JP5213876B2 - Beam forming system and method - Google Patents

Beam forming system and method Download PDF

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JP5213876B2
JP5213876B2 JP2009542231A JP2009542231A JP5213876B2 JP 5213876 B2 JP5213876 B2 JP 5213876B2 JP 2009542231 A JP2009542231 A JP 2009542231A JP 2009542231 A JP2009542231 A JP 2009542231A JP 5213876 B2 JP5213876 B2 JP 5213876B2
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signal
plurality
signals
beam forming
beam
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JP2010514311A (en
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アンドリュー・マーク・ビショップ
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アストリウム・リミテッド
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/14Relay systems
    • H04B7/15Active relay systems
    • H04B7/185Space-based or airborne stations; Stations for satellite systems
    • H04B7/1851Systems using a satellite or space-based relay
    • H04B7/18515Transmission equipment in satellites or space-based relays
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842Weighted combining

Description

  The present invention relates to a beam forming technique, and more particularly to a beam forming technique used in a satellite communication system.

  Various communication systems, such as mobile phones, cable TV, the Internet, and military communications, transfer signals using satellites that orbit the earth. The satellite uplink communication signal is transmitted from one or more ground stations to the satellite and then retransmitted by the satellite as a downlink communication signal to another satellite or to the earth. This covers a desired reception area according to a specific application. Typically, uplink and downlink signals are transmitted on different frequencies.

  Satellite communication systems can incorporate multi-beam array antennas that use beamforming techniques. Such an array antenna is very useful for forming multiple simultaneous beams covering a wide angle. Receive beamforming is a process by which signals received from several different antenna elements are combined to enhance the desired signal and attenuate or reduce the unwanted signal. As shown in FIG. 1a, a plurality of input signals from the antenna elements 1 to n (not shown) to the reception beam forming unit respectively have continuous values synthesized by applying a series of weighting factors w1 to wn. Have. As a result, each beamformer output generates a signal representing a potentially different vector that combines the input signals. By adjusting a series of weighting factors w1-wn applied to the input signal, the beamformer can dynamically change the direction and content of some or all of the beams generated by the antenna array. . Due to the directivity of the output beam, most of the spatially separate beams from a series of receive antenna elements can reuse the same frequency spectrum. Thus, beamforming techniques allow a substantial increase in the number of users supported by a given satellite throughout a given service area.

  Similarly, as shown in FIG. 1b, transmit beamforming is performed on the transmit signal for each element 1-n of the antenna array to control the direction and content of some or all of the beams transmitted by the antenna array. With application of weighting factors w1-wn.

  The weighting factor may be based on any of a variety of known techniques used for beamforming and can be applied to the incoming signal using any suitable analog or digital means. Analog RF beamforming systems adjust the phase and / or amplitude of the signal at the RF or intermediate frequency (IF) stage of the transmitter and / or receiver chain associated with the antenna. On the other hand, a digital beam forming system digitally adjusts the phase and / or amplitude of a signal. In a digital beamforming receiver, the signal is processed after analog-to-digital conversion. In a digital beamforming transmitter, the signal is processed before digital-to-analog conversion. In particular, digital beamforming is advantageous because of the reproducibility of digital signals and processing and the common and stable nature of digital processing systems for beamforming signal weighting operations.

  In satellite communication systems, constant efforts are being made to reduce the overall computational complexity and increase efficiency. Typically, the antenna array used in such a system consists of a myriad of individual array elements. Since conventional beamforming techniques require the application of different weighting functions to signals sent to or received from every element of the array, the amount of processing requirements that arise increases in proportion to the size of the array. .

  In many array systems, the majority of the beam formed uses only a portion of the antenna array elements due to the nature of the antenna system. In an array fed reflector (AFR) antenna, the beam is formed after reflecting the signal from the large antenna, even if the feed array is not directed to the target beam position. The effect of the large reflector is to increase the apparent size of the feed array and improve the spatial resolution of the beam forming process. In some configurations, this means that each individual element in the array is responsible for a portion of the overall coverage area of the antenna system. In such a system, unused array elements are typically assigned a weighting function of 0 in the beamforming process, but the system structure receives input from each of the individual element beams of the array. It is configured to receive and process. Thus, apart from the redundancy problem of many array elements, such systems still have unnecessary complexity.

  In order to reduce the number of inputs to the digital processor, it is known to divide the array into predefined subarrays and combine a plurality of physical antenna elements using analog techniques. This has the advantage of increasing the number of antenna elements for the same number of digital processor inputs or reducing the number of digital processor inputs for the same number of elements.

  Typically, receive and transmit beamforming are performed separately. Usually this is done by operating the same functional block in the opposite direction (ie by making all signal flows bidirectional and selecting one or the other depending on the mode). . Of course, it is also advantageous to provide a beamforming block that is unidirectional in nature, but that only performs either receive or transmit beamforming with the required minimum fitness. Can not.

  One object of the present invention is to reduce the complexity and processing requirements associated with beamforming techniques used in satellite communication systems.

  Another object of the present invention is to improve the efficiency of the beam forming structure used in the active antenna system. In this case, not all of the antenna elements are responsible for each beam.

  Yet another object of the present invention is to provide a single DSP design with both transmit and receive beamforming functions.

  In a first aspect, the present invention belongs to a beamforming system, which system is configured to process uplink signal channelization means and both transmit and receive uplink channel signals. And means for recombining a plurality of downlink channel signals. Since the same beamforming system can be used for both receive and transmit beamforming, a single DSP design with both transmit and receive beamforming functions can be realized. At this time, the same input and output interfaces exist and the same data flow exists. The number of inputs and outputs depends on the type of beamforming (receive or transmit), but the DSP structure is the same. Thus, a single DSP device can change either type of beamforming by changing only the number of inputs and outputs (or by enabling the required number of inputs and outputs from a larger set). Can also be used.

  According to a second aspect, the present invention belongs to a beamforming system, which inputs means for receiving samples of a plurality of signals and all sample signals associated with the same beamformed frequency band. Switching means for sending to a predetermined processing block; means for sequentially selecting a predetermined number of transmitted sample signals according to a predetermined criterion; and a signal selected with a predetermined fixed number of weighting factors Weighting means for applying to, a means for accumulating a plurality of weighted signals to form a composite signal, and means for selecting a plurality of signals from the composite signal and sending them to the appropriate output It has. Each sample includes one band of a plurality of frequencies.

  The system can be used for receive beamforming, where the received sample is a composite signal from multiple beams received at each of the multiple antenna elements, and the transmitted sample signal is the source of the signal. It is selected according to the beam. Alternatively, the system can be used for transmit beamforming, where the received samples are signals from multiple beams transmitted on each of multiple antenna elements, and the transmitted sample signal is the signal Are selected according to the antenna element to be transmitted.

  The beam forming technique of the present invention selects a signal that is related to the signal transmitted to each beam or to each element, with different distinct weighting functions conventionally required for each individual element of the antenna array. Replace with configured switching function. A smaller fixed number of weighting functions are then applied to the selected signal, and processing for a single frequency is performed on the same processing block for all of the elements. This substantially reduces the computational complexity of the beam forming process and facilitates frequency reuse. It also makes it easier to use more effective algorithms. Furthermore, the combination of switching functions facilitates maximum resilience to the selection of any part of the array antenna elements for subsequent beamforming processes.

  The present invention also belongs to a beamforming method, the method comprising: (a) receiving a plurality of signal samples; and (b) predetermining all sample signals associated with the same beamformed frequency band. Sending to the processing block, (c) sequentially selecting a predetermined number of transmitted sample signals according to a predetermined criterion, and (d) a signal with a predetermined determined number of weighting factors selected. (E) accumulating a plurality of weighted signals to form a composite signal, (c) repeating steps (c) to (e) a predetermined number of times, and (f) a signal from the composite signal Selecting and sending to the appropriate output. Each sample includes one band of a plurality of frequencies. The method can be used for receive beamforming, wherein step (a) comprises receiving a sample of the composite signal from a plurality of signals received at each of a plurality of antenna elements, and step (c) Comprises selecting a signal according to the beam from which the transmitted sample signal is derived. Alternatively, the method can be used for transmit beamforming, wherein step (a) comprises receiving samples of signals from a plurality of beams transmitted at each of a plurality of antenna elements, and c) comprises selecting a signal according to the antenna element to which the transmitted sample signal is transmitted.

  The present invention also belongs to a receive beamforming system, which has input means for receiving samples of a composite signal from a plurality of beams received by each of a plurality of antenna elements, and the same beamformed frequency. Switching means for sending all band-related sample signals to a given processing block; means for sequentially selecting a given number of sent sample signals according to the beam from which the signal originated; Weighting means for applying a predetermined and determined number of weighting factors to the selected signal, means for accumulating a plurality of weighted signals to form a composite signal, and selecting a signal from the composite signal And means for sending to an appropriate output. Each sample includes one band of a plurality of frequencies.

  In accordance with another aspect, the present invention belongs to a transmit beamforming system, the system comprising: an input means for receiving signal samples from a plurality of beams transmitted by each of a plurality of antenna elements; Switching means for sending all sample signals associated with the formed frequency band to a given processing block, and for selecting a given number of sent sample signals in order according to the antenna element to which the signals are transmitted Means for applying a predetermined and determined number of weighting factors to the selected signal, means for accumulating a plurality of weighted signals to form a composite signal, and a composite signal Means for selecting a signal from and sending it to an appropriate output. Each sample includes one band of a plurality of frequencies.

FIG. 2 is a simplified representation of a known receive and transmit beamforming system. FIG. 2 is a simplified representation of a known receive and transmit beamforming system. It is a block diagram showing the receiver system used with a satellite by this invention. FIG. 3 is a configuration diagram illustrating a preferred embodiment of the digital receive beamforming system shown in FIG. 2. FIG. 4 is a block diagram illustrating a transmission system with a beamforming system of the type shown in FIG. FIG. 4 is a block diagram illustrating a beamforming system of the type shown in FIG. 3 that can be used for both a receiving system and a transmitting system. FIG. 6 is a block diagram illustrating a modified embodiment of the present invention, showing a receive beamforming system in which each of the inputs to the beamforming system comes from two antenna elements. FIG. 4 is a block diagram illustrating another embodiment of the present invention comprising a plurality of receive beamforming systems, each of which is shown in FIG. 3, but not combined with the same input and output frame switch. It has the same core processor function. FIG. 4 is a block diagram illustrating another embodiment of the present invention comprising a plurality of receive beamforming systems, each beamforming system being used to process signals associated with a subset of antenna elements.

  Embodiments of the present invention will now be described for purposes of illustration with reference to the accompanying drawings.

  The following description of an embodiment of the present invention directed to a satellite antenna system is not intended to limit the invention, but illustrates its application or use.

FIG. 2 shows a block diagram of a satellite receiver system 20 according to a preferred embodiment of the present invention. Although the configuration diagram describes a satellite, the present system can also be applied to a base station or a radar system receiver. As shown in FIG. 2, the RF front end includes N antenna elements 22 1 to 22 N , and receives a plurality of transmitted RF signals. Each element is connected to a low noise amplifier (LNA) (not shown) as is known, and the received RF signal is amplified. The amplified element signals are sent to the down conversion mixer 24. The conversion to the intermediate frequency (IF) is performed using respective signals from a local oscillator (not shown). Next, the IF signal is converted into a digital signal by the A / D converter 26 and sent to the digital channelizer 28.

  Digital channelizer 28 implements a channel filter bank to divide the downconverted composite digital signal containing individual signals from each element of the antenna array into a predetermined number N of digital channel signals. The digital channelizer 28 can be considered as an analysis digital filter bank with each filter having a predetermined bandwidth. The digital channelizer 28 comprises a series of convolutional digital filters and a fast Fourier transform (FFT) processor. A convolutional digital filter uses multirate digital filter techniques such as multiplexing and summing, or polyphasing, to group multiple samples of a downconverted signal together, multiply the sample group by a convolution function, and then Efficiently implement a digital filter bank by sending samples to the FFT for conversion to N individual channel signals. Of course, however, the filter bank may be implemented using any of several different techniques.

  Thus, the channelizer 28 has the function of dividing the input bandwidth including individual IF signals independent of each other in frequency, phase and electrical amplitude into a plurality of time-parallel frequency output channels. In other words, the channelizer frequency splits or sorts the various frequencies within the combined IF bandwidth into fixed channel widths or ranges numbered 1 to N within the frequency. Of course, conversion to IF is not required for this process, and the channelizer may operate directly on the RF input bandwidth.

In this embodiment, the N inputs from the channelizer 28 to the beamformer 30 can be considered as time division multiplexing (TDM) of multiple samples. TDM means that individual data signals are transmitted continuously in time following the same signal path so that one signal path can be shared among a plurality of signals. Thus, for multiple frequencies, each TDM includes samples from one of antenna elements 22 1 to 22 N , and the timing of the samples in the various TDMs on the input is the same frequency band or the same The elements 22 1 to 22 N are selected so that they do not appear at more than one input at the same time. However, of course, the execution of TDM is not essential and various other transmission schemes can be envisaged.

The configuration and operation of the beam forming unit 30 in FIG. 2 will be described with reference to FIG. The beam forming unit 30 includes an input frame switch 32. The input frame switch 32 receives N input signals corresponding to N different antenna elements 22 1 to 22 N. Different frequencies in the received element signal represent that all signals in a single time have different frequencies at different times during the TDM frame period L TDM over a set of inputs. The input frame switch 32 is such that signals of the same beamformed frequency from all antenna elements 22 1 to 22 N are directed to a particular one of the F core processing blocks 34 1 to 34 F. The route of the signal from the array antennas 22 1 to 22 N is determined. Of course, the frequency in this case means a single frequency band from the channelizer 28. Each TDM sample input to the input frame switch is subjected to a different switching function and up to F signals of N inputs are sent to different core processors 34 1 to 34 F at each sample time, respectively. It is done. At a given sample time, the number of inputs routed may be less than F, but never exceeds F. If F <N, not all frequencies are used for beamforming, so only some channels are switched. If all frequencies are used for beamforming, the value of F must be at least equal to N. The switching operation is repeated in each frame so that the same switching function is applied to the same time slot in all frames. For each time slot in the TDM frame, each output signal is a duplicate of one of the multiple signals present at one of the N inputs.

Within each core processing block 34 1 -34 F , each signal sample routed at a particular frequency processed by that processing block is duplicated into a plurality of TDM signals routed to time switches 36 1 -36 M. The Here, the number M of switches is a parameter determined in advance according to the average of the number of elements 22 1 to 22 N to be beam-formed and the number of elements used for each beam. The functions of the time switches 36 1 to 36 M allow the signals output from the frame switch 32 to be rearranged in an arbitrary time slot order required for subsequent processing, and a plurality of input samples can be overlapped at different times. Each of the time switches 36 1 to 36 M stores the entire contents of the input TDM frame in a table. The data is then read from the table at program time to perform the required time ordering.

Beam forming is accomplished by selecting items from this table in a programmable order, as well as being performed individually in each of the frequency bands, as described below. Thereby, all the individual elements 22 1 to 22 N associated with a particular beam are selected and processed as described. The complete beam formed for a single frequency will probably use all of the antenna elements 22 1 to 22 N , so all of the element signals for this single frequency are required for multiple elements. Need to be processed together so that all combinations can be formed.

Initially, M at the same time are sequentially selected on each TDM frame slot L TDM so that all of the element signals for the first beam provide sufficient data to form the first beam. The The outputs of the time switches 36 1 to 36 M for the first beam are sent to a series of multipliers 38 1 to 38 M , and a programmable weighting factor is applied to each signal. Since the time switches 36 1 to 36 M for the first beam independently select samples, the signals on each multiplier 38 1 to 38 M at a particular time are not replicated. As described above, each weighting factor applies an appropriate phase and amplitude weight to the signal. By adjusting a series of weighting factors applied to each of the M input signals, the direction and content of the output beam can be dynamically changed. The outputs of the multipliers 38 1 to 38 M in the core processors 34 1 to 34 F are added together by an adder 40 to form a single value for each TDM sample.

Next, all of the element signals for the second beam are selected sequentially by time switches 36 1 -36 M and weighted as they are selected. The calculation results for the second beam are added together and output after adding the signals for the last element 22 associated with the beam. This process is repeated for the total number of beams formed.

If the number of element signals required to form the beam is greater than the number M of multiplexing operations performed on each TDM frame slot L TDM , an additional accumulation stage is performed in the accumulator 42. This accumulation occurs over successive feedback in time slot A of each frame so that a total of M × A signal samples are selected and a plurality of weighted element signals are accumulated. The value of A is programmable and depends on the number of element signals required to form the beam. The value of A can be determined dynamically according to traffic to some extent. Since the total TDM frame length is fixed, the majority of samples can reduce the number of different outputs that can be formed. Changing the value of A does not change the amount of hardware required. On the other hand, changing the value of M changes the number of time switches and multipliers required.

  If M × A sufficient element signal samples to form a beam having the desired characteristics are weighted, the addition result is passed to the output time switch 44. The output time switch 44 is configured to rearrange a plurality of beam signals in the TDM. The main purpose of the output time switch 44 is to select only useful signals by the multiply / add function and to output those signals simultaneously. Thereby, those signals can be delivered to the required destination. A plurality of output signals from the output time switch 44 are sent to the output frame switch 46. And then they are sent to the appropriate channel combiner 44 (shown in the figure) to form the output signal from the beamforming processor.

  As shown in FIG. 3, the beam forming unit includes F core processors, each of which generates a series of beams of a specific frequency. The value of M is fixed for each processing block, but does not have to be the same in all of the F core processors. Further, A is programmable and may be different for all core processors. For example, the global beam covers the entire satellite coverage area typically used by satellite operators for signaling to terminals for call initiation and termination. That the beam covers all of the coverage area means that there is overlap and interference between them, so that the frequency used for that beam cannot be reused for other beams. Typically, this will use the same frequency for many beams, for every few elements, or for every few (sometimes just one) beam using many or all elements. In such a case, if the TDM length is smaller than the number of elements, M = 1 is satisfied. However, the value of A must be much larger because more elements are used for the processing block that forms the global beam. A large amount of frequency reuse tends to use few elements per beam, so A is smaller for the same M. For a small amount of frequency reuse, more elements are used and A must be large.

  The use of a fixed number of weighting functions for a single frequency makes the process considerably easier so that the complexity associated with sharing resources (multiple operations) between two or more frequencies is avoided. . Of course, a fixed number of weighting functions can be shared between a small number of frequencies, or multiple fixed numbers can be used for a single frequency. By maintaining a fixed number, many such functions can be performed without the required interconnections, avoiding complexity.

  Following the channelizer 28 and beamformer 30, the demodulator demodulates the digital signal, and then the demodulated signal bits are converted into data packets and sent to the appropriate destination. The destination may be another subscriber link, a cross link, or a feeder link. Data packets are routed and then the downlink process described above occurs. The downlink process varies depending on what type of link (eg, subscriber, cross, or feeder link) is used.

  As explained above, the present invention allows the use of a fixed number of weighting functions for each frequency. This can use a large number of beams with a small number of elements associated with each beam, or a small number of beams with a large number or all elements associated with each beam. Not all elements contribute to all beam coverage areas, but in many cases one beam uses all elements. Also, as described above, since the global beam covers all of the coverage area, the frequency used for the beam cannot be reused for multiple beams due to overlap and interference between them. Typically, this results in a small number of elements using a large number of beams using the same frequency, or a small number (sometimes only one) of using many or all elements.

  In order to illustrate the computational complexity reduction achieved by the system of the present invention, an example is given below.

The satellite has an antenna with 120 (N) elements and forms a total of 30 beams in each of the 20 frequency bands. In a conventional digital beam forming unit in which beam weighting is applied to all elements, the total number of weighting operations is as follows.
120 × 30 × 20 = 72,000

In the beam forming unit of the present invention, if each beam is formed by only 24 elements, the number of weighting operations is given by the following equation.
24 × 30 × 20 = 14,440

This is the TDM length L TDM of 24 (A × M) elements per beam, 20 (F) frequency channels (one per frequency), and 180 (30 beams × A = TDM length). Can be implemented by a beamformer with M = 4 time switches that select samples over A = 6 first time slots of each frame.

FIG. 4 shows a block diagram of a subscriber unit transmitter system 50 according to a preferred embodiment of the present invention. The transmitter system includes a down conversion mixer 52. Here, conversion of the RF transmission signal to an intermediate frequency (IF) is performed using each signal from a local oscillator (not shown). The IF signal is converted into a digital signal by the A / D converter 54 and sent to the channelizer combiner 56, and then sent to the beam forming unit 58. After beam forming, the beam is sent to a respective digital channel combiner, where the combined digital signal containing the individual signals transmitted by each element of the antenna array is divided into a predetermined number N of digital channel signals. . These channel signals are converted to analog signals by a D / A converter and up-converted to RF before being transmitted by the respective elements 60 1 to 60 N of the antenna 60.

The transmit beamforming according to the preferred embodiment of the present invention will now be described with reference again to FIG. As described above, transmit beamforming involves the application of weighting factors to the transmit signal for each element of the array. The input to the beam forming unit 30 is various channel signals to be transmitted, and all channel signals having a single frequency band at the array element outputs 60 1 to 60 N are transmitted through the input frame switch 32 to a predetermined core It is sent to the processing block 34 1 ~34 F.

Within the appropriate processing blocks 34 1 -34 F , the delivered signal is replicated with a number of time switches 36 1 -36 M in a manner similar to that described above for the receive beamformer 30. In this case, the number of switches M is a parameter corresponding to the number of beams formed on a single frequency from each element. In addition, the signals are reordered as described above with respect to receive beamforming.

Each TDM samples, all the signals from the time switch 36 1 ~ 36 M associated with the first antenna element 60 1, along with selected sequentially, is sent to a series of multipliers 38 1 to 38 DEG M. The signals are then weighted there and then added together by an adder 40. This is then repeated for signals relating to each of the individual antenna elements 60 2 to 60 N. In this case, the addition of the weighted signal for each element facilitates the reuse of the frequency compared to the combination of elements as in the case of the reception beam forming described above.

If the number of beams on one frequency for transmitting to each element 60 1 to 60 N exceeds the number of multiplication operations M performed on each TDM frame slot L TDM , a total of A × M weighted Accumulation over A sample periods is required so that the element signal is accumulated. The value of A is not only a programmable, determined by the number of beams transmitted by each element 60 1 to 60 N. The output of this second stage accumulation is a TDM that contains the transmitted signals for all of the array elements 60 1 to 60 N. The combined TDM is sent to an output time switch 44 that is configured to reorder the beam signals within the TDM. In this case, the reordering of the signals ensures that the frequency signals are delivered to the appropriate elements 60 1 to 60 N , so that each element and each frequency does not repeat within any TDM frame slot. An output signal from the output time switch stage 44 is sent to the output frame switch 46. There, the signal is then delivered to the appropriate channel combiner to form the output signal from the beamforming processor.

  Since the beam forming unit has the same beam forming for both reception and transmission, for example, a single DSP design having both transmission and reception beam forming functions as shown in FIG. 5 can be realized. is there. The number of inputs and outputs depends on the type of beamforming (receive or transmit), but the DSP structure is the same. Thus, a portion of the DSP device can be used for either type of beamforming only by changing the number of inputs and outputs (or by enabling the required number of inputs and outputs from a larger set). it can. However, this single DSP can only be realized if the beamformer has the same input and output interfaces and operates with the same data flow for both reception and transmission.

  Of course, a DSP may use both transmit and receive beamforming simultaneously. Some inputs are from the antenna array, and some inputs are from the feeder uplink. At the same time, some outputs are to the antenna array and some outputs are to the feeder downlink. In this case, the single beam forming unit can be used to simultaneously perform reception beam formation from the antenna array to the feeder link and transmission beam formation from the feeder link to the antenna array. However, beamforming does not occur at all inputs and outputs, and there is no connection from the beamformed input to the beamformed output. Some of the F core processing blocks are used for reception and some are used for transmission.

  A modified embodiment of the present invention for receiving beam formation will now be described. This is used when the TDM frame length is greater than the number of time slots A increased by the number of beams. Each core processing block is configured to process signals for two or more frequency bands. In contrast to the previous example, it is assumed that the TDM frame length is 180 (A × 30 (the number of beams on the same frequency)), and only one frequency can be used. Assume that the TDM frame length is 360 and two frequency bands are shared by one core processor. One of the two frequencies is used for the first part of the TDM frame and the other is used for the second part. In this case, each time slot on multiple inputs to the input frame switch 32 must not contain the same frequency as other inputs delivered to the same core processor.

  For transmit beamforming, the equivalent condition is that the TDM frame length is greater than the number of time slots A increased by the number of elements. Each core processing block can then be used to generate element signals in more than one frequency band. Of course, any suitable number of frequencies can be processed by a single core processor depending on system parameters. In this case, each time slot on multiple outputs from the output frame switch 46 should not contain the same frequency.

  Also, for receive beamforming, if the TDM frame length is smaller than the number of time slots required for a single frequency, for example 90 instead of 180, each beam uses A = 6 TDM time slots. Therefore, time is insufficient to form a total of 30 beams in the frame. Given that the same input signal is sent to two core processors, each processor can form half of the beam for the entire element. No additional weighting operations are required, the only difference being that the operations are shared among multiple core processors. For transmit beamforming, the transmitted set of beam signals is replicated to the two core processors. Each processor generates an entire beam for half of the elements. Of course, any suitable number of core processors can be used to process a single frequency, depending on the system parameters.

  Another embodiment of the present invention is shown in FIG. Here, a single beam former is used. For receive beamforming, each of the N inputs to the input frame switch 32 is input from two elements rather than from a single element, as shown in FIGS. Signals from the two elements are sent to the dual channelizer. Thus, the various frequencies within those IF bandwidths are frequency divided into fixed channel widths or capacities with frequencies numbered from 1 to N. This configuration changes the TDM condition on the signal at the input frame switch, but the processing at the beam forming unit is the same. Instead of including the same frequency from the same element, each time slot on multiple inputs must now not include the same frequency from any of the element groups connected to the same input. This is a combination of an input source and a core processor and should appear only once for every N inputs per time slot. In the illustrated embodiment, two elements are used for each input to the input frame switch, but it should be understood that any suitable number of elements can be used for each input. For transmit beamforming, the beamformer output is delivered to a group of elements rather than to a single element.

  With reference to FIG. 7, another embodiment of the present invention will be described. In this embodiment, multiple beamformers, each of the type shown in FIG. 3, are provided, but a set of core processor functions are not combined in the same input and output frame switch. For receive beamforming, each channelizer must deliver some of its signals to each of the beamformers, but on the beamformer output they do not require any interconnection. For transmit beamforming, the input to the beamformer can be input from individual sources, but the outputs must be coupled to the same channel combiner. Although only two beam formers are shown in FIG. 7, it will be appreciated that any number of beam formers appropriate to the system parameters can be used to process a set of channels. This implementation is used when the requested amount of computation (multiplication and accumulation stages) and storage (time switch stage) cannot be physically contained within a single physical block (one integrated circuit). . Thus, multiple ICs can be used, each IC processing a beamformed frequency fragment.

  A further embodiment of the present invention will now be described with reference to FIG. Here, multiple beam formers are provided, each beam former being used to process signals associated with a subset of elements. If the beamformer's throughput is insufficient to process an array with a certain number of elements (eg, due to a lack of physical inputs), they will have multiple elements per beamformer input. Apply.

  For receive beamforming, in this case, the N inputs to the frame switch 32 correspond to N different groups of antenna elements that share a common processing means. In the above example of a satellite having an antenna with 120 elements that form a total of 30 beams in each of the 20 frequency bands, half of the elements are transmitted to the first beam former for each beam. At the same time, the other half is transmitted to the second beam forming unit. Each beam forming unit executes 12 (maximum number of elements per beam) × 30 (number of beams) instead of executing 720 times of weighting for each frequency. The outputs of the two beamformers are then summed, and using the same number of weights and a minimum amount of external hardware, the result is numerically identical to the original beamformer. This requires an additional processing stage to combine multiple beamformer functions to process all elements. This embodiment requires repetition of all beamformer components, not just the core processing block. Each complete beamformer is configured to process signals for half of the plurality of antenna elements, and the only combination required is addition, not weighting, which is more complex to implement. For transmit beamforming, the input signal is replicated in two beamformers, and each beamformer processes all the beams for half of the elements. Addition at the output is supplemented by duplication at the input.

  Of course, while the time switch operation used to continuously select the element signal for each beam formed supplements the rest of the process, there are many other ways in which this operation can be performed. For example, instead of TDM and time switches, crossbar (or other) switches can perform channel relocation. In this case, the rearrangement is performed between a plurality of different outputs, not between a plurality of different time slots during the same output. This arrangement is suitable for analog mounting due to problems in forming an analog TDM.

  In the above embodiment, a digital beam forming system is used, but it should be understood that the present invention is applicable to an analog beam forming system as well. Furthermore, the present invention can be applied to a sonar system using a frequency other than RF, for example, an audio frequency.

22 1 , 22 N antenna elements 24 1 , 24 N down conversion mixers 26 1 , 26 N A / D converters 28 1 , 28 N digital channelizer 30 beam forming unit 32 input frame switch 34 1 , 34 F core processing block 36 1 , 36 M input time switch 38 1 , 38 M multiplier 40 adder 42 accumulator 44 output time switch 46 output frame switch

Claims (23)

  1. A beam forming system,
    Input means for receiving a plurality of signal samples;
    And switching means for sending all the sample signal containing the same frequency band formed bicycloalkyl over beam to a predetermined processing block of each
    Means for sequentially selecting a predetermined number of transmitted sample signals according to a predetermined criterion;
    Weighting means for applying a predetermined determined number of weighting factors to the selected signal;
    Means for accumulating a plurality of weighted signals to form a composite signal;
    Means for selecting the composite signal and sending the composite signal to an appropriate output;
    A beam forming system, wherein each sample includes a band of a plurality of frequencies.
  2. The received sample is a composite signal from multiple beams received by multiple antenna elements,
    The beam forming system according to claim 1, wherein the transmitted sample signal is selected according to the beam from which the signal was derived.
  3. The received samples are signals from multiple beams transmitted by multiple antenna elements,
    The beamforming system according to claim 1, wherein the transmitted sample signal is selected according to the antenna element to which the signal is transmitted.
  4. The means for sequentially selecting a predetermined number of transmitted sample signals is configured to perform a selection whose number of times depends on the number of antenna elements and the number of elements per beam. The beam forming system according to claim 2.
  5. Means for sequentially selecting a predetermined number of transmitted sample signals are configured to perform a selection that is determined by the number of beams formed on a single frequency from each antenna element . The beam forming system according to claim 3.
  6. The selection of a predetermined number M of signal samples is repeated a predetermined number of times A,
    Multiple sets of M signal samples are selected by repeatedly in A times, beamforming system according to any one of claims 2 to 5, characterized in that it comprises a different signal samples from each other.
  7.   7. The beam forming system according to claim 6, wherein the number of times the selection of the signal is repeated depends on the number of basic signals required to form the beam.
  8. 7. The beam forming system according to claim 6, wherein the number of times the selection of the signal is repeated depends on the number of beams transmitted at each element 60 1 to 60 N.
  9. Beamforming system according to claim 1, 2, 4 or 7, and further comprising a plurality of processing blocks which respectively generate a series of beams for each of the frequency bands.
  10. A plurality of processing blocks for generating a series of antenna element signals for each of the frequency bands of the sample signal sent to the processing block, respectively. 9. The beam forming system according to 6 or 8.
  11. And characterized in that the means for sequential selecting a predetermined number of transmitted sample signal, is configured to perform a selection that different from each other in two or more processing blocks of the plurality of processing blocks The beam forming system according to claim 9 or 10.
  12. Weighting coefficient number the is predetermined, determined to be applied to the selected signal, claim 9, characterized in that are different from each other in two or more processing blocks of the plurality of processing blocks, or The beam forming system according to claim 11.
  13. The input means is configured to receive a stream of TDM frames of signal samples;
    The beam forming system according to any one of claims 1 to 12, wherein the switching means is configured to apply a different switching function to each time slot of each TDM frame.
  14. 14. The beam forming system according to any one of claims 1 to 13, wherein the switching means is configured to send all sample signals associated with a plurality of frequency bands to the same processing block.
  15. Switching means is configured to send all sample signal containing the same frequency band formed bicycloalkyl over beam into a plurality of processing blocks,
    14. Each of a plurality of subsets constituting all sample signals including the same beamformed frequency is sent to one processing block of the plurality of processing blocks . 2. The beam forming system according to item 1.
  16. A system in which a plurality of beam forming systems according to any one of claims 1 to 15 are combined,
    Each beamforming system processes a portion of a set of beamformed frequency bands,
    Consequently, the entire beamformed frequency band is processed by a complete beamforming system.
  17. A system according to any one of claims 1, 2, 4, 6, 7, and 9, and a combination of a plurality of beam forming systems according to any one of claims 11 to 15 , or a system according to claim 16 ,
    The input means of each beam forming system is configured to receive sample signals from a plurality of beams received by a predetermined number of antenna elements of the plurality of antenna elements;
    The system further comprising means for combining the outputs of each beamforming system.
  18. A system comprising a combination of a plurality of beamforming systems according to any one of claims 1, 3, 5, 6, and 8, and 10 to 15 , or a system according to claim 16 ,
    The input means of each beamforming system is configured to receive the same sample of signals for multiple beams for each beamforming system ;
    A system, wherein each beam forming system is configured to process a beam transmitted by some of the plurality of elements.
  19.   19. A beam forming system according to any one of the preceding claims, wherein the beam forming system is configured to process both transmit and receive channel signals with a single digital processor.
  20. Beamforming system according to claim 19, characterized in that the act of processing the operation and the reception channel signal for processing the transmission channel signal by a single digital processor are simultaneously performed.
  21. A beam forming method comprising:
    (A) receiving a plurality of signal samples;
    (B) the steps of sending all the sample signal containing the same frequency band that is bi over beam formed to a predetermined processing block of each
    (C) sequentially selecting a predetermined number of transmitted sample signals according to a predetermined criterion;
    (D) applying a predetermined determined number of weighting factors to the selected signal;
    (E) accumulating a plurality of weighted signals to form a composite signal;
    Repeating steps (c) to (e) a predetermined number of times to form a plurality of combined signals;
    (F) selecting a synthesized signal from the plurality of synthesized signals and sending the selected synthesized signal to an appropriate output;
    A beam forming method, wherein each sample includes one band of a plurality of frequencies.
  22. Step (a) comprises receiving a sample of the composite signal from a plurality of beams received by a plurality of antenna elements;
    The beamforming method according to claim 21, wherein step (c) comprises selecting a signal according to the beam from which the transmitted sample signal is derived.
  23. Stage (a) comprises receiving samples of signals from a plurality of beams transmitted by a plurality of antenna elements;
    22. The beamforming method according to claim 21, wherein step (c) comprises selecting a signal according to an antenna element through which the transmitted sample signal is transmitted.
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EP06270108 2006-12-20
EP06270108.1 2006-12-20
PCT/GB2007/050763 WO2008075099A1 (en) 2006-12-20 2007-12-17 Beamforming system and method

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GB2324912B (en) * 1994-04-18 1999-02-24 Int Mobile Satellite Org Beam-forming network
US5754138A (en) * 1996-10-30 1998-05-19 Motorola, Inc. Method and intelligent digital beam forming system for interference mitigation
US6122260A (en) * 1996-12-16 2000-09-19 Civil Telecommunications, Inc. Smart antenna CDMA wireless communication system
US5764187A (en) * 1997-01-21 1998-06-09 Ail Systems, Inc. Direct digital synthesizer driven phased array antenna
WO2002069443A1 (en) * 2001-02-28 2002-09-06 Itt Manufacturing Enterprises, Inc. Integrated beamformer/method architecture
US8923785B2 (en) * 2004-05-07 2014-12-30 Qualcomm Incorporated Continuous beamforming for a MIMO-OFDM system
KR20060130806A (en) * 2005-06-08 2006-12-20 삼성전자주식회사 Apparatus and method for transmitting and receiving in close loop mimo system by using codebooks

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