Broadband SAR semi-physical simulation experiment system and echo signal power calibration method

Abstract

The invention belongs to the technical field of radar system simulation, and particularly discloses a broadband SAR semi-physical simulation experiment system and an echo signal power calibration method, in the SAR echo signal simulation process, power calculation of SAR scene echo signals is achieved according to parameter setting, and the calibration accuracy is improved. The SAR scene echo signal power calibration method is given through theoretical derivation and engineering constraint analysis, the technical problems that in a traditional experiment, SAR scene echo signal power is difficult to calibrate, and a simulation experiment with a certain interference-to-signal ratio cannot be quantitatively carried out are solved, a support is provided for carrying out an SAR semi-physical simulation experiment under the certain interference-to-signal ratio, and the method is suitable for popularization and application. Good popularization and application values are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of radar system simulation, and specifically discloses a broadband SAR semi-physical simulation experiment system and an echo signal power calibration method. Background Art

[0002] Synthetic aperture radar, especially spaceborne SAR, as an active sensor that uses microwaves for perception, has the ability to observe the earth around the clock and in all weather conditions, and has become an important means of military reconnaissance. Several modern high-tech wars have shown us the tremendous power of synthetic aperture radar in wars. SAR has also become an irreplaceable key node in the battlefield perception network. Electromagnetic interference, as an effective means of countering SAR reconnaissance, has played an important role in covering targets and shielding SAR reconnaissance, and has received increasing attention from all parties. In order to effectively verify the performance of jamming equipment, a variety of means are currently commonly used, including actual field flight, semi-physical simulation, and digital simulation. Among them, semi-physical simulation plays an increasingly important role as a means of conducting experiments with high cost-effectiveness and high efficiency and low consumption.

[0003] When conducting a wideband SAR anti-interference semi-physical simulation experiment, the calibration of the SAR echo signal power is the basis for the simulation experiment under a certain interference-to-signal ratio. In the traditional narrowband radar anti-interference experiment, the target echo signal power received by the radar receiver can be theoretically calculated through the target backscatter coefficient RCS, radar working parameters, relative position relationship and other parameters. At the same time, the received interference signal power can also be calculated through theoretical formulas. The interference-to-signal ratio can be adjusted according to the actual settings to analyze the experimental results. However, due to the fluctuation characteristics and nonlinear superposition characteristics of the SAR echo signal, when conducting a semi-physical simulation experiment, the wideband SAR echo signal power is generally only estimated through the ground object RCS, radar parameters, relative distance and other parameters. There is no signal power calculation method for typical targets in the wideband SAR echo signal; and the SAR echo signal simulation mostly uses the gray value of the image as input, and the corresponding relationship between its gray value and echo signal power needs to be calibrated through actual flight, making it difficult to calculate the interference-to-signal ratio consistent with the actual scene through theoretical calculation. At this time, the wideband SAR semi-physical simulation experiment under a certain interference-to-signal ratio can only qualitatively analyze the experimental results, and quantitative analysis is more difficult. Summary of the invention

[0004] In order to solve the problem in the background technology, the present invention discloses a broadband SAR semi-physical simulation experiment system and an echo signal power calibration method, which realizes the power calculation of the SAR scene echo signal according to parameter setting, and provides support for carrying out SAR semi-physical simulation experiments under a certain interference-to-signal ratio.

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0006] A broadband SAR semi-physical simulation experiment system includes an echo signal simulation device, a signal processing device, an interference simulation device and a high-power attenuator, wherein:

[0007] The echo signal simulation device includes an echo signal digital simulation unit, a signal generating unit and an up-conversion unit. The echo signal digital simulation unit is used to generate a SAR echo digital signal according to an input grayscale image. The signal generating unit converts the echo digital signal into an intermediate frequency SAR echo signal. The up-conversion unit up-converts the intermediate frequency SAR echo signal into a radio frequency signal and adjusts the echo signal power according to a set interference-to-signal ratio.

[0008] The interference simulation equipment controls the output interference signal power through a high-power attenuator;

[0009] The signal processing device includes a signal synthesis unit, a down-conversion unit, a signal acquisition unit and a data processing unit. The signal synthesis unit is used to receive interference signals and echo signals, complete signal synthesis to generate SAR echo signals including interference, the down-conversion unit is used to down-convert the SAR echo signals including interference into intermediate frequency signals, the signal acquisition unit is used to generate digital signals after acquiring the intermediate frequency signals, and send the digital signals to the data processing unit for processing, and the data processing unit completes the imaging, recognition and interference effect analysis of the digital echo signals under a certain interference-to-signal ratio.

[0010] A method for calibrating the power of a broadband SAR semi-physical simulation experiment echo signal is provided, which utilizes the above-mentioned simulation experiment system to implement the power calibration of the broadband SAR semi-physical simulation experiment echo signal, and comprises the following steps:

[0011] 1) Use the echo signal digital simulation unit to simulate the SAR digital echo signal, take the single point target image as input, and the single point target gray value A gray Set to 255. The backscatter coefficient RCS corresponding to this value is obtained through absolute calibration and is temporarily set to σ0. The grayscale values ​​of the pixels except the point target in the input single-point image are set to 0. The maximum amplitude output A in the digital echo signal is recorded. max1 , quantize the value to the full-scale output value of the signal generating unit, that is, the corresponding value of the 14-bit DAC is 16383, so that when the point target gray value is equal to 255, the intermediate frequency output signal is the DAC full-scale output, and use the up-conversion unit to convert the intermediate frequency signal generated by the signal generating unit into a radio frequency signal output;

[0012] 2) Connect the output of the up-conversion unit to a spectrum analyzer, set the spectrum analyzer Trace display to Max Hold, and record the maximum output signal power of a single point of the echo signal

[0013] 3) When performing echo simulation based on actual SAR images, each scattering unit can be considered as a point target, and the grayscale value of each scattering unit linearly reflects the strength of the backscattering coefficient. The actual power of the theoretical echo signal of the point target is calculated by the following formula (1):

[0014]

[0015] Where: P t is the SAR radar transmission signal power, G t is the transmitting antenna gain, λ is the signal wavelength, R is the distance between the radar and the imaging target point, Loss is the target RCS value σ0 and the system fixed insertion loss;

[0016] 4) The actual power of the theoretical echo signal in formula (1) is P target Corresponding to the target RCS value σ0, synchronously corresponds to the point target gray value 255;

[0017] 5) Using the intensity value A gray The grayscale image distributed between 0 and 255 is used as the input image to generate the SAR digital echo signal, and the maximum amplitude output A in the digital echo signal is recorded. max2 , quantize the value to the full-scale output value of the signal generating unit, so that the maximum value output of the echo signal is the full-scale output of the DAC, and use the up-conversion unit to convert the intermediate frequency signal generated by the signal generating unit into a radio frequency signal output;

[0018] 6) At this time, the maximum amplitude of the scene echo signal is quantized and compared with the gray value of the point target A gray The echo signal output power is set to 255. The actual power of the scene echo signal is calculated using the following formula:

[0019]

[0020] 7) Use the following formula (3) to calculate the theoretical input power of the interference signal received by the radar receiver:

[0021]

[0022] Where: P J is the transmitter power of the interference simulation device, G t is the radar transmitting antenna gain, G J is the gain of the transmitting antenna of the interference simulation device, λ is the signal wavelength, and R is the distance between the radar and the imaging target point;

[0023] 8) The theoretical interference-to-signal ratio of the SAR echo signal to the interference signal is calculated using formula (1) and formula (3). The specific interference-to-signal ratio is achieved by the power adjustment function of the high-power attenuator and the up-conversion unit. In this case, the interference-to-signal ratio JSR in the actual scenario is = P Jam-P sum , at this time the set attenuation value of the high power attenuator is At this point, the interference signal and the SAR echo signal have achieved power calibration of a specific interference-to-signal ratio. If the interference-to-signal ratio needs to be further adjusted, it can be achieved by adjusting the attenuation value of the attenuator.

[0024] 9) After completing the interference-to-signal ratio modulation, the interference signal and the SAR scene echo signal are synthesized into RF signals through the signal synthesis unit of the signal processing device;

[0025] 10) The down-conversion unit converts the RF synthesized signal into an intermediate frequency signal and sends it to the signal acquisition unit. The signal acquisition unit completes the analog-to-digital conversion of the intermediate frequency signal to generate a digital signal. The data processing unit completes the imaging, detection and recognition processing of the digital signal, and then completes the broadband SAR semi-physical simulation experiment under a certain interference-to-signal ratio.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The invention discloses a broadband SAR semi-physical simulation experiment echo signal power calibration method. During the SAR echo signal simulation process, the power calculation of the SAR scene echo signal is realized according to parameter settings. The SAR scene echo signal power calibration method is given through theoretical derivation and engineering constraint analysis. The technical difficulties that the SAR scene echo signal power is difficult to calibrate in traditional experiments and the simulation experiment with a certain interference-to-signal ratio cannot be quantitatively carried out are solved. The invention provides support for carrying out SAR semi-physical simulation experiments under a certain interference-to-signal ratio and has great promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 It is a connection block diagram of the broadband SAR semi-physical simulation experiment system in the present invention; DETAILED DESCRIPTION

[0030] In order to better understand the present invention, the content of the present invention is further clearly set forth in conjunction with the embodiments below, but the protection content of the present invention is not limited to the following embodiments. In the following description, a large number of specific details are provided in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0031] Combined with Figure 1 , a broadband SAR semi-physical simulation experimental system of the present invention is described in detail, which is characterized by including an echo signal simulation device, a signal processing device, an interference simulation device and a high-power attenuator, wherein,

[0032] The echo signal simulation device includes an echo signal digital simulation unit, a signal generating unit and an up-conversion unit. The echo signal digital simulation unit is used to generate a SAR echo digital signal according to an input grayscale image. The signal generating unit converts the echo digital signal into an intermediate frequency SAR echo signal. The up-conversion unit up-converts the intermediate frequency SAR echo signal into a radio frequency signal and adjusts the echo signal power according to a set interference-to-signal ratio.

[0033] The interference simulation equipment controls the output interference signal power through a high-power attenuator;

[0034] The signal processing device includes a signal synthesis unit, a down-conversion unit, a signal acquisition unit and a data processing unit. The signal synthesis unit is used to receive interference signals and echo signals, complete signal synthesis to generate SAR echo signals including interference, the down-conversion unit is used to down-convert the SAR echo signals including interference into intermediate frequency signals, the signal acquisition unit is used to generate digital signals after acquiring the intermediate frequency signals, and send the digital signals to the data processing unit for processing, and the data processing unit completes the imaging, recognition and interference effect analysis of the digital echo signals under a certain interference-to-signal ratio.

[0035] When conducting a broadband SAR semi-physical simulation experiment, first turn on the echo signal simulation equipment, signal processing equipment, and interference simulation equipment, prepare high-power attenuators, cables, spectrum analyzers and other equipment, and the SAR echo simulation input image is the intensity value A gray A grayscale image ranging from 0 to 255.

[0036] A method for calibrating the power of a broadband SAR semi-physical simulation experiment echo signal is provided, which utilizes the above-mentioned simulation experiment system to implement the power calibration of the broadband SAR semi-physical simulation experiment echo signal, and comprises the following steps:

[0037] 1) Use the echo signal digital simulation unit to simulate the SAR digital echo signal, take the single point target image as input, and the single point target gray value A gray Set to 255. The backscatter coefficient RCS corresponding to this value is obtained through absolute calibration and is temporarily set to σ0. The grayscale values ​​of the pixels except the point target in the input single-point image are set to 0. The maximum amplitude output A in the digital echo signal is recorded. max1, quantize the value to the full-scale output value of the signal generating unit, that is, the corresponding value of the 14-bit DAC is 16383, so that when the point target gray value is equal to 255, the intermediate frequency output signal is the DAC full-scale output, and use the up-conversion unit to convert the intermediate frequency signal generated by the signal generating unit into a radio frequency signal output;

[0038] 2) Connect the output of the up-conversion unit to a spectrum analyzer, set the spectrum analyzer Trace display to Max Hold, and record the maximum output signal power of the echo signal at a single point.

[0039]

[0040] 3) When performing echo simulation based on actual SAR images, each scattering unit can be considered as a point target, and the grayscale value of each scattering unit linearly reflects the strength of the backscattering coefficient. The actual power of the theoretical echo signal of the point target is calculated by the following formula (1):

[0041]

[0042] Where: P t is the SAR radar transmission signal power, G t is the transmitting antenna gain, λ is the echo signal wavelength, R is the distance between the radar and the imaging target point, Loss is the target RCS value σ0 and the system fixed insertion loss;

[0043] 4) The actual power of the theoretical echo signal in formula (1) is P target Corresponding to the target RCS value σ0, synchronously corresponds to the point target grayscale value 255. The corresponding relationship established at this time is similar to the corresponding relationship between the narrow-band radar single-point echo signal power and the target RCS value;

[0044] 5) To calibrate the absolute power of the scene echo signal, first simulate the scene echo signal and use the intensity value A gray The grayscale image distributed between 0 and 255 is used as the input image to generate the SAR digital echo signal, and the maximum amplitude output A in the digital echo signal is recorded. max2 , quantize the value to the full-scale output value of the signal generating unit, that is, the corresponding value of the 14-bit DAC is 16383, so that the maximum value output of the echo signal is the full-scale output of the DAC, and use the up-conversion unit to convert the intermediate frequency signal generated by the signal generating unit into a radio frequency signal output;

[0045] 6) At this time, the maximum amplitude of the scene echo signal is quantized and compared with the gray value of the point target A gray The echo signal output power is set to 255. The actual power of the scene echo signal is calculated using the following formula:

[0046]

[0047] 7) Use the following formula (3) to calculate the theoretical input power of the interference signal received by the radar receiver:

[0048]

[0049] Where: P J is the transmitter power of the interference simulation device, G t is the radar transmitting antenna gain, G J is the gain of the transmitting antenna of the interference simulation device, λ is the signal wavelength, and R is the distance between the radar and the imaging target point;

[0050] 8) The theoretical interference-to-signal ratio of the SAR echo signal to the interference signal is calculated using formula (1) and formula (3). The specific interference-to-signal ratio is achieved by the power adjustment function of the high-power attenuator and the up-conversion unit. In this case, the interference-to-signal ratio JSR in the actual scenario is = P Jam -P sum , at this time the set attenuation value of the high power attenuator is At this point, the interference signal and the SAR echo signal have achieved power calibration of a specific interference-to-signal ratio. If the interference-to-signal ratio needs to be further adjusted, it can be achieved by adjusting the attenuation value of the attenuator.

[0051] 9) After completing the interference-to-signal ratio modulation, the interference signal and the SAR scene echo signal are synthesized into RF signals through the signal synthesis unit of the signal processing device;

[0052] 10) The down-conversion unit of the signal processing equipment converts the RF synthesized signal into an intermediate frequency signal and sends it to the signal acquisition unit. The signal acquisition unit completes the analog-to-digital conversion of the intermediate frequency signal to generate a digital signal. The data processing unit completes the imaging, detection and recognition processing of the digital signal, and then completes the broadband SAR semi-physical simulation experiment under a certain interference-to-signal ratio.

[0053] The invention discloses a broadband SAR semi-physical simulation experiment echo signal power calibration method. During the SAR echo signal simulation process, the power calculation of the SAR scene echo signal is realized according to parameter settings. The SAR scene echo signal power calibration method is given through theoretical derivation and engineering constraint analysis. The technical difficulties that the SAR scene echo signal power is difficult to calibrate in traditional experiments and the simulation experiment with a certain interference-to-signal ratio cannot be quantitatively carried out are solved. The invention provides support for carrying out SAR semi-physical simulation experiments under a certain interference-to-signal ratio and has great promotion and application value.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A broadband SAR semi-physical simulation experiment system, characterized in that: It includes an echo signal simulation device, a signal processing device, an interference simulation device and a high-power attenuator, wherein the echo signal simulation device includes an echo signal digital simulation unit, a signal generating unit and an up-conversion unit, the echo signal digital simulation unit is used to generate a SAR echo digital signal according to an input grayscale image, the signal generating unit converts the echo digital signal into an intermediate frequency SAR echo signal, the up-conversion unit up-converts the intermediate frequency SAR echo signal into a radio frequency signal, and adjusts the echo signal power according to a set interference-to-signal ratio; The interference simulation equipment controls the output interference signal power through a high-power attenuator; The signal processing device includes a signal synthesis unit, a down-conversion unit, a signal acquisition unit and a data processing unit. The signal synthesis unit is used to receive interference signals and echo signals, complete signal synthesis to generate SAR echo signals including interference, the down-conversion unit is used to down-convert the SAR echo signals including interference into intermediate frequency signals, the signal acquisition unit is used to generate digital signals after acquiring the intermediate frequency signals, and send the digital signals to the data processing unit for processing, and the data processing unit completes the imaging, recognition and interference effect analysis of the digital echo signals under a certain interference-to-signal ratio.

2. A method for calibrating echo signal power in a broadband SAR semi-physical simulation experiment, characterized in that: The simulation experiment system described in claim 1 is used to realize the calibration of echo signal power of broadband SAR semi-physical simulation experiment, comprising the following steps: 1) Use the echo signal digital simulation unit to simulate the SAR digital echo signal, take the single point target image as input, and the single point target gray value A gray Set to 255. The backscatter coefficient RCS corresponding to this value is obtained through absolute calibration and is temporarily set to σ0. The grayscale values ​​of the pixels except the point target in the input single-point image are set to 0. The maximum amplitude output A in the digital echo signal is recorded. max1 , quantize the value to the full-scale output value of the signal generating unit, that is, the corresponding value of the 14-bit DAC is 16383, so that when the point target gray value is equal to 255, the intermediate frequency output signal is the DAC full-scale output, and use the up-conversion unit to convert the intermediate frequency signal generated by the signal generating unit into a radio frequency signal output; 2) Connect the output of the up-conversion unit to a spectrum analyzer, set the spectrum analyzer Trace display to Max Hold, and record the maximum output signal power of a single point of the echo signal 3) When performing echo simulation based on actual SAR images, each scattering unit can be considered as a point target, and the grayscale value of each scattering unit linearly reflects the strength of the backscattering coefficient. The actual power of the theoretical echo signal of the point target is calculated by the following formula (1): Where: P t is the SAR radar transmission signal power, G t is the transmitting antenna gain, λ is the signal wavelength, R is the distance between the radar and the imaging target point, Loss is the target RCS value σ0 and the system fixed insertion loss; 4) The actual power of the theoretical echo signal in formula (1) is P target Corresponding to the target RCS value σ0, synchronously corresponds to the point target gray value 255; 5) Using the intensity value A gray The grayscale image distributed between 0 and 255 is used as the input image to generate the SAR digital echo signal, and the maximum amplitude output A in the digital echo signal is recorded. max2 , quantize the value to the full-scale output value of the signal generating unit, so that the maximum value output of the echo signal is the full-scale output of the DAC, and use the up-conversion unit to convert the intermediate frequency signal generated by the signal generating unit into a radio frequency signal output; 6) At this time, the maximum amplitude of the scene echo signal is quantized and compared with the gray value of the point target A gray The echo signal output power is set to 255. The actual power of the scene echo signal is calculated using the following formula: 7) Use the following formula (3) to calculate the theoretical input power of the interference signal received by the radar receiver: Where: P J is the transmitter power of the interference simulation device, G t is the radar transmitting antenna gain, G J is the gain of the transmitting antenna of the interference simulation device, λ is the signal wavelength, and R is the distance between the radar and the imaging target point; 8) The theoretical interference-to-signal ratio of the SAR echo signal to the interference signal is calculated using formula (1) and formula (3). The specific interference-to-signal ratio is achieved by the power adjustment function of the high-power attenuator and the up-conversion unit. In this case, the interference-to-signal ratio JSR in the actual scenario is = P Jam -P sum , at this time the set attenuation value of the high power attenuator is At this point, the interference signal and the SAR echo signal have achieved power calibration of a specific interference-to-signal ratio. If the interference-to-signal ratio needs to be further adjusted, it can be achieved by adjusting the attenuation value of the attenuator. 9) After completing the interference-to-signal ratio modulation, the interference signal and the SAR scene echo signal are synthesized into RF signals through the signal synthesis unit of the signal processing device; 10) The down-conversion unit converts the RF synthesized signal into an intermediate frequency signal and sends it to the signal acquisition unit. The signal acquisition unit completes the analog-to-digital conversion of the intermediate frequency signal to generate a digital signal. The data processing unit completes the imaging, detection and recognition processing of the digital signal, and then completes the broadband SAR semi-physical simulation experiment under a certain interference-to-signal ratio.

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