Rapid calibration method and device for large digital array

Abstract

The invention provides a rapid calibration method and device for a large digital array, and the method comprises the steps: S1, transmitting different random sequences to a plurality of transmitting channels at the same time, setting the lengths of the random sequences to be the same, and carrying out the cyclic transmission of the random sequences in each channel of an antenna array; s2, a far field receiving end in the antenna array is provided with a signal collector, the signal collector is used for receiving the radio frequency signals transmitted by the plurality of transmitting channels, the starting time point of the transmitted signals is analyzed, and then the random sequence in each transmitting channel and the digital IQ data received by the signal collector are respectively used for cross-correlation operation; and S3, according to the obtained cross-correlation value information, calculating by using a channel estimation algorithm to obtain multiple hardware circuit characteristics for calibration, and compensating the multiple hardware circuit characteristics to each path for calibration. The problems that an existing large antenna array is low in calibration speed, and calibration can be achieved only by additionally preparing a public channel are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of large-scale digital array calibration, and more specifically, to a fast calibration method and device for a large-scale digital array. Background Art

[0002] The accuracy of the antenna array beam output is highly dependent on the accuracy and consistency of the delay, gain and phase of each channel. When the three indicators of each channel differ greatly, the RF signal cannot form the expected beam in the air. The calibration of the gain and phase of each channel is divided into online calibration and offline calibration. The ground calibration is called offline calibration and mainly relies on instruments. The online calibration is divided into open-loop and closed-loop. The open-loop calibration relies on the compensation table of the transceiver channel, and the closed-loop calibration relies on the feedback circuit and amplitude phase judgment circuit of each channel in the array. Digital antenna arrays usually refer to arrays whose receiving and transmitting signals are digitized after a short analog circuit. Regardless of whether they are receiving or transmitting, the changes in phase and amplitude are completed by digital processing. The commonly used method for multi-channel calibration of digital arrays is to prepare an additional common RF path, because the interface visible to the outside of the digital array is usually the baseband at one end and the air interface of the RF antenna output at the other end. Multi-channel calibration usually uses multi-channel coherent instruments such as vector network analyzers. Therefore, an additional common RF path is required on the array to apply both RF ports in coherent instruments such as vector network analyzers for calibration. In addition, the current channel calibration scheme usually calibrates each channel in turn in time-sharing. Although this has better calibration performance, it is very time-consuming when calibrating very large arrays.

[0003] Therefore, in order to solve the above-mentioned problem of amplitude and phase calibration of multiple channels of the digital array, in the present invention, when calibrating the digital array, by finding the relative values ​​of the delay, amplitude and phase between multiple channels, it is possible to achieve rapid calibration of multiple channels without preparing an extra common channel and only using the transceiver channel itself. Summary of the invention

[0004] The present invention aims to overcome at least one defect (shortcoming) of the above-mentioned prior art and provide a method and device for rapid calibration of a large digital array, so as to solve the problems of slow calibration of existing large antenna arrays and the need to prepare an additional common channel to achieve calibration.

[0005] The technical solution adopted by the present invention is a fast calibration method for a large digital array, the method comprising:

[0006] S1: Send different random sequences to multiple transmission channels at the same time, set the lengths of the random sequences to be the same and send them cyclically in each channel of the antenna array;

[0007] S2: A signal collector is provided at the far-field receiving end of the antenna array, and is used to receive the RF signals transmitted from multiple transmission channels, analyze the starting time point of the transmission signal, and then use the random sequence in each transmission channel to perform cross-correlation operation with the digital IQ data received by the signal collector;

[0008] S3: Calculate multiple hardware circuit characteristics for calibration using a channel estimation algorithm based on the obtained cross-correlation value information, and compensate them to each channel for calibration.

[0009] In the present application, by sending different random sequences to multiple transmission channels at the same time, the cross-correlation performance can be effectively improved, the synchronization accuracy and robustness of the system can be enhanced, and a signal collector is set up, and the random sequences in each transmission channel and the digital IQ data received by the signal collector are cross-correlated. Thus, the hardware circuit characteristics such as delay, amplitude, and phase can be calculated by the channel estimation algorithm through the cross-correlation value, and the calibration can be achieved by compensating them to each path, so that there is no need to prepare an extra common channel, and the calibration of multiple channels can be completed through the transceiver channel itself. Moreover, since the collected signal characteristics are close to the signal characteristics actually used by the antenna array, sending or receiving signals through multiple channels together can make the calibration process very fast, and the calibration of large digital arrays can be completed in seconds, and the calibration accuracy fully meets the actual usage.

[0010] Preferably, the step S2 includes: setting a cross-correlation operation function according to the transmitted signal and the received signal, and the cross-correlation operation function formula is:

[0011]

[0012] Wherein, x[n] is the transmitted signal; y[n] is the received signal; t is the delay, which indicates the time offset of signal y[n] relative to signal x[n]; and n is the time index.

[0013] By using the cross-correlation function to analyze the signal similarity between different channels, since the random sequence sent by each channel is known, the receiving end can estimate the hardware circuit characteristics by calculating the cross-correlation function between the received signal and the known sequence. Based on the results of the cross-correlation analysis, the calibration parameters of each channel can be calculated and the calibration parameters can be compensated to each path for calibration.

[0014] Preferably, in step S3, the multiple hardware circuit characteristics at least include:

[0015] By obtaining the cross-correlation value R xyThe optimal delay is obtained by maximizing [t], so as to determine the alignment moment of the signal to achieve signal synchronization; the phase difference and amplitude difference are calculated based on the obtained cross-correlation value, and the formulas are: phase difference Φ = angle (Rxy); amplitude difference A = |Rxy|.

[0016] Further preferably, the multiple hardware circuit characteristics also include obtaining the in-band fluctuation h of the channel through channel estimation, and the formula is:

[0017]

[0018] Where, F represents Fourier transform; F -1 Represents the inverse Fourier transform.

[0019] Therefore, by using the cross-correlation value calculated by the cross-correlation function, the channel estimation can be performed to obtain multiple different hardware circuit characteristics such as delay, amplitude, phase and in-band fluctuation, so that these hardware circuit characteristic compensation amounts can be applied to each transmission channel to realize channel calibration, which can effectively improve the signal quality and help reduce the bit error rate, thereby improving the overall performance of the wireless communication system. For delay compensation: according to the delay estimation, the signal of each channel is time-aligned so that the starting point of the signal is consistent; for amplitude compensation: by adjusting the gain of each channel, the signal amplitude is unified; for phase compensation: by adjusting the phase of each channel, all signals are phase-aligned; for in-band fluctuation compensation: compensate for the gain fluctuation and phase fluctuation of the channel, so that the received signal is restored to a state as close as possible to the transmitted signal, thereby reducing the bit error rate.

[0020] Preferably, the method further comprises interpolating the cross-correlation function to obtain a more accurate delay. Specifically, the preliminary delay t0 is first calculated, that is, the maximum value of the cross-value is obtained, and then the interpolation interval is determined, and several time points near t0 are selected for interpolation, and then a linear, quadratic or cubic interpolation method is used to perform interpolation calculations, and a curve is fitted according to the above points to obtain a more accurate delay estimate, and finally the obtained more accurate delay estimate is used in the subsequent compensation process to further improve the accuracy of calibration.

[0021] Preferably, in step S3, when compensating multiple hardware circuit characteristics into each path for calibration, it also includes: monitoring whether a resolvable autocorrelation level is maintained between multiple transmission channels to set the number of transmission channels to be calibrated simultaneously, wherein the resolvable level of each hardware circuit characteristic can be set according to the calibration requirement level of the antenna array.

[0022] Since the number of channels that can work depends on the impact of multiple channels working together on the cross-correlation characteristics of each channel, especially when multiple channels are superimposed with different amplitudes, phases, delays, passband amplitude fluctuations, passband phase fluctuations and other characteristics, by judging whether the multiple channels still maintain a resolvable autocorrelation level, the system can flexibly judge which transmission channels are necessary under the current calibration requirements and which can be merged or temporarily do not need calibration. By dynamically optimizing and adjusting the number of transmission channels that need to be calibrated at the same time, the calibration process can be made more flexible, effectively reducing the system's calculation burden, reducing resource consumption, and improving the overall efficiency of the calibration process.

[0023] Preferably, in step S1, the sequence sending time of some channels may be set to be staggered with other channels by several symbols for sending, or some channels may be set to use sequences of different lengths for sending, so as to obtain better cross-correlation performance.

[0024] Preferably, when calibrating in step S3, all channels or local channels of the antenna array can be selected for calibration according to the specifications of the antenna array. When multiple hardware circuit characteristics are compensated for all channels of the antenna array, the entire antenna array is calibrated at one time; when multiple hardware circuit characteristics are compensated for part of the channels of the antenna array, the global calibration data of the entire array surface can be obtained by performing multiple local tests, utilizing the characteristics that there is a certain amount of overlap between local arrays and the channel state remains unchanged at the overlap.

[0025] For full channel calibration: when the hardware circuit characteristics of the antenna array are compensated for the entire array, calibrating all channels at one time can complete the comprehensive calibration in a short time, ensuring the performance consistency and accuracy of the entire array, which is suitable for scenarios that require fast and full coverage calibration; for partial channel calibration: when compensation is only for some channels, through the repeated coverage characteristics of the local array, the repeated area can be used as a reference to ensure the stability and consistency of the calibration results, and it can be calibrated step by step in stages without processing all channels at once, which can significantly reduce the computational complexity and time consumption of each calibration, especially in the case of large-scale arrays, reducing the complexity of global calibration and making the calibration process more flexible.

[0026] Preferably, the method also includes: calibrating the receiving path, only needing to generate a sequence with good autocorrelation characteristics, sending the sequence to multiple receiving channels using a signal source in the mid- and far-field, and after acquiring the sequence, sending it to a channel estimation module for channel characteristic calculation, so as to obtain the hardware circuit characteristics of multiple channels and realize rapid calibration.

[0027] Multi-channel calibration is performed using the same autocorrelation signal sequence to ensure that the hardware characteristics of all receiving channels are consistent and can remain consistent during subsequent signal reception, reducing errors caused by differences in hardware characteristics between different channels and achieving rapid calibration.

[0028] On the other hand, the present invention also provides a fast calibration device for a large digital array, the device comprising at least a plurality of transmission channels, a channel characteristic calculation module and a signal collector arranged in the far field of the antenna array, wherein the transmission channel comprises at least a characteristic compensation module, a DAC+up modulation module, a power amplifier module and an antenna unit;

[0029] The signal collector is connected to the channel characteristic calculation module, and is used to receive the radio frequency signals transmitted from multiple transmission channels, analyze the starting time point of the transmission signal, and then use the random sequence in each transmission channel and the digital IQ data received by the signal collector to perform cross-correlation operations, and send the obtained cross-correlation values ​​to the channel characteristic calculation module for channel characteristic calculation to obtain multiple hardware circuit characteristics for calibration;

[0030] One end of the channel characteristic calculation module is connected to the incident end of each transmission channel for receiving the random sequence in each channel; the other end is connected to the characteristic compensation unit of each transmission channel for compensating the multiple hardware circuit characteristics used for calibration into each transmission path for calibration.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: in the present application, by sending different random sequences to multiple transmission channels at the same time, the cross-correlation performance can be effectively improved, the synchronization accuracy and robustness of the system can be enhanced, and by setting a signal collector, the random sequences in each transmission channel and the digital IQ data received by the signal collector are cross-correlated, so that the hardware circuit characteristics such as delay, amplitude, and phase can be calculated by the channel estimation algorithm through the cross-correlation value, and the calibration can be achieved by compensating them to each path, so that there is no need to prepare an extra common channel, and the calibration of multiple channels can be completed through the transceiver channel itself, and because the collected signal characteristics are close to the signal characteristics actually used by the antenna array, sending or receiving signals through multiple channels together can make the calibration process very fast, and the calibration of large digital arrays can be completed in seconds, and the calibration accuracy fully meets the actual usage. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the method flow provided in this embodiment.

[0033] Figure 2 This is a structural diagram of the transmission channel calibration device provided in this embodiment.

[0034] Figure 3 A schematic diagram of the time domain superposition of multi-channel calibration signals provided in this embodiment.

[0035] Figure 4 This is a structural diagram of the receiving channel calibration device provided in this embodiment.

[0036] Figure 5 This is a structural diagram of another transmission channel calibration device provided in this embodiment. DETAILED DESCRIPTION

[0037] The drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0038] Example 1

[0039] like Figure 1 As shown, this embodiment provides a fast calibration method for a large digital array, the method comprising:

[0040] Step S1: sending different random sequences to multiple transmission channels at the same time, setting the lengths of the random sequences to be the same and cyclically sending them in each channel of the antenna array;

[0041] Among them, the random sequences sent can achieve very high autocorrelation values ​​and very low cross-correlation values, and the delay, amplitude, and phase of the autocorrelation are very stable. Even if the transmitter and receiver are completely out of time synchronization, the starting time point of the transmitted signal can still be quickly analyzed from the received signal, such as Figure 2 As shown, for better cross-correlation performance, multiple channels send different random sequences, the marking signal 1 can be but not limited to using a ZC sequence, the calibration signal 2 can be but not limited to using an m sequence, the calibration signal N can be but not limited to using a PN sequence, etc. The type of sequence sent by each channel can be selected according to actual needs, thereby effectively reducing interference and improving the accuracy of signal detection. In addition, by cyclically sending the random sequence, the signal sent by each channel can be repeated periodically, thereby ensuring that the receiving end accumulates enough signal samples in multiple transmissions and increasing the accuracy of calibration.

[0042] Preferably, if Figure 3As shown, in step S1, the sequence transmission time of some channels can also be set to be staggered with other channels by several symbols for transmission, or some channels can be set to use sequences of different lengths for transmission, so as to obtain better cross-correlation performance. The selection of the above channels can include but is not limited to the position in the array that is most susceptible to interference, and can also be given according to empirical values.

[0043] Step S2: Figure 2 As shown, a signal collector is provided at the far-field receiving end of the antenna array, and is used to receive radio frequency signals transmitted from multiple transmission channels, analyze the starting time point of the transmission signal, and then use the random sequence in each transmission channel to perform cross-correlation operation with the digital IQ data received by the signal collector;

[0044] Preferably, the step S2 includes: setting a cross-correlation operation function according to the transmitted signal and the received signal, and the cross-correlation operation function formula is:

[0045]

[0046] Wherein, x[n] is the transmitted signal; y[n] is the received signal; t is the delay, which indicates the time offset of signal y[n] relative to signal x[n]; and n is the time index.

[0047] By using the cross-correlation function to analyze the signal similarity between different channels, since the random sequence sent by each channel is known, the receiving end can estimate the hardware circuit characteristics by calculating the cross-correlation function between the received signal and the known sequence. Based on the results of the cross-correlation analysis, the calibration parameters of each channel can be calculated and the calibration parameters can be compensated to each path for calibration.

[0048] Step S3: Calculate multiple hardware circuit characteristics for calibration using a channel estimation algorithm based on the obtained cross-correlation value information, and compensate them to each channel for calibration.

[0049] Specifically, in step S3, the multiple hardware circuit characteristics at least include:

[0050] By obtaining the cross-correlation value R xy The maximum value of [t] is used to obtain the optimal delay, thereby determining the alignment moment of the signal to achieve signal synchronization; if R xy The value of [t] is very large, indicating that under the delay t, the two signals have a high degree of overlap and a strong correlation, and the optimal alignment time can be obtained to achieve signal synchronization.

[0051] The phase difference and amplitude difference are calculated based on the obtained cross-correlation value, and the formulas are: phase difference Φ = angle (Rxy); amplitude difference A = |Rxy|. The calculated phase difference reflects the phase change caused by factors such as multipath effect, reflection or phase rotation during signal propagation. By using it to adjust the phase of the signal, the phase of the signal can be made consistent. The amplitude difference reflects the amplitude change caused by factors such as attenuation and path loss during the propagation of the signal. By performing gain compensation on the signal of each channel, the signal amplitude of all channels can be made consistent.

[0052] Further preferably, the multiple hardware circuit characteristics also include obtaining the in-band fluctuation h of the channel through channel estimation, and the formula is:

[0053]

[0054] Where, F represents Fourier transform; F -1 Represents the inverse Fourier transform.

[0055] In-band fluctuations refer to the changes in the channel within the transmission bandwidth. The existence of these fluctuations will directly affect the quality of the received signal, increase the bit error rate, and reduce the communication performance of the system. Therefore, calibrating and compensating for these fluctuations is also very important to ensure the reliability of the communication system.

[0056] Therefore, in this embodiment, by using the cross-correlation function to calculate the cross-correlation value, channel estimation can be performed to obtain multiple different hardware circuit characteristics such as delay, amplitude, phase, and in-band fluctuation, so that these hardware circuit characteristic compensation amounts are applied to each transmission channel to realize channel calibration, which can effectively improve signal quality and help reduce the bit error rate, thereby improving the overall performance of the wireless communication system. For delay compensation: according to the delay estimation, the signal of each channel is time-aligned so that the starting point of the signal is consistent; for amplitude compensation: by adjusting the gain of each channel, the signal amplitude is unified; for phase compensation: by adjusting the phase of each channel, all signals are phase-aligned; for in-band fluctuation compensation: compensate for the gain fluctuation and phase fluctuation of the channel, so that the received signal is restored to a state as close as possible to the transmitted signal, thereby reducing the bit error rate.

[0057] Preferably, the method also includes interpolating the cross-correlation function to obtain a more accurate delay. Specifically, first calculate the preliminary delay t0, that is, obtain the maximum value of the cross-value, then determine the interpolation interval, select several time points near t0 for interpolation, and then use linear, quadratic or cubic interpolation methods to perform interpolation calculations. Fit the curve according to the above points to obtain a more accurate delay estimate. The delay accuracy can be improved to the nanosecond level through interpolation, thereby improving the system's ability to compensate for delays. Finally, the more accurate delay estimate is used in the subsequent compensation process to further improve the accuracy of calibration.

[0058] Preferably, in step S3, when compensating multiple hardware circuit characteristics into each path for calibration, it also includes: monitoring whether a resolvable autocorrelation level is maintained between multiple transmission channels to set the number of transmission channels to be calibrated simultaneously, wherein the resolvable level of each hardware circuit characteristic can be set according to the calibration requirement level of the antenna array.

[0059] like Figure 2 As shown, in this embodiment, m channels are combined for transmission and one channel is unified for reception, that is, m transmit and one receive, so the actual transmission signal S and the actual reception signal T are:

[0060] S=x1+x2+x3+…x m ; T = y1 + y2 + y3 + ... y m

[0061] When the cross-correlation characteristics of the transmission sequences of each channel are good enough, the correlation result between the random sequence x sent by each channel and the actual received signal T of all channels is approximately equal to the correlation result when the channel is sent and received alone.

[0062]

[0063] At the same time, since how many channels can work depends on the influence of the cross-correlation characteristics of each channel when multiple signals work together, especially after the multiple signals are superimposed with different amplitudes, phases, delays, passband amplitude fluctuations, passband phase fluctuations and other characteristics, by judging whether the resolvable autocorrelation level is still maintained between the multiple channels, the system can flexibly judge which transmission channels are necessary under the current calibration requirements, and which can be merged or temporarily do not need calibration. By dynamically optimizing and adjusting the number of transmission channels that need to be calibrated simultaneously, the calibration process can be made more flexible, effectively reducing the calculation burden of the system, reducing resource consumption, and improving the overall efficiency of the calibration process. In this embodiment, the resolvable level can be set according to the calibration requirement level of the antenna array. For example, the amplitude resolvable level can be set to 0.2dB, and the phase resolvable level can be set to 2dB. The specific indicators are set according to the actual project requirements. Therefore, according to the resolvable level of each hardware circuit characteristic set, the number of channels that can be calibrated simultaneously can be increased until the calibration resolution no longer meets the indicator requirements.

[0064] Preferably, when calibrating in step S3, all channels or local channels of the antenna array can be selected for calibration according to the specifications of the antenna array. When multiple hardware circuit characteristics are compensated to all channels of the antenna array, the entire antenna array is calibrated at one time. When the antenna array is too large to make far-field testing difficult, only a part of the array surface can be calibrated. By compensating multiple hardware circuit characteristics to some channels of the antenna array, and utilizing the characteristics that there is a certain amount of overlap between local arrays and the channel state remains unchanged at the overlap, global calibration data for the entire array surface can be obtained by performing multiple local tests.

[0065] For full channel calibration: when the hardware circuit characteristics of the antenna array are compensated for the entire array, calibrating all channels at one time can complete the comprehensive calibration in a short time, ensuring the performance consistency and accuracy of the entire array, which is suitable for scenarios that require fast and full coverage calibration; for partial channel calibration: when compensation is only for some channels, through the repeated coverage characteristics of the local array, the repeated area can be used as a reference to ensure the stability and consistency of the calibration results, and it can be calibrated step by step in stages without processing all channels at once, which can significantly reduce the computational complexity and time consumption of each calibration, especially in the case of large-scale arrays, reducing the complexity of global calibration and making the calibration process more flexible.

[0066] Therefore, in this embodiment, by sending different random sequences to multiple transmission channels at the same time, the cross-correlation performance can be effectively improved, the synchronization accuracy and robustness of the system can be enhanced, and by setting a signal collector, the random sequence in each transmission channel and the digital IQ data received by the signal collector are cross-correlated. Therefore, the cross-correlation value can be used to calculate the hardware circuit characteristics such as delay, amplitude, and phase using the channel estimation algorithm, and the calibration can be achieved by compensating it to each path, so that there is no need to prepare an extra common channel, and the multi-channel calibration can be completed through the transceiver channel itself. Moreover, since the collected signal characteristics are close to the signal characteristics actually used by the antenna array, sending or receiving signals through multiple channels together can make the calibration process very fast, and the calibration of large digital arrays can be completed in seconds, and the calibration accuracy fully meets the actual usage.

[0067] Preferably, the method further comprises: calibrating the receiving path, from Figure 4 It can be seen that it is an antenna array with one channel for transmission and m channels for reception, that is, one transmit and m receive. Therefore, it is only necessary to generate a sequence with good autocorrelation characteristics, and use the signal source in the mid- and far-field to send the sequence to the multi-channel receiving channels. After the sequence is collected, it is sent to the channel estimation module for channel characteristic calculation, and the hardware circuit characteristics of the multi-channel can be obtained to achieve rapid calibration.

[0068] Multi-channel calibration is performed using the same autocorrelation signal sequence to ensure that the hardware characteristics of all receiving channels are consistent and can remain consistent during subsequent signal reception, reducing errors caused by differences in hardware characteristics between different channels and achieving rapid calibration.

[0069] Example 2

[0070] like Figure 2 As shown, this embodiment provides a fast calibration device for a large digital array, the device at least includes a plurality of transmission channels, a channel characteristic calculation module and a signal collector arranged in the far field of the antenna array, wherein the transmission channel at least includes a characteristic compensation module, a DAC+upper modulation module, a power amplifier module and an antenna unit, and the characteristic compensation module, the DAC+upper modulation module, the power amplifier module and the antenna unit are connected in sequence;

[0071] The signal collector is connected to the channel characteristic calculation module, and is used to receive the radio frequency signals transmitted from multiple transmission channels, analyze the starting time point of the transmission signal, and then use the random sequence in each transmission channel and the digital IQ data received by the signal collector to perform cross-correlation operations, and send the obtained cross-correlation values ​​to the channel characteristic calculation module for channel characteristic calculation to obtain multiple hardware circuit characteristics for calibration;

[0072] One end of the channel characteristic calculation module is connected to the incident end of each transmission channel for receiving the random sequence in each channel; the other end is connected to the characteristic compensation unit of each transmission channel for compensating the multiple hardware circuit characteristics used for calibration into each transmission path for calibration.

[0073] The rapid calibration device for a large digital array provided in the embodiment of the present scheme is used to execute the rapid calibration method for a large digital array described in Example 1. Its implementation method is consistent with the implementation method of the rapid calibration method for a large digital array provided in Example 1 of the present scheme, and can achieve the same beneficial effects, which will not be repeated here.

[0074] Example 3

[0075] like Figure 5 As shown, on the basis of embodiments 1 and 2, in order to further realize the calibration of large digital arrays, reduce the bit error rate, and improve the signal quality, an interference estimation module is further added in this embodiment to offset the influence of the downlink received signal intermodulation on the uplink transmitted signal, thereby further improving the anti-interference performance of the antenna array and improving the signal quality by combining the two architectures. Specifically, Figure 5 As shown, one end of the interference estimation module is connected to the characteristic compensation module of the transmission channel, and is used to collect data from the transmission channel that needs to perform interference cancellation; one end is connected to the signal collector set at the mid- and far-field receiving end, and is used to collect data from the receiving channel.

[0076] Then, based on the collected data, optimization processing is performed in the interference estimation module to obtain the cancellation coefficient of the receiving channel and the uplink transmission interference, and the cancellation coefficient is used to build an anti-interference model. In the anti-interference model, the cancellation coefficient is combined with the downlink receiving signal to obtain a cancellation signal with the same magnitude and opposite phase as the uplink transmission interference. The generated cancellation signal is added or subtracted from the uplink transmission signal to affect the phase, thereby effectively solving the out-of-band interference of transmission on reception in the antenna array.

[0077] Specifically, the optimization process includes:

[0078] Step S41: constructing a fitting intermodulation signal using the downlink received signal and the power amplifier intermodulation model according to the collected data, and performing uplink shaping filtering on the fitting intermodulation signal to obtain a fitting intermodulation signal containing only the uplink passband part;

[0079] Preferably, the power amplifier intermodulation model in this embodiment uses a Volterra series model, and the power amplifier intermodulation model actually used is obtained for the component of the signal falling in the uplink passband, and its formula is:

[0080] Y′(k)=y(k)G(t)

[0081] Among them, y(k) is the output of the Volterra series model; G(t) is the output of the uplink shaping filter; Y′(k) represents the output of the power amplifier intermodulation model, which is a fitted intermodulation signal containing only the uplink passband part.

[0082] And because the power amplifier model is centered on the downlink receive signal, and the uplink shaping filter is centered on the uplink transmit signal, it is also necessary to perform band-limiting operation on the power amplifier intermodulation model to align the frequencies of the power amplifier intermodulation model and the uplink shaping filter.

[0083] Step S42: performing a cross-correlation operation on the fitted intermodulation signal filtered in step S41 and the actual interference signal of the uplink transmission, and comparing the cross-correlation operation result with a preset threshold value. If the cross-correlation result is greater than the threshold value, it means that the intermodulation of the downlink receiving channel has an impact on the reception of the uplink transmission signal;

[0084] Wherein, the cross-correlation calculation formula is:

[0085]

[0086] Among them, x * (kt) represents the transmitted signal; Y′(k) represents the output of the power amplifier intermodulation model; r yx (t) represents the cross-correlation result.

[0087] Step S43: If the cross-correlation result is greater than the threshold, an optimization algorithm is used to estimate the cancellation coefficient of the downlink receiving channel and the uplink transmission interference, and the cancellation coefficient is used to construct an anti-interference model. In the anti-interference model, the cancellation coefficient is combined with the downlink receiving signal to obtain a cancellation signal that is equal to the uplink transmission interference in magnitude and opposite in phase. The generated cancellation signal is added or subtracted from the uplink transmission signal to affect the phase, thereby eliminating the interference falling within the uplink band.

[0088] Preferably, in step S43, the using of an optimization algorithm to estimate the cancellation coefficient of the downlink receiving channel and the uplink transmitting interference specifically includes:

[0089] S51: Obtain an error e(k) of the anti-interference model by subtracting the output Y′(k) of the power amplifier intermodulation model from the actual interference signal x(k) transmitted uplink;

[0090] e(k)=x(k)-Y′(k)

[0091] Use the optimization algorithm to find the appropriate compensation coefficient h so that

[0092]

[0093] Since the overdetermined equation has no unique solution, the least squares method is used to solve the approximate solution of the optimal offset coefficient, thereby obtaining a series of offset coefficients, the formula of which is:

[0094] H=(y*y H ) -1 y H x

[0095] Wherein, y represents the downlink received signal; x represents the uplink transmitted signal; and H represents the cancellation coefficient set.

[0096] At this time, if the series of cancellation coefficients H obtained in the above steps cannot cancel the interference signal below the bottom noise, the following operations are performed:

[0097] S52: Select a set of offset coefficients with the best offset effect to form a new initial set, recorded as initial set C = [H1H2H3 ...H a ];

[0098] S53: Optimizing the cancellation coefficients in the initial set C until the obtained cancellation coefficients can cancel the interference signal below the bottom noise.

[0099] Specifically, the optimization process in step S53 includes:

[0100] S531: Select two sets of cancellation coefficients with the best cancellation effect from the initial set C, then randomly exchange a of the cancellation coefficients, and calculate the cancellation errors of the two new sets of cancellation coefficients. If the cancellation error of the new cancellation coefficient set is better than the cancellation error of the worst performance set in the initial set C by more than 1 dB, then add the newly generated cancellation coefficient sets H′1 and H′2 to the initial set C to form a new set C1;

[0101] S532: Randomly select two sets of cancellation coefficient sets in set C1, and randomly exchange a coefficients therein, calculate the cancellation errors of the two new sets of cancellation coefficient sets, and if the cancellation error of the new cancellation coefficient set is better than the cancellation error of the worst performance set in the initial set C by more than 1 dB, then add the newly generated cancellation coefficient sets H″1 and H″2 to set C1 to form a new set C2;

[0102] S533: Randomly select a set of offset coefficients from set C2, and then randomly select The offset coefficients are: b is the number of offset coefficients in this group. Indicates rounding up; then the amplitudes of the selected cancellation coefficients are changed to random values ​​in the interval [0.95A, 1.05A] until the cancellation error of the new cancellation coefficient set is more than 1dB better than the cancellation error of the worst performance group in the initial set C, then the newly generated cancellation coefficient set is added to the initial set C to form a new set C3;

[0103] S534: Determine the number of cancellation coefficient sets in set C3. If the number is greater than 4b, delete several sets of cancellation coefficients with the worst performance until the number of elements in the set is less than or equal to 4b.

[0104] S535: Repeat steps S531-S534 until the obtained cancellation coefficient can cancel the interference signal below the noise floor.

[0105] Therefore, in this embodiment, while embodiments 1 and 2 effectively solve the problems of slow calibration of existing large antenna arrays and the need to prepare an additional common channel to achieve calibration, the use of digital interference cancellation is further combined to further solve the out-of-band interference of transmission on reception in the antenna array. The combination of the two architectures can achieve rapid calibration of large digital arrays while improving the anti-interference performance of the antenna array.

[0106] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A fast calibration method for a large digital array, characterized in that: The method comprises: S1: Send different random sequences to multiple transmission channels at the same time, set the lengths of the random sequences to be the same and send them cyclically in each channel of the antenna array; S2: A signal collector is provided at the far-field receiving end of the antenna array, and is used to receive the RF signals transmitted from multiple transmission channels, analyze the starting time point of the transmission signal, and then use the random sequence in each transmission channel to perform cross-correlation operation with the digital IQ data received by the signal collector; S3: Calculate multiple hardware circuit characteristics for calibration using a channel estimation algorithm based on the obtained cross-correlation value information, and compensate them to each channel for calibration.

2. A fast calibration method for a large digital array according to claim 1, characterized in that: The step S2 includes: setting a cross-correlation operation function according to the transmitted signal and the received signal, wherein the cross-correlation operation function formula is: Wherein, x[n] is the transmitted signal; y[n] is the received signal; t is the delay, which indicates the time offset of signal y[n] relative to signal x[n]; and n is the time index.

3. A fast calibration method for a large digital array according to claim 2, characterized in that: In step S3, the multiple hardware circuit characteristics at least include: By obtaining the cross-correlation value R xy The optimal delay is obtained by maximizing [t], so as to determine the alignment moment of the signal to achieve signal synchronization; the phase difference and amplitude difference are calculated based on the obtained cross-correlation value, and the formulas are: phase difference Φ = angle (Rxy); amplitude difference A = |Rxy|.

4. The rapid calibration method for a large digital array according to claim 2, characterized in that: The multiple hardware circuit characteristics also include obtaining the in-band fluctuation h of the channel through channel estimation, and the formula is: Where, F represents Fourier transform; F -1 represents the inverse Fourier transform.

5. The rapid calibration method for a large digital array according to claim 3, characterized in that: The method further comprises performing interpolation processing on the cross-correlation function to obtain a more accurate time delay.

6. A fast calibration method for a large digital array according to any one of claims 1 to 5, characterized in that: In the step S3, when compensating multiple hardware circuit characteristics into each path for calibration, it also includes: monitoring whether a resolvable autocorrelation level is maintained between multiple transmission channels to set the number of transmission channels to be calibrated simultaneously, wherein the resolvable level of each hardware circuit characteristic can be set according to the calibration requirement level of the antenna array.

7. A fast calibration method for a large digital array according to any one of claims 1 to 5, characterized in that: In step S1, the sequence transmission time of some channels may be set to be staggered with other channels by several symbols for transmission, or some channels may be set to use sequences of different lengths for transmission, so as to obtain better cross-correlation performance.

8. A fast calibration method for a large digital array according to any one of claims 1 to 5, characterized in that: When calibrating in step S3, all channels or local channels of the antenna array can be selected for calibration according to the specifications of the antenna array. When multiple hardware circuit characteristics are compensated for all channels of the antenna array, the entire antenna array is calibrated at one time; when multiple hardware circuit characteristics are compensated for part of the channels of the antenna array, the global calibration data of the entire array surface can be obtained by performing multiple local tests, utilizing the characteristics that there is a certain amount of overlap between local arrays and the channel state remains unchanged at the overlap.

9. A fast calibration method for a large digital array according to claim 8, characterized in that: The method also includes: calibrating the receiving path, only one sequence with good autocorrelation characteristics needs to be generated, and the sequence is sent to multiple receiving channels using a signal source in the mid- and far-field. After the sequence is collected, it is sent to a channel estimation module for channel characteristic calculation, so that the hardware circuit characteristics of the multiple channels can be obtained to achieve rapid calibration.

10. A fast calibration device for a large digital array, characterized in that: The device comprises at least a plurality of transmission channels, a channel characteristic calculation module and a signal collector arranged in the far field of the antenna array, wherein the transmission channel comprises at least a characteristic compensation module, a DAC+up-modulation module, a power amplifier module and an antenna unit; The signal collector is connected to the channel characteristic calculation module, and is used to receive the radio frequency signals transmitted from multiple transmission channels, analyze the starting time point of the transmission signal, and then use the random sequence in each transmission channel and the digital IQ data received by the signal collector to perform cross-correlation operations, and send the obtained cross-correlation values ​​to the channel characteristic calculation module for channel characteristic calculation to obtain multiple hardware circuit characteristics for calibration; One end of the channel characteristic calculation module is connected to the incident end of each transmission channel for receiving the random sequence in each channel; the other end is connected to the characteristic compensation unit of each transmission channel for compensating the multiple hardware circuit characteristics used for calibration into each transmission path for calibration.

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