed for providing low-cost and compact Ka-band circular polarization waveguides with single polarization transmit (TX) and dual or single polarization receive (RX). 
     In one or more aspects, a polarization waveguide network includes a reactive power splitter and multiple RX-reject waveguide filters to reject RX frequencies. The polarization waveguide network further includes a quadrature junction coupler that can couple the RX-reject waveguide filters to an antenna port. The polarization waveguide network is configured to be fabricated in just three pieces, with two zero-current split planes and a first piece of three pieces which couples to the antenna port. 
     In other aspects, an antenna array system includes an antenna array consisting of a number of antenna elements and a polarization array implemented using multiple polarization waveguide networks. Each polarization waveguide network is coupled to an antenna port of the antenna elements and includes a reactive TX power splitter and number of RX-reject waveguide filters to reject RX frequencies. Each polarization waveguide network further includes a pair of branch-line couplers to couple the RX-reject waveguide filters to the reactive TX power splitter, and a quadrature junction coupler that couples the RX-reject waveguide filters to an antenna port of the antenna element. Each waveguide network of the polarization array can be fabricated in three pieces with two zero-current split planes, and the first of the three pieces can be coupled to the antenna port. 
     In yet other aspects, a method of manufacturing a polarization waveguide network includes fabricating a first piece comprising air cavities including a reactive TX power splitter, a number of RX-reject waveguide filters, a pair of branch-line couplers to couple the plurality of RX-reject waveguide filters to the reactive TX power splitter and a quadrature junction coupler (QIC) for coupling the RX-reject waveguide filters to an antenna port. The method further includes fabricating a second piece comprising air cavities including a circular waveguide comprising a first portion for coupling to the antenna port and a second portion for coupling to an RX port, and fabricating a third piece comprising air cavities including an RX network supporting right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) modes and also including a TX-reject waveguide filter, an RX branch-line coupler, a circular waveguide and two RX ports. 
     The foregoing has outlined rather broadly the features of the present disclosure so that the following detailed description can be better understood. Additional features and advantages of the disclosure, which form the subject of the claims, will be described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions to be taken in conjunction with the accompanying drawings describing specific aspects of the disclosure, wherein: 
         FIG. 1  is a conceptual diagram illustrating an example of the TX portion of a broadband polarization waveguide network, according to certain aspects of the disclosure. 
         FIGS. 2A, 2B, 2C, 2D, 2E and 2F  are diagrams illustrating various views of air-cavity models of an example broadband polarization waveguide network, according to certain aspects of the disclosure. 
         FIGS. 3A, 3B, 3C, 3D and 3E  are schematic diagrams illustrating various views of air-cavity models and a shelled mode of an example broadband polarization waveguide network, according to certain aspects of the disclosure. 
         FIG. 4  is a schematic diagram illustrating a shelled model with split planes of an example broadband polarization waveguide network, according to certain aspects of the disclosure. 
         FIGS. 5A and 5B  are schematic diagrams illustrating views of air-cavity models of an example broadband polarization waveguide network before and after removal of the transmit (TX) network, according to certain aspects of the disclosure. 
         FIGS. 6A, 6B, 6C, and 6D  are schematic diagrams illustrating air-cavity models of various components of an example broadband polarization waveguide network, according to certain aspects of the disclosure. 
         FIGS. 7A and 7B  are a schematic diagram illustrating an air-cavity model of an example branch-line coupler of a broadband polarization waveguide network and a chart showing an example optimized performance of the branch-line coupler, according to certain aspects of the disclosure. 
         FIGS. 8A and 8B  are schematic diagrams illustrating views of an air-cavity model of an example quadrature junction coupler (QJC) of a broadband polarization waveguide network, according to certain aspects of the disclosure. 
         FIG. 9  is a schematic diagram illustrating an example array configuration of broadband polarization waveguide networks, according to certain aspects of the disclosure. 
         FIGS. 10A, 10B and 10C  are charts illustrating return-loss performance as well as RHCP to LHCP isolation in RX of an example broadband polarization waveguide network and a corresponding air-cavity model, according to certain aspects of the disclosure. 
         FIGS. 11A, 11B and 11C  are charts illustrating axial-ratio performance of an example broadband polarization waveguide network and a corresponding air-cavity model, according to certain aspects of the disclosure. 
         FIGS. 12A and 12B  are a chart illustrating a mode-purity performance of an example broadband polarization waveguide network and a corresponding air-cavity model, according to certain aspects of the disclosure. 
         FIGS. 13A, 13B and 13C  are charts illustrating transmit (TX)-receive (RX) isolation performance of an example broadband polarization waveguide network and a corresponding air-cavity model, according to certain aspects of the disclosure. 
         FIG. 14  is a flow diagram of a method of manufacturing a polarization waveguide network, according to certain aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below is intended as a description of various configurations of the subject technology and is not intended to represent the only configurations in which the subject technology can be practiced. The appended drawings are incorporated herein and constitute a part of the detailed description. The detailed description includes specific details for the purpose of providing a thorough understanding of the subject technology. However, it will be clear and apparent to those skilled in the art that the subject technology is not limited to the specific details set forth herein and can be practiced using one or more implementations. In one or more instances, well-known structures and components are shown in block-diagram form in order to avoid obscuring the concepts of the subject technology. 
     Methods and configurations are described for providing a low-cost and compact Ka-band circular polarization waveguides. In particular, the subject technology relates to microwave circular polarization waveguides with single polarization transmit (TX) and dual or single polarization receive (RX) in the Ka-band (e.g., 17.70 to 20.20 GHz and 27.50 to 30.00 GHz) of the electromagnetic spectrum. In some implementations, the circular polarization waveguide of the subject technology can be a simple waveguide with three pieces of direct machined aluminum with split planes mostly on the zero-current line. The feed can be desirably fit under the smallest aperture sizes for array configurations. 
     In some implementations, by utilizing two E-plane couplers rather than just one, the subject technology allows completing the entire transmit portion, for example, right-handed circular polarization (RHCP) or left-handed circular polarization (LHCP) single polarization operation in just one split plane. In some implementations, there is no need to jump the waveguides over one another as is the case in the traditional approach which utilizes only one branch-line coupler. In one or more implementations, the disclosed RX network can be a dual LHCP and/or RHCP RX network. Existing solutions are typically at a much higher level of complexity (e.g., multipart multi-component assembly). The circular polarization (CP) is typically generated using just one E-plane coupler and the waveguides are then routed to the common waveguide pipes, using a symmetric network, which hop over each other (e.g., with many split planes). The disclosed waveguide can be made of three pieces of direct machined material (e.g., aluminum) at a cost of only a fraction (e.g., about 10%) of the cost of the traditional approach. Furthermore, the CP waveguide of the subject technology can be assembled and tested in a schedule which is greatly accelerated and with no tuning. 
     For the purposes of the present disclosure TX is the lower operating band and RX is the higher operating band. However, the TX and RX nomenclature here could be reversed as would be typical of a ground antenna rather than a space antenna. 
       FIG. 1  is a conceptual diagram illustrating an example of a broadband polarization waveguide network  100 , according to certain aspects of the disclosure. Broadband polarization waveguide network  100  (hereinafter, “polarizer  100 ”) includes a quadrature junction coupler (QJC)  110 , four RX-reject waveguide filters  120 , a pair of branch-line couplers (also referred to as “E-plane couplers”)  130 , and a TX power splitter  160 . QJC  110  can be a circular waveguide that couples RX-reject waveguide filters  120  to an antenna (e.g., horn antenna) port. Branch-line couplers  130  are coupled to the TX power splitter  160  via TX recombination-path waveguides  132 . The use of two branch-line couplers  130  by the subject technology overcomes the manufacturing hurdles facing the existing solution and allows fabrication of polarizer  100  in three pieces with two zero-current split planes. Polarizer  100  of the subject technology can be fabricated using a suitable material such as aluminum or other material, for example, by machining, electroplating, three-dimensional (3-D) printing or other fabrication techniques. 
       FIGS. 2A, 2B, 2C, 2D, 2E and 2F  are diagrams illustrating various views of air-cavity models of an example broadband polarization waveguide network, according to certain aspects of the disclosure.  FIG. 2A  is perspective view of an air-cavity model  200 A of the example broadband polarization waveguide network (e.g., polarizer  100  of  FIG. 1 ). Air-cavity model  200 A includes three pieces, a first piece  202 , a second piece  204  and a third piece  206 , which are joined together to collectively perform the functionalities of polarizer  100 . Further details of air cavity model  200 A is provided with respect to various polarizer components herein. 
       FIG. 2B  shows a front-view  200 B of air-cavity model  200 A. The top-view  200 B shows a QJC  210 , four RX-reject waveguide filters  220 , a pair of branch-line couplers  230 , and a TX power splitter  260 . QJC  210  is a circular waveguide and couples RX-reject waveguide filters  220  to an antenna (e.g., horn antenna) port. Branch-line couplers  230  are coupled to the TX power splitter  260  via a pair of TX recombination-path waveguides  232 . The pair of TX recombination-path waveguides  232  are similar (e.g., substantially identical) in phase length and are structurally mirror images of each other. RX-reject waveguide filters  220  are configured to reject RX frequencies (e.g., within a range of about 27-30 GHz). Each of branch-line couplers  230  has four ports, two input ports and two output ports. The two output ports are coupled to RX-reject waveguide filters  220 . One of the two input ports is coupled to one of the pair of TX recombination-path waveguides  232  and the other one is coupled to an impedance matching load  250 . 
       FIG. 2C  shows a top view of TX power splitter  260 . TX power splitter  260  includes an input waveguide  262  that divides an input power to two output waveguides  264 - 1  and  264 - 2 , which are coupled to TX recombination-path waveguides  232 . 
       FIG. 2D  shows a front view of branch-line coupler  230 . In some implementations, branch-line coupler  230  can have three or more branches. 
       FIG. 2E  shows a front view of RX-reject waveguide filter  220 . In some implementations, RX-reject waveguide filter  220  is a single-sided structure with three or more branches (teeth). 
       FIG. 2F  shows a top view of TX-reject waveguide filter  270 , which is implemented in third piece  206 , as will be discussed in more detail herein. In some implementations, TX-reject waveguide filter  270  has a first circular waveguide  272  that supports both RX and TX modes of propagation and a second circular waveguide  274  that has a cutoff over the TX frequencies (e.g., within a range of about 17-20 GHz). 
       FIGS. 3A, 3B, 3C, 3D and 3E  are schematic diagrams illustrating various views of air-cavity models and shelled models of an example broadband polarization waveguide network, according to certain aspects of the disclosure.  FIG. 3A  is a perspective view of an air-cavity model  300 A of polarizer  100  of  FIG. 1  and is similar to air-cavity model  200 A of  FIG. 2A . Air-cavity model  300 A includes a first piece  302 , a second piece  304  and a third piece  306 . First piece  302 , as described above, includes a QJC, four RX-reject waveguide filters, a pair of branch-line couplers, and a TX power splitter. More structural detail of second piece  304  and third piece  306  will be discussed below.  FIG. 3B  shows a perspective view of a shelled model  300 B of polarizer  100 . The shelled model is a fabrication model and shows an RX port  305 , a TX port  308  and an antenna port  307  that can be coupled to a radio-frequency (RF) antenna.  FIG. 3C  shows a front view of third piece  306  of shelled model (fabrication model)  300 B.  FIG. 3D  shows a front view of second piece  304  of shelled model  300 B, and  FIG. 3E  depicts a front view of first piece  302  of shelled model  300 B. 
       FIG. 4  is a schematic diagram illustrating a shelled model  400  with split planes of an example broadband polarization waveguide network, according to certain aspects of the disclosure. In shelled model  400 , three pieces  402 ,  404  and  406  are the same as first piece  302 , second piece  304  and third piece  306  of  FIG. 3A . Three pieces  402 ,  404  and  406  are joined at two split planes  403  and  405 , which are low-risk, zero-current planes that reduce the necessity of perfect contacts, resulting in more fabrication error tolerance. 
       FIGS. 5A and 5B  are schematic diagrams illustrating views of air-cavity models  500 A and  500 B of an example broadband polarization waveguide network before and after removal of the TX network, according to certain aspects of the disclosure.  FIG. 5A  shows a perspective view of the air-cavity model  500 A, which is similar to the air-cavity model  300 A of  FIG. 3A  and includes a piece  502 , a second piece  504  and a third piece  506 . The perspective view shown in  FIG. 5A  is from a different angle from the one shown in  FIG. 3A  to revel the structure of the air-cavity implemented in second piece  504 , which includes waveguides described with respect to  FIG. 2B . 
       FIG. 5B  shows a perspective view of air-cavity model  500 B of polarizer shown in  FIG. 5A , after removal of the TX network included in first piece  502  and second piece  504 . Air-cavity model  500 B includes a waveguide  510 , an impedance matching ring  512 , a major step  514 , an impedance matching step  516 , a transition region  518  and an antenna port  520 . Waveguide  510  is coupled to a TX-reject filter in third piece  506  and allows for free propagation of RX signals, in particular in the TE11 dominant mode. Major step  514  is a step in the TX cutoff and is the beginning part of the TX-reject filter. Transition region  518  is the region where the RX-reject waveguide filters mate up. 
       FIGS. 6A, 6B, 6C, and 6D  are schematic diagrams illustrating air-cavity models of various components of an example broadband polarization waveguide network, according to certain aspects of the disclosure.  FIG. 6A  shows a perspective air-cavity model  600 A of TX power splitter  260  of  FIGS. 2B and 2C  discussed above. A waveguide  662  is the input waveguide where the full TX power is received and delivered to two output waveguides  664  each receives a 3 dB portion of the input power and hands it to a TX recombination-path waveguide for input to a branch-line coupler at a phase equal to zero. 
       FIG. 6B  shows a perspective air-cavity model  600 B of TX recombination-path waveguides  632 , which are 3-D models of TX recombination-path waveguides  232  of  FIG. 2B . TX recombination-path waveguides  632  have similar steps but their end portions clock differently. 
       FIG. 6C  depicts a perspective air-cavity model  600 C of an RX-reject waveguide filter  620 , which is a 3-D model of one of RX-reject waveguide filters  220  of  FIG. 2B . The RX-reject waveguide filter  620  is a single-sided corrugated low-pass waveguide filter. Corrugation  622  is implemented on one side (top) of the waveguide only (rather than on two sides) to make the geometry more readily foldable. The corrugation  622  is folded over to create some room for the TX power splitter. The corrugations create a low-pass response which rejects the higher Rx frequencies. 
       FIG. 6D  illustrates a perspective air-cavity model  600 D of a branch-line coupler  630 , which is a 3-D model of branch-line coupler  230  of  FIG. 2B . Air-cavity model  600 D shows impedance matching load  650  and ports  672 ,  674  and  676 . Port  672  is a 6-dB port with a phase of zero degrees and couples to the RX-reject waveguide filters and the QJC (e.g.,  210  of  FIG. 2B ). Port  674  is a 3-dB port for coupling to TX recombination-path waveguides  632 . Port  676  is a 6-dB port with phase of 90 degrees for coupling to the RX-reject waveguide filters and the QJC. 
       FIGS. 7A and 7B  are a schematic diagram illustrating an air-cavity model  700 A of an example branch-line coupler of a broadband polarization waveguide network and a chart  700 B showing an example optimized performance of the branch-line coupler, according to certain aspects of the disclosure. The air-cavity model  700 A of the branch-line coupler  730  has a similar structure as branch-line coupler  630  of  FIG. 6D  and is provided herein for reference. Ports  772 ,  774  and  776  are similar to ports  672 ,  674  and  676  of  FIG. 6D . Port  778  can be coupled to a load (e.g.,  650  of  FIG. 6D ). 
     Chart  700 B depicts the optimized performance of the branch-line coupler  730  and includes plots  710  and  720  of power to ports  772  and  776 . Polarizer  100 , which utilizes two such branch-line couplers, achieves an axial ratio of 0.48 dB, which is similar to the best power split offered by an optimized same-size stand-alone branch coupler (e.g., 0.45 dB). Therefore, this proves no degradation in axial ratio due to the use of two branch-line couplers. 
       FIGS. 8A and 8B  are schematic diagrams illustrating views of an air-cavity model  800 A of an example QJC  810  of a broadband polarization waveguide network, according to certain aspects of the disclosure.  FIG. 8A  shows a perspective view of air-cavity model  800 A of example QJC  810  (e.g., similar to  210  of  FIG. 2B ) with ports for coupling to four RX-reject waveguide filters. 
       FIG. 8B  shows a front-view model  800 B of the QJC, depicting ports  802 ,  804 ,  806  and  808 . Ports  802  and  808  are zero-degree and 6-dB ports, and ports  804  and  806  are 90-degree and 6-dB ports. The power that is initially split to 3 dB at the reactive power splitter (e.g.,  600 A of  FIG. 6A ) and then to 6 dB (with a 90-degree phase shift) by the branch-line coupler (e.g.,  630  of  FIG. 6D ) is recombined here at QJC  810 . Due to the phase shift (90 degrees) generated herein, RHCP or LHCP can regain the full power initially presented to the splitter. The RHCP or LHCP is determined by the recombination path mating to the branch-line coupler. 
       FIG. 9  is a schematic diagram illustrating an example array configuration  900  of broadband polarization waveguide networks, according to certain aspects of the disclosure. Array configuration  900  includes a number of broadband polarization waveguide network elements  910  arranged in multiple rows and columns. Broadband polarization waveguide network elements  910  are clocked 45 degrees such that they fit under the smallest Ka-band aperture size of about 1.7 inches. Array configuration  900  can be coupled to an antenna array, where each element of the antenna array (e.g., a horn antenna) is coupled to an antenna port of the broadband polarization waveguide network elements  910 . 
       FIGS. 10A, 10B and 10C  are charts  1000 A and  1000 B illustrating return-loss performance of an example broadband polarization waveguide network and a corresponding air-cavity model  1000 C, according to certain aspects of the disclosure. Chart  1000 A shows a plot  1010  of the variation of TX return loss at a TX port 3 of air-cavity model  1000 C. The return-loss values, as depicted by plot  1010 , are lower than −27 dB and well below a specification limit of about −18 dB, as shown by a line  1020 . 
     Chart  1000 B depicts plots  1030 ,  1040  and  1050 . Plot  1030  shows variation of RHCP to LHCP isolation between RX ports 5 and 6 of air-cavity model  1000 C. Plot  1040  shows variation of return loss at RX port 6 of air-cavity model  1000 C, and Plot  1050  illustrates variation of return loss at RX port 5 of air-cavity model  1000 C. The return-loss values, as depicted by plots  1030 ,  1040  and  1050 , are lower than −25 dB, which is well below a specification limit of about −18 dB, as shown by a line  1060 . 
       FIGS. 11A, 11B and 11C  plus charts  1100 A and  1100 B illustrate axial-ratio performance of an example broadband polarization waveguide network and a corresponding air-cavity model  1100 C, according to certain aspects of the disclosure. Chart  1100 A shows a plot  1110  of the variation of TX axial ratio at a TX port 3 of air-cavity model  1100 C. The TX axial ratio values, as depicted by plot  1110 , are lower than about 0.48 dB and well below a specification limit of about 0.7 dB, as shown by a line  1120 . 
     Chart  1100 B depicts a plot  1130  that is RHCP and LHCP axial ratio of air-cavity model  1100 C. The RX axial ratio values, as depicted by plot  1130  are lower than about 0.39 dB, which is well below a specification limit of about 0.7 dB, as shown by the line  1140 . 
       FIGS. 12A and 12B  are a chart  1200 A illustrating a mode-purity performance of an example broadband polarization waveguide network and a corresponding air-cavity model  1200 B, according to certain aspects of the disclosure. Chart  1200 A shows plots  1210 ,  1220  and  1230 . Plot  1210  depicts the variation of mode purity of a TM01 mode at TX port 3 and antenna port 1 of air-cavity model  1200 C. Plots  1220  and  1230  depict the variation of mode purity of a TE21 mode at TX port 3 and antenna port 1 of air-cavity model  1200 C. It should be noted that ports 4 and 5 (of branch-line couplers  230  of  FIG. 2B , not shown in  FIG. 12B  for simplicity) are coupled to impedance loads (e.g.,  250  of  FIG. 2B ). The higher order modes in excess of 40 dB will degrade off-axis cross-polarization and axial-ratio performance. The higher order content is less than 75 dB. 
       FIGS. 13A, 13B and 13C  are charts  1300 A and  1300 B illustrating TX-RX isolation performance of an example broadband polarization waveguide network and a corresponding air-cavity model  1300 C, according to certain aspects of the disclosure. Chart  1300 A shows plots  1310  and  1320  (overlapping plots) of the variation of RX-to-TX port isolation between RX ports 5 and 6 and a TX port 3 of air-cavity model  1300 C. The RX-to-TX port isolation values, as depicted by plots  1310  and  1320 , are lower than about −70 dB and well below a specification limit of about −55 dB, as shown by a line  1330 . 
     Chart  1300 B shows plots  1340  and  1350  (overlapping plots) of the variation of TX-to-RX port isolation between a TX port 3 and RX ports 5 and 6 of air-cavity model  1300 C. The TX-to-RX isolation values, as depicted by plots  1340  and  1350 , are lower than about −75 dB and well below a specification limit of about −55 dB, as shown by a line  1360 . 
       FIG. 14  is a flow diagram of a method  1400  of manufacturing a polarization waveguide network (e.g.,  100  of  FIG. 1 , or  300 A of  FIG. 3A ), according to certain aspects of the disclosure. Method  1400  includes fabricating a first piece (e.g.,  202  of  FIG. 2A ) comprising air cavities including a reactive TX power splitter (e.g.,  260  of  FIGS. 2B and 2C ), a number of RX-reject waveguide filters (e.g.,  220  of  FIGS. 2B and 2E ), a pair of branch-line couplers (e.g.,  230  of  FIGS. 2B and 2D ) to couple the plurality of RX-reject waveguide filters to the reactive TX power splitter and a QJC (e.g.,  210  of  FIG. 2B ) for coupling the RX-reject waveguide filters to an antenna port (e.g.,  306  of  FIG. 3B ) ( 1410 ). The method further includes fabricating a second piece (e.g.,  304  of  FIGS. 3A and 3D ) comprising air cavities including a circular waveguide (e.g.,  270  of  FIG. 2F ) comprising a first portion (e.g.,  272  of  FIG. 2F ) for coupling to the antenna port and a second portion (e.g.,  274  of  FIG. 2F ) for coupling to an RX port (e.g.,  5  and  6  of  FIG. 10C ) ( 1420 ). The method further includes fabricating a third piece (e.g.,  306  of  FIG. 3C ) comprising air cavities including an RX network supporting RHCP and LHCP modes and including a TX-reject waveguide filter, an RX branch-line coupler, a circular waveguide and two RX ports (e.g.,  5  and  6  of  FIG. 10C ) ( 1430 ). 
     In some aspects, the subject technology is related to antenna technology, and more particularly to a broadband single polarization TX, dual polarization RX, circular polarization waveguide network. In some aspects, the subject technology may be used in various markets, including, for example and without limitation, sensor technology, communication systems and radar technology markets. 
     Those of skill in the art would appreciate that the various illustrative blocks, modules, elements, components, methods, and algorithms described herein may be implemented as electronic hardware, computer software, or combinations of both. To illustrate this interchangeability of hardware and software, various illustrative blocks, modules, elements, components, methods, and algorithms have been described above generally in terms of their functionalities. Whether such functionalities are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionalities in varying ways for each particular application. Various components and blocks may be arranged differently (e.g., arranged in a different order, or partitioned in a different way), all without departing from the scope of the subject technology. 
     It is understood that any specific order or hierarchy of blocks in the processes disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes may be rearranged, or that all illustrated blocks may be performed. Any of the blocks may be performed simultaneously. In one or more implementations, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single hardware and software product or packaged into multiple hardware and software products. 
     The description of the subject technology is provided to enable any person skilled in the art to practice the various aspects described herein. While the subject technology has been particularly described with reference to the various figures and aspects, it should be understood that these are for illustration purposes only and should not be taken as limiting the scope of the subject technology. 
     A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” The term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the above description. 
     Although the invention has been described with reference to the disclosed aspects, one having ordinary skill in the art will readily appreciate that these aspects are only illustrative of the invention. It should be understood that various modifications can be made without departing from the spirit of the invention. The particular aspects disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative aspects disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and operations. All numbers and ranges disclosed above can vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any subrange falling within the broader range are specifically disclosed. Also, the terms in the claims have their plain, ordinary meanings unless otherwise explicitly and clearly defined by the patentee. If there is any conflict in the usage of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definition that is consistent with this specification should be adopted.