An online calibration system and method for a digital receive array

Abstract

The application provides an online correction system of a digital receiving array, which comprises a digital processing module, a correction transmitting channel, an N-path array receiving channel and a correction coupling network; the digital processing module is used for generating a correction sample signal and inputting the correction sample signal to the correction transmitting channel; the correction transmitting channel is used for receiving a signal output by the N-path array receiving channel, performing beam synthesis processing and generating a correction table; the correction transmitting channel is used for transmitting the correction sample signal after relevant processing to the correction coupling network; the correction coupling network is used for coupling the signal transmitted by the correction transmitting channel with an antenna and then injecting the coupled signal into the N-path array receiving channel; the N-path array receiving channel is used for transmitting the coupled signal after relevant processing to a digital beam synthesis module and a correction table generation module in the digital processing module. In the application, the array correction and the array signal receiving work simultaneously, the work flow interruption caused by the array correction is avoided, the correction flow is simplified, and the work efficiency of the system is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of digital arrays, and in particular to an online calibration system and method for a digital receiving array. Background Technology

[0002] The conventional digital receiver array channel calibration process first involves a digital processor generating a digital intermediate frequency (IF) signal via a digital signal generator (DDS) as a calibration sample signal, which is then output to the calibration transmitter channel. This forms an RF calibration sample signal, which is then injected into each receiver channel through a calibration coupling network. The signal is then amplified, filtered, down-converted, filtered by the intermediate frequency (IF), and sampled by an ADC to form calibration sample signals for N channels. After the beamforming mode is cut off, the calibration sample signals are subjected to orthogonal digital down-conversion, and the channel phase difference and amplitude difference are extracted to form a calibration table for the current frequency band.

[0003] However, the problem with this correction method is that the array needs to switch to correction mode during correction, which interrupts the normal working process and affects the system's efficiency to some extent. Summary of the Invention

[0004] To address the problems existing in the prior art, an online calibration system and method for digital receiving arrays are provided. By adopting a new calibration sample signal, online calibration of the digital receiving array is achieved, that is, beamforming and array calibration work simultaneously, avoiding task interruption caused by array calibration, thereby improving system efficiency.

[0005] The technical solution adopted in this invention is as follows: an online calibration system for a digital receiving array, comprising: a digital processing module, a calibration transmission channel, N array receiving channels, a power divider, and a calibration coupling network;

[0006] The digital processing module includes a calibration sample signal generation module, a digital beamforming module, and a calibration table generation module. The calibration sample signal generation module generates calibration sample signals and inputs them into the calibration transmission channel. The digital beamforming module receives signals output from the N-channel array receiving channels, performs channel calibration using a calibration table, and then performs beamforming processing. The calibration table generation module receives signals output from the N-channel array receiving channels, performs digital signal processing to generate a calibration table, and transmits it to the digital beamforming module.

[0007] The calibration transmission channel performs digital-to-analog conversion, intermediate frequency filtering, up-conversion, and radio frequency filtering on the input calibration sample signal, and then transmits it to the calibration coupling network after power division by a power divider.

[0008] The calibration coupling network is used to couple the signal transmitted through the calibration transmit channel with the signal received by the N antennas, and then inject it into the N array receive channels;

[0009] The N-channel array receiving channel is used to amplify, RF filter, down-convert, IF filter, and analog-to-digital converter the coupled signal before transmitting it to the digital beamforming module and calibration table generation module in the digital processing module.

[0010] Furthermore, the digital processing module also includes a code generator for generating two identical encoded sequences. One sequence is input into the correction sample signal generation module to assist in generating correction sample signals; the other sequence is input into the correction table generation module to assist in digital signal processing.

[0011] Furthermore, the correction sample signal generation module includes a Direct Digital Frequency Synthesizer (DDS) circuit and a modulator. The DDS generates a digital intermediate frequency signal, which is input into the modulator. The modulator simultaneously receives a coding sequence generated by the code generator and performs BPSK modulation between the coding sequence and the digital intermediate frequency signal to obtain the correction sample signal.

[0012] Furthermore, the calibration table generation module includes N sequentially connected quadrature downconverter modules, demodulators, integral clearing modules, and calibration data smoothing calculation modules. The signals transmitted by the N array receiving channels are correspondingly input into the N quadrature downconverter modules, and digital quadrature downconversion, demodulation, and integral clearing are performed sequentially to obtain calibration amplitude and phase signals, which are then input into the calibration data smoothing calculation module to complete the smoothing calculation and form a calibration table.

[0013] The code generator generates another encoded sequence, which is then input into N demodulators for demodulation. The quadrature downconverter module simultaneously receives the digital intermediate frequency signal generated by the DDS circuit and performs digital quadrature downconversion processing together with the signal transmitted through the receiving channel.

[0014] Furthermore, the digital beamforming module uses set weights to perform a weighted summation on the received signals to obtain the synthesized digital beam.

[0015] Furthermore, the digital processing module sends the signals transmitted from the N array receiving channels to the digital beamforming module and the calibration table generation module, respectively.

[0016] Furthermore, it also includes a local oscillator source, used to provide a local oscillator signal when performing frequency conversion processing for the N-channel array receiving channel and the correction transmitting channel; the digital processing module also includes a frequency control module, which is connected to the local oscillator source and used to control the frequency of the output local oscillator signal.

[0017] Furthermore, the calibration transmission channel includes a DAC module, an intermediate frequency filter module, an up-conversion module, an radio frequency filter module, and an amplification module connected in sequence. These modules sequentially perform digital-to-analog conversion, intermediate frequency filtering, up-conversion, radio frequency filtering, and signal amplification on the input signal, and finally input the signal to the power divider.

[0018] Furthermore, the N-channel array receiving channels are identical in composition, each including a low-noise amplifier (LNA) module, an RF filter module, a down-conversion module, an intermediate frequency filter module, and an ADC module connected in sequence. These modules amplify, filter, down-convert, filter, and convert the input signal to digital in sequence, and finally input the signal to the digital processing module.

[0019] This invention also proposes an online calibration method for the online calibration system based on the aforementioned digital receiving array. The digital processing module generates one coded signal as a calibration sample signal, which is injected into N array receiving channels via a calibration transmit channel, a power divider, and a calibration coupling network. This signal is coupled with the received signals from the N antennas and then returns to the digital processing module after passing through the N array receiving channels. In the digital processing module, the received signal is split into two paths: one is sent to the digital beamforming module, and the other is sent to the calibration table generation module. In the calibration table generation module, the signal generated by the DDS is first used to perform digital quadrature down-conversion on the signals output from the N array receiving channels. Then, the same coding sequence is used to demodulate and integrate the N digitally quadrature down-converted signals to obtain the calibration amplitude and phase of the N receiving channels, thereby calculating the calibration table. In the digital beamforming module, the calibration table is used to perform channel calibration on the signals output from the N array receiving channels, and then digital beams are synthesized.

[0020] Compared with the prior art, the beneficial effects of adopting the above technical solution are as follows: the online calibration system and method proposed in this invention can operate simultaneously with array calibration and array signal reception, avoiding the interruption of the workflow caused by array calibration, thereby improving the system's working efficiency. Attached Figure Description

[0021] Figure 1 This is a block diagram illustrating the principle of online calibration of the digital receiving array channel proposed in this invention.

[0022] Figure 2 This is an amplitude consistency curve for conventional and online correction of a digital receiver array channel in one embodiment of the present invention.

[0023] Figure 3 This is a phase consistency curve for conventional and online correction of a digital receiver array channel in one embodiment of the present invention.

[0024] Figure 4This refers to the baseband envelope output by the digital beamforming module in one embodiment of the present invention, both when there is no online correction signal and when there is an online correction signal.

[0025] Figure 5 This refers to the signal spectrum output by the digital beamforming module in one embodiment of the present invention, with and without an online correction signal.

[0026] Figure 6 This is an array beam scan diagram of the digital beamforming module in one embodiment of the present invention, showing the conditions with and without an online correction signal. Detailed Implementation

[0027] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar modules or modules having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Rather, the embodiments of this application include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0028] Example 1

[0029] To address the issue that existing digital receiver arrays require switching to calibration mode during calibration, interrupting normal operation and impacting system efficiency, this embodiment proposes an online calibration system for digital receiver arrays that can simultaneously perform array calibration and array signal reception. The specific solution is as follows:

[0030] like Figure 1 As shown, an online calibration system for a digital receiver array includes: a digital processing module, a calibration transmission channel, N array receiving channels, a power divider, and a calibration coupling network;

[0031] The digital processing module includes a calibration sample signal generation module, a digital beamforming module, and a calibration table generation module. The calibration sample signal generation module generates calibration sample signals and inputs them into the calibration transmission channel. The digital beamforming module receives signals output from the N-channel array receiving channels, performs channel calibration using the calibration table, and then performs beamforming processing. The calibration table generation module receives signals output from the N-channel array receiving channels, performs digital signal processing to generate a calibration table, and transmits it to the digital beamforming module for channel calibration, and then synthesizes the beam.

[0032] The calibration transmission channel performs digital-to-analog conversion, intermediate frequency filtering, up-conversion, and radio frequency filtering on the input calibration sample signal, and then transmits it to the calibration coupling network after power division by a power divider.

[0033] The calibration coupling network is used to couple the signal transmitted through the calibration transmit channel with the signal received by the N antennas, and then inject it into the N array receive channels;

[0034] The N-channel array receiving channel is used to amplify, RF filter, down-convert, IF filter, and analog-to-digital converter the coupled signal before transmitting it to the digital beamforming module and calibration table generation module in the digital processing module.

[0035] In this embodiment, the digital processing module further includes a code generator, which generates two identical encoded sequences. One sequence is input to the correction sample signal generation module to assist in generating the correction sample signal; the other sequence is input to the correction table generation module to assist in digital signal processing.

[0036] Specifically, the correction sample signal generation module includes a direct digital frequency synthesis (DDS) circuit and a modulator. The DDS circuit generates a digital intermediate frequency (IF) signal which is input to the modulator. The modulator simultaneously receives a coded sequence generated by the code generator and modulates the coded sequence with the digital IF signal using BPSK modulation to obtain the correction sample signal.

[0037] In this embodiment, the digital processing module sends the signals transmitted by the N array receiving channels to the digital beamforming module and the calibration table generation module respectively, thereby realizing simultaneous array calibration and array signal reception.

[0038] Furthermore, the calibration table generation module includes N quadrature downconverter modules, demodulators, integral clearing modules, and calibration data smoothing calculation modules connected in sequence. The signals transmitted by the N array receiving channels are correspondingly input into the N quadrature downconverter modules, and digital quadrature downconversion, demodulation, and integral clearing are performed in sequence to obtain calibration amplitude and phase signals, which are then input into the calibration data smoothing calculation module to complete the smoothing calculation and form the calibration table.

[0039] The code generator generates another encoded sequence, which is then input into N demodulators for demodulation. The quadrature downconverter module simultaneously receives the digital intermediate frequency signal generated by the DDS circuit and performs digital quadrature downconversion processing together with the signal transmitted through the receiving channel.

[0040] The digital beamforming module uses set weights to sum the received signals to obtain the synthesized digital beam.

[0041] The calibration system proposed in this embodiment also includes a local oscillator source, which provides a local oscillator signal when performing frequency conversion processing on the array receiving channel and the calibration transmitting channel; correspondingly, the digital processing module also includes a frequency control module, which is connected to the local oscillator source and is used to control the frequency of the output local oscillator signal.

[0042] In this embodiment, the calibration transmission channel includes a DAC module, an intermediate frequency filter module, an up-conversion module, an radio frequency filter module, and an amplification module connected in sequence. The input signal is sequentially processed by digital-to-analog conversion, intermediate frequency filtering, up-conversion, radio frequency filtering, and signal amplification, and finally the signal is input to the power divider.

[0043] In this embodiment, the N-channel array receiving channels are identical, each including a low-noise amplifier (LNA) module, an RF filter module, a down-conversion module, an intermediate frequency filter module, and an ADC module connected in sequence. These modules amplify, filter, down-convert, filter, and convert the input signal to digital in sequence, and finally input the signal to the digital processing module.

[0044] Since the correction signal in this invention is an encoded signal, which is equivalent to thermal noise, it will raise the noise floor of the received signal, but will not affect the reception of the signal.

[0045] Example 2

[0046] This embodiment also proposes an online calibration method based on the online calibration system of the digital receiving array described in Embodiment 1. The digital processing module generates one coded signal as a calibration sample signal, which is injected into N array receiving channels after passing through a calibration transmit channel, a power divider, and a calibration coupling network. This signal is coupled with the N antenna received signals and then returns to the digital processing module after passing through the N array receiving channels. In the digital processing module, the received signal is split into two paths: one is sent to the digital beamforming module, and the other is sent to the calibration table generation module. In the calibration table generation module, the signal generated by the DDS circuit is first used to perform digital quadrature downconversion on the signals output from the N array receiving channels. Then, the same coding sequence is used to demodulate and integrate the N digitally quadrature downconverted signals to obtain the calibration amplitude and phase of the N receiving channels, thereby calculating the calibration table. In the digital beamforming module, the calibration table is used to perform channel calibration on the signals output from the N array receiving channels, and then digital beams are synthesized.

[0047] The correction process will be explained in further detail below:

[0048] The digital processing module generates a digital intermediate frequency (IF) signal x(t) as a correction excitation signal through a DDS circuit. Simultaneously, a code generator produces an encoded sequence c(t). The encoded sequence is then BPSK modulated with the IF signal to obtain the corrected sample signal x′(t), expressed as:

[0049] x′(t)=x(t)c(t) (1)

[0050] The x′(t) signal is output to the calibration transmit channel, and after passing through a DAC, intermediate frequency filter, up-conversion, and RF filter, it is injected into the N-channel array receive channel via a coupling calibration network. After coupling with the antenna input signal, it passes through low-noise amplification, RF filtering, down-conversion, intermediate frequency filtering, and ADC acquisition to obtain the received signal x. i "(t), the expression is:

[0051]

[0052] In the formula, i=0,1,2,...N-1, a i For the additional amplitude and phase of channel i, n i For the thermal noise of channel i, r i (t) represents the received signal from channel i. This is the delayed version of c(t) after passing through the calibrated transmit channel, the calibrated coupling network, and the N array receive channels. The coupling calibration network usually has good consistency, or its inter-channel errors can be measured in advance.

[0053] The received signal is input into the digital processing module, one path is sent to the digital beamforming module, and the other path is sent to the calibration table generation module.

[0054] In the calibration table generation module, the N received signals and the calibration excitation signal x(t) undergo digital quadrature downconversion, and then demodulate and integrate the resulting coded sequence c′(t) generated by the code generator to obtain... The expression is:

[0055]

[0056] In the formula, * denotes conjugate, and c′(t) and It is phase aligned, therefore it has T is the period of the code sequence, that is, the code sequence repeats at time intervals T.

[0057] right After smoothing filtering, the estimated values ​​of the channel's amplitude and phase parameters can be obtained. Create a correction table and estimate the value. The expression is:

[0058]

[0059] In the formula, function f is the smoothing filter function. In the third equation, the second term is the encoded input signal, which can be equivalent to random noise, and the third term is thermal noise. Using a long-period encoding sequence (i.e., increasing T) can effectively suppress the power of the noise term, thereby improving... The estimation accuracy is relatively high.

[0060] In the digital beamforming module, weight w is used. i For the received signal x i We perform a weighted summation on ″(t) to obtain the digital beam z(t), which is expressed as:

[0061]

[0062] As can be seen, the first term in the formula is the synthesized beam, the second term is the thermal noise of the receiving channel, and the third term is the correction sample signal. Since the correction signal is an encoded signal, it is equivalent to thermal noise, which will raise the noise floor of the received signal, but will not affect the signal reception.

[0063] Taking an 8-channel digital array as an example, Figure 2 and Figure 3 The amplitude and phase consistency curves for conventional and online corrections are provided. Figure 2 Only the correction signal is present. Figure 3 The system contains a correction signal and an input signal, and the correction signal has a power 20dB lower than the input signal. This indicates that the two correction curves have good consistency.

[0064] Figure 4 , Figure 5 and Figure 6 The baseband envelope, signal spectrum, and array beam scan diagram of the digital beamforming module are shown with and without an online correction signal. The curves under the two conditions are basically consistent, indicating that online correction has little impact on array signal reception.

[0065] It should be noted that, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances. The accompanying drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0066] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An online calibration system for a digital receiver array, characterized in that, include: Digital processing module, calibration transmit channel, N-channel array receive channel, power divider, and calibration coupling network; The digital processing module includes a calibration sample signal generation module, a digital beamforming module, and a calibration table generation module. The calibration sample signal generation module generates calibration sample signals and inputs them into the calibration transmission channel. The digital beamforming module receives signals output from the N-channel array receiving channels, performs channel calibration using a calibration table, and then performs beamforming processing. The calibration table generation module receives signals output from the N-channel array receiving channels, performs digital signal processing to generate a calibration table, and transmits it to the digital beamforming module. The correction sample signal generation module includes a direct digital frequency synthesis circuit and a modulator. The direct digital frequency synthesis circuit generates a digital intermediate frequency signal, which is then input to the modulator. The modulator simultaneously receives one encoded sequence generated by the code generator, and modulates the encoded sequence with the digital intermediate frequency signal using BPSK to obtain the correction sample signal. The calibration table generation module includes N quadrature downconverter modules, demodulators, integral clearing modules, and calibration data smoothing calculation modules connected in sequence. The signals transmitted by the N array receiving channels are input into the N quadrature downconverter modules, and digital quadrature downconversion, demodulation, and integral clearing are performed in sequence to obtain calibration amplitude and phase signals, which are then input into the calibration data smoothing calculation module to complete the smoothing calculation and form the calibration table. The calibration transmission channel performs digital-to-analog conversion, intermediate frequency filtering, up-conversion, and radio frequency filtering on the input calibration sample signal, and then transmits it to the calibration coupling network after power division by a power divider. The calibration coupling network is used to couple the signal transmitted through the calibration transmit channel with the signal received by the N antennas, and then inject it into the N array receive channels; The N-channel array receiving channel is used to amplify, RF filter, down-convert, IF filter, and analog-to-digital converter the coupled signal before transmitting it to the digital beamforming module and calibration table generation module in the digital processing module.

2. The online calibration system for a digital receiver array according to claim 1, characterized in that, The digital processing module also includes a code generator, which generates two identical coded sequences. One sequence is input to the correction sample signal generation module to assist in generating correction sample signals; the other sequence is input to the correction table generation module to assist in digital signal processing.

3. The online calibration system for a digital receiving array according to claim 2, characterized in that, The code generator generates another encoded sequence, which is then input into the N demodulators for demodulation. The quadrature downconversion module simultaneously receives the digital intermediate frequency signal generated by the direct digital frequency synthesis circuit and performs digital quadrature downconversion processing together with the signal transmitted through the receiving channel.

4. The online calibration system for a digital receiver array according to claim 1, characterized in that, The digital beamforming module uses set weights to perform a weighted summation of the received signals to obtain the synthesized digital beam.

5. The online calibration system for a digital receiver array according to claim 1, characterized in that, The digital processing module sends the signals transmitted from the N array receiving channels to the digital beamforming module and the calibration table generation module, respectively.

6. The online calibration system for a digital receiver array according to claim 1, characterized in that, It also includes a local oscillator source, which provides a local oscillator signal when performing frequency conversion processing for the N-channel array receiving channel and the correction transmitting channel; the digital processing module also includes a frequency control module, which is connected to the local oscillator source and is used to control the frequency of the output local oscillator signal.

7. The online calibration system for a digital receiver array according to claim 1, characterized in that, The calibration transmission channel includes a DAC module, an intermediate frequency filter module, an up-conversion module, an radio frequency filter module, and an amplification module connected in sequence. The input signal is sequentially processed by digital-to-analog conversion, intermediate frequency filtering, up-conversion, radio frequency filtering, and signal amplification, and finally the signal is input to the power divider.

8. The online calibration system for a digital receiver array according to claim 1, characterized in that, The N-channel array receiving channels are identical, each including a low-noise amplifier module, an RF filter module, a down-conversion module, an intermediate frequency filter module, and an ADC module connected in sequence. These modules amplify, filter, down-convert, filter, and convert the input signal to digital in sequence, and finally input the signal to the digital processing module.

9. An online calibration method for an online calibration system based on any one of claims 1-8, characterized in that, The digital processing module generates one coded signal as a correction sample signal, which is injected into the N array receiving channels through the correction transmission channel, power divider and correction coupling network, and coupled with the N antenna receiving signals. After passing through the N array receiving channels, it returns to the digital processing module. In the digital processing module, the received signal is split into two paths: one path is sent to the digital beamforming module, and the other path is sent to the calibration table generation module. In the calibration table generation module, the signal generated by the DDS is first used to perform digital quadrature downconversion on the signal output from the N array receiving channels. Then, the same coding sequence is used to demodulate and integrate the N digitally quadrature downconverted signals to obtain the calibration amplitude and phase of the N receiving channels, and then the calibration table is calculated. In the digital beamforming module, a calibration table is used to perform channel calibration on the signals output from the N array receiving channels, and then the digital beam is synthesized.

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