Method for calibrating relative time delay of uplink channel and downlink channel between antennas

Abstract

The invention discloses a method for calibrating relative time delay of an uplink channel and a downlink channel between antennas, which comprises the following steps of: calibrating relative signal time delay difference of the downlink channels of the antennas in an antenna array to obtain relative signal time delay of the downlink channels of each antenna in the antenna array; and calibrating the relative signal delay inequality of the uplink channels of the antennas in the antenna array to obtain the relative signal delay inequality of the uplink channels of the antennas in the antenna array. The method is simple, reliable and convenient to implement, and the requirement for relative time delay of signals of the uplink channel and the downlink channel of each antenna of the antenna array in engineering practice can be met.

Description

Technical Field

[0001] The present application relates to the field of antenna technology, and in particular to a method for calibrating the relative time delays of uplink channels and downlink channels between antennas. Background Art

[0002] Antenna arrays use multiple small-aperture antennas to form an equivalent large-aperture antenna for space targets. Due to their flexibility and low engineering costs, antenna arrays have gained increasing attention in deep space exploration in recent years, becoming a hot area of ​​research for novel antenna systems.

[0003] A key technical issue in implementing antenna arrays is how to complete the uplink and downlink arraying of the antenna array by synthesizing the uplink and downlink signals of the array antennas. The basic principle of uplink and downlink signal synthesis of the array antenna is to compensate the signal delays of each antenna in the array to the same point to complete the signal synthesis. Therefore, we need to calibrate the relative delay differences of the uplink and downlink channels between the antennas in the array. Generally speaking, since we can use multiple antennas to simultaneously receive the downlink signal transmitted by the far-field calibration antenna, we can easily calibrate the relative signal delay of the downlink channel between the antennas in the array by comparing the downlink signals received by multiple antennas simultaneously. However, calibrating the relative signal delay of the uplink channel between the antennas in the array is difficult because multiple antennas transmitting uplink signals simultaneously will cause mutual interference. Summary of the Invention

[0004] In view of this, the present application provides a method for calibrating the relative delay of the uplink channel and the downlink channel between antennas, using the calibrated downlink channel delay to calibrate the relative delay of the antenna uplink channel signal through compensation.

[0005] The present application discloses a method for calibrating the relative delay of uplink and downlink channels between antennas, which includes:

[0006] Step 1: Calibrate the relative signal delay difference of the downlink channel of the antennas in the antenna array to obtain the relative signal delay of the downlink channel of each antenna in the antenna array;

[0007] Step 2: Calibrate the relative signal delay difference of the uplink channels of the antennas in the antenna array to obtain the relative signal delay difference of the uplink channels of each antenna in the antenna array.

[0008] Furthermore, the step 1 includes:

[0009] Step 11: Select an antenna from the antenna array as a reference antenna. Use the calibration antenna to transmit signals to the antennas in the antenna array. Calculate the relative delay difference between the signals received by any antenna in the antenna array and the reference antenna.

[0010] Step 12: Based on the relative delay difference obtained in step 11, obtain the relative signal delay of the downlink channel between any antenna in the antenna array and the reference antenna.

[0011] Furthermore, the step 11 includes:

[0012] The calibration antenna transmits signals to the antennas in the antenna array, and the phase slope estimation method based on the FX structure is used to obtain the relative delay difference between the signals received by any antenna in the antenna array and the reference antenna.

[0013] Furthermore, the phase slope estimation method based on the FX structure is used to obtain the relative delay difference between the signal received by any antenna in the antenna array and the reference antenna, including:

[0014] Performing frequency domain transformation on the signals received by any antenna in the antenna array and the reference antenna to obtain a first spectrum signal and a second spectrum signal;

[0015] A cross-correlation operation is performed on the first spectrum signal and the second spectrum signal, and a signal delay difference of a signal received by any antenna relative to a signal received by a reference antenna is obtained according to the result of the cross-correlation operation.

[0016] Furthermore, the step 12 includes:

[0017] According to the positions of the calibration antenna and the antennas in the antenna array, the relative signal delay difference caused by the spatial path difference between any antenna in the antenna array and the reference antenna and the calibration antenna is obtained;

[0018] The relative signal delay of the downlink channel between any antenna in the antenna array and the reference antenna is obtained by calculating the relative signal delay difference between the signals received by any antenna in the antenna array and the reference antenna, which is equal to the sum of the relative signal delay difference caused by the spatial path difference between the arbitrary antenna and the reference antenna and the relative signal delay difference caused by the difference between the downlink channels of the arbitrary antenna and the reference antenna.

[0019] Furthermore, the step 2 includes:

[0020] Step 21: Obtain a signal delay difference between the closed loop formed by any antenna in the antenna array and the calibration antenna based on the signal delay of the closed loop formed by the reference antenna and the calibration antenna, and the signal delay of the closed loop formed by the reference antenna and the calibration antenna.

[0021] Step 22: Obtain the relative delay difference of the uplink channel between the arbitrary antenna and the reference antenna based on the closed loop signal delay difference between the arbitrary antenna and the reference antenna and the relative signal delay of the downlink channel between the arbitrary antenna and the reference antenna.

[0022] Furthermore, the step 21 includes:

[0023] Any antenna in the antenna array and the calibration antenna simultaneously transmit two uplink signals at different frequencies. These two uplink signals at different frequencies are converted into two downlink signals at different frequencies after passing through the downconverter of the calibration antenna. These signals are received by the arbitrary antenna and the calibration antenna respectively, thereby forming a closed loop formed by the arbitrary antenna and the calibration antenna.

[0024] Measure the signal delay of the closed loop formed by any antenna and the calibration antenna, as well as the signal delay of the closed loop formed by the reference antenna and the calibration antenna;

[0025] The signal delay difference of the closed loop formed by the arbitrary antenna and the reference antenna is obtained by subtracting the signal delay of the closed loop formed by the arbitrary antenna and the reference antenna.

[0026] Furthermore, the signal delay of the closed loop formed by the arbitrary antenna and the calibration antenna is equal to the sum of the uplink channel delay of the arbitrary antenna, twice the delay caused by the signal passing through the spatial path between the calibration antenna and the arbitrary antenna, the device delay of the calibration antenna, and the downlink channel delay of the arbitrary antenna;

[0027] The signal delay of the closed loop formed by the reference antenna and the calibration antenna is equal to the sum of the uplink channel delay of the reference antenna, twice the delay caused by the signal passing through the spatial path between the calibration antenna and the reference antenna, the downlink channel delay of the reference antenna, and the downlink channel delay of the reference antenna.

[0028] Furthermore, the signal delay difference of the closed loop formed by the arbitrary antenna and the reference antenna is equal to the sum of the relative signal delay difference of the downlink channel and the relative signal delay difference of the uplink channel.

[0029] Furthermore, the step 22 includes:

[0030] The relative signal delay difference of the uplink channel is obtained by subtracting the signal delay difference of the closed loop formed by any antenna and the reference antenna from the obtained relative signal delay difference of the downlink channel.

[0031] Due to the adoption of the above technical solution, this application has the following advantages:

[0032] 1. Solve the problem of detecting the channel delay of each antenna in the antenna array system. This application uses antenna comparison to obtain the relative signal delay difference of the downlink channel, and finally measures the relative delay difference of the antenna uplink channel using the measured downlink channel delay, solving a key problem in antenna array system design.

[0033] 2. Simple implementation, low resource usage, and reduced system design costs. This application does not require complex circuits and is relatively simple to implement. It utilizes only existing system equipment, eliminating the need for additional equipment. It also uses a software algorithm to calibrate the relative delay difference between the uplink and downlink channels of the two antennas, facilitating automated operation and reducing system design costs.

[0034] 3. This application is easy and quick to operate, facilitating system design. The application has a simple operation process, and the channel delays of each antenna in the antenna array system can be gradually detected by mutual comparison, facilitating the location and troubleshooting of problems in the engineering implementation of the antenna array system.

[0035] 4. The method proposed in this application for calibrating the relative delay difference between the uplink and downlink channels between antennas aims to provide a simple, reliable and easy-to-implement method for calibrating the relative delay of the uplink and downlink channels of each antenna in the antenna array. This application does not require any external equipment, which facilitates the design of an antenna array system that meets the index requirements in engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0037] Figure 1 2 is a schematic diagram of an embodiment of the present application of using an external calibration antenna to calibrate the relative signal delay difference of the channels of each antenna of the antenna array;

[0038] Figure 2 1 is a schematic diagram of an embodiment of the present application of using an external calibration antenna to calibrate the relative signal delay difference of the downlink channel of each antenna of the antenna array;

[0039] Figure 3 1 is a schematic diagram of using a cross-correlation method to solve the relative signal delay of two signals according to an embodiment of the present application;

[0040] Figure 4 This is a schematic diagram of an embodiment of the present application using an external calibration antenna to calibrate the relative signal delay difference of the uplink channels of each antenna of the antenna array. DETAILED DESCRIPTION

[0041] The present application is further described with reference to the accompanying drawings and embodiments. The embodiments described are only a part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field should fall within the scope of protection of the embodiments of the present application.

[0042] Traditionally, the relative delay of downlink signals between antennas in an array can be easily calibrated by comparing the downlink signals transmitted by the calibration antennas and received simultaneously by multiple antennas. However, calibrating the relative delay of uplink signals between antennas is difficult because multiple antennas transmitting uplink signals simultaneously will cause mutual interference.

[0043] Based on the characteristics of the antenna's uplink and downlink signal delays, this application proposes a method for compensating the relative signal delay of the uplink channel using the relative signal delay of the antenna's downlink channel. This method calibrates the relative signal delays of the uplink and downlink channels of each antenna in the antenna array. This method is simple, reliable, and easy to implement, meeting the requirements for the relative signal delays of the uplink and downlink channels of each antenna in the antenna array in engineering practice. Using this method, antenna array systems that meet these requirements can be designed in engineering practice.

[0044] Regarding the need to calibrate the relative delay of the uplink and downlink signals of each antenna in the antenna array system when synthesizing the signal of the far-field space target, see Figure 1 The present application provides an embodiment of a method for calibrating the relative delay of uplink channels and downlink channels between antennas, which includes:

[0045] Step 1: Calibrate the relative signal delay difference of the downlink channel of the antennas in the antenna array to obtain the relative signal delay of the downlink channel of each antenna in the antenna array;

[0046] Step 2: Calibrate the relative signal delay difference of the uplink channels of the antennas in the antenna array to obtain the relative signal delay difference of the uplink channels of each antenna in the antenna array.

[0047] The relative signal delay of the downlink channel of each antenna in the antenna array is the downlink channel signal delay compensation value required for each antenna in the antenna array to synthesize the received signals. The relative signal delay of the uplink channel of each antenna in the antenna array is the uplink channel signal delay compensation value required for each antenna in the antenna array to synthesize the received signals. Finally, the signal synthesis of the antenna array system is completed.

[0048] Optionally, step 1 includes:

[0049] Step 11: Select an antenna from the antenna array as a reference antenna. Use the calibration antenna to transmit signals to the antennas in the antenna array. Calculate the relative delay difference between the signals received by any antenna in the antenna array and the reference antenna.

[0050] Step 12: Based on the relative delay difference obtained in step 11, obtain the relative signal delay of the downlink channel between any antenna in the antenna array and the reference antenna.

[0051] Optionally, step 11 includes:

[0052] The calibration antenna transmits signals to the antennas in the antenna array, and the phase slope estimation method based on the FX structure is used to obtain the relative delay difference between the signals received by any antenna in the antenna array and the reference antenna.

[0053] Optionally, the adopting of the FX structure-based phase slope estimation method to obtain the relative delay difference of the signal received by any antenna in the antenna array and the reference antenna includes:

[0054] Performing frequency domain transformation on the signals received by any antenna in the antenna array and the reference antenna to obtain a first spectrum signal and a second spectrum signal;

[0055] A cross-correlation operation is performed on the first spectrum signal and the second spectrum signal, and a signal delay difference of a signal received by any antenna relative to a signal received by a reference antenna is obtained according to the result of the cross-correlation operation.

[0056] Optionally, step 12 includes:

[0057] According to the positions of the calibration antenna and the antennas in the antenna array, the relative signal delay difference caused by the spatial path difference between any antenna in the antenna array and the reference antenna and the calibration antenna is obtained;

[0058] The relative signal delay of the downlink channel between any antenna in the antenna array and the reference antenna is obtained by calculating the relative signal delay difference between the signals received by any antenna in the antenna array and the reference antenna, which is equal to the sum of the relative signal delay difference caused by the spatial path difference between the arbitrary antenna and the reference antenna and the relative signal delay difference caused by the difference between the downlink channels of the arbitrary antenna and the reference antenna.

[0059] Optionally, step 2 includes:

[0060] Step 21: Obtain a signal delay difference between the closed loop formed by any antenna in the antenna array and the calibration antenna based on the signal delay of the closed loop formed by the reference antenna and the calibration antenna, and the signal delay of the closed loop formed by the reference antenna and the calibration antenna.

[0061] Step 22: Obtain the relative delay difference of the uplink channel between the arbitrary antenna and the reference antenna based on the closed loop signal delay difference between the arbitrary antenna and the reference antenna and the relative signal delay of the downlink channel between the arbitrary antenna and the reference antenna.

[0062] Optionally, step 21 includes:

[0063] Any antenna in the antenna array and the calibration antenna simultaneously transmit two uplink signals at different frequencies. These two uplink signals at different frequencies are converted into two downlink signals at different frequencies after passing through the downconverter of the calibration antenna. These signals are received by the arbitrary antenna and the calibration antenna respectively, thereby forming a closed loop formed by the arbitrary antenna and the calibration antenna.

[0064] Measure the signal delay of the closed loop formed by any antenna and the calibration antenna, as well as the signal delay of the closed loop formed by the reference antenna and the calibration antenna;

[0065] The signal delay difference of the closed loop formed by the arbitrary antenna and the reference antenna is obtained by subtracting the signal delay of the closed loop formed by the arbitrary antenna and the reference antenna.

[0066] Optionally, the signal delay of the closed loop formed by the arbitrary antenna and the calibration antenna is equal to the sum of the uplink channel delay of the arbitrary antenna, twice the delay caused by the signal passing through the spatial path between the calibration antenna and the arbitrary antenna, the device delay of the calibration antenna, and the downlink channel delay of the arbitrary antenna;

[0067] The signal delay of the closed loop formed by the reference antenna and the calibration antenna is equal to the sum of the uplink channel delay of the reference antenna, twice the delay caused by the signal passing through the spatial path between the calibration antenna and the reference antenna, the downlink channel delay of the reference antenna, and the downlink channel delay of the reference antenna.

[0068] Optionally, the signal delay difference of the closed loop formed by the arbitrary antenna and the reference antenna is equal to the sum of the relative signal delay difference of the downlink channel and the relative signal delay difference of the uplink channel.

[0069] Optionally, step 22 includes:

[0070] The relative signal delay difference of the uplink channel is obtained by subtracting the signal delay difference of the closed loop formed by any antenna and the reference antenna from the obtained relative signal delay difference of the downlink channel.

[0071] For ease of understanding, this application provides a more specific embodiment:

[0072] See Figure 1The antenna array is composed of multiple antennas in the antenna array, which complete the synthesis of the received downlink signal (downlink array) or the synthesis of the transmitted uplink signal (uplink array) by compensating the delay and phase of the signal received or transmitted by each antenna, so as to improve the signal-to-noise ratio of the received or transmitted signal. In order to complete the signal synthesis function of the antenna array, it is necessary to perform downlink delay compensation (downlink signal synthesis) on the signal received by each antenna and uplink delay compensation (uplink signal synthesis) on the signal transmitted by each antenna. The downlink delay compensation value and uplink delay compensation value of each antenna in the array include the relative signal delay difference of the antenna's own uplink channel and the relative signal delay difference of the downlink channel. Therefore, it is necessary to calibrate the relative signal delay difference of the channel of each antenna in the antenna array. Figure 1 As shown, using a calibration antenna T installed at a known position, the relative signal delay difference of the uplink channel and the relative signal delay difference of the downlink channel of each antenna participating in the array (antenna 1, antenna 2, ..., antenna k, ..., antenna n) are calibrated.

[0073] See Figure 2 and Figure 3 , for the calibration of the relative signal delay difference of the antenna downlink channel, the signal transmitted by the calibration antenna can be received by two antennas at the same time, and the relative delay difference of the two signals can be obtained by using the phase slope estimation method based on the FX structure. Figure 2 As shown in the figure, the same signal is transmitted via two paths, and the received signals are in the form of r(t) and r(t-Δτ), where Δτ is the transmission delay difference, which mainly considers the delay difference introduced by the difference in the signal propagation path in space. Since the frequency of the received signal is often very high, it is down-converted using a sinusoidal signal generated by a local clock, and then quantized and encoded before being sent to the correlation processing station for correlation processing. The signal received by the correlator can be equivalent to:

[0074]

[0075] Where f0 is the down-conversion frequency, is the phase noise.

[0076] To S a (f) Perform Fourier transform to obtain:

[0077]

[0078] Similarly, S b (f) The processed spectrum is:

[0079]

[0080] Correlation between the two signals in the frequency domain yields the cross-correlation spectrum:

[0081]

[0082] It can be seen that due to the existence of delay difference, the phase of the cross-correlation function varies linearly with frequency, which is the fringe phenomenon. The calculation of Δτ is as follows:

[0083]

[0084] In practical applications, if the received signal-to-noise ratio is low, it is necessary to perform smoothing and other processing on the stripes.

[0085] like Figure 3 As shown, the downlink signal transmitted by the calibration antenna is received by antenna k and antenna k′ and is processed accordingly. Figure 2 The given delay estimation method can obtain the relative delay difference Δτ of the signals received by antenna k and antenna k′ 下行信号kk′ Due to the relative delay difference Δτ of the signals received by antenna k and antenna k′ 下行信号kk′ The relative signal delay difference caused by the spatial path difference between antenna k and antenna k′ and the relative signal delay difference caused by the difference in the downlink channels of antenna k and antenna k′ are:

[0086] Δτ 下行信号kk′ =(Δτ 空间路径k -Δτ 空间路径k′ )+)Δτ 下行通道k -Δτ 下行通道k′ ) (6)

[0087] Where: Δτ 空间路径k is the signal delay caused by the spatial path between antenna k and the calibration antenna; Δτ 空间路径k′ is the signal delay caused by the spatial path between antenna k′ and the calibration antenna; Δτ 下行通道k The signal delay caused by the downlink channel of antenna k itself; Δτ 下行通道k′ is the signal delay caused by the downlink channel of antenna k′ itself.

[0088] Since the position information of the calibration antenna is known, the relative signal delay difference (Δτ) caused by the spatial path difference between antenna k and antenna k′ and the calibration antenna can be calculated using the position information of antenna k and antenna k′ as well as the position information of the calibration antenna. 空间路径k -Δτ 空间路径k′ ), thus obtaining the relative signal delay Δτ of the downlink channel of antenna k and k′ 下行通道kk′ for:

[0089] Δτ 下行通道kk′ =Δτ 下行信号kk′ -(Δτ 空间路径k -Δτ 空间路径k′ )=Δτ下行通道k -Δτ 下行通道k′ (7)

[0090] See Figure 4 , the calibration of the relative delay difference of the antenna uplink channel can be obtained through the loop delay of the signal. Figure 4 As shown, the two antennas k and k' in the array simultaneously send two uplink signals at different frequencies. After passing through the downconverter of the calibration antenna, these two signals are converted into two downlink signals at different frequencies and received and processed by antennas k and k' respectively. The signal delay Δτ of the closed loop formed by antenna k and the calibration antenna can be measured through algorithm processing. 上行环路k And the signal delay Δτ of the closed loop formed by antenna k′ and the calibration antenna 上行环路k′ for:

[0091]

[0092] Where Δτ 上行通道k is the uplink channel delay of antenna k; Δτ 空间路径k is the time delay caused by the signal passing through the spatial path between the calibration antenna and antenna k; Δτ 标校天线 The device delay for calibrating the antenna; Δτ 下行通道k is the downlink channel delay of antenna k; Δτ 上行通道k′ is the uplink channel delay of antenna k′; Δτ 空间路径k′ is the time delay caused by the signal passing through the space path between the calibration antenna and the deep space antenna k′; Δτ 标校天线 is the device delay on the calibration antenna; Δτ 下行通道k′ is the downlink channel delay of antenna k′. Since the position information of the calibration antenna is known, the delay caused by the spatial path of antennas k and k′ can be deducted through algorithm processing, that is:

[0093]

[0094] Taking the difference between the two equations in (9) we can get:

[0095]

[0096] The first term on the right side of the above equation is the relative delay difference Δτ between the two uplink channels. 上行通道kk′ , the second term is the relative delay difference Δτ between the two downlink channels 下行通道kk′ Since the measurement problem of the relative delay difference of the downlink channels of the two antennas has been dealt with in the previous section, the relative delay difference Δτ of the downlink channels of the two antennas obtained in formula (10) and formula (7) is 下行通道kk′ , we can get the relative delay difference Δτ of the uplink channels of the two antennas 上行通道kk′ for:

[0097] Δτ 上行通道kk′ =Δτ′ 上行环路kk′ -Δτ 下行通道kk′ (11)

[0098] For an antenna array system composed of multiple antennas, one of the antennas can be selected as the reference antenna. The above method can be used to obtain the signal delay compensation values ​​of the downlink channel and the uplink channel of the signal synthesis of each antenna participating in the array, and finally complete the signal synthesis of the antenna array system.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present application should be included in the scope of protection of the claims of the present application.

Claims

1. A method for calibrating the relative delay of uplink and downlink channels between antennas, characterized in that: include: Step 1: Calibrate the relative signal delay difference of the downlink channel of the antennas in the antenna array to obtain the relative signal delay of the downlink channel of each antenna in the antenna array; Step 2: Calibrate the relative signal delay difference of the uplink channels of the antennas in the antenna array to obtain the relative signal delay difference of the uplink channels of each antenna in the antenna array.

2. The method according to claim 1, characterized in that The step 1 comprises: Step 11: Select an antenna from the antenna array as a reference antenna. Use the calibration antenna to transmit signals to the antennas in the antenna array. Calculate the relative delay difference between the signals received by any antenna in the antenna array and the reference antenna. Step 12: Based on the relative delay difference obtained in step 11, obtain the relative signal delay of the downlink channel between any antenna in the antenna array and the reference antenna.

3. The method according to claim 2, characterized in that The step 11 comprises: The calibration antenna transmits signals to the antennas in the antenna array, and the phase slope estimation method based on the FX structure is used to obtain the relative delay difference between the signals received by any antenna in the antenna array and the reference antenna.

4. The method according to claim 3, characterized in that The phase slope estimation method based on the FX structure is used to obtain the relative delay difference of the signal received by any antenna in the antenna array and the reference antenna, including: Performing frequency domain transformation on the signals received by any antenna in the antenna array and the reference antenna to obtain a first spectrum signal and a second spectrum signal; A cross-correlation operation is performed on the first spectrum signal and the second spectrum signal, and a signal delay difference of a signal received by any antenna relative to a signal received by a reference antenna is obtained according to the result of the cross-correlation operation.

5. The method according to claim 2, characterized in that The step 12 includes: According to the positions of the calibration antenna and the antennas in the antenna array, the relative signal delay difference caused by the spatial path difference between any antenna in the antenna array and the reference antenna and the calibration antenna is obtained; The relative signal delay of the downlink channel between any antenna in the antenna array and the reference antenna is obtained by calculating the relative signal delay difference between the signals received by any antenna in the antenna array and the reference antenna, which is equal to the sum of the relative signal delay difference caused by the spatial path difference between the arbitrary antenna and the reference antenna and the relative signal delay difference caused by the difference between the downlink channels of the arbitrary antenna and the reference antenna.

6. The method according to claim 1, wherein The step 2 includes: Step 21: Obtain a signal delay difference between the closed loop formed by any antenna in the antenna array and the calibration antenna based on the signal delay of the closed loop formed by the reference antenna and the calibration antenna, and the signal delay of the closed loop formed by the reference antenna and the calibration antenna. Step 22: Obtain the relative delay difference of the uplink channel between the arbitrary antenna and the reference antenna based on the closed loop signal delay difference between the arbitrary antenna and the reference antenna and the relative signal delay of the downlink channel between the arbitrary antenna and the reference antenna.

7. The method according to claim 6, characterized in that The step 21 includes: Any antenna in the antenna array and the calibration antenna simultaneously transmit two uplink signals at different frequencies. These two uplink signals at different frequencies are converted into two downlink signals at different frequencies after passing through the downconverter of the calibration antenna. These signals are received by the arbitrary antenna and the calibration antenna respectively, thereby forming a closed loop formed by the arbitrary antenna and the calibration antenna. Measure the signal delay of the closed loop formed by any antenna and the calibration antenna, as well as the signal delay of the closed loop formed by the reference antenna and the calibration antenna; The signal delay difference of the closed loop formed by the arbitrary antenna and the reference antenna is obtained by subtracting the signal delay of the closed loop formed by the arbitrary antenna and the reference antenna.

8. The method according to claim 7, characterized in that The signal delay of the closed loop formed by the arbitrary antenna and the calibration antenna is equal to the sum of the uplink channel delay of the arbitrary antenna, twice the delay caused by the signal passing through the spatial path between the calibration antenna and the arbitrary antenna, the equipment delay of the calibration antenna, and the downlink channel delay of the arbitrary antenna; The signal delay of the closed loop formed by the reference antenna and the calibration antenna is equal to the sum of the uplink channel delay of the reference antenna, twice the delay caused by the signal passing through the spatial path between the calibration antenna and the reference antenna, the downlink channel delay of the reference antenna, and the downlink channel delay of the reference antenna.

9. The method according to claim 7, characterized in that The signal delay difference of the closed loop formed by the arbitrary antenna and the reference antenna is equal to the sum of the relative signal delay difference of the downlink channel and the relative signal delay difference of the uplink channel.

10. The method according to claim 6, characterized in that The step 22 includes: The relative signal delay difference of the uplink channel is obtained by subtracting the signal delay difference of the closed loop formed by any antenna and the reference antenna from the obtained relative signal delay difference of the downlink channel.

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