A Channel Consistency Calibration Method for an Optical Fiber Digital Array Receiver System

Abstract

This invention discloses a channel consistency calibration method for a fiber optic digital array receiving system, belonging to the field of array antenna measurement and control. It is implemented based on a calibration system, which includes a standard subarray, a subarray under test, a transmitting device, a time-frequency device, a vector network analyzer, and a power divider. Based on an externally unified time-frequency standard, the amplitude and phase of multiple receiving channels of the standard subarray and the subarray under test are calibrated separately, achieving phase-level fusion between signals of the fiber optic digital receiving array. This invention does not rely on complex signal processing algorithms and has advantages such as simple structure, strong practicality, and high accuracy.

Description

Technical Field

[0001] This invention relates to the fields of communication measurement and control and phased array radar technology, and particularly to a channel consistency calibration method for a fiber optic digital array receiving system. This method is applied to the multi-channel receiving of carrier signals in a fiber optic digital array receiving system to eliminate the inconsistencies in amplitude and phase introduced by different receiving subarrays and different receiving channels, thereby achieving phase-level fusion of signals received by a large fiber optic digital array. Background Technology

[0002] Digital array antennas possess the ability to rapidly alter the beam pattern of the array by adjusting the amplitude and phase weighting values ​​of each element, thereby enhancing the signal of interest and suppressing interference. They hold a crucial position in multi-beam telemetry, communication, and phased array radar. To achieve precise control of the antenna beam, it is essential to ensure that the characteristics of all receiving channels in the antenna array are consistent. However, due to the nonlinearity of RF devices and differences in layout and wiring in different receiving channels, the consistency of signal amplitude and phase changes after the carrier signal passes through different receiving channels cannot be guaranteed. To eliminate the influence of these factors, accurate amplitude and phase calibration values ​​for each receiving channel are required; therefore, amplitude and phase calibration is necessary.

[0003] For large digital array systems, amplitude and phase calibration is required not only between all receiving channels of a single receiving subarray, but also between receiving channels of different receiving subarrays. Conventional channel calibration methods for digital array receiving systems primarily target different receiving channels within a single subarray. However, channel calibration for multiple subarrays often relies on complex signal processing algorithms, and the calibration accuracy is significantly affected by these algorithms. This invention aims to provide a universal multi-channel calibration method for large digital receiving arrays. Based on a unified time and frequency, multiple subarrays are calibrated separately. The calibration results are only related to the hardware characteristics of the receiving channels, exhibiting high accuracy and high reliability. Summary of the Invention

[0004] The main objective of this invention is to provide a calibration method for the amplitude and phase consistency of multiple receiving channels across multiple independent subarrays. This method uses a second pulse signal provided by an external time-frequency device as a reference to calibrate multiple receiving channels in a single subarray one by one, while simultaneously calibrating the consistency of receiving channels across multiple subarrays. It features a simple system structure and high calibration accuracy.

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

[0006] A channel consistency calibration method for a fiber optic digital array receiving system, based on a calibration system comprising a standard subarray, a subarray under test, a transmitting device, a vector network analyzer, and a power divider, specifically including the following processes:

[0007] (1) Use a vector network analyzer to generate a sweep frequency signal with the required bandwidth, and connect it to the N receiving channels of the standard subarray through a power divider and multiple equal-length stable RF cables respectively.

[0008] (2) The control standard subarray uses the first receiving channel as a reference channel and transmits the sampling signal of the first receiving channel to the transmitting equipment through optical fiber;

[0009] (3) Control the transmitting equipment to connect the sampled signal received by the optical fiber to the vector network analyzer through the calibration transmitting channel to form a signal closed loop;

[0010] (4) Zero the vector network analyzer, save the current state, and record the amplitude and phase of the first receiving channel signal;

[0011] (5) Control the standard subarray to transmit the sampling signals of the 2nd to Nth receiving channels to the vector network analyzer through optical fiber and transmitting equipment in sequence;

[0012] (6) Based on the results of the vector network analyzer, record the amplitude difference and phase difference between the sampled signals of the 2nd to Nth receiving channels of the standard subarray and the reference channel in sequence;

[0013] (7) Replace the standard subarray with the subarray under test, and control the subarray under test to transmit the sampling signals of the first to N receiving channels to the vector network analyzer through optical fiber and transmitting equipment in sequence. According to the results of the vector network analyzer, record the amplitude difference and phase difference between the sampling signals of the first to N receiving channels of the subarray under test and the reference channel in sequence.

[0014] (8) Repeat step 7 to complete the tests of other receiving subarrays in sequence and record the test results.

[0015] Furthermore, the calibration system also includes a time and frequency device, which generates a sampling clock signal and a second pulse. The sampling clock signal is used to sample the second pulse signal to obtain the rising edge of the second pulse signal. The rising edge of the second pulse signal is used as the write start time of the receiving subarray buffer, and the rising edge of the second pulse signal is used to delay the read start time of the transmitting device by M sampling clock cycles; where M is a set value.

[0016] Furthermore, the calibration system is based on a fiber optic digital platform, enabling digital array receiving systems to calibrate signals with ultra-wide bandwidth.

[0017] Compared with traditional digital array receiver channel consistency calibration methods, the present invention has the following advantages:

[0018] 1. The channel consistency calibration method for an optical fiber digital array receiving system proposed in this invention can complete the consistency calibration of all receiving channels among multiple independent receiving subarrays, and eliminates the impact of calibration link reconstruction on the consistency calibration results of receiving channels.

[0019] 2: The channel consistency calibration method for an optical fiber digital array receiving system proposed in this invention has the advantages of simple structure, easy engineering implementation, and high calibration accuracy.

[0020] 3: The calibration system of this invention is applicable not only to the calibration of a single digital array receiving system, but also to the calibration of multiple distributed independent digital array receiving systems. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the calibration system structure of an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram illustrating the data transmission link between the receiving subarray and the transmitting device in an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram illustrating the relationship between the sampling clock and the second pulse signal of a time-frequency device in an embodiment of the present invention. Detailed Implementation

[0024] 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.

[0025] The proposed method for channel consistency calibration of a fiber optic digital array receiving system is based on a calibration system. The proposed phase calibration system consists of one standard subarray (subarray A, 16 receiving channels), one subarray under test (subarray B, 16 receiving channels), one transmitting device (device C, including one calibration transmitting channel), one time-frequency device (providing second pulse signals and sampling clock signals), one vector network analyzer, and one N-channel power divider. The connection method between the devices is as described above. Figure 1The vector network analyzer generates the required bandwidth sweep signal and calculates the phase and amplitude difference between the signal output port PORT1 and the signal input port PORT2. The power divider splits the signal from PORT1 into 16 channels, which are then connected to the 16 receiving channels of the standard subarray A (subarray B under test). To eliminate external errors, the power divider and the receiving subarray are connected using equal-length, phase-stable RF cables. The time and frequency equipment provides sampling clock signals and second pulse signals to the receiving and transmitting equipment. The sampling clock signals are used for AD sampling in the receiving subarray and DA playback in the transmitting equipment. The second pulse signal is used to eliminate fiber optic transmission delay jitter. The phase relationship between the sampling clock signal and the second pulse signal 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... Figure 3 As shown. The receiving subarray and transmitting equipment are connected by optical fiber, using the Aurora high-speed data transmission protocol. A single-channel transmission line rate supports 10Gb / s. The signal processing flow of the AD sampling signals from different receiving channels between receiving subarray A(B) and transmitting equipment C is as follows. Figure 2 As shown;

[0026] To facilitate understanding, before describing the specific calibration process of the present invention, the implementation principle of the present invention will be briefly explained as follows:

[0027] The phase difference between different receiving channels is essentially caused by the different time delays of the swept signal looping through different paths. For the phase calibration system proposed in this invention, the time delay difference along the loop path of the swept signal mainly consists of two parts: the path delay difference between different receiving channels and the fiber optic transmission delay difference. The purpose of this invention is to use an external second pulse signal to eliminate the phase change of the sampling signal caused by the fiber optic transmission delay difference. The specific implementation method is as follows: Figure 2 The sampling clock signal and the second pulse signal are generated by a set of time-frequency equipment, therefore they originate from the same source. By sampling the second pulse signal using the sampling clock signal, the rising edge of the second pulse signal can be obtained. This rising edge is used as the write start time for the receiving subarray FIFO buffer module, and the rising edge is used to delay the read start time of the transmitting device FIFO buffer module by M sampling clock cycles. This determines the data transmission link delay to be M sampling cycles, eliminating the fiber optic transmission delay difference. Therefore, the path delay difference of the sweep signal loopback in the calibration system is determined only by the path delay difference of different receiving channels, i.e., the phase consistency of different receiving channels, which can be accurately measured by a vector network analyzer. The amplitude consistency of different receiving channels is determined only by the devices on the different receiving channel paths. Therefore, as long as the sweep signal loopback path is successfully established, the amplitude consistency of different receiving channels can be measured by a vector network analyzer.

[0028] The amplitude and phase calibration process for the two sets of receiving subarrays with a total of 32 receiving channels in this invention is as follows:

[0029] (1): A wideband sweep frequency signal is generated using port1 of a vector network analyzer and connected to the 16 receiving channels of standard subarray A through a 16-channel power divider and 16 equal-length stable RF cables.

[0030] (2): Control standard subarray A to use the first receiving channel as a reference channel and transmit the sampling signal of the first receiving channel to the transmitting device C through optical fiber;

[0031] (3): Control the transmitting device C to receive the original sampling signal of the corresponding receiving channel received by the optical fiber and connect it to port2 of the vector network analyzer through the calibration transmitting channel to form a signal closed loop;

[0032] (4): Zero the vector network analyzer, save the current state and record the amplitude and phase (A1,φ1)=(0,0) of the first receiving channel signal of the standard subarray A;

[0033] (5): Control the standard subarray A to transmit the sampling signals of the 2nd to Nth receiving channels to the vector network analyzer through optical fiber and transmitting device C in sequence;

[0034] (6): Based on the results of the vector network analyzer, record the amplitude and phase (A2,φ2),...,(A16,φ16) of the acquired signals of the 2nd to 16th receiving channels of the standard subarray A in sequence, that is, the amplitude difference and phase difference with the reference channel, and complete the consistency calibration of the A16 receiving channels of the subarray.

[0035] (7): Replace the standard subarray A with the subarray to be tested B, and control the receiving subarray B to transmit the sampling signals of the first to 16 receiving channels to the vector network analyzer through optical fiber and transmitting device C in sequence;

[0036] (8): Based on the results of the vector network analyzer, record the amplitude and phase (B1,φ1),...,(B16,φ16) of the acquired signals of the first to Nth receiving channels of the subarray B under test in sequence, that is, the amplitude difference and phase difference with the reference channel, and complete the consistency calibration of all receiving channels of the subarray B.

[0037] Using the above calibration system, consistency calibration of different receiving channels among multiple devices can be achieved.

Claims

1. A channel consistency calibration method for an optical fiber digital array receiving system, based on a calibration system, wherein the calibration system includes a standard subarray, a subarray under test, a transmitting device, a vector network analyzer, and a power divider, characterized in that, Specifically, the process includes the following: (1) Use a vector network analyzer to generate a sweep frequency signal with the required bandwidth, and connect it to the N receiving channels of the standard subarray through a power divider and multiple equal-length stable RF cables respectively. (2) The control standard subarray uses the first receiving channel as a reference channel and transmits the sampling signal of the first receiving channel to the transmitting equipment through optical fiber; (3) Control the transmitting equipment to connect the sampled signal received by the optical fiber to the vector network analyzer through the calibration transmitting channel to form a signal closed loop; (4) Zero the vector network analyzer, save the current state, and record the amplitude and phase of the first receiving channel signal; (5) The control standard subarray sequentially transmits the sampling signals of the 2nd to Nth receiving channels to the vector network analyzer through optical fiber and transmitting equipment; (6) Based on the results of the vector network analyzer, record the amplitude difference and phase difference between the sampled signals of the 2nd to Nth receiving channels of the standard subarray and the reference channel in sequence; (7) Replace the standard subarray with the subarray under test, and control the subarray under test to transmit the sampling signals of the first to N receiving channels to the vector network analyzer through optical fiber and transmitting equipment in sequence. According to the results of the vector network analyzer, record the amplitude difference and phase difference between the sampling signals of the first to N receiving channels of the subarray under test and the reference channel in sequence. (8) Repeat step 7 to complete the testing of other receiving subarrays in sequence and record the test results; The calibration system also includes a time-frequency device, which generates a sampling clock signal and a second pulse. The sampling clock signal is used to sample the second pulse signal to obtain the rising edge of the second pulse signal. The rising edge of the second pulse signal is used as the write start time of the receiving subarray buffer. At the same time, the rising edge of the second pulse signal is used to delay the read start time of the transmitting device buffer by M sampling clock cycles, where M is a set value, in order to eliminate the additional phase difference introduced by the optical fiber transmission delay.

2. The channel consistency calibration method for an optical fiber digital array receiving system according to claim 1, characterized in that, The calibration system is based on a fiber optic digital platform and can calibrate ultra-wide bandwidth signals for digital array receiving systems.

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