Calibration system, device and calibration method thereof for wideband target array

Abstract

The application provides a wideband target array calibration system, device and calibration method thereof, which comprises a master control module, a digital signal processing module, a frequency conversion module and a four-element antenna; the four-element antenna is connected with the frequency conversion module through a microwave cable; the frequency conversion module is connected with the digital signal processing module through a microwave cable and a serial cable; the digital signal processing module is connected with the master control module through an optical fiber; and the master control module, the digital signal processing module, the frequency conversion module and the four-element antenna are connected to form the wideband target array calibration system. The application independently completes the calibration work at each working frequency point in the wideband and the calibration work in the instantaneous bandwidth, and does not depend on high-end instruments, so that the defect of long time consumption in the traditional calibration using the sweep frequency mode is overcome, and the calibration time is reduced.

Description

Technical Field

[0001] This invention relates to the field of target array system calibration technology, specifically to a calibration system, apparatus and method for broadband target arrays, and more particularly to a built-in calibration method and apparatus for broadband target arrays. Background Technology

[0002] The target array system is a laboratory-based system that simulates airborne radio frequency (RF) target signals and is a key component of RF hardware-in-the-loop (HIFU) simulation systems. RF simulation tests compensate for the shortcomings of fully digital simulations, providing a more realistic simulation of the electromagnetic environment in combat and a more accurate assessment of the performance of radar guidance systems in real-world situations. Therefore, the accuracy of the target array system simulation has a significant impact on evaluating equipment performance.

[0003] The principle behind the target array system's simulation of target position is primarily based on the amplitude-centroid formula proposed by Boeing. This formula controls the signal amplitude separately and spatially synthesizes three phase-consistent signals. The accuracy of the target array system is limited by the amplitude-phase consistency of each signal. Therefore, to ensure the accuracy of the system's target position simulation, calibration of the target array system is necessary, specifically, calibrating the amplitude-phase consistency of each signal.

[0004] Traditional target array calibration methods typically consist of three main components: a standard signal source, a vector network analyzer, and a four-speaker receiving antenna. They utilize the principle of interference to perform amplitude, phase, and angle calibration of the target array antenna using a point-frequency continuous wave. This method heavily relies on standard instruments, has complex system connections, cannot be integrated, and is extremely time-consuming due to the use of continuous waves as the calibration signal.

[0005] Patent document CN104391187A discloses a multi-frequency antenna array calibration device and calibration method, including the following steps: a calibration control and management module performs antenna array calibration control and data processing; a microwave signal source generates the antenna array microwave signal during calibration; a four-horn receiving antenna receives the radiated radio frequency signal from the antenna array; a receiver module receives the radiated signal from the antenna and performs mixing and amplification; a vector network analyzer compares the amplitude and phase of the amplified intermediate frequency signal from the receiver module. Based on the operating frequency of the tested equipment, the antenna array is calibrated to its initial value, and the angular simulation accuracy and initial value verification are measured and calibrated to ensure that the radio frequency output signal of the three-element antenna of the antenna array meets the amplitude and phase consistency requirements.

[0006] Patent document CN104391187A fails to fundamentally improve efficiency and is highly dependent on instruments, thus failing to achieve true low cost. Most importantly, traditional methods similar to the above cannot obtain the absolute amplitude and phase at each frequency point. This means that such methods cannot calibrate the instantaneous bandwidth of the target array, which prevents the target array system from simulating the targets of current mainstream high-resolution imaging radars. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the purpose of this invention is to provide a calibration system, apparatus and calibration method for broadband target arrays.

[0008] A calibration system for a broadband target array according to the present invention includes a main control module, a digital signal processing module, a frequency conversion module, and a quad-element antenna.

[0009] The quad antenna is connected to the frequency conversion module via a microwave cable. The frequency conversion module is connected to the digital signal processing module via a microwave cable and a serial cable. The digital signal processing module is connected to the main control module via an optical fiber, forming a calibration system for the broadband target array.

[0010] Preferably, the main control module is used for target array calibration control, storing acquired data, and data processing;

[0011] The data processing includes obtaining the instantaneous amplitude and phase characteristics of each antenna element of the target array through the collected signal time-domain data.

[0012] Preferably, the digital signal processing module includes: an optical fiber communication module, a channel compensation module, a data acquisition module, and a signal generation module;

[0013] The optical fiber communication module is used to receive control commands in real time, transmit collected data to the main control module, and provide reference signals.

[0014] The data acquisition module is used to simultaneously acquire microwave signals received by the quad-element antenna;

[0015] The signal generation module is used to generate signals, including extremely narrow pulse signals with adjustable frequency, amplitude, modulation, pulse width, and period parameters, frequency conversion control parameters, and microwave signals during calibration.

[0016] The channel compensation module is used to compensate for channel errors.

[0017] Preferably, the frequency conversion module upconverts the input intermediate frequency signal to radio frequency and downconverts the input radio frequency signal to intermediate frequency.

[0018] Preferably, the quad-element antenna is used to receive the radio frequency signal radiated by the target array during calibration;

[0019] The quad antenna consists of multiple dual-polarized horn antennas that can be switched according to the polarization direction of the array under test.

[0020] According to the calibration method of the broadband target array of the calibration system provided by the present invention, before the target array is put into use in the microwave hardware-in-the-loop simulation test, the frequency band covered by the target array needs to be calibrated sequentially so that the radio frequency signal output by the target array triple antenna meets the amplitude and phase consistency requirements. The broadband target array calibration includes: target array initial value calibration and target array angular error measurement.

[0021] The target array initial value calibration involves acquiring, digitally processing, and analyzing the signal characteristics of each antenna link of the target array to obtain the amplitude and phase, and generating a broadband initial value table based on the difference between the amplitude and phase of the antenna link radiated signal and the reference signal.

[0022] The target array angular error measurement is to measure the position of the target array ternary combination after loading the broadband initial value table, and obtain the actual composite angle value based on the theoretical composite angle and angular error.

[0023] Preferably, the target array amplitude and phase initial value calibration step is as follows:

[0024] Step S1.1: Split the output port of the inverter's digital-to-analog converter into two paths. One path is connected to any input port of the inverter to provide a reference signal; the other path is connected to the simulation system and sent to the antenna in the selected target array through the simulation system's power supply link and radiates outward.

[0025] Step S1.2: Connect the main control module to the simulation system via optical fiber. The main control module sends the current frequency point to be calibrated and the position of the antenna in the target array to the simulation system. The simulation system selects the corresponding antenna.

[0026] Step S1.3: The main control module issues a control command, the digital signal processing module generates an extremely narrow pulse signal, and transmits the extremely narrow pulse signal through the channel corresponding to the digital-to-analog converter output port of the frequency converter to the channel corresponding to any input port of the frequency converter connected to the frequency converter module; one path passes through the target array system antenna link, transmitting an extremely narrow pulse signal that introduces the amplitude error and phase error corresponding to the currently selected channel;

[0027] Step S1.4: The extremely narrow pulse signal is down-converted by the frequency conversion module to the corresponding intermediate frequency extremely narrow pulse signal, and then the digital signal processing module synchronously acquires the intermediate frequency extremely narrow pulse signal and transmits it to the main control module through the optical fiber communication module;

[0028] Step S1.5: The main control module performs pulse matched filtering on the intermediate frequency extremely narrow pulse signal of the current selected channel within a single pulse period to obtain the signal amplitude and phase within the synthesized large bandwidth, and then generates the amplitude-frequency characteristic curve and phase-frequency characteristic curve within the synthesized large bandwidth, and records the data;

[0029] Step S1.6: The main control module performs pulse train matched filtering on the two acquired intermediate frequency extremely narrow pulse signals within a single frame signal length to obtain the amplitude and phase difference of the corresponding signals, and records the data. At the same time, it generates the current calibrated antenna number and completion flag.

[0030] Step S1.7: Determine whether the initial value calibration of all target array antennas is complete. If yes, trigger step S1.8; otherwise, repeat steps S1.2 to S1.6.

[0031] Step S1.8: Using the amplitude value of the antenna radiated by the antenna with the smallest amplitude difference between the target array antenna and the reference signal as the benchmark, generate a broadband initial value table and load it into the simulation system to complete the broadband amplitude and phase initial value calibration.

[0032] Preferably, the target array angular error measurement steps are as follows:

[0033] Step S2.1: Connect the output port of the inverter's digital-to-analog converter to the simulation system, and send the control command through the simulation system's power supply link to the antenna in the currently selected target array and radiate it outward to synthesize the target position in space;

[0034] Step S2.2: Connect the main control module to the simulation system. The main control module sends the current frequency point to be calibrated and the location of the synthesized target to the simulation system. The simulation system selects the corresponding antenna according to the instruction.

[0035] Step S2.3: The main control module sends a control command and transmits an extremely narrow pulse signal through the corresponding output port channel of the inverter's digital-to-analog converter. The quad-element antenna simultaneously receives the radio frequency signal radiated by the corresponding target array.

[0036] Step S2.4: After downconverting to intermediate frequency by the frequency converter module and synchronously acquiring the data by the digital signal processing module, the signal is transmitted to the main control module through the fiber optic module.

[0037] Step S2.5: Perform pulse train matched filtering on the received intermediate frequency extremely narrow pulse signal within a single frame signal length to obtain the distance from the synthesized position to the two antennas, and then obtain the corresponding azimuth error and elevation error, and generate the corresponding angle sequence number and completion mark;

[0038] Step S1.7: Determine whether all target array angular error measurements have been completed. If yes, then calibrate all of them; otherwise, repeat steps S2.2 to S2.5.

[0039] A calibration apparatus for a broadband target array according to the present invention includes a calibration system for the broadband target array.

[0040] Preferably, the calibration device for the broadband target array is mounted on a turntable in the simulation system, with the aperture of the quadrature antenna coinciding with the rotation center of the turntable. The turntable can be rotated to the antenna direction that needs to be calibrated via control commands.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. This invention independently completes the calibration work at each working frequency point and instantaneous bandwidth within the system's large working bandwidth, without relying on high-end instruments. This overcomes the time-consuming drawback of traditional calibration using frequency sweeping methods and reduces calibration time.

[0043] 2. This invention uses synthesized extremely narrow pulses to achieve instantaneous broadband effect in a simple way, which solves the problem that the instantaneous bandwidth expansion of the system is affected by the frequency sweep step in the traditional calibration accuracy, and reduces the pressure on the hardware performance of traditional receiver AD.

[0044] 3. Although the system structure of this invention is simple, it is inexpensive and highly versatile. Attached Figure Description

[0045] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0046] Figure 1 This is a schematic diagram of the components of a traditional antenna array calibration system.

[0047] Figure 2 This is a schematic diagram of the antenna array calibration system based on the present invention.

[0048] Figure 3 This is a schematic diagram of the composition of the calibration system for the broadband target array in this invention.

[0049] Figure 4 This is a schematic diagram illustrating the channel self-calibration principle of the present invention.

[0050] Figure 5 This is a schematic diagram illustrating the initial value calibration principle of the target array amplitude and phase of the present invention.

[0051] Figure 6 This is a schematic diagram illustrating the target array angular error calibration principle of the present invention.

[0052] Figure 7 This is a schematic diagram of the time-frequency domain characteristics of a synthesized extremely narrow pulse signal.

[0053] Figure 7 In the diagram, the horizontal axis represents time, and the vertical axis represents frequency, where Δf represents the frequency step. Detailed Implementation

[0054] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0055] This invention can independently complete calibration work at various operating frequencies within the system's large operating bandwidth and within a large instantaneous bandwidth. It overcomes the dependence of traditional calibration methods on high-end instruments such as standard signal sources and vector network analyzers, the time-consuming nature of traditional frequency sweeping methods, and the problem that the accuracy of traditional calibration is affected by the frequency sweeping step, thus impacting the system's instantaneous bandwidth expansion. Specifically, the antenna array calibration system corresponding to traditional calibration methods, such as... Figure 1 As shown, the antenna array calibration system corresponding to the calibration method of this invention is as follows: Figure 2 As shown.

[0056] According to the present invention, a calibration system for a broadband target array is provided, such as... Figure 2 and Figure 3 As shown, it includes a main control module, a digital signal processing module, a frequency conversion module, and a four-element antenna:

[0057] The quad antenna is connected to the frequency conversion module via a microwave cable. The frequency conversion module is connected to the digital signal processing module via a microwave cable and a serial cable. The digital signal processing module is connected to the main control module via an optical fiber, forming a calibration system for the broadband target array.

[0058] The main control module is used for target array calibration control, storage of acquired data, and data processing; the data processing includes obtaining the instantaneous amplitude and phase characteristics of each antenna element of the target array through the acquired signal time-domain data.

[0059] The digital signal processing module includes: an optical fiber communication module, a channel compensation module, a data acquisition module, and a signal generation module; wherein, the optical fiber communication module is used to receive control commands in real time, transmit acquired data to the main control module, and provide reference signals; the data acquisition module is used to simultaneously acquire microwave signals received by the four-element antenna; the signal generation module is used to generate signals, including extremely narrow pulse signals with adjustable frequency, amplitude, modulation, pulse width, and period parameters, frequency conversion control parameters, and microwave signals during calibration; the channel compensation module is used to compensate for channel errors.

[0060] The digital signal processing module receives the control parameters, controls the corresponding channel to perform signal acquisition and signal playback, and controls the frequency conversion module through the serial port according to the corresponding timing.

[0061] The frequency conversion module upconverts the input intermediate frequency (IF) signal to radio frequency (RF) and downconverts the input RF signal to IF. Based on corresponding control commands, it converts the signal received by the quad-element antenna to IF and sends it to the digital signal processing module for processing. The signal is then sent to the main control module for amplitude measurement, phase measurement, and broadband phase comparison to generate a system calibration table.

[0062] The quad antenna is used to receive the radio frequency signal radiated by the target array during calibration; the quad antenna is a plurality of dual-polarized horn antennas that can be switched according to the polarization direction of the array under test.

[0063] According to the calibration method of the broadband target array of the calibration system provided by the present invention, before the target array is put into use in the microwave hardware-in-the-loop simulation test, the frequency band covered by the target array needs to be calibrated sequentially so that the radio frequency signal output by the target array triple antenna meets the amplitude and phase consistency requirements. The broadband target array calibration includes: target array initial value calibration and target array angular error measurement.

[0064] The initial value calibration of the target array involves acquiring, digitally processing, and analyzing the signal characteristics of each antenna link of the target array to obtain its amplitude and phase. A broadband initial value table is then generated based on the difference in amplitude and phase between the antenna link radiated signal and the reference signal. The initial value calibration steps for the target array amplitude and phase are as follows:

[0065] Step S1.1: Split the output port of the inverter's digital-to-analog converter into two paths. One path is connected to any input port of the inverter to provide a reference signal; the other path is connected to the simulation system and sent to the antenna in the selected target array through the simulation system's power supply link and radiates outward.

[0066] Step S1.2: Connect the main control module to the simulation system via optical fiber. The main control module sends the current frequency point to be calibrated and the position of the antenna in the target array to the simulation system. The simulation system selects the corresponding antenna.

[0067] Step S1.3: The main control module issues a control command, the digital signal processing module generates an extremely narrow pulse signal, and transmits the extremely narrow pulse signal through the channel corresponding to the digital-to-analog converter output port of the frequency converter to the channel corresponding to any input port of the frequency converter connected to the frequency converter module; one path passes through the target array system antenna link, transmitting an extremely narrow pulse signal that introduces the amplitude error and phase error corresponding to the currently selected channel;

[0068] Step S1.4: The extremely narrow pulse signal is down-converted by the frequency conversion module to the corresponding intermediate frequency extremely narrow pulse signal, and then the digital signal processing module synchronously acquires the intermediate frequency extremely narrow pulse signal and transmits it to the main control module through the optical fiber communication module;

[0069] Step S1.5: The main control module performs pulse matched filtering on the intermediate frequency extremely narrow pulse signal of the current selected channel within a single pulse period to obtain the signal amplitude and phase within the synthesized large bandwidth, and then generates the amplitude-frequency characteristic curve and phase-frequency characteristic curve within the synthesized large bandwidth, and records the data;

[0070] Step S1.6: The main control module performs pulse train matched filtering on the two acquired intermediate frequency extremely narrow pulse signals within a single frame signal length to obtain the amplitude and phase difference of the corresponding signals, and records the data. At the same time, it generates the current calibrated antenna number and completion flag.

[0071] Step S1.7: Determine whether the initial value calibration of all target array antennas is complete. If yes, trigger step S1.8; otherwise, repeat steps S1.2 to S1.6.

[0072] Step S1.8: Using the amplitude value of the antenna radiated by the antenna with the smallest amplitude difference between the target array antenna and the reference signal as the benchmark, generate a broadband initial value table and load it into the simulation system to complete the broadband amplitude and phase initial value calibration.

[0073] The target array angular error measurement involves measuring the combined position of the three elements of the target array after loading the broadband initial value table, and obtaining the actual combined angle value based on the theoretical combined angle and the angular error. The target array angular error measurement steps are as follows:

[0074] Step S2.1: Connect the output port of the inverter's digital-to-analog converter to the simulation system, and send the control command through the simulation system's power supply link to the antenna in the currently selected target array and radiate it outward to synthesize the target position in space;

[0075] Step S2.2: Connect the main control module to the simulation system. The main control module sends the current frequency point to be calibrated and the location of the synthesized target to the simulation system. The simulation system selects the corresponding antenna according to the instruction.

[0076] Step S2.3: The main control module sends a control command and transmits an extremely narrow pulse signal through the corresponding output port channel of the inverter's digital-to-analog converter. The quad-element antenna simultaneously receives the radio frequency signal radiated by the corresponding target array.

[0077] Step S2.4: After downconverting to intermediate frequency by the frequency converter module and synchronously acquiring the data by the digital signal processing module, the signal is transmitted to the main control module through the fiber optic module.

[0078] Step S2.5: Perform pulse train matched filtering on the received intermediate frequency extremely narrow pulse signal within a single frame signal length to obtain the distance from the synthesized position to the two antennas, and then obtain the corresponding azimuth error and elevation error, and generate the corresponding angle sequence number and completion mark;

[0079] Step S1.7: Determine whether all target array angular error measurements have been completed. If yes, then calibrate all of them; otherwise, repeat steps S2.2 to S2.5.

[0080] A calibration device for a broadband target array according to the present invention includes a calibration system for the broadband target array. The calibration device for the broadband target array is mounted on a turntable in a simulation system, with the aperture of the four-element antenna coinciding with the rotation center of the turntable. The turntable can be rotated to the antenna direction requiring calibration via control commands.

[0081] In the calibration device of the broadband target array of this invention, each module responds to the command scheduling of the main control module in real time. The digital signal processing module provides reference signals and collects echo signals. The main control module performs data processing, analysis, and calculation to generate a three-dimensional error mapping table. Finally, the amplitude, phase, and composite angle errors of each antenna element of the target system are obtained. After the channel compensation module compensates for the errors, the spatial position of the simulated radiation target of the radar hardware-in-the-loop simulation system under different operating frequencies and large instantaneous bandwidths is realized. Finally, the ability of the radar guidance system to detect and track targets at different operating frequencies is tested.

[0082] Specifically, the present invention is achieved through the following steps:

[0083] Step 1: Fix the calibration device of the broadband target array on the flight turntable, and make sure that the aperture of the quad antenna coincides with the rotation center of the turntable;

[0084] Step 2: The digital signal processing module simultaneously acquires four intermediate frequency signals according to the four-channel synchronous acquisition algorithm; and generates an extremely narrow pulse signal with adjustable parameters such as frequency, amplitude, modulation, pulse width, and period through the synthesis of an extremely narrow pulse generation algorithm.

[0085] Step 3: The frequency converter module performs up-conversion and down-conversion of five signals in real time according to the control instructions;

[0086] Step 4: The fiber optic module receives control commands and transmits the acquired signals to the main control module in real time;

[0087] Step 5: The main control module uses the instantaneous bandwidth amplitude-phase-frequency characteristic curve extraction algorithm to obtain the instantaneous amplitude-phase characteristics of each antenna element of the target array using the collected signal time-domain data; and uses the one-dimensional high-resolution signal processing algorithm to obtain accurate distance data to calculate the angular error.

[0088] Specifically, the workflow mechanism of this invention is as follows:

[0089] First, the device is installed on the flight turntable of the simulation system, and the main control module controls the flight turntable to point to the coordinates of the antenna array antenna to be measured;

[0090] Then, for different test functions, the calibration is as follows: 1. Divide the output port 5 of the frequency converter module into four channels, and connect them to channels 1 to 4 to complete self-calibration; 2. Or divide the output port 5 of the frequency converter module into two channels, one channel to provide a reference signal and the other channel to the target array system, which is then radiated outward through the antenna to complete the initial value calibration; 3. Or directly send the signal to the target array system, which is then radiated outward through the antenna to complete the angle error calibration.

[0091] Next, the digital signal processing module connects the main control module to the simulation system via the fiber optic module. The main control module sends the frequency points to be calibrated and the positions of the antennas in the target array to the simulation system. The simulation system adjusts the turntable direction and selects the corresponding antennas according to the instructions.

[0092] Next, the main control module issues control commands, the control device transmits a synthesized extremely narrow pulse signal through channel 5, control channel 1 collects space radiation signals, control channel 2 collects coupling signals collected by channel 5; the signals are down-converted by the frequency conversion module, synchronously collected by the digital signal processing module, and then transmitted to the main control module through the fiber optic module.

[0093] Finally, the main control module processes the acquired channel data, generates initial amplitude and phase values ​​and angular errors, and records the data; the main control module controls the working sequence and information exchange of other modules in real time.

[0094] Furthermore, the present invention will be further described and illustrated by way of example:

[0095] Assume the frequency point that the target array needs to be calibrated is f. C The instantaneous bandwidth is B, and the frequency range is f. c -B / 2~ f c +B / 2.

[0096] First, calibrate the channels of the device itself, such as... Figure 4 As shown, an extremely narrow pulse signal is generated. for:

[0097]

[0098]

[0099] Where i represents the number of pulses, j represents the imaginary number, rect() represents the rectangular function, exp represents the exponential function, t represents time, τ represents the transmit pulse width, and T r The pulse repetition period of the signal is represented by f0, the carrier frequency start frequency is f0, the pulse width of a single sub-pulse is B, the number of carrier frequency steps is N, and Δf is the carrier frequency step size. The time-frequency domain characteristics of the synthesized extremely narrow pulse signal are as follows: Figure 7 As shown.

[0100] The control digital signal processing module generates the aforementioned synthesized extremely narrow pulse signal, which is output to the frequency converter module via channel 5. The signal then passes through four power dividers connected to channels 1-4 of the frequency converter. The signal is acquired by channels 1-4 of the digital signal processing module and transmitted to the main control module via the fiber optic communication module. The main control module performs pulse compression processing on each sub-pulse of the synthesized extremely narrow pulse signal to obtain a set of amplitude and phase signals, denoted as F. i A i ,φ i Where i = 0, 1, 2, ..., n-1, and n represents the number of synthesized extremely narrow pulse signal sub-pulses, ultimately yielding the channel amplitude-phase-frequency response table. As shown in Table 1:

[0101] Table 1

[0102]

[0103] Taking channel 1 as an example, as shown in Table 2, the amplitude characteristic of an ideal channel is constant, and the phase characteristic is linear. Therefore, based on the amplitude-phase-frequency characteristics of the channel, an amplitude-phase-frequency compensation characteristic table can be obtained. Using a channel intelligent algorithm such as particle swarm optimization, the compensation filter coefficients {a1,a2,…,a(M+1)} of order M can be solved, where M represents the order, and the number of FIR filter coefficients is order + 1. Loading these coefficients into the channel compensation module within the digital signal processing module completes the amplitude-phase characteristic calibration of each channel within the measured instantaneous bandwidth of the calibration device.

[0104] Table 2

[0105]

[0106] Then, after the device's own channels are calibrated, the initial amplitude and phase values ​​of the target array are calibrated, such as... Figure 5 As shown, the output port 5 of the inverter of the device is split into two paths. One path is connected to the input port B of the inverter to provide a reference signal to the device; the other path is connected to the simulation system. Through the control command, the signal can be sent to the antenna in the selected target array via the power supply link of the simulation system and then radiated outward through the antenna.

[0107] A very narrow pulse signal is radiated and synthesized through device channel 5, i.e., the signal received by channel 2 is as follows:

[0108]

[0109] The signal received through the target array system antenna link introduces amplitude and phase errors Ai and φi, resulting in the following signal received by channel 1:

[0110]

[0111] The digital signal processing module uploads the two acquired data streams to the main control module. The main control module performs pulse compression processing on each sub-pulse signal within the same frame to obtain the amplitude and phase parameters ∑(F) at each step frequency point of the target array. i A i ,φ i );

[0112] The same frame signal from channels 1 and 2 is subjected to pulse train compression processing to obtain the high-precision amplitude and phase parameters F at the test frequency. c ΔA, Δφ, after all antenna elements of the target array have been calibrated,

[0113] The amplitude ΔA_min of the radiated signal with the smallest amplitude difference is selected as the reference. The amplitude and phase parameters ∑(F_min) of all antennas are obtained by subtracting ΔA_min from the amplitude difference of each antenna. c ,ΔAi-ΔA_min, Δφi), this value is the initial calibration value of the target array at this frequency point, and ∑(F i A i ,φ i ) minus (F c By calculating ΔA-ΔA_min, Δφ, we can obtain the amplitude-phase-frequency response table of the target array with the test frequency as the center and the bandwidth as B, as shown in Table 3. This leads to the three-dimensional error mapping table, as shown in Table 4.

[0114] Table 3

[0115]

[0116] Table 4

[0117]

[0118] Next, after loading the three-dimensional error mapping table into the simulation system, the angular error of the target array is measured and calibrated, such as... Figure 6 As shown, the same synthesized extremely narrow pulse signal is used as the transmitted signal.

[0119] Connect the inverter output port 5 of the device to the simulation system. Control commands can be sent to the triple antenna in the selected target array via the simulation system feed link. The antenna radiates outward to synthesize the target position in space.

[0120] The device receives signals radiated by the target array through channels 1, 2, 3, and 4. The digital signal processing module uploads the acquired data from the two channels to the main control module.

[0121] The main control module performs pulse train compression processing on the same frame signal in channel 1 and channel 2 to obtain the distances R1 and R2 from the synthesized position to antennas A and B, respectively. The azimuth error is then calculated using the following formula:

[0122]

[0123] Where θ represents the azimuth error, and d1 represents the distance between antennas A and B; similarly, pulse train compression is performed on the same frame signal in channels 3 and 4 to obtain the distances R3 and R4 from the synthesized position to antennas C and D. The elevation angle error φ is calculated using the following formula:

[0124] φ=

[0125] Where φ represents the elevation angle error, and d2 represents the distance between antennas C and D;

[0126] The actual combined angle error of all triples of the target array is measured sequentially to obtain a database of theoretical angle and measured angle error, thus completing the angular error calibration of the target array.

[0127] The calibration method for broadband target arrays only requires a calibration device for the broadband target array, making the calibration relatively inexpensive. Meanwhile, the traditional antenna array calibration method described in the background art relies on standard instruments and generally cannot obtain the absolute amplitude, phase, and frequency characteristics within the instantaneous bandwidth of the target array, thus failing to calibrate the instantaneous broadband of the target array. In contrast, the broadband target array calibration method not only overcomes the dependence on standard instruments but also allows calibration of target arrays in various frequency bands by replacing the frequency converter front-end and the four-element antenna. Furthermore, the calibration of the instantaneous broadband of the target array is equally applicable, making the system more versatile.

[0128] During the design and development of this invention, the data processing algorithm of the main control module, the four-channel synchronous acquisition of the digital signal processing module, and the method for generating extremely narrow pulse signals were relatively complex. However, they are very convenient and efficient in actual use, with very low development costs, relatively simple maintenance, and strong versatility. This invention independently completes the calibration work at various operating frequencies and instantaneous bandwidths within the system's large operating bandwidth through a self-built acquisition and analysis module within the device.

[0129] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0130] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A calibration system for a broadband target array, characterized in that, Includes a main control module, a digital signal processing module, a frequency conversion module, and a quad-element antenna: The quad antenna is connected to the frequency conversion module via a microwave cable. The frequency conversion module is connected to the digital signal processing module via a microwave cable and a serial cable. The digital signal processing module is connected to the main control module via an optical fiber, forming a calibration system for the broadband target array. The main control module is used for target array calibration control, storage of acquired data, and data processing. The data processing includes obtaining the instantaneous amplitude and phase characteristics of each antenna element of the target array through the collected signal time-domain data; The digital signal processing module includes: an optical fiber communication module, a channel compensation module, a data acquisition module, and a signal generation module; The fiber optic communication module is used to receive control commands in real time, transmit collected data to the main control module, and provide reference signals. The data acquisition module is used to simultaneously acquire microwave signals received by the quad-element antenna; The signal generation module is used to generate signals, including extremely narrow pulse signals with adjustable frequency, amplitude, modulation, pulse width, and period parameters, frequency conversion control parameters, and microwave signals during calibration. The channel compensation module is used to compensate for channel errors; The digital signal processing module provides reference signals and acquires echo signals. The control device transmits a synthesized extremely narrow pulse signal through the channel.

2. The calibration system for a broadband target array according to claim 1, characterized in that, The frequency conversion module upconverts the input intermediate frequency signal to radio frequency and downconverts the input radio frequency signal to intermediate frequency.

3. The calibration system for a broadband target array according to claim 1, characterized in that, The quad antenna is used to receive the radio frequency signal radiated by the target array during calibration. The quad antenna consists of multiple dual-polarized horn antennas that can be switched according to the polarization direction of the array under test.

4. A calibration method for a broadband target array in a calibration system for a broadband target array according to claim 1, characterized in that, Before the target array in the microwave hardware-in-the-loop simulation test is put into use, the frequency bands covered by the target array need to be calibrated sequentially so that the radio frequency signal output by the target array triple antenna meets the amplitude and phase consistency requirements. The broadband target array calibration includes: target array initial value calibration and target array angular error measurement. The target array initial value calibration involves acquiring, digitally processing, and analyzing the signal characteristics of each antenna link of the target array to obtain the amplitude and phase, and generating a broadband initial value table based on the difference between the amplitude and phase of the antenna link radiated signal and the reference signal. The target array angular error measurement is to measure the position of the target array ternary combination after loading the broadband initial value table, and obtain the actual composite angle value based on the theoretical composite angle and angular error.

5. The calibration method for a broadband target array in the calibration system for a broadband target array according to claim 4, characterized in that, The target array amplitude and phase initial value calibration steps are as follows: Step S1.1: Split the output port of the inverter's digital-to-analog converter into two paths. One path is connected to any input port of the inverter to provide a reference signal; the other path is connected to the simulation system and sent to the antenna in the selected target array through the simulation system's power supply link and radiates outward. Step S1.2: Connect the main control module to the simulation system via optical fiber. The main control module sends the current frequency point to be calibrated and the position of the antenna in the target array to the simulation system. The simulation system selects the corresponding antenna. Step S1.3: The main control module issues a control command, the digital signal processing module generates an extremely narrow pulse signal, and transmits the extremely narrow pulse signal through the channel corresponding to the digital-to-analog converter output port of the frequency converter to the channel corresponding to any input port of the frequency converter connected to the frequency converter module; one path passes through the target array system antenna link, transmitting an extremely narrow pulse signal that introduces the amplitude error and phase error corresponding to the currently selected channel; Step S1.4: The extremely narrow pulse signal is down-converted by the frequency conversion module to the corresponding intermediate frequency extremely narrow pulse signal, and then the digital signal processing module synchronously acquires the intermediate frequency extremely narrow pulse signal and transmits it to the main control module through the optical fiber communication module; Step S1.5: The main control module performs pulse matched filtering on the intermediate frequency extremely narrow pulse signal of the current selected channel within a single pulse period to obtain the signal amplitude and phase within the synthesized large bandwidth, and then generates the amplitude-frequency characteristic curve and phase-frequency characteristic curve within the synthesized large bandwidth, and records the data; Step S1.6: The main control module performs pulse train matched filtering on the two acquired intermediate frequency extremely narrow pulse signals within a single frame signal length to obtain the amplitude and phase difference of the corresponding signals, and records the data. At the same time, it generates the current calibrated antenna number and completion flag. Step S1.7: Determine whether the initial value calibration of all target array antennas is complete. If yes, trigger step S1.8; otherwise, repeat steps S1.2 to S1.

6. Step S1.8: Using the amplitude value of the antenna radiated by the antenna with the smallest amplitude difference between the target array antenna and the reference signal as the benchmark, generate a broadband initial value table and load it into the simulation system to complete the broadband amplitude and phase initial value calibration.

6. The calibration method for a broadband target array in the calibration system for a broadband target array according to claim 4, characterized in that, The target array angular error measurement steps are as follows: Step S2.1: Connect the output port of the inverter's digital-to-analog converter to the simulation system, and send the control command through the simulation system's power supply link to the antenna in the currently selected target array and radiate it outward to synthesize the target position in space; Step S2.2: Connect the main control module to the simulation system. The main control module sends the current frequency point to be calibrated and the location of the synthesized target to the simulation system. The simulation system selects the corresponding antenna according to the instruction. Step S2.3: The main control module sends a control command to transmit an extremely narrow pulse signal through the corresponding output port channel of the inverter's digital-to-analog converter, while the quad-element antenna simultaneously receives the radio frequency signal radiated by the corresponding target array; Step S2.4: After downconverting to intermediate frequency by the frequency converter module and synchronously acquiring the data by the digital signal processing module, the signal is transmitted to the main control module through the fiber optic module. Step S2.5: Perform pulse train matched filtering on the received intermediate frequency extremely narrow pulse signal within a single frame signal length to obtain the distance from the synthesized position to the two antennas, and then obtain the corresponding azimuth error and elevation error, and generate the corresponding angle sequence number and completion mark; Step S2.6: Determine whether all target array angular error measurements have been completed. If yes, then calibrate all of them; otherwise, repeat steps S2.2 to S2.

5.

7. A calibration device for a broadband target array, characterized in that, The calibration system includes the broadband target array described in any one of claims 1 to 3.

8. The calibration apparatus for a broadband target array according to claim 7, characterized in that, The calibration device for the broadband target array is installed on a turntable in the simulation system, with the aperture of the quad-element antenna coinciding with the rotation center of the turntable. The turntable can be rotated to the antenna direction that needs to be calibrated via control commands.

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