An array full-duplex system

Abstract

The present application discloses an array full-duplex system, comprising: a transmitting array unit, a receiving array unit and a signal processing unit; the transmitting array unit comprises J transmitting array elements, the receiving array unit comprises K receiving array elements, the signal processing unit comprises K first digital filters, and the signal processing unit is used to control the array full-duplex system to enter an external interference channel test mode to obtain a first channel response; and control the array full-duplex system to enter a radio frequency cancellation channel test mode to obtain a second channel response; according to the first channel response and the second channel response, a first filter coefficient is obtained and loaded into a corresponding first digital filter; the array full-duplex system is controlled to enter a normal working mode, and each first digital filter is used to reconstruct a baseband transmitting signal, obtain a reconstructed signal and send it to a corresponding receiving array element, and the baseband signal is offset in a second coupler of each receiving array element using a radio frequency cancellation signal conditioned by the reconstructed signal.

Description

Technical Field

[0001] The present application relates to the technical field of signal processing, and in particular to an array full-duplex system. Background Art

[0002] The In-Band Full-Duplex (IBFD) system enables radio terminals to transmit and receive radio signals at the same time and in the same frequency band. According to the number of antennas, the In-Band Full-Duplex system can be divided into a single-input single-output (SISO) full-duplex system and an array (MIMO) full-duplex system. The array full-duplex system is also called a multiple-input multiple-output full-duplex system, which includes multiple transmitting antennas and multiple receiving antennas. Compared with the SISO full-duplex system, the array full-duplex system has greater technical challenges, which are as follows:

[0003] First, there are not only strong self-interference signals, but also mutual interference signals, and the circuit structure for canceling interference signals is more complicated. Second, the total suppression ratio is required to be higher, which is usually expressed by the equivalent omnidirectional isolation (Effective Isotropic Isolation, abbreviated as EII). The equivalent omnidirectional isolation increases with the increase of the number of array channels. Taking 8 signal channels as an example, the equivalent omnidirectional isolation is usually required to reach more than 145dB, while the equivalent omnidirectional isolation of the single-input single-output full-duplex system is usually around 120dB. Third, the array full-duplex system has problems such as nonlinear spurious and noise caused by power amplifiers, and the manifestation is more complicated and the cancellation cost is greater.

[0004] In view of the above problems, the aperture-level array full-duplex system (ALSTAR) with a split-transmitting and receiving array architecture is the most representative in the prior art. The core idea of ​​ALSTAR is to adjust the strong interference signals of each receiving unit of the transmitting array coupled to the receiving array to zero respectively through adaptive transmit beamforming and digital signal processing methods, so that the interference power of each receiving unit is less than the maximum level of the receiver while maintaining high sensitivity, ensuring that it will not be clamped or saturated, and reducing the self-interference from each transmitting unit through receiving adaptive beamforming. However, ALSTAR has at least the following problems:

[0005] First, whether adjusting transmit adaptive beamforming or receive adaptive beamforming, the gain and even the directivity of the original directional beam will be sacrificed;

[0006] Second, it may increase the sidelobe leakage of the transmit or receive beam;

[0007] Third, as the number of array channels increases, the computational cost of beamforming constraints and optimization increases significantly, and can even become overwhelming.

[0008] Fourth, the transmit adaptive beamforming method and the receive adaptive beamforming method are not robust and are prone to divergence;

[0009] Fifth, the degree of freedom of transmit adaptive beamforming or receive adaptive beamforming is limited. Summary of the invention

[0010] In view of the problems existing in the above-mentioned ALSTAR array full-duplex system, an embodiment of the present application provides an array full-duplex system to overcome at least one of the above-mentioned problems.

[0011] The present application embodiment adopts the following technical solutions:

[0012] The embodiment of the present application provides an array full-duplex system, including: a transmitting array unit, a receiving array unit and a signal processing unit; the transmitting array unit includes J transmitting array elements, each transmitting array element includes a first transceiver, a first coupler and a transmitting antenna, the receiving array unit includes K receiving array elements, each receiving array element includes a second transceiver, a second coupler and a receiving antenna, J and K are positive integers not less than 2, the receiving array unit can receive a signal of interest and an interference signal, the interference signal includes a baseband signal, the working mode of the array full-duplex system includes a channel test mode and a normal working mode, the channel test mode includes an external interference channel test mode and a radio frequency offset channel test mode, the signal processing unit includes K first digital filters, the K first digital filters correspond to the K receiving array elements one by one, and the signal processing unit is used to:

[0013] Controlling the array full-duplex system to enter the external interference channel test mode to obtain a first channel response of the external interference channel; and controlling the array full-duplex system to enter the radio frequency cancellation channel test mode to obtain a second channel response of each radio frequency cancellation channel;

[0014] Obtaining first filter coefficients of each first digital filter according to the first channel response and the second channel response, and loading the first filter coefficients into the corresponding first digital filter;

[0015] The array full-duplex system is controlled to enter the normal working mode. When a baseband transmission signal is transmitted through the receiving array unit and a signal is received through the receiving array unit at the same time, each first digital filter is used to reconstruct the baseband transmission signal, and the reconstructed baseband transmission signal is obtained and sent to the corresponding receiving array element. In the second coupler of each receiving array element, the baseband signal in the interference signal is canceled by using the radio frequency cancellation signal conditioned by the reconstructed baseband transmission signal.

[0016] At least one of the above-mentioned technical solutions adopted in the embodiments of the present application can achieve the following beneficial effects: in the embodiments of the present application, K first digital filters are designed in the signal processing unit, and the K first digital filters are made to correspond one-to-one with the K receiving array elements, and the first filter coefficients of the K first digital filters are obtained by controlling the array full-duplex system to enter the external interference channel test mode and the RF cancellation channel test mode. In this way, after the array full-duplex system enters the normal working mode, the K first digital filters can be used to reconstruct the baseband transmission signal, and the reconstructed signal can be sent to the corresponding receiving array, so that the baseband signal can be cancelled in the second coupler of each receiving array element using the RF cancellation signal conditioned by the reconstructed baseband transmission signal, so as to cancel most of the baseband signals in the interference signal.

[0017] In the interference signal cancellation process, the embodiment of the present application does not need to restrict the transmit and receive beamforming, so there are no related problems caused by the limited freedom of the transmit and receive beamforming. In addition, the embodiment of the present application performs a signal reconstruction operation in the digital domain, and the reconstruction operation is for the baseband signal. Therefore, the signal reconstruction process will not affect the signal transmission process, thereby ensuring that the array full-duplex system can perform signal reception and transmission processing in the same frequency band at the same time. Also, because the embodiment of the present application performs channel-level conditioning on the reconstructed signal through the receiving array element, rather than directly performing amplitude and phase processing on the reconstructed signal itself, it is not affected by the signal waveform and bandwidth, and can adapt to various waveforms such as fixed frequency, frequency hopping, and pulse. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0019] Figure 1 A schematic diagram of the system structure of an array full-duplex system entering an external interference channel test mode shown in one embodiment of the present application;

[0020] Figure 2 A schematic diagram of the system structure of an array full-duplex system entering a radio frequency cancellation channel test mode shown in one embodiment of the present application;

[0021] Figure 3 A schematic diagram of the system structure of an array full-duplex system entering a digital cancellation channel test mode shown in one embodiment of the present application;

[0022] Figure 4 A schematic diagram of the system structure of an array full-duplex system entering a normal working mode shown in one embodiment of the present application;

[0023] Figure 5 A schematic diagram of a processing flow of transmit beamforming shown in one embodiment of the present application;

[0024] Figure 6 This is a schematic diagram of a processing flow of receive beamforming shown in an embodiment of the present application;

[0025] Figure 7 It is a schematic diagram of the structure of a transceiver shown in one embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0027] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0028] The array full-duplex system has two structural forms, one is a form in which the receiving array elements and the transmitting array elements are separated, and the other is a form in which the receiving array elements and the transmitting array elements are shared. The shared form means that the receiving array elements and the transmitting array elements share the same set of antennas, and the separated form means that the receiving array elements and the transmitting array elements have their own independent antennas. For the array full-duplex system in which the receiving array elements and the transmitting array elements are separated, in order to solve the problem caused by the limited freedom of the receiving and transmitting waveforms of the ALSTAR array full-duplex system, the basic technical concept of the present application is: designing the working mode of the array full-duplex system to support the channel test mode and the normal working mode, calculating the first filter coefficients of K first digital filters in the channel test mode, and reconstructing the baseband transmit signal using the K first digital filters, and using the RF cancellation signal conditioned by the reconstructed signal to cancel the baseband signal in the corresponding receiving array element, so as to cancel most of the baseband signals in the interference signal.

[0029] Preferably, the present application also calculates the second filter coefficients of J second digital filters in the channel test mode, so as to use the J second digital filters to reconstruct the feedback baseband signal to obtain the baseband cancellation signal to cancel the nonlinear signal and the noise signal, and further cancel the residual baseband signal.

[0030] Further preferably, the present application also designs an adaptive filter, which cancels the residual interference signal through the adaptive filter, and cancels the interference signal to the greatest extent through the above-mentioned three-stage cancellation processing. During the entire interference signal cancellation process, no additional adjustment of the transmit waveform forming and the receive beam forming is required, thereby overcoming the problems existing in the ALSTAR array full-duplex system.

[0031] Figure 1 This is a schematic diagram of the system structure of an array full-duplex system entering an external interference channel test mode shown in an embodiment of the present application. Figure 2 This is a schematic diagram of the system structure of an array full-duplex system entering a radio frequency cancellation channel test mode shown in one embodiment of the present application. Figure 4 This is a schematic diagram of the system structure of an array full-duplex system entering a normal working mode shown in an embodiment of the present application, combined with Figure 1 , Figure 2 and Figure 4 As shown, an embodiment of the present application provides an array full-duplex system, including: a transmitting array unit, a receiving array unit and a signal processing unit.

[0032] The transmitting array unit includes J transmitting array elements, each transmitting array element includes a first transceiver, a first coupler and a transmitting antenna, and the receiving array unit includes K receiving array elements, each receiving array element includes a second transceiver, a second coupler and a receiving antenna, and J and K are positive integers not less than 2.

[0033] The receiving array unit is capable of receiving a signal of interest (SOI) and an interference signal, wherein the interference signal includes at least a baseband signal. The working modes of the array full-duplex system include a channel test mode and a normal working mode, wherein the channel test mode includes an external interference channel test mode and a radio frequency offset channel test mode, wherein the signal processing unit includes K first digital filters, wherein the K first digital filters correspond one-to-one to the K receiving array elements, and the one-to-one correspondence between the first digital filter and the receiving array element can be understood as the output of the first digital filter being connected to the baseband signal transmitting end of the second transceiver of the corresponding receiving array element.

[0034] The external interference channel of the embodiment of the present application is used to transmit the transmission signal of the transmitting array unit to the second coupler of the K receiving array elements of the receiving array unit through the external physical space, and the RF cancellation channel is used to transmit the output signals of the K first digital filters to the second coupler of the receiving array element corresponding to each first digital filter.

[0035] In the embodiment of the present application, the signal processing unit is used to:

[0036] Controlling the array full-duplex system to enter an external interference channel test mode to obtain a first channel response of the external interference channel; and controlling the array full-duplex system to enter a radio frequency offset channel test mode to obtain a second channel response of each radio frequency offset channel; here, there is no strict execution order restriction for the external interference channel test mode and the radio frequency offset channel test mode;

[0037] Obtaining first filter coefficients of each first digital filter according to the first channel response and the second channel response, and loading the first filter coefficients into the corresponding first digital filter;

[0038] The array full-duplex system is controlled to enter a normal working mode. When a baseband transmission signal is transmitted through a receiving array unit and a signal is received through the receiving array unit at the same time, each first digital filter is used to reconstruct the baseband transmission signal, and the reconstructed baseband transmission signal is obtained and sent to the corresponding receiving array element. In the second coupler of each receiving array element, a radio frequency cancellation signal conditioned by the reconstructed baseband transmission signal is used to cancel the baseband signal in the interference signal.

[0039] like Figure 1 It can be seen that in this embodiment, K first digital filters are designed in the signal processing unit, and the K first digital filters are made to correspond one-to-one with the K receiving array elements. The first filter coefficients of the K first digital filters are obtained by controlling the array full-duplex system to enter the external interference channel test mode and the RF cancellation channel test mode. In this way, after the array full-duplex system enters the normal working mode, the K first digital filters can be used to reconstruct the baseband transmission signal, and the reconstructed signal can be sent to the corresponding receiving array, so that the baseband signal can be cancelled in the second coupler of each receiving array element using the RF cancellation signal conditioned by the reconstructed baseband transmission signal, so as to cancel most of the baseband signals in the interference signal.

[0040] In the interference signal cancellation process, the present embodiment does not need to restrict the transmit and receive beamforming, so there are no related problems caused by the limited freedom of the transmit and receive beamforming. In addition, the present embodiment performs a signal reconstruction operation in the digital domain, and the reconstruction operation is for the baseband signal. Therefore, the signal reconstruction process will not affect the signal transmission process, thereby ensuring that the array full-duplex system can perform signal reception and transmission processing in the same frequency band at the same time. Also, because the embodiment performs channel-level conditioning on the reconstructed signal through the receiving array element instead of directly performing amplitude and phase processing on the reconstructed signal, it is not affected by the signal waveform and bandwidth and can adapt to various waveforms such as fixed frequency, frequency hopping, and pulse.

[0041] As mentioned above, the interference signals received by the receiving array unit include not only the baseband signal, which accounts for a large proportion, but also some nonlinear signals and noise signals. The RF cancellation signal can cancel most of the baseband signals in the interference signal. After the RF cancellation, the interference signal also includes the residual baseband signal, as well as the nonlinear signal and noise signal, which account for a small proportion.

[0042] To address this problem, in some embodiments of the present application, Figure 3 As shown, the signal processing unit further includes J second digital filters, and the J second digital filters correspond to the J transmitting array elements one-to-one. The one-to-one correspondence between the second digital filter and the transmitting array element can be understood as the input of the first digital filter is connected to the baseband signal receiving end of the first transceiver of the corresponding transmitting array element. At this time, the channel test mode of this embodiment also includes a digital cancellation channel test mode, and the signal processing unit is further used for:

[0043] After loading the first filter coefficients into the corresponding first digital filters, the control array full-duplex system enters the digital cancellation channel test mode, obtains the third channel response of the digital cancellation channel, obtains the second filter coefficients of each second digital filter according to the third channel response, and loads the second filter coefficients into the corresponding second digital filters.

[0044] After the second filter coefficients are loaded into the second digital filter, if the array full-duplex system enters a normal operating mode, the RF signal cancellation in the analog domain is performed first, and then the baseband signal cancellation in the digital domain is performed.

[0045] Specifically, refer to Figure 4 , the signal processing unit is also used for:

[0046] After the baseband signal in the interference signal is cancelled by the radio frequency cancellation signal in each second coupler, the baseband signal to be cancelled twice output by each receiving array element is obtained, and the baseband signal to be cancelled twice includes a nonlinear signal, a noise signal and a residual baseband signal; the baseband signals to be cancelled twice output by the K receiving array elements are subjected to receiving beamforming processing to obtain a synthesized baseband signal and input it to the negative input end of the subtractor; the feedback baseband signals of the baseband transmission signals output by the J transmitting array elements are obtained, and the baseband feedback signals are respectively reconstructed by using the corresponding second digital filters to obtain a baseband cancellation signal, and the baseband cancellation signals of the J second digital filters are added to obtain a superimposed baseband cancellation signal and input it to the positive input end of the subtractor; the nonlinear signal, the noise signal and the residual baseband signal in the synthesized baseband signal are cancelled by using the superimposed baseband cancellation signal through the subtractor to obtain the baseband signal after the secondary cancellation.

[0047] The feedback baseband signal in this embodiment refers to a signal output by the baseband signal receiving end of the first transceiver, when the first coupler of the transmitting array element sends a coupled signal obtained from the transmitter of the first transceiver to the baseband signal receiving end of the first transceiver. Since the feedback baseband signal includes a baseband signal, a nonlinear signal and a noise signal, the baseband cancellation signal obtained by reconstructing the feedback baseband signal using J second digital filters can cancel the nonlinear signal, the noise signal and the residual baseband signal in the baseband signal to be cancelled twice.

[0048] In some scenarios of actual applications, the interference signal is first offset by the RF cancellation signal in the analog domain, and then by the baseband cancellation signal in the digital domain. The baseband signal obtained after the secondary cancellation may still contain some residual interference signals.

[0049] With respect to the above residual interference signal, in some embodiments of the present application, the signal processing unit further includes an adaptive filter, and the signal processing unit is further configured to:

[0050] The baseband signal after the secondary cancellation is used as the desired signal of the adaptive filter, the baseband transmission signal is used as the signal to be cancelled by the adaptive filter, and the final signal of interest is obtained through the error output signal of the adaptive filter.

[0051] The adaptive filter of this embodiment can use adaptive filtering methods such as LMS (Least Mean Square, also known as minimum mean square error), NLMS (Normalized Least Mean Square, also known as normalized minimum mean square error), RLS (Recursive Least Squares, also known as recursive least squares) to offset the residual interference signal.

[0052] Continue to refer Figure 4 Taking the adaptive filter using LMS adaptive filtering technology as an example, the output signal en of the subtractor is used as the desired signal dn, and the baseband transmission signal xn is used as the signal to be cancelled un. The desired signal dn and the signal to be cancelled un are respectively sent to the LMS adaptive filter for adaptive filtering. The error output signal errn of the LMS adaptive filter is the final signal of interest SOI.

[0053] To facilitate understanding of the following embodiments of the present application, the structure of the array full-duplex system of the embodiments of the present application is first described in detail.

[0054] In the present application, the signal processing unit is the core of the array full-duplex system, which includes a central processing unit (CPU), a random access memory (RAM), an input / output interface (IO interface), a transmission beamforming module, a receiving beamforming module, K first digital filters, J second digital filters and an adaptive filter, etc. The central processing unit can generate a test signal source. Because the single-tone signal is relatively simple, it is easy to generate. Therefore, the test signal source of the present embodiment is preferably a single-tone signal source. Of course, in practical applications, those skilled in the art can also flexibly select the type of the test signal source. Optionally, the array full-duplex system of the present embodiment can also obtain the test signal source from an external signal source.

[0055] Among them, the transmit beamforming module can be Figure 5 The process shown in the figure performs a transmit beamforming process on the transmit signal, and the transmit signal power in the specified spatial direction is enhanced by the transmit beamforming process, such as the transmit signal x(n) is subjected to J-path weight factors (w1, w2…w J ) after conditioning, the J-way branch signal out is obtained j , the j-th branch signal out j The baseband signal transmitting end IQ-TX of the first transceiver sent to the j-th transmitting array element, where j=1, 2, ...J.

[0056] The receive beamforming module can be Figure 6 The process performs a receiving beamforming process on the received signal, and the power of the received signals from different wave directions is enhanced by the receiving beamforming process, such as the output signal in the baseband signal receiving end IQ-RX of the second transceiver of the K receiving array elements k After the corresponding weight factors (w1, w2…w J ) are conditioned and added to obtain the combined signal yn.

[0057] refer to Figures 1 to 4 As shown, each transmitting array element of the array full-duplex system of this embodiment includes a first transceiver, a first coupler and a transmitting antenna, and each receiving array element includes a second transceiver, a second coupler and a receiving antenna. Here, the first transceiver and the second transceiver have the same structure, also known as a radio transceiver. The radio transceiver is a receiver and a transmitter pair from radio frequency to baseband and from baseband to radio frequency. Figure 7 As shown, the first transceiver and the second transceiver both include a digital up converter (Digital Up Converter, abbreviated as DUC), a digital frequency converter, a digital-to-analog converter (Digital-to-Analog Converter, abbreviated as DAC), a transmitter, a digital down converter (Digital Down Converter, abbreviated as DDC), an analog-to-digital converter (Analog-to-Digital Converter, abbreviated as ADC) and a receiver.

[0058] The first end of the digital up-converter is the baseband signal transmitting end IQ-TX of the transceiver, the second end of the digital up-converter is connected to the first end of the digital converter, the third end of the digital converter is connected to the first end of the digital-to-analog converter, the second end of the digital-to-analog converter is connected to the first end of the transmitter, and the second end of the transmitter is the radio frequency signal transmitting end RF-TX of the transceiver; the first end of the receiver is the radio frequency signal receiving end RF-RX of the transceiver, the second end of the receiver is connected to the first end of the analog-to-digital converter, the second end of the analog-to-digital converter is connected to the fourth end of the digital converter, the second end of the digital converter is connected to the first end of the digital down-converter, and the second end of the digital down-converter is the baseband signal receiving end IQ-RX of the transceiver.

[0059] The digital frequency converter included in the transceiver of this embodiment includes Figure 7 The digital local oscillator (NCO) and digital mixer shown in the figure, the transmitter and the receiver include but are not limited to a common local oscillator. In the embodiment of the present application, the transmitter and the receiver included in the transceiver require at least that the transmitter and the receiver are coherent. The working system of the transmitter and the receiver includes but is not limited to an analog frequency conversion technology system, and can also be a system such as a direct acquisition of RF without analog frequency conversion.

[0060] For each transmitting array element, the RF signal transmitting end RF-TX of the first transceiver is connected to the input end of the first coupler, the output end of the first coupler is connected to the transmitting antenna, and the coupling end of the first coupler is connected to the RF signal receiving end RF-RX of the first transceiver, wherein the output ends of the first couplers of different transmitting array elements are connected to different transmitting antennas.

[0061] For each receiving array element, the RF signal transmitting end RF-TX of the second transceiver is connected to the coupling end of the second coupler, the input end of the second coupler is connected to the receiving antenna, and the output end of the second coupler is connected to the RF signal receiving end RF-RX of the second transceiver, wherein the input ends of the second couplers of different receiving array elements are connected to different receiving antennas.

[0062] refer to Figure 1 , the external interference channel includes K channels formed by the transmitting array unit, the external physical space, and K receiving array elements in sequence. Figure 2 The radio frequency cancellation channel includes K channels formed by the signal transmission channel of the second transceiver of the K receiving array elements, the second coupler, and the signal receiving channel of the second transceiver. Figure 3 The digital cancellation channel includes three channel branches. The first channel branch refers to J channels formed by the signal transmission channel of the first transceiver of the J transmitting array elements, the first coupler, and the signal receiving channel of the first transceiver in sequence. The second channel branch refers to K channels formed by the transmitting array unit, the external physical space, and K receiving array elements in sequence. The third channel branch refers to K channels formed by K first digital filters, the signal transmission channel of the second transceiver of the K receiving array elements, and the second coupler in sequence, wherein the second channel branch and the third channel branch are crossed and synthesized into one channel branch in the second coupler.

[0063] Thus, the control process of the signal processing unit on the channel test mode is described in detail through the following two aspects.

[0064] The first aspect includes an external interference channel test mode, a radio frequency offset channel test mode, and a first filter coefficient calculation:

[0065] For the external interference channel test mode, the signal processing unit is used to control the array full-duplex system to enter the external interference channel test mode through the following steps to obtain the first channel response of the external interference channel:

[0066] The test signal source is controlled to transmit the test baseband signal xp in sequence at each set frequency point in the system working frequency band, and the test baseband signal xp is subjected to transmit beamforming processing to obtain J test baseband branch signals; each test baseband branch signal is transmitted through the corresponding transmitting array element, and after being transmitted through the external physical space, it is received by K receiving array elements; wherein, in order to avoid the input of other strong interference signals, the second transceivers of the K receiving array elements are set not to transmit signals in this embodiment, that is, the baseband signal transmitting end IQ-TX of each second transceiver of the receiving array unit is connected to 0; the baseband response signal of the test baseband signal output by each receiving array element is received, that is, the baseband response signals yp1, yp2 ... yp are received through the baseband signal receiving end IQ-RX of the second transceiver of each receiving array element. K ; According to the test baseband signal xp of each set frequency point of each receiving array element and the baseband response signal yp1, yp2...yp of the test baseband signal K , obtain the first channel response Hpi corresponding to the receiving array element, where i = 1, 2, ...K.

[0067] For example, assume that the array full-duplex system of this embodiment includes 8 transmitting array elements and 8 receiving array elements, the bandwidth of the system operating frequency band is 150 MHz, N=4096 samples are collected at each set frequency point (N can also take other values, which are not limited in this embodiment), the local oscillator frequency of the digital local oscillator of the first transceiver and the second transceiver is 2.4 GHz, the sampling frequency of the digital-to-analog converter and the analog-to-digital converter are both 3.2 GHz, the multipliers of the digital down converter and the digital up converter are both 16 times, the first digital filter and the second digital filter are both FIR filters, and a 4-stage half-band extraction FIR filter is used.

[0068] Thus, within the instantaneous bandwidth of the system operating frequency band, the signal processing unit first performs a step-by-step analysis on the test baseband signal xp and the baseband response signals yp1, yp2…yp K The acquisition is performed until the entire working instantaneous bandwidth is covered to complete the signal acquisition. Then the test baseband signal xp and baseband response signal yp1, yp2…yp at each set frequency point ωm are collected. K Perform Fourier transform to obtain the frequency domain value FFT(xp) of the test baseband signal xp and the baseband response signals yp1, yp2…yp k The frequency domain values ​​of FFT(yp1), FFT(yp2)…FFT(yp K ), take the corresponding frequency baseband response signal yp1, yp2…yp k The frequency domain values ​​of FFT(yp1), FFT(yp2)…FFT(yp K ) divided by the frequency domain value FFT(xp) of the test baseband signal xp is taken as the first channel response Hpi corresponding to the i-th receiving array element.

[0069]

[0070] In formula (1), i=1, 2, ...K, m is the total number of set frequency points, and ωm is the mth set frequency point.

[0071] In the external interference channel test process, the number of S parameters hm of the array channel between the transmitter and receiver is theoretically 8×8=64. This embodiment proposes that the test baseband signal xp is processed by the transmit beamforming module and output simultaneously, which can reduce the number of channel measurements between the transmitter and receiver arrays to 8, greatly simplifying the test steps and saving test time.

[0072] For the RF cancellation channel test mode, the signal processing unit is used to control the array full-duplex system to enter the RF cancellation channel test mode through the following steps to obtain the second channel response of each RF cancellation channel:

[0073] Control the test signal source to transmit the test baseband signals xc1, xc2, ..., xc in sequence at each set frequency point in the system working frequency band K To the second transceiver of the K receiving array elements, that is, to send the test baseband signal xc1 to the baseband signal transmitting end IQ-TX of the second transceiver of the first receiving array element, and to send the test baseband signal xc2 to the baseband signal transmitting end IQ-TX of the second transceiver of the second receiving array element. K The baseband signal is sent to the baseband signal transmitting end IQ-TX of the second transceiver of the Kth receiving array element, and then the test baseband signal is transmitted to the corresponding second coupler through the corresponding second transceiver, and coupled back to the corresponding second transceiver through the coupling end of the second coupler. Here, the first transceiver of the J transmitting array elements does not transmit a signal, that is, the signal processing unit sets the input signal of the transmit beamforming module to 0 to avoid external interference signal input; the baseband response signal of the test baseband signal output by the second transceiver of the K receiving array elements is received, that is, the baseband response signal yc1 output by the baseband signal receiving end IQ-RX of the second transceiver of the first receiving array element is received, the baseband response signal yc2 output by the baseband signal receiving end IQ-RX of the second transceiver of the second receiving array element is received, and the baseband response signal yc1 output by the baseband signal receiving end IQ-RX of the second transceiver of the Kth receiving array element is received. K ; According to the test baseband signal of each set frequency point of each receiving array element and the baseband response signal of the test baseband signal, the second channel response corresponding to the receiving array element is obtained.

[0074] It should be noted that, in order to avoid mutual influence between transmitting array elements, optionally, the test process of K RF cancellation channels corresponding to K receiving array elements should be performed sequentially, and try to avoid performing them simultaneously to avoid the interference generated affecting the test accuracy. For example, after receiving the baseband response signal yc1 output by the baseband signal receiving end IQ-RX of the second transceiver of the first receiving array element, the test baseband signal xc2 is sent to the baseband signal transmitting end IQ-TX of the second transceiver of the second receiving array element, and the K RF cancellation channels are tested sequentially in this way.

[0075] If the second coupler is implemented by a directional coupler, in order to improve the test efficiency, K radio frequency cancellation channels can also be tested simultaneously. In practical applications, those skilled in the art can reasonably select a test method for K radio frequency cancellation channels according to test requirements.

[0076] In the RF cancellation channel test mode, the channel processing unit tests the baseband signals xc1, xc2, ..., xc K and the baseband response signals yc1, yc2, ..., yc of the test baseband signal K The acquisition process is similar to the signal acquisition process in the external interference channel test mode, and this embodiment will not be given an example here.

[0077] After completing the test baseband signals xc1, xc2, ..., xc K and the baseband response signals yc1, yc2, ..., yc of the test baseband signal K When collecting signals, for each set frequency point ωm, the test baseband signal xc1, xc2, ..., xc K and baseband response signals yc1,yc2,…,yc K Perform Fourier transform to obtain the test baseband signal xc i The frequency domain value FFT(xc i ) and baseband response signal yc i The frequency domain value FFT (yc i ), take the baseband response signal yp of the corresponding frequency point i The frequency domain value FFT (yc i ) divided by the baseband response signal xc i The frequency domain value FFT(xc i ) is taken as the second channel response Hci corresponding to the i-th receiving array element, where i = 1, 2, ...K.

[0078]

[0079] For the first filter coefficient calculation process, the signal processing unit is used to obtain the first filter coefficient of each first digital filter according to the first channel response and the second channel response through the following steps:

[0080] The frequency domain value of the first channel response and the frequency domain value of the second channel response of each receiving array element are obtained respectively; the result of dividing the frequency point corresponding to the frequency domain value of the first channel response by the frequency domain value of the second channel response is calculated, and the frequency domain reconstruction response of the first digital filter corresponding to the receiving array element is obtained by the inverse of the result; that is, the first filter coefficients of K first digital filters are calculated by the following formula (3):

[0081] HCi=-Hpi. / Hci (3)

[0082] In equation (3), the operator . / represents the division of corresponding frequency points, and HCi represents the first filter coefficient of the i-th first digital filter.

[0083] Perform an inverse Fourier transform on the frequency domain reconstructed response of the first digital filter, and truncate the inverse Fourier transform result according to the length of the first digital filter to obtain the first filter coefficient of the first digital filter, such as obtaining the first filter coefficient through an FIR filter design method of a windowed Fourier series or a mathematical optimization method, and load the first filter coefficient into the corresponding first digital filter.

[0084] The second aspect includes a digital cancellation channel test mode and a second filter coefficient calculation.

[0085] For the RF cancellation channel test mode, the signal processing unit is used to control the array full-duplex system to enter the digital cancellation channel test mode through the following steps to obtain the third channel response of the digital cancellation channel:

[0086] Control the test signal source to transmit the test baseband signal xp in sequence at each set frequency point in the system working frequency band, send the test baseband signal xp to K first digital filters respectively for signal reconstruction, each first digital filter sends the reconstructed test baseband signal to the corresponding receiving array element and conditions it into a radio frequency cancellation test signal in the second coupler of the receiving array element, that is, each first digital filter reconstructs the test baseband signal xp, sends the reconstructed test baseband signal to the baseband signal transmitting end IQ-TX of the second transceiver of the receiving array element corresponding to the first digital filter, and the second transceiver conditions the reconstructed test baseband signal to obtain the radio frequency cancellation test signal in the second coupler;

[0087] The signal processing unit also performs transmit beamforming processing on the test baseband signal xp to obtain J test baseband branch signals, and transmits each test baseband branch signal through a corresponding transmitting array element, and after being transmitted through an external physical space, is received by K receiving array elements and baseband signal cancellation is performed in a second coupler of each receiving array element based on a radio frequency cancellation test signal;

[0088] The signal processing unit receives the feedback baseband test signals xob1, xob2, ..., xob from the test baseband signals output by the J transmitting array elements. J , and receiving the baseband test signals to be secondary canceled output by the K receiving array elements, and performing receiving beamforming processing on the baseband test signals to be secondary canceled output by the K receiving array elements to obtain a synthesized baseband test signal yob;

[0089] According to the feedback baseband test signals xob1, xob2, ..., xob at each set frequency point of each transmitting array element J And synthesize the baseband test signal yob to obtain the third channel response corresponding to the transmitting array element.

[0090] Specifically: obtain the feedback baseband test signal xob of each transmitting array element at each set frequency point j The frequency domain value FFT(xob j ) and the frequency domain value FFT(yob) of the synthesized baseband test signal yob; the corresponding frequency point of the frequency domain value FFT(yob) of the synthesized baseband test signal of each transmitting array element at each set frequency point is divided by the frequency domain value FFT(xob) of the feedback baseband test signal j ), the frequency domain value of the third channel response corresponding to the transmitting array element is obtained, such as the frequency domain value of the third channel response corresponding to each transmitting array element is obtained by the following formula (4):

[0091]

[0092] In formula (4), j = 1, 2, ...J.

[0093] For the second filter coefficient calculation process, the signal processing unit is used to obtain the second filter coefficient of each second digital filter according to the third channel response through the following steps:

[0094] An inverse Fourier transform is performed on the frequency domain value of the third channel response corresponding to each transmitting array element, and the inverse Fourier transform result is intercepted according to the length of the second digital filter to obtain a second filter coefficient of the second digital filter corresponding to the transmitting array element.

[0095] After completing the channel test mode through the above embodiment, the signal processing unit can switch to the normal working mode based on the instruction to perform the above interference signal cancellation process.

[0096] It should be noted that the filter coefficients of the K first digital filters and the J second digital filters in the embodiment of the present application are related to the weight factors w1, w2…w in the transmit beamforming and the receive beamforming. J Relatedly, when the weight factors w1, w2…w in transmit beamforming and receive beamforming areJ When changes occur, the weight factors w1, w2…w should be selected to match the transformed weight factors J The corresponding filter coefficients.

[0097] Based on this, in one embodiment of the present application, a correspondence table between weight factors and filter coefficients is also stored in the signal processing unit. When a change in the weight factor of the array full-duplex system is detected, the filter coefficient corresponding to the transformed weight factor is searched based on the correspondence table and loaded into the corresponding digital filter. The filter coefficients in the correspondence table include a first filter coefficient and a second filter coefficient, and the weight factor refers to a weight factor used for transmit beamforming and receive beamforming.

[0098] The array full-duplex system provided in the above-mentioned embodiments of the present application utilizes a signal processing unit to perform online testing and self-calibration on the RF interference path response, generates accurate filter coefficients in the digital domain, and cancels the interference signal in real time, thereby solving the problems of beam gain loss and high constraint optimization cost caused by limited freedom of the transmitting and receiving beams in the ALSTAR array full-duplex system. The system has the characteristics of wide cancellation bandwidth, high interference suppression ratio, and strong practicality. In addition, the array full-duplex system provided in the embodiments of the present application can realize signal transmission and reception in the array full-duplex under one aperture, and has wide commercial and military application value.

[0099] It should be understood that although the terms first, second, third, etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information.

[0100] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. An array full-duplex system, comprising: A transmitting array unit, a receiving array unit and a signal processing unit; The transmitting array unit includes J transmitting array elements, each transmitting array element includes a first transceiver, a first coupler and a transmitting antenna, the receiving array unit includes K receiving array elements, each receiving array element includes a second transceiver, a second coupler and a receiving antenna, J and K are positive integers not less than 2, the receiving array unit can receive a signal of interest and an interference signal, the interference signal includes a baseband signal, and is characterized in that the working mode of the array full-duplex system includes a channel test mode and a normal working mode, the channel test mode includes an external interference channel test mode and a radio frequency cancellation channel test mode, the radio frequency cancellation channel includes K channels formed by the signal transmission channel of the second transceiver of the K receiving array elements, the second coupler, and the signal receiving channel of the second transceiver in sequence, the signal processing unit includes K first digital filters, the K first digital filters correspond to the K receiving array elements one by one, and the signal processing unit is used to: Controlling the array full-duplex system to enter the external interference channel test mode to obtain a first channel response of the external interference channel; and controlling the array full-duplex system to enter the radio frequency cancellation channel test mode to obtain a second channel response of each radio frequency cancellation channel; According to the first channel response and the second channel response, a first filter coefficient of each first digital filter is obtained, and the first filter coefficient is loaded into the corresponding first digital filter; the array full-duplex system is controlled to enter the normal working mode, when a baseband transmission signal is transmitted through the transmitting array unit and a signal is received through the receiving array unit at the same time, each first digital filter is used to reconstruct the baseband transmission signal, and the reconstructed baseband transmission signal is obtained and sent to the corresponding receiving array element, and the baseband signal in the interference signal is offset by the RF offset signal conditioned by the reconstructed baseband transmission signal in the second coupler of each receiving array element; The signal processing unit further includes J second digital filters, the J second digital filters correspond to the J transmitting array elements one by one, the channel test mode further includes a digital cancellation channel test mode, the digital cancellation channel includes three channel branches, the first channel branch refers to the J channels formed by the signal transmission channel of the first transceiver of the J transmitting array elements, the first coupler, and the signal receiving channel of the first transceiver in sequence, the second channel branch refers to the K channels formed by the transmitting array unit, the external physical space, and the K receiving array elements in sequence, and the third channel branch refers to the K channels formed by the K first digital filters, the signal transmission channel of the second transceiver of the K receiving array elements, and the second coupler in sequence; The signal processing unit is further used to: after loading the first filter coefficient into the corresponding first digital filter, control the array full-duplex system to enter the digital cancellation channel test mode, obtain the third channel response of the digital cancellation channel, obtain the second filter coefficient of each second digital filter according to the third channel response, and load the second filter coefficient into the corresponding second digital filter; The interference signal also includes a nonlinear signal and a noise signal. The signal processing unit is further used for: after the baseband signal in the interference signal is offset by the radio frequency offset signal in each second coupler, obtaining the baseband signal to be offset twice output by each receiving array element, and performing receive beamforming processing on the baseband signals to be offset twice output by K receiving array elements to obtain a synthesized baseband signal and input it to the positive input end of the subtractor; obtaining feedback baseband signals of baseband transmission signals output by J transmitting array elements, respectively reconstructing the feedback baseband signals by using corresponding second digital filters to obtain a baseband offset signal, and adding the baseband offset signals of the J second digital filters to obtain a superimposed baseband offset signal and input it to the negative input end of the subtractor; and using the superimposed baseband offset signal to offset the nonlinear signal, the noise signal and the residual baseband signal in the synthesized baseband signal by the subtractor to obtain the baseband signal after the secondary offset.

2. The array full-duplex system according to claim 1, characterized in that: The signal processing unit further includes an adaptive filter, and the signal processing unit is further configured to: The baseband signal after the secondary cancellation is used as the desired signal of the adaptive filter, the baseband transmission signal is used as the signal to be cancelled of the adaptive filter, and the final signal of interest is obtained through the error output signal of the adaptive filter.

3. The array full-duplex system according to claim 1, characterized in that: The signal processing unit is used to control the array full-duplex system to enter the external interference channel test mode through the following steps to obtain the first channel response of the external interference channel: Controlling the test signal source to transmit the test baseband signal in sequence at each set frequency point in the system working frequency band, and performing transmit beamforming processing on the test baseband signal to obtain a J-path test baseband branch signal; Each test baseband branch signal is transmitted through the corresponding transmitting array element, and after being transmitted through the external physical space, it is received by the K receiving array elements, and the second transceiver of the K receiving array elements does not transmit a signal; Receiving a baseband response signal of the test baseband signal output by each receiving array element; According to the test baseband signal at each set frequency point of each receiving array element and the baseband response signal of the test baseband signal, a first channel response corresponding to the receiving array element is obtained.

4. The array full-duplex system according to claim 3, characterized in that: The signal processing unit is used to control the array full-duplex system to enter the RF cancellation channel test mode through the following steps to obtain the second channel response of each RF cancellation channel: Control the test signal source to transmit the test baseband signal to the second transceivers of the K receiving array elements in sequence at each set frequency point in the system working frequency band, transmit the test baseband signal to the corresponding second coupler through the corresponding second transceiver, couple it back to the corresponding second transceiver through the coupling end of the second coupler, and the first transceiver of the J transmitting array elements does not transmit a signal; Receiving a baseband response signal of the test baseband signal output by a second transceiver of the K receiving array elements; According to the test baseband signal at each set frequency point of each receiving array element and the baseband response signal of the test baseband signal, a second channel response corresponding to the receiving array element is obtained.

5. The array full-duplex system according to claim 4, characterized in that: The signal processing unit is used to obtain the first filter coefficient of each first digital filter according to the first channel response and the second channel response through the following steps: Respectively obtaining a frequency domain value of the first channel response and a frequency domain value of the second channel response of each receiving array element; Calculate a result of dividing a frequency point corresponding to a frequency domain value of the first channel response by a frequency domain value of the second channel response, and obtain a frequency domain reconstruction response of a first digital filter corresponding to the receiving array element by the inverse of the result; An inverse Fourier transform is performed on the frequency domain reconstructed response of the first digital filter, and the inverse Fourier transform result is truncated according to the length of the first digital filter to obtain a first filter coefficient of the first digital filter.

6. The array full-duplex system according to claim 1, characterized in that: The signal processing unit is used to control the array full-duplex system to enter the digital cancellation channel test mode through the following steps to obtain the third channel response of the digital cancellation channel: Control the test signal source to transmit the test baseband signal in sequence at each set frequency point in the system working frequency band, send the test baseband signal to K first digital filters respectively for signal reconstruction, and each first digital filter sends the reconstructed test baseband signal to the corresponding receiving array element and condition it into a radio frequency cancellation test signal at the second coupler of the receiving array element; The test baseband signal is also subjected to transmit beamforming processing to obtain J test baseband branch signals, each test baseband branch signal is transmitted through a corresponding transmitting array element, and after being transmitted through an external physical space, is received by the K receiving array elements and baseband signal cancellation is performed in a second coupler of each receiving array element based on the radio frequency cancellation test signal; Receiving a feedback baseband test signal of the test baseband signal output by J transmitting array elements, and receiving a baseband test signal to be secondary-cancelled output by K receiving array elements, and performing receive beamforming processing on the baseband test signal to be secondary-cancelled output by the K receiving array elements to obtain a synthesized baseband test signal; According to the feedback baseband test signal and the synthesized baseband test signal at each set frequency point of each transmitting array element, a third channel response corresponding to the transmitting array element is obtained.

7. The array full-duplex system according to claim 6, characterized in that: The signal processing unit is used to obtain a third channel response corresponding to the transmitting array element according to the feedback baseband test signal and the synthesized baseband test signal at each set frequency point of each transmitting array element through the following steps: Acquire the frequency domain value of the feedback baseband test signal and the frequency domain value of the synthesized baseband test signal of each transmitting array element at each set frequency point; The frequency domain value of the third channel response corresponding to each transmitting array element is obtained according to the result of dividing the frequency domain value corresponding to the frequency point of the synthetic baseband test signal of each transmitting array element at each set frequency point by the frequency domain value of the feedback baseband test signal.

8. The array full-duplex system according to claim 7, characterized in that: The signal processing unit is used to obtain the second filter coefficient of each second digital filter according to the third channel response through the following steps: An inverse Fourier transform is performed on the frequency domain value of the third channel response corresponding to each transmitting array element, and the inverse Fourier transform result is truncated according to the length of the second digital filter to obtain a second filter coefficient of the second digital filter corresponding to the transmitting array element.

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