Abstract:
A high altitude communication device is provided using a first array element comprising a plurality of patches and a second array element comprising a plurality of patches. The first array element and the second array element are for receiving communication signals. A patch in the first array element is shared by the second array element. At least one grouping network selects the first array element for a first time interval and selects the second array element for a time interval after the first time interval to convert and form digital combined signals from the communication signals. A method of digitally controlling received signals within a high altitude communication device is also provided.

Description:
This application claims the priority and benefit of U.S. Provisional Application No. 60/266,689, filed Feb. 5, 2001, for “Digital Controlled Overlapping Subarray For Improved Axial Ratio”, inventor: Donald C. D. Chang, which application is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to multiple beam communication systems and more particularly, to a method and apparatus for digitally controlling a received signal that is manipulated by a digital beam former. 
     BACKGROUND OF THE INVENTION 
     Current commercial high altitude communication devices having conventional multiple beam architectures, which use multipatch antennas, incorporate digital beam forming (DBF) techniques. Multipatch antennas receive and convert communication signals into received signals. Multipatch antennas are also very useful in forming multiple simultaneous beams covering a large field of view (FOV). 
     Now referring to FIG. 1, a block diagrammatic view of a receiving circuit  10  of a conventional high altitude communication device is shown. Typical mobile satellite payloads have a multipatch antenna  12 . The multipatch antenna  12  includes a plurality of patches  14 , each patch  14  receives communication signals  16 . Each patch  14  is preferably used only once in receiving communication signals  16  to prevent signal to noise degradation. 
     The configurations of the patches  14  affect the optimization of multipatch antenna axial ratio (AR). Typical multipatch antennas usually have a poor AR. With a good design, 2 db AR over a large FOV is commonly accepted. For limited FOV applications such as a geosynchronous orbit satellite, grouping patches  14  with proper orientation significantly improves the AR to 0.2 db or less. 
     Orientations of the patches  14  also affect the amount of created grating lobes. The patches  14  have element patterns. When element patterns overlap grating lobes are created. Grating lobes reduce multipatch antenna directivity and gain as known in the art. 
     The patches  14  are combined in even numbered groups by combining networks  18  to form array elements  19 . The combining networks  18  convert the communications signals  16  into combined signals  20 . Each combining network  18  is connected to several components for signal-conditioning the combined signals  20  prior to connecting to a digital beam former  22 . The combining networks  18  are connected to a plurality of low noise amplifiers (LNAs)  24 , which amplify the combined signals  20  to form received signals  26 . The LNAs  24  are connected to a plurality of downconverters  28 . The downconverters  28  convert the high frequency received signals  26  to baseband or intermediate frequency (IF) signals  30 . The baseband signals  30  are then transformed into digital signals  32  by analog-to-digital (A/D) converters  34 . 
     Now referring to FIG. 2, a schematic view of sample array element  19  and a combining network  18 , which together optimize axial ratio and prevent grating lobes is shown. The communication signals  16  are received by patches  14  and combined by 3 db hybrids  36  and circular ring hybrids  38  to form the combined signals  20 . The patches  14  are oriented 90° in sequence. The 3 db hybrids  36  are at 90° and the circular ring hybrids  38  are at 180°. The 3db hybrids  36  and the circular ring hybrids  38  cause signal losses due to their internal characteristics. 
     Now referring to FIG. 3, a block diagrammatic view of the multipatch antenna  12  showing the positioning of the array elements  19  is shown. The patches  14  are positioned to minimize overlapping of element patterns, thereby, suppressing grating lobes and maximizing gain. By orienting the patches  14  and array elements  19  so that spacing between patches  14  is approximately equal to half the wavelength of the received signal  26  and spacing between array elements  19  is approximately equal to the wavelength of the received signal  26 , grating lobes can be prevented. 
     In high altitude communication devices there is a continuing effort to decrease the amount of components in the system thereby decreasing the size and weight of the system, decreasing hardware, decreasing costs, decreasing power consumption, and increasing efficiency. 
     In space systems, where up to thousands of array elements may be used, a reduction in satellite payload components may cause tremendous savings. In other communication systems, in which many array elements are used the savings in cost, weight, and power will also be increased. 
     Therefore a need exists to reduce the number of components in the high altitude communication device. Also a need exists to produce a high altitude communication device having zero grating lobes, good axial ratio, and a reduced amount of signal loss over existing high altitude communication device. 
     SUMMARY OF THE INVENTION 
     The forgoing and other advantages are provided by a method and apparatus of digitally controlling a received signal within a high altitude communication device. The high altitude communication device uses a first array element comprising a plurality of patches and a second array element comprising a plurality of patches. The first array element and the second array element are for receiving communication signals. A patch in the first array element is shared by the second array element. 
     A method of digitally controlling received signals within a high altitude communication device is provided. The method includes clocking an array element and receiving communication signals. The communication signals are converted to digital baseband signals by the plurality of grouping networks. The plurality of grouping networks also transforms the digital baseband signals into digital combined signals. 
     The present invention has several advantages over existing signal controlling techniques. One advantage of the present invention is that it reduces the number of high altitude communication device components by eliminating the use of hybrids and combining networks. The reduction in components reduces weight and saves space within a high altitude communication device. Furthermore, the reduction in components reduces costs involved in production and implementation of satellite systems. 
     Another advantage of the present invention is that it minimizes signal losses due to the elimination of the hybrids and combining networks. 
     Yet another advantage of the present invention is that an arbitrary number of patches may be grouped together as opposed to a fixed hardwired even amount of patches. 
     Moreover, the present invention eliminates grating lobes and optimizes the high altitude communication device axial ratio. The present invention also reduces A/D dynamic range requirements and may be easily calibrated and recalibrated. 
     Therefore, a high altitude communication device having a minimal number of components, which can digitally control received signals, is possible due to the stated method advantages. The present invention itself, together with further objects and attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying drawing. 
     BRIEF DESCRIPTION OF THE DRAWING 
     For a more complete understanding of this invention reference should now be had to the embodiments illustrated in greater detail in the accompanying figures and described below by way of example. 
     In the figures: 
     FIG. 1 is a block diagrammatic view of a receiving circuit of a conventional high altitude communication device. 
     FIG. 2 is a schematic view of an array element in conjunction with a combining network of a conventional high altitude communication device. 
     FIG. 3 is a block diagrammatic view of a multipatch antenna of a conventional high altitude communication device showing positioning of array elements. 
     FIG. 4 is a perspective view of a communication system, utilizing a method and apparatus for sampling communication signals according to the present invention. 
     FIG. 5 is a block diagrammatic view of a high altitude communication device in accordance with the present invention. 
     FIG. 6 is a block diagrammatic view of a receiving circuit of a high altitude communication device in accordance with the present invention. 
     FIG. 7 is a block diagrammatic view of a multipatch antenna of a mobile satellite payload in accordance with the present invention. 
     FIG. 8 is a block diagrammatic view of clocking groups of patches in accordance with the present invention. 
     FIG. 9 is a flow chart illustrating a method of digitally controlling received signals within a high altitude communication device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention may be applied in various applications such as a fixed satellite service communication system, general packet radio service, universal mobile telecommunication system, or other terrestrial mobile communication applications. The present invention may also be incorporated into communication systems using various payload designs such as a low profile array, a surface mount antenna, or a digital design. 
     While the present invention is described with respect to a method and apparatus for digitally controlling a received signal for a multiple beam high altitude communication device, the following sampling method is capable of being adapted for various purposes and is not limited to the following applications: a ground based base-station, mobile terminal, mobile satellite, or any other electronic or communication device. 
     In the following figures the same reference numerals are used to refer to the same components. Also in the following description, various operating parameters and components are described for one constructed embodiment. These specific parameters and components are included as examples and are not meant to be limiting. 
     Referring now to FIG. 4, a communication system  50  is shown including a total service geographic area  52  covered by a relatively large number of uplink and downlink spot beams having individual foot-prints  54 . High gain uplink and downlink beams are preferably utilized to support mobile terminals  56 , with high-data-rate transmission. More importantly, the combination of uplink and downlink beams provides for multiple reuse of the same limited frequency spectrum by a high altitude communication device  58 , thus creating a high-capacity mobile communication system  50  which can serve mass markets for numerous communication services. High altitude communication device  58  may be a satellite, a stratospheric platform or other communication device. The uplink and downlink spot beams may be generated or radiated from the high altitude communication device  58  or by a cell tower  59 . A network control center (NCC)  60  provides overall transmission control and uplink/downlink frequency assignment for the mobile terminals  56 , the high altitude communication device  58 , and cell tower  59 . 
     Referring now to FIG. 5, a high altitude communication device  58  utilizing one embodiment of the present invention is shown. The communication device  58  includes a receiving circuit  61  with a multipatch antenna  62 . The multipatch antenna  62  has a plurality of patches  64  for collecting communication signals  66 . The communication signals  66  are amplified by a plurality of low noise amplifiers (LNAs)  68  to form received signals  70 . The received signals  70  are converted to baseband signals  72  by a plurality of downconverters  74 . The baseband signals  72  are transformed into digital signals  76  by a plurality of analog-to-digital (A/D) converters  78 . The A/D converters  78  transfer the digital signals to a digital network  80 , which is part of a digital beam former (DBF)  82 . Although the digital network  80  is shown as part of an integrated circuit within the DBF  82 , it may be a separate individual component or group of components. The DBF  82  forms separate beams with different directional vectors to accommodate various communication signals  16  arriving from different directions or different transmitting devices. The DBF  82  transfers the beams to beam channelizers  84 , which transform the digital signals including amplitude and phase information into digital data streams. The beam channelizers  84  provide the digital stream over to data packet switch elements  86 . The data packet switch elements  86  packetize the data streams and the packets are transmitted accordingly over crosslink antennas  88 . The crosslink antennas  88  transmit signals to and receive signals from other mobile satellite payloads. The data packet switch elements  86  also provide a data stream representing one individual antenna beam to each beam synthesizer module  90 . Beam synthesizer modules  90  convert the data streams to digital output signals that represent the analog waveforms that are transmitted. The beam synthesizer  90  couples the digital output signals to the DBF  82 . The DBF  82  determines proper signal weights for each patch  64  and transmit radiating element  92 . The DBF  82  analyzes incoming signals using a suitable algorithm and determines proper signal weights. The weighted analog transmitting signals are converted to a digital signal by a digital-to-analog (D/A) converter  94 . The D/A converter  94  transforms the digital output signals for each patch  64  into corresponding analog signals for each transmit radiating element  92 . The D/A converter  94  transfers the analog signals to a plurality of transmitter modules  96 . The transmitter modules  96  have two components, an upconverter  98 , and an amplifier  100 . The analog signals are converted, via the upconverter  98  and the amplifier  100 , into suitable signals for transmission to the earth station terminals  56 . 
     Referring now also to FIG. 6, a block diagrammatic view of a receiving circuit  61  of the present invention is shown. Each patch is part of an array element  104  having a preselected arbitrary number of patches  64 . The digital network  80  in combination with the LNAs  68 , downconverters  74 , and A/D converters  78  form grouping networks  102 . Each array element  104  transfers communication signals  16  to a grouping network  102 . The digital network  80  transforms digital baseband signals  76  into combined signals  106 . The digital baseband signals  76  are transferred to strip-lines  110  within the digital network  80  of the DBF  82 . The strip-lines  110  separate a preselected arbitrary number of digital baseband signals  76 , which are transferred to polarizers  112 . The polarizers  112  convert the digital baseband signals  76  into polarized signals  114 . The polarized signals  114  are dynamically controlled and may invert the digital baseband signal  76  depending on location of a corresponding patch  64 . A preselected arbitrary number of polarized signals  114  are then summed to form digital combined signals  106  by elements  118 . 
     Referring now also to FIG. 7, a block diagrammatic view of the multipatch antenna  62  having array elements  104  is shown. The grouping networks  102  are represented by the center nodes  120  having electrical connections  122 . Each patch  64  may be used four times for each of four different array elements  104 . For example patch X is part of four different array elements  1 ,  2 ,  3 ,  4  within a grouping network  102 . Since there are no hybrids combining the patches  64  there is no signal to noise degradation. The array elements  104  share adjacent patches  64 , which may be referred to as overlapping of the patches  64 . The overlapping of patches  64  increases the efficiency of each patch  64 . The overlapping of patches  64  in combination with the elimination of hybrids also decreases the dynamic range required for each A/D converter  78 . Therefore the space between array elements  104  is equal to the space between patches  64 . This spacing prevents grating lobes. Also since the patches  64  are digitally controlled the axial ratio is improved to approximately less then 0.2 db. Furthermore, since the received communication signals  16  are transformed into digital baseband signals  76  and combined digitally the receiving circuit  61  may be easily calibrated and recalibrated. 
     Referring now to FIG. 8, a block diagrammatic view of clocking array elements  104  in accordance with the present invention is shown. The array elements  104  are clocked using preferably a satellite payload internal clock for receiving communication signals  16 . Since adjacent array elements share patches  64  the array elements  104  are timed as to prevent more than one array element  104  from using the same patch  64  at the same time. The electrical connections  122  show an example of a preselected set of array elements receiving communication signals  16  for a particular time interval. The preselected combination of array elements shown is meant to be an example of a possible combination for a particular time interval. An infinite combination of array elements may be selected and used at various time intervals. 
     Referring now to FIG. 9, a flow chart illustrating a method of digitally controlling received signals  70  within the satellite payload  58  is shown. 
     In step  150 , the array elements  104  are clocked to receive communication signals  66  at selected time intervals. 
     In step  152 , the preselected array elements  104  receive the communication signals  66  for a particular time interval. 
     In step  154 , the communication signals  66  are converted into received signals  70  by the LNAs  68 . 
     In step  156 , the grouping networks  102  transform the received signals  70  into digital baseband signals  76 , which are digitally converted into digital combined signals  106  by the digital network  80 . 
     The above-described invention, by eliminating the hybrids and combined networks, not only reduces the number of components in the satellite payload but also reduces the amount of signal loss. The reduction of the number of mobile satellite payload components may reduce weight, costs, and hardware of the mobile satellite payload. Furthermore by overlapping and orienting the patches in accordance with the present invention eliminates grating lobes and optimizes satellite payload axial ratio. 
     The above-described sampling method, to one skilled in the art, is capable of being adapted for various purposes and is not limited to the following applications: a ground based mobile terminal, base stations, or any other terrestrial electronic or communication devices that receive or transmit signals. The above-described invention may also be varied without deviating from the true scope of the invention