A Conformity Testing Method for Phased Array Transmit Channels Based on an Optical Fiber Data Platform

Abstract

This invention relates to the field of phased array radar signal processing, particularly to the simultaneous transmission of signals from multiple independent subarrays, which are then beamformed to achieve target range and azimuth detection. A phased array transmission channel consistency testing method based on a fiber optic data platform is proposed. This method uses a 1PPS signal and sampling clock signal provided by an external time-frequency device as a basis, and employs post-processing methods to calibrate the amplitude and phase of the transmitted signals from multiple array elements within a single node. Simultaneously, using a set of nodes as a reference, the transmitted signals from multiple nodes are calibrated. This invention uses a novel transmission phase calibration method to identify the amplitude and phase differences between different array elements, achieving phase-level fusion of phased array transmitted signals, improving transmitted signal power, and better achieving target detection. It features a simple operation process and a fast and accurate data processing algorithm.

Description

Technical Field

[0001] This invention relates to the field of phased array radar signal processing, particularly to the simultaneous transmission of signals by multiple independent subarrays, which are then beamformed to achieve target range and azimuth detection. Background Technology

[0002] As a new and advanced type of phased array radar, digital phased array radar has unique advantages over traditional analog phased array radar in terms of beam flexibility, anti-jamming, and other aspects. Therefore, it is increasingly being used in military electronic equipment in ground, airborne, and spaceborne fields.

[0003] Digital phased array antennas represent a crucial direction in the development of active phased array antennas. The core of signal processing is beamforming. To achieve high antenna combining efficiency and ensure sufficient signal transmission power, it is essential to maintain amplitude and phase consistency between transmitted signals from different array elements; this requires amplitude and phase calibration before signal transmission. Conventional phased array calibration methods require long distances to meet the far-field conditions of large phased arrays, and place high demands on anechoic chamber space and antenna array structure. Furthermore, they involve complex data processing algorithms, inaccurate calibration values, and cumbersome operations. This invention aims to solve this complex operational process by enabling rapid and accurate amplitude and phase calibration of transmitted signals in a safe environment using a data processing platform. Summary of the Invention

[0004] In view of this, the main objective of this invention is to provide a phased array transmission channel consistency testing method based on an optical fiber data platform. Due to the fixed distance difference between independent subarrays in a phased array, coupled with differences in antenna structure and manufacturing processes, amplitude and phase differences exist in the transmitted signals between subarrays. To achieve beamforming, the signals of each transmission channel must undergo amplitude and phase consistency calibration before phased array antenna signal synthesis. This invention uses a novel transmission phase calibration method to identify the amplitude and phase differences between different array elements, achieving phase-level fusion of phased array transmitted signals, improving transmitted signal power, and better achieving target detection.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A phased array transmission channel conformance testing method based on an optical fiber data platform is implemented using a calibration system. The calibration system includes a node under test, a reference node, a time-frequency device, a horn antenna, a data processing platform, and a mixer. The node under test contains at least two transmission channels. The method specifically includes the following steps:

[0007] (1) Based on the sampling clock and 1PPS second pulse provided by the external time and frequency equipment, the node under test will process the intermediate frequency single tone signal through two stages of upconversion by the digital processing board and the TR component to obtain the radio frequency single tone signal, and select a transmission channel to radiate the radio frequency single tone signal according to the parameters issued by the monitoring.

[0008] (2) In an anechoic environment, adjust the polarization direction of the horn antenna to be consistent with the polarization direction of the antenna of the node under test, receive the radio frequency mono signal of the node under test, and transmit it to the mixer through the radio frequency cable of the horn antenna out of the anechoic room.

[0009] (3) The mixer mixes the radio frequency single tone signal and outputs the intermediate frequency signal to the reference node;

[0010] (4) After receiving the intermediate frequency signal, the reference node performs digital down-conversion and filtering, and then frames and packages the signal before transmitting it to the data processing platform via optical fiber.

[0011] (5) By monitoring the parameters sent, the tested node switches the transmission channel and returns to step (2) until all transmission channels of the tested node have been switched.

[0012] (6) After receiving all the data from the transmission channels, the data processing platform performs frame de-framing and calculates the amplitude and phase values ​​of each channel of the tested node.

[0013] (7) Compare the calculated amplitude values ​​of each channel and find the one with the smallest amplitude value as the basis for amplitude calibration;

[0014] (8) Using the phase value of the first channel of the node under test and the minimum amplitude value found in step (7) as a reference, perform amplitude and phase consistency calibration on the remaining channels of the node under test.

[0015] The phase relationship between the sampling clock and the 1PPS second pulse satisfies that the rising edge of the 1PPS second pulse signal is aligned with the falling edge of the sampling clock.

[0016] In step (3), the local oscillator signal of the mixer is from the same source as the sampling clock and 1PPS.

[0017] In step (6), the digital processing platform uses the rising edge of the 1PPS pulse signal for control when performing frame deframe processing.

[0018] The advantages of this invention are:

[0019] This invention uses a 1PPS signal and a sampling clock signal provided by an external time-frequency device as a basis. It employs post-processing methods to calibrate the amplitude and phase of the transmitted signals from multiple array elements within a single node. Simultaneously, it uses a set of nodes as a reference to calibrate the transmitted signals from multiple nodes. It features a simple operation process and a fast and accurate data processing algorithm. Attached Figure Description

[0020] Figure 1 This is an overall signal block diagram of the present invention;

[0021] Figure 2Flowchart for node signal transmission;

[0022] Figure 3 This is a schematic diagram illustrating the relationship between the sampling clock and the second pulse signal in the time-frequency device implemented in this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0024] The present invention presents a consistency calibration method for phased array transmission channels based on an optical fiber data platform, implemented using a digital processing platform. This system consists of two sets of nodes, a set of time-frequency equipment, a horn antenna with sufficiently high receiving power, a mixer, and a data processing platform. The connections between the devices are as follows: Figure 1 One of the two sets of nodes is the tested node, which contains 16 transmitting array elements. The internal transmission signal flow of the tested node is as follows: Figure 2 As shown, a set of reference nodes transmits data to the data processing platform via optical fiber through one receiving element in the reference node. The time and frequency equipment provides local oscillators, sampling clocks, and 1PPS signals to both sets of nodes. Driven by the sampling clock signal, the required intermediate frequency single-tone signal is logically generated according to the phase accumulator principle. The reset signal generated by the signal is required to be correlated with the rising edge of the 1PPS signal pulse to achieve phase consistency during power-on and power-off. To avoid additional errors in phase measurement caused by fiber jitter, the rising edge of the 1PPS second pulse signal is required to control the data processing platform's frame decoding. The phase relationship between the sampling clock and the 1PPS second pulse should satisfy the condition that the rising edge of the second pulse signal is aligned with the falling edge of the sampling clock, and the jitter error of the second pulse signal is controlled within 1 nanosecond, specifically as follows... Figure 3 As shown, the data processing platform performs frame de-framing and algorithm analysis on the data transmitted by the optical fiber, calculating the amplitude and phase of the 16 signals for subsequent calibration.

[0025] To facilitate understanding, before describing the specific calibration process of this invention, the implementation principle of this invention will be briefly explained as follows: When the same signal radiated by different array elements reaches the same receiving point, a phase difference will occur due to the path difference. In addition, differences in antenna installation structure will also lead to differences in the amplitude of the same transmitted signal received at the receiving point. Conventional vector calibrator calibration of multi-channel transmitted signals requires manual operation and monitoring, cannot simultaneously process transmitted channel data, is inconvenient for data analysis, and has low calibration efficiency for multi-element antennas. This invention utilizes a simple operation method and rapid data processing to accurately calculate the amplitude and phase difference between different array elements, and uses the measured value as zero value to pre-compensate each transmitted channel for uplink signal synthesis. Sampling the 1PPS signal using a sampling clock signal yields the rising edge of the 1PPS signal. This rising edge is used as the reset signal for signal generation, ensuring that each power-on / off cycle does not affect the generated signal phase, thus ensuring the validity of the measured zero value. Simultaneously, the rising edge of the second pulse signal is used to precisely control the frame de-framing of the data processing platform to eliminate transmission delay differences caused by fiber jitter.

[0026] The amplitude and phase calibration process for a specific set of transmitting nodes with 16 transmitting channels in this invention is as follows:

[0027] (1) Based on the principle of generating single-tone signals using a phase accumulator, the signal will be generated using f s The sampling rate generates the f0 signal, and the phase difference between every two sampling points is... If a phase cycle is 2π, and it is assumed to be divided into M parts, where M = 2^N, then the phase resolution is 2π / M, i.e. Minimum output frequency The output frequency f0 is adjusted using the frequency control word k, thus the output frequency... In this algorithm, the sampling rate f s Given 243MHz, N=32, and f0=64MHz, calculate the frequency control word k. By monitoring and issuing the frequency control word k, intermediate frequency signals of different frequencies can be generated.

[0028] The generated 64MHz signal is up-converted through a digital board and a TR two-stage process. Assuming the generated single-tone signal is: S = cos(2πf0t + θ0) + 1 / j * sin(2πf0t + θ0), after several stages of processing, the single-tone signal transmitted through the antenna is:

[0029]

[0030] Among them, A ∑ For the signal amplitude weighted sum, f L f is the local oscillator signal, f0 is the intermediate frequency signal, f cl The sampling clock signal is θ0, which is the initial phase of the generated signal. This is the initial phase of the sampling clock. From this, it can be seen that when the frequency of the single-tone signal is tuned to f... L -f0-f cl The phase changes from θ0 to -θ0.

[0031] (2) In an anechoic environment, adjust the polarization direction of the horn antenna to be consistent with the polarization direction of the antenna of the node under test, receive the radio frequency mono signal of the node under test, and transmit it to the mixer through the radio frequency cable of the horn antenna out of the anechoic room.

[0032] (3) The mixer mixes the radio frequency single tone signal and outputs the intermediate frequency signal to the reference node. The local oscillator of the mixer is provided by an external time and frequency device. The intermediate frequency signal output by the mixer is connected to the reference node.

[0033] (4) After receiving the intermediate frequency signal, the reference node performs digital down-conversion and filtering, and then frames and packages the signal before transmitting it to the data processing platform via optical fiber.

[0034] (5) By monitoring the parameters sent, the tested node switches the transmission channel and returns to step (2) until all transmission channels of the tested node have been switched.

[0035] (6) After receiving all the data from the transmission channels, the data processing platform performs frame de-framing and uses the algorithm to calculate the amplitude and phase values ​​of the 16 channels in the tested node as follows:

[0036] (A1,θ1)(A2,θ2)(A3,θ3)(A4,θ4)…(A 16 ,θ 16 )

[0037] Using antenna 1 as a reference, the phases of the 16 signals are re-expressed as follows:

[0038] θ=[0,Δθ 21 ,Δθ 31 ,Δθ 41 ,Δθ 51 ,…,Δθ 81 ,Δθ 91 ,…,Δθ 161 ]

[0039] (7) Using the method in step (6), the compensation algorithm is as follows:

[0040] a) Using the smallest amplitude among the 16 channels as a reference, normalize the amplitudes of the 16 channels. Assuming A2 is the minimum value, the normalized amplitudes of the 16 channels are as follows:

[0041]

[0042] b) Adjust the input signal using the 16 sets of phase values ​​from step (6), that is, after zero-value compensation, each signal becomes:

[0043]

[0044] After high-frequency local oscillator mixing, the signal phase will be inverted, becoming:

[0045]

[0046] Therefore, taking antenna 1 and antenna 2 as examples, after high local oscillator mixing, the phase difference between the two signals is θ1-θ2. The phase difference between the two signals measured by the calibration system due to path and other factors is θ2-θ1, which is exactly the difference.

[0047] Therefore, the compensated signal S is as follows:

[0048]

[0049] The aforementioned calibration system can be used to uniformly calibrate the channels of multiple nodes.

[0050] Based on the calibration method proposed in this invention, the following is a consistency calibration of 3200 transmission channels across 200 transmission subarrays in a radar system. One transmission subarray, with 16 transmission channels, was tested under the conditions of a local oscillator frequency of 1614MHz and a transmission intermediate frequency of 307MHz. The amplitude and phase measurement results are as follows:

[0051]

[0052]

[0053] The data in the table shows that the method proposed in this invention can be used to calibrate the amplitude and phase consistency of multiple transmission channels of multiple independent subarrays, and at the same time perform power-on and power-off tests. The amplitude error is less than 0.5dB and the phase error is less than 3.5°. Therefore, the calibration method based on this invention is stable and reliable.

Claims

1. A method for testing the consistency of phased array transmission channels based on an optical fiber data platform, implemented using a calibration system, wherein the calibration system includes a node under test, a reference node, a time-frequency device, a horn antenna, a data processing platform, and a mixer, and the node under test contains at least two transmission channels; characterized in that, Specifically, the process includes the following: (1) Based on the sampling clock and 1PPS pulse signal provided by the external time and frequency equipment, the node under test will process the intermediate frequency single tone signal through two stages of upconversion by the digital processing board and the TR component to obtain the radio frequency single tone signal, and select a transmission channel to radiate the radio frequency single tone signal according to the parameters issued by the monitoring. The radiated radio frequency single-tone signal is: In the formula, For the signal amplitude weighted sum, This is the local oscillator signal. It is an intermediate frequency signal. For sampling clock signals, To generate the initial phase of the signal, This is the initial phase of the sampling clock; (2) In an anechoic environment, adjust the polarization direction of the horn antenna to be consistent with the polarization direction of the antenna of the node under test, receive the radio frequency mono signal of the node under test, and transmit it to the mixer through the radio frequency cable of the horn antenna out of the anechoic room. (3) The mixer mixes the radio frequency single-tone signal and outputs the intermediate frequency signal to the reference node; wherein, the local oscillator signal of the mixer is from the same source as the sampling clock and 1PPS; (4) After receiving the intermediate frequency signal, the reference node performs digital down-conversion and filtering, and then frames and packages the signal before transmitting it to the data processing platform via optical fiber. (5) By monitoring the parameters sent, the tested node switches the transmission channel and returns to step (2) until all transmission channels of the tested node have been switched. (6) After receiving all the data from the transmission channels, the data processing platform performs frame de-framing and calculates the amplitude and phase values ​​of each channel of the tested node. (7) Compare the calculated amplitude values ​​of each channel and find the one with the smallest amplitude value as the basis for amplitude calibration; (8) Using the phase value of the first channel of the node under test and the minimum amplitude value found in step (7) as a reference, perform amplitude and phase consistency calibration on the remaining channels of the node under test.

2. The method for testing the consistency of a phased array transmission channel based on an optical fiber data platform according to claim 1, characterized in that, The phase relationship between the sampling clock and the 1PPS pulse satisfies that the rising edge of the 1PPS pulse signal is aligned with the falling edge of the sampling clock.

3. The phased array transmission channel consistency test method based on an optical fiber data platform according to claim 1, characterized in that, In step (6), the digital processing platform uses the rising edge of the 1PPS pulse signal for control when performing frame de-framing.

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