A spaceborne radar signal transmitting and receiving method and device, equipment and medium

Abstract

The present disclosure discloses a kind of spaceborne radar signal transmission, receiving method and device, equipment and medium, it is related to aerospace technical field, and specific implementation scheme is: according to the working wave band ability range of spaceborne synthetic aperture radar, the radio frequency operating center frequency point of current imaging task is determined;According to radio frequency operating center frequency point and fixed radio frequency local oscillator frequency, the target intermediate frequency signal frequency is calculated;According to anti-interference demand information, generate out-of-band preset signal;The digital waveform of main imaging signal is generated, and the digital waveform of out-of-band preset signal is superimposed and embedded to the pulse front of main imaging signal, to generate composite digital baseband signal;Composite digital baseband signal is converted into analog signal, after intermediate frequency filtering to analog signal under target intermediate frequency signal frequency, it is up-converted to radio frequency carrier frequency band, and after power amplification, the transmission signal is obtained;Through antenna, transmission signal is radiated to target area.

Description

Technical Field

[0001] This invention belongs to the field of aerospace technology, particularly to the fields of aerospace engineering and remote sensing technology, and specifically relates to a method and apparatus for transmitting satellite radar signals, a method and apparatus for receiving satellite radar signals, electronic equipment, and a computer-readable storage medium. Background Technology

[0002] Spaceborne Synthetic Aperture Radar (SAR) offers advantages such as all-weather, all-day operation and high resolution, making it a crucial tool for Earth observation. Currently, most high-resolution X-band spaceborne SAR systems operate with a transmission carrier center frequency of 9.6 GHz, resulting in a maximum signal bandwidth of 1200 MHz. Within this ultra-wideband operating frequency range, spaceborne SAR is highly susceptible to receiving active or passive signals from ground-based or airborne radars operating at the same frequency, leading to degraded image quality, reduced measurement accuracy, and system malfunction. Especially given the relatively fixed operating carrier frequency of spaceborne SAR, overlapping radar signal sources exist in certain areas, making most imaging in those regions prone to interference. Furthermore, with the development of ground-based electronic countermeasures technology, various ground-based jamming devices can intercept spaceborne SAR transmission signals, identify parameters, synchronize targeting, and suppress noise, resulting in a decrease in the signal-to-noise ratio of normal radar echoes, blurred imaging, and even complete suppression of ground features by noise.

[0003] The satellite-borne SAR signal transmission link typically includes baseband signal generation, intermediate frequency (IF) processing, radio frequency (RF) up-conversion, amplification, distribution, and transmission. The baseband signal is generated using a digital-to-analog converter (DAC) to achieve wideband linear frequency modulation (LFM) analog signal generation. After amplitude and phase adjustment, an analog IF signal is output, carrying information from the baseband signal. The RF module generates a high-precision local oscillator frequency (LOF) via a phase-locked loop (PLL). After filtering and amplification, the LLF is split into two LLF signals, one for the FM source and the other for the receiver module. The IF and LLF signals are fed into the RF integration unit, where IF filtering, up-conversion, and power amplification are performed. The LLF signal is then transmitted via a high-frequency cable to the SAR antenna feed network, and finally, the waveguide antenna element is excited by the time-delay amplification (TR) component, ultimately radiating into the imaging observation area. Currently, most commercial SAR satellite payload RF designs use a "fixed LLF + fixed IF" scheme, which cannot flexibly adapt to multi-bandwidth and multi-frequency switching and has weak anti-interference capabilities. In addition, existing spaceborne SAR pulse transmissions all use a direct-start transmission method based on LFM (Linear Frequency Modulation) imaging signals, lacking dedicated anti-interference waveform construction and pulse leading-edge spectrum isolation design. The RF power amplifier jumps instantaneously from zero power to its rated operating point, easily causing severe nonlinear power-on impacts, leading to significant pulse leading-edge spectrum spread and large out-of-band spurious leakage. All of these factors make most existing spaceborne SAR systems unsuitable for current on-orbit operating scenarios with strong electromagnetic countermeasures. Summary of the Invention

[0004] The purpose of this disclosure is to solve the technical problems of existing spaceborne SAR and to provide a spaceborne radar signal transmission method and apparatus, a spaceborne radar signal reception method and apparatus, an electronic device, and a computer-readable storage medium. The first aspect of this disclosure provides a spaceborne radar signal transmission method, which includes: determining the radio frequency (RF) operating center frequency of the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar; calculating the target intermediate frequency (IF) signal frequency based on the RF operating center frequency and a fixed RF local oscillator frequency; generating an out-of-band preset signal based on anti-interference requirements, wherein the frequency band of the out-of-band preset signal deviates from the bandwidth of the main imaging signal of the current imaging mission by a preset ratio, the duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal, and it is embedded in the pulse leading edge of the main imaging signal; generating a digital waveform of the main imaging signal and superimposing and embedding the digital waveform of the out-of-band preset signal into the pulse leading edge of the main imaging signal to generate a composite digital baseband signal; converting the composite digital baseband signal into an analog signal, performing IF filtering on the analog signal at the target IF signal frequency, up-converting it to the RF carrier frequency band, and amplifying it to obtain the transmitted signal; and radiating the transmitted signal to the target area through an antenna.

[0005] The second aspect of this disclosure provides a method for receiving spaceborne radar signals. The method includes: receiving radar reflected echo signals from a target area via an antenna, wherein the radar reflected echo signals are signals formed after reflection from a target by a transmitted signal obtained using the spaceborne radar signal transmission method described in the first aspect; performing down-conversion processing on the radar reflected echo signals using the same radio frequency local oscillator frequency as the transmitter to obtain an analog intermediate frequency (IF) echo signal; filtering and performing analog-to-digital conversion on the analog IF echo signals at the target IF signal frequency to obtain a digital baseband echo signal; filtering out echo components corresponding to out-of-band preset signals from the digital baseband echo signals based on the main imaging signal bandwidth and frequency parameters to extract effective echo data corresponding to the main imaging signal; and performing synthetic aperture radar (SAR) imaging processing using the effective echo data.

[0006] This disclosure provides a third aspect of a spaceborne radar signal transmitting apparatus, comprising: a determining unit configured to determine the radio frequency (RF) operating center frequency of the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar; a calculating unit configured to calculate the target intermediate frequency (IF) signal frequency based on the RF operating center frequency and a fixed RF local oscillator frequency; a generating unit configured to generate an out-of-band preset signal based on anti-interference requirement information, wherein the frequency band of the out-of-band preset signal deviates from the bandwidth of the main imaging signal of the current imaging mission by a preset ratio, the duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal, and it is embedded in the pulse leading edge of the main imaging signal; an embedding unit configured to generate a digital waveform of the main imaging signal and superimpose and embed the digital waveform of the out-of-band preset signal into the pulse leading edge of the main imaging signal to generate a composite digital baseband signal; a obtaining unit configured to convert the composite digital baseband signal into an analog signal, perform IF filtering on the analog signal at the target IF signal frequency, up-convert the signal to the RF carrier band, and amplify the signal to obtain a transmitted signal; and a transmitting unit configured to radiate the transmitted signal to the target area through an antenna.

[0007] This disclosure provides a fourth aspect of a spaceborne radar signal receiving device, comprising: a receiving unit configured to receive radar reflected echo signals from a target area via an antenna, the radar reflected echo signals being signals formed after reflection from a target by a transmitted signal obtained by a spaceborne radar signal transmitting device as described in the third aspect; a frequency conversion unit configured to perform down-conversion processing on the radar reflected echo signals using the same radio frequency local oscillator frequency as the transmitting end, to obtain an analog intermediate frequency echo signal; a conversion unit configured to perform filtering and analog-to-digital conversion on the analog intermediate frequency echo signals at the target intermediate frequency signal frequency, to obtain a digital baseband echo signal; an extraction unit configured to filter out echo components corresponding to out-of-band preset signals from the digital baseband echo signals based on the bandwidth and frequency parameters of the main imaging signal, to extract effective echo data corresponding to the main imaging signal; and a processing unit configured to perform synthetic aperture radar imaging processing using the effective echo data.

[0008] The fifth aspect of this disclosure provides a computer device including a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method as described in the first or second aspect.

[0009] The sixth aspect of this disclosure provides a computer-readable storage medium in which a computer program, when executed by a processor, implements the steps of the method as described in the first or second aspect.

[0010] The spaceborne radar signal transmission method and apparatus provided in the embodiments of this disclosure firstly determine the radio frequency (RF) operating center frequency of the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar; secondly, calculate the target intermediate frequency (IF) signal frequency based on the RF operating center frequency and a fixed RF local oscillator frequency; thirdly, generate an out-of-band preset signal based on anti-interference requirements, wherein the frequency band of the out-of-band preset signal deviates from the bandwidth of the main imaging signal of the current imaging mission by a preset ratio, the duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal, and it is embedded in the pulse leading edge of the main imaging signal; next, generate a digital waveform of the main imaging signal, and superimpose and embed the digital waveform of the out-of-band preset signal into the pulse leading edge of the main imaging signal to generate a composite digital baseband signal; then, convert the composite digital baseband signal into an analog signal, perform IF filtering on the analog signal at the target IF signal frequency, up-convert it to the RF carrier frequency band, and amplify it to obtain the transmitted signal; finally, radiate the transmitted signal to the target area through an antenna. Therefore, by combining a fixed RF local oscillator frequency with a flexible calculation of the target intermediate frequency signal, flexible switching between multiple frequency points and multi-level bandwidths can be achieved without modifying the RF link hardware. This confines the operating frequency band to the high-quality range and avoids spectral truncation and amplitude-phase distortion after ultra-wideband signal jumps. At the same time, superimposing a short-time out-of-band preset signal at the leading edge of the main imaging signal pulse serves two purposes. First, it acts as a pre-stabilizer for the RF transmission pulse, effectively mitigating the nonlinear impact and spectral spread caused by the instantaneous power-on of the power amplifier. Second, through the combined camouflage of the frequency domain (out-of-band offset) and the time domain (leading edge embedding), it disrupts the carrier frequency detection, pulse synchronization, and modulation identification of the ground jammer without affecting the main signal. This causes the jamming equipment to experience feature confusion and missynchronization, thereby significantly improving the active anti-interference and survivability of spaceborne SAR in complex electromagnetic environments. Attached Figure Description

[0011] Figure 1 This is a flowchart of one embodiment of the spaceborne radar signal transmission method according to the present disclosure;

[0012] Figure 2 This is a flowchart of an embodiment of the spaceborne radar signal receiving method according to the present disclosure; Figure 3 This is a schematic diagram of a structure of an embodiment of a spaceborne radar signal transmitting device according to the present disclosure; Figure 4 This is a schematic diagram of a structure of an embodiment of the spaceborne radar signal receiving device according to the present disclosure; Figure 5 This is a block diagram of an electronic device used to implement the spaceborne radar signal transmission method of the embodiments of this disclosure. Detailed Implementation

[0013] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0014] The technical solution of the present invention is illustrated below through specific embodiments. It should be understood that the one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0015] The raw materials and instruments used in the examples are not subject to any specific restrictions on their source; they can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0016] The problems with existing technologies are as follows: Existing spaceborne SARs usually transmit linear frequency modulated signals with a fixed center frequency and fixed bandwidth. Their spectral characteristics and time-domain structure are highly regular, making them easy for ground jammers to quickly intercept, sort, and lock onto.

[0017] Fixed local oscillator + fixed intermediate frequency: It cannot flexibly adapt to switching between multiple bandwidths and multiple frequency points, and it does not have the ability to actively resist interference from known ground-based fixed interference sources at the same frequency.

[0018] Fixed local oscillator + coarse intermediate frequency adjustment: When operating in ultra-wideband (900MHz-1200MHz), the intermediate frequency offset is too large. Affected by the in-band roll-off characteristics of the RF filter, the spectrum of the ultra-wideband LFM imaging signal is prone to spectral truncation and amplitude-phase distortion on both sides, resulting in increased image sidelobes.

[0019] Traditional waveforms lack anti-interference design, spectral isolation, pulse pre-stabilization, and out-of-band presets. During RF transmission, they are prone to severe nonlinear power-on surges, leading to significant spectral broadening at the pulse leading edge and out-of-band spurious leakage. Furthermore, they are susceptible to co-channel interference, adjacent-channel interference, suppression interference, and self-interference in complex electromagnetic environments, resulting in weak anti-interference capabilities. Nonlinear power-on surges occur when the RF power amplifier abruptly transitions from a static state (zero power or low power consumption) to its rated saturation operating point at the pulse initiation of a broadband radar pulse. This nonlinear distortion is caused by transient response hysteresis and thermal effects. This nonlinear power-on surge leads to severe spectral broadening at the pulse leading edge and generates substantial out-of-band spurious leakage.

[0020] This disclosure provides a method for transmitting spaceborne radar signals. Figure 1 A flowchart 100 illustrates an embodiment of a spaceborne radar signal transmission method, which includes the following steps: Step 101: Determine the radio frequency center point of the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar.

[0021] This disclosure belongs to the field of spaceborne synthetic aperture radar technology, specifically involving spaceborne SAR transmit carrier frequency conversion, transmit waveform design, intermediate frequency filtering and up-conversion, etc., especially involving the design of X-band multi-frequency point, multi-bandwidth, strong anti-interference carrier transmission system, which can be directly applied to ultra-high resolution SAR satellite payload systems and other technical fields.

[0022] The satellite radar signal transmission method provided in this embodiment adopts a multi-frequency RF center frequency + fixed high local oscillator + variable intermediate frequency joint frequency modulation system, combined with pulse leading edge out-of-band offset preset waveform pre-stabilization transmission technology. No new hardware equipment is required. The invention purpose is achieved only through RF frequency conversion parameter linkage configuration and pulse timing waveform segmented modulation. It belongs to the category of electrical RF modulation and timing control methods.

[0023] Step 101 above includes: before the spaceborne synthetic aperture radar performs a transmission mission, the receiving channel is turned on to enter a brief passive listening mode to perform real-time spectrum scanning of the noise floor and external signals within the operating band capability range (e.g., 9.2GHz to 10.4GHz); the signal processing unit analyzes the spectrum data acquired by the scan to identify the current interference frequency band and peak frequency of the ground co-channel interference source; based on multiple preset discrete radio frequency working center frequencies (e.g., 9.35GHz, 9.65GHz, 9.80GHz, 9.95GHz, 10.25GHz), the frequency band isolation between each candidate frequency point and the peak interference frequency is calculated; the discrete frequency point with the largest frequency band isolation and capable of accommodating the bandwidth required by the current mission is selected as the radio frequency working center frequency point of the current imaging mission.

[0024] Optionally, step 101 may further include: obtaining the location of the target area for the current imaging task and querying the system's preset spectrum planning database (which records the frequency band distribution of known fixed interference sources in the local area); within the operating band capability range of the spaceborne synthetic aperture radar (e.g., 9.2 GHz to 10.4 GHz), eliminating frequency points that overlap with the frequency bands of known interference sources in the target area from a preset set of multiple discrete radio frequency operating center points; and selecting one from the remaining safe frequency points as the radio frequency operating center point for the current imaging task.

[0025] Step 102: Calculate the target intermediate frequency signal frequency based on the RF operating center frequency and the fixed RF local oscillator frequency.

[0026] In this embodiment, the target intermediate frequency (IF) signal frequency serves as the reference frequency for subsequent IF sampling and digital signal processing, ensuring that the echo signal is shifted to a fixed IF band suitable for analog-to-digital converter processing before digitization. Flexible switching between different RF center frequencies is achieved by changing the target IF signal frequency without requiring modifications to the local oscillator hardware.

[0027] In this embodiment, this can be achieved by querying a pre-defined mapping table. Specifically, a mapping table between the carrier radio frequency center frequency and the intermediate frequency signal frequency is pre-established and stored in the storage unit of the spaceborne radar system (e.g., containing discrete mappings such as 9.35GHz corresponding to 3.45GHz, 9.80GHz corresponding to 3.00GHz, etc.). After determining the radio frequency operating center frequency of the current imaging mission, the signal processing unit directly uses this center frequency as an index to query the aforementioned mapping table, thereby retrieving and determining the corresponding target intermediate frequency signal frequency. By using a table lookup method instead of real-time subtraction operations, the computational load of the spaceborne signal processor is effectively reduced, and the response speed of frequency hopping switching is improved.

[0028] Optionally, step 102 includes: obtaining the basic intermediate frequency by subtracting the fixed RF local oscillator frequency from the RF operating center frequency, and further obtaining the hardware status parameters or small frequency offset requirements of the current RF link or spectrum planning; generating an intermediate frequency compensation deviation based on the hardware status parameters or small frequency offset requirements; and algebraically adding the basic intermediate frequency and the intermediate frequency compensation deviation to obtain the final iteratively optimized target intermediate frequency signal frequency, thereby ensuring the amplitude and phase consistency of the ultra-wideband signal when passing through the RF filter.

[0029] Step 103: Generate out-of-band preset signals based on anti-interference requirements.

[0030] In this embodiment, the out-of-band preset signal refers to a very short waveform artificially superimposed on the leading edge of the main pulse during the digital baseband generation stage before the main imaging signal (such as a linear frequency modulated signal) is transmitted by the spaceborne SAR. The frequency of this signal falls outside the bandwidth of the main imaging signal (but is still within the physical bandwidth of the RF channel). The out-of-band preset signal has a dual function: first, it acts as a "decoy" in the time and frequency domains, disrupting the carrier frequency detection, pulse synchronization, and modulation identification of the ground jammer (causing the jammer to lock onto the wrong frequency point or be unable to extract the correct frequency modulation slope); second, it acts as a "pre-stabilization signal," enabling the RF power amplifier to enter the working state in advance before the arrival of the main signal, avoiding the nonlinear power-on impact and pulse leading edge spectrum spread caused by the RF power amplifier jumping from zero to full power instantaneously. The out-of-band preset signal can effectively smooth out the severe spectrum broadening of the pulse leading edge caused by the nonlinear power-on impact.

[0031] In this embodiment, the frequency band of the out-of-band preset signal deviates from the preset ratio of the bandwidth of the main imaging signal of the current imaging mission. The duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal, and it is embedded in the pulse leading edge of the main imaging signal. The out-of-band preset signal is not only for hardware pre-stabilization, but more importantly, at the electromagnetic warfare level, it forms a false spectral peak in the spectrum. This causes enemy electronic reconnaissance equipment on the ground to mistakenly identify this short-duration signal as the main signal when conducting broadband reconnaissance, thus leading to incorrect parameter setting of the targeting jammer.

[0032] In this embodiment, step 103 includes: analyzing the jammer's detection bandwidth characteristics in the anti-interference requirement information; if, based on the jammer's detection bandwidth characteristics, the ground interference source is determined to be narrowband targeting jamming, a single-frequency continuous wave is generated as an out-of-band preset signal to form an extremely sharp independent spectral peak outside the band, inducing the jammer to lose frequency lock; if, based on the jammer's detection bandwidth characteristics, the ground interference source is determined to be broadband detection jamming, a short linear frequency modulated pulse with a bandwidth not exceeding 60MHz is generated as an out-of-band preset signal, causing the jammer to experience multi-frequency confusion during broadband detection. During the above dynamic generation process, regardless of the waveform system used, the start and end frequency bands of the out-of-band preset signal are strictly constrained to deviate from the main imaging signal bandwidth by a preset ratio (e.g., ≥10%), and its duration is controlled within 0.2-1μs and precisely embedded into the leading edge of the main signal pulse.

[0033] Optionally, step 103 includes: based on the modulation recognition algorithm characteristics of the jammer in the anti-interference requirement information, when generating the out-of-band preset signal, the signal generation module does not use a smooth amplitude envelope for it, but instead sets a specific initial phase and envelope slope based on the modulation recognition algorithm characteristics, and generates the out-of-band preset signal based on the initial phase and envelope slope. When the out-of-band preset signal (whose frequency band also deviates from the preset proportion of the main signal bandwidth and has an extremely short duration) is superimposed and embedded into the pulse leading edge of the main imaging signal, a strong transient phase change and amplitude step are deliberately created at the time domain junction of the out-of-band preset signal and the main imaging signal.

[0034] Step 104: Generate the digital waveform of the main imaging signal, and superimpose and embed the digital waveform of the out-of-band preset signal into the pulse leading edge of the main imaging signal to generate a composite digital baseband signal.

[0035] In this embodiment, the form of the digital waveform of the main imaging signal is a mature technology and will not be described in detail here.

[0036] In this embodiment, the digital waveform of the main imaging signal is obtained by linear frequency modulation or phase encoding to achieve the required resolution and imaging quality. At the same time, the digital waveform of the out-of-band preset signal is superimposed and embedded into the pulse leading edge of the main imaging signal with a specific amplitude ratio and time delay relationship, so that the two are seamlessly connected in the time domain and do not overlap in the frequency domain, thereby generating a composite digital baseband signal that has both main imaging function and out-of-band suppression characteristics. After digital-to-analog conversion, this signal can be directly used for subsequent up-conversion and power amplification processing.

[0037] Step 105: Convert the composite digital baseband signal into an analog signal, perform intermediate frequency filtering on the analog signal at the target intermediate frequency signal frequency, upconvert the signal to the radio frequency carrier band, and amplify the signal to obtain the transmitted signal.

[0038] In this embodiment, the composite digital baseband signal is converted into an analog signal by a high-speed digital-to-analog converter. Then, it is filtered by a bandpass filter at the target intermediate frequency to suppress image frequencies and out-of-band spurious signals. The filtered intermediate frequency signal is then mixed with a local oscillator for up-conversion and shifted to the radio frequency carrier band. Finally, it is amplified by a power amplifier to obtain a radio frequency transmission signal that meets the transmission power requirements and is fed to the transmitting antenna for radiation.

[0039] Step 105 may further include: filtering the digital baseband signal through an intermediate frequency filter, retaining the out-of-band preset signal and the main signal, and simultaneously performing amplitude stabilization and phase compensation to improve the stability and purity of the signal. Subsequently, the intermediate frequency signal is up-converted to the radio frequency carrier frequency of the spaceborne SAR through mixing and filtering, and after power amplification and other processing, the transmitted signal is obtained.

[0040] Step 106: Radiate the transmitted signal to the target area via the antenna.

[0041] In this embodiment, the forward transmission signal is amplified to the required power level by a power amplifier and then fed to the antenna unit phase system. The antenna unit phase system converts the electrical signal into electromagnetic waves and radiates them directionally to the target area. The transmitted signal propagates through space and illuminates the ground target area. The antenna type is selected according to the application scenario, either a phased array antenna or a parabolic antenna, to ensure beam pointing accuracy and energy concentration.

[0042] The spaceborne radar signal transmission method provided in this disclosure firstly determines the radio frequency (RF) center frequency of the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar. Secondly, it calculates the target intermediate frequency (IF) signal frequency based on the RF center frequency and a fixed RF local oscillator frequency. Thirdly, it generates an out-of-band preset signal based on anti-interference requirements. The frequency band of the out-of-band preset signal deviates from the bandwidth of the main imaging signal of the current imaging mission by a preset ratio, the duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal, and it is embedded in the pulse leading edge of the main imaging signal. Next, it generates a digital waveform of the main imaging signal and superimposes and embeds the digital waveform of the out-of-band preset signal into the pulse leading edge of the main imaging signal to generate a composite digital baseband signal. Then, it converts the composite digital baseband signal into an analog signal, performs IF filtering on the analog signal at the target IF signal frequency, up-converts it to the RF carrier frequency band, and amplifies it to obtain the transmitted signal. Finally, it radiates the transmitted signal to the target area through an antenna. Therefore, by combining a fixed RF local oscillator frequency with a flexible calculation of the target intermediate frequency signal, flexible switching between multiple frequency points and multi-level bandwidths can be achieved without modifying the RF link hardware. This confines the operating frequency band to the high-quality range and avoids spectral truncation and amplitude-phase distortion after ultra-wideband signal jumps. At the same time, superimposing a short-time out-of-band preset signal at the leading edge of the main imaging signal pulse serves two purposes. First, it acts as a pre-stabilizer for the RF transmission pulse, effectively mitigating the nonlinear impact and spectral spread caused by the instantaneous power-on of the power amplifier. Second, through the combined camouflage of the frequency domain (out-of-band offset) and the time domain (leading edge embedding), it disrupts the carrier frequency detection, pulse synchronization, and modulation identification of the ground jammer without affecting the main signal. This causes the jamming equipment to experience feature confusion and missynchronization, thereby significantly improving the active anti-interference and survivability of spaceborne SAR in complex electromagnetic environments.

[0043] In some optional implementations of this disclosure, determining the radio frequency (RF) operating center frequency for the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar includes: determining the signal bandwidth required for the current imaging mission based on the imaging mode, resolution requirements, and operating band capability range of the spaceborne synthetic aperture radar; selecting the RF operating center frequency corresponding to the signal bandwidth based on a preset hierarchical bandwidth matching rule; wherein the hierarchical bandwidth matching rule is formed by a plurality of preset discrete RF operating center frequencies and their configured maximum support bandwidth; in the hierarchical bandwidth matching rule, the RF operating center frequency located at the center of the operating band is configured with the maximum support bandwidth, and the RF operating center frequency located at the edge of the operating band is configured with a smaller support bandwidth.

[0044] In this optional implementation, the hierarchical bandwidth matching rule refers to a preset mapping rule between the multiple discrete RF operating center frequencies of the spaceborne SAR and their maximum supported signal bandwidth. Due to the in-band roll-off characteristics of RF filters, amplitude and phase distortion is highly likely to occur when the signal bandwidth is close to the filter edge. This hierarchical bandwidth matching rule stipulates that frequencies closer to the physical center of the operating band are allocated the maximum allowed bandwidth (e.g., 1200MHz ultra-wideband); frequencies closer to the physical edge of the band are allocated a smaller maximum bandwidth (e.g., 300MHz narrowband). This ensures that the signal spectrum will not be truncated by the hardware filter when switching operation at any frequency, achieving distortion-free transmission under all operating conditions.

[0045] In this optional implementation, a reasonable operating center frequency point for the radio frequency carrier is divided according to the operating band capability range of the spaceborne SAR payload. Depending on actual needs, it can be divided into 5 different frequency points, for example... , , , , .in The default RF operating center frequency is 9.2GHz to 10.4GHz. In actual implementation, the X-band carrier frequency of the spaceborne SAR satellite can operate in the range of 9.2GHz to 10.4GHz, with 9.8GHz being the conventional default operating frequency. Considering common transmit signal bandwidth requirements, five discrete RF operating center frequencies are designed: 9.35GHz, 9.65GHz, 9.80GHz, 9.95GHz, and 10.25GHz. A hierarchical bandwidth matching design is adopted: the two outer edges (9.35GHz and 10.25GHz) can accommodate a maximum operating bandwidth of 300MHz, the middle edges (9.65GHz and 9.95GHz) can accommodate a maximum wideband operating bandwidth of 900MHz, and the center (9.80GHz) can accommodate a maximum ultra-wideband operating bandwidth of 1200MHz, thus meeting the requirements of multi-mode imaging missions.

[0046] In this optional implementation, the executing entity will combine the signal bandwidth required by the current imaging task (such as 300MHz, 900MHz or 1200MHz ultra-wideband) and follow the principle of "the center frequency point is adapted to the large bandwidth and the edge frequency point is adapted to the small bandwidth": if the current task requires 1200MHz, then 9.80GHz, which is located at the center of the band, will be selected; if the current task only requires 300MHz, then 9.35GHz, which is located at the edge of the band, can be flexibly selected.

[0047] Optionally, the above-mentioned hierarchical bandwidth matching rule is obtained through the following steps: dividing the working band capability range into a default center frequency, two first adjacent frequencies, and two edge frequencies; wherein, the default center frequency is configured with the maximum supported bandwidth to adapt to the ultra-wideband imaging mode; the two first adjacent frequencies are symmetrically distributed on both sides of the default center frequency and configured with a first degraded supported bandwidth to adapt to the wideband imaging mode; the two edge frequencies are symmetrically distributed at both ends of the working band capability range and configured with a second degraded supported bandwidth to adapt to the narrowband imaging mode, wherein the second degraded supported bandwidth is less than the first degraded supported bandwidth.

[0048] In some optional implementations of this disclosure, the above-mentioned calculation of the target intermediate frequency signal frequency based on the radio frequency operating center frequency and the fixed radio frequency local oscillator frequency includes: subtracting the fixed radio frequency local oscillator frequency from the radio frequency operating center frequency to obtain the target intermediate frequency signal frequency.

[0049] In this optional implementation, a fixed RF local oscillator frequency can be obtained through a frequency synthesizer and an internal phase-locked loop. Generally, the fixed RF local oscillator frequency is 12.8 GHz by default. After determining the RF operating center frequency, the fixed RF local oscillator frequency can be directly subtracted from the RF operating center frequency to obtain the target intermediate frequency (IF) signal frequency. For the aforementioned RF operating center frequency, the baseband waveform generation unit generates 5 sets of target IF signal frequencies. The bandwidths are 3.45GHz, 3.15GHz, 3.00GHz, 2.85GHz and 2.55GHz, respectively, which correspond to the linear frequency modulation signal design requirements satisfied by the graded bandwidths shown in Table 1.

[0050] Table 1

[0051] In some optional implementations of this disclosure, generating an out-of-band preset signal based on anti-interference requirements includes: determining an out-of-band center frequency based on anti-interference requirements so that the start and end frequency bands of the initial preset signal deviate from the bandwidth of the main imaging signal by a preset ratio; setting the duration of the initial preset signal to be less than the pulse width of the main imaging signal and limiting the initial preset signal to the leading edge period of the main signal pulse; setting the intensity of the initial preset signal to be lower than the intensity of the main imaging signal, and generating an out-of-band preset signal.

[0052] In this optional implementation, a short-time out-of-band preset signal is generated based on the anti-interference requirement information. The out-of-band preset signal includes the signal center frequency, frequency offset, and out-of-band duration. And bandwidth, etc. The out-of-band preset signal is embedded in the digital baseband signal generation stage. Before generating the analog intermediate frequency signal, the preset signal and the main signal are superimposed through digital domain signal synthesis, and then output to the antenna through subsequent frequency conversion, amplification, and other links. The specific design requirements for the out-of-band preset signal are as follows: Spectrum design ensures "out-of-band" performance—the start and end frequency bands of the preset signal are deviated from the bandwidth of the main imaging signal by ≥10% (e.g., if the main signal bandwidth is 600MHz, the offset of the out-of-band preset signal is ≥60MHz) to avoid overlap with the main signal spectrum. In terms of time domain characteristics, the "short-time" duration is typically 0.2-1μs, much shorter than the pulse width of the main imaging signal, and strictly limited to the leading edge of the main signal pulse. The waveform type can be selected according to the function; the preset signal waveform can be a single-frequency continuous wave or a short linear frequency modulated pulse. The signal center frequency and bandwidth should not exceed 60MHz, and the signal strength should be approximately 0.5 times that of the main signal to avoid affecting the main imaging signal.

[0053] Optionally, generating the out-of-band preset signal based on the anti-interference requirement information includes: setting the start and end frequency bands of the out-of-band preset signal to deviate from the bandwidth of the main imaging signal by at least 10% to achieve spectral isolation from the main imaging signal; setting the duration of the out-of-band preset signal to be 0.2 microseconds to 1 microsecond to strictly limit it to the leading edge period of the main imaging signal pulse; setting the waveform type of the out-of-band preset signal to be a single-frequency continuous wave or a short-time linear frequency modulated pulse; and setting the amplitude intensity of the out-of-band preset signal to be 0.5 times the intensity of the main imaging signal to provide waveform pre-stabilization when the RF power amplifier is powered on, without affecting the signal-to-noise ratio of the main imaging signal.

[0054] In some optional implementations of this disclosure, the above-mentioned method of superimposing and embedding the digital waveform of the out-of-band preset signal into the pulse leading edge of the main imaging signal to generate a composite digital baseband signal includes: setting the trigger time of the digital waveform of the main imaging signal as the initial reference time; controlling the digital waveform of the out-of-band preset signal to start outputting from the initial reference time and ending outputting after the duration of the out-of-band preset signal; compensating for the path delay difference between the out-of-band preset signal and the main imaging signal in the generation link through a digital delay line; and linearly superimposing the digital sampled value of the timing-synchronized out-of-band preset signal with the digital sampled value of the leading edge of the main imaging signal to obtain the composite digital baseband signal.

[0055] In this optional implementation, the digital delay line is a digital domain time delay module implemented within digital signal processing or a field-programmable gate array (FPGA) through shift registers or memory read / write pointer offsets. Since the out-of-band preset signal and the main imaging signal have different computational paths in the digital generation link, to ensure the preset signal is accurately and seamlessly stitched and embedded in the pulse leading edge of the main imaging signal, the digital delay line performs nanosecond-level or even picosecond-level timing alignment compensation on the two digital sampled values ​​before linear superposition and synthesis.

[0056] In this optional implementation, digital baseband signal parameters are automatically calculated based on the imaging task. For example, based on the imaging mode (e.g., sliding mode, strip mode, and scanning mode), image resolution, and imaging angle, the parameters of the main imaging signal and the out-of-band preset signal are calculated. The signal processing unit, DAC module, frequency synthesizer, mixer, power amplifier, and antenna beamforming unit of the spaceborne SAR are activated, and the timing of each module is synchronized through the system clock. According to the correspondence table of "carrier radio frequency center frequency - intermediate frequency signal frequency," the intermediate frequency signal frequency of the high-speed DAC is calculated. For example, if the transmit frequency is 9.8 GHz and the local oscillator frequency is 12.8 GHz, then the intermediate frequency signal frequency is set to 3 GHz. The signal processing unit generates the digital waveform of the main imaging LFM signal, with the trigger time recorded as T0. Using T0 as a reference, the signal processing unit generates the digital waveform of the out-of-band preset signal according to the preset parameters. The trigger timing of the preset signal generation starts from T0 and is output. At the end of the time, ensure that it is fully embedded in the leading edge of the main signal pulse; compensate for the path delay difference between the preset signal and the main signal in the generation link by using a digital delay line to achieve time synchronization of the two signals; linearly superimpose the digital sampled value of the preset signal after timing synchronization with the digital sampled value of the leading edge of the main signal to generate a composite digital baseband signal.

[0057] Optionally, after obtaining the composite digital baseband signal, the method further includes: performing digital intermediate frequency filtering on the composite digital baseband signal to constrain the signal bandwidth and retain the out-of-band preset signal and the main imaging signal; performing amplitude stabilization processing and phase compensation calculation on the filtered composite digital baseband signal to eliminate the spectral distortion caused by the ultra-wideband signal jump; and outputting the corrected composite digital baseband signal to the digital-to-analog converter circuit.

[0058] The spaceborne radar signal transmission methods provided in the above embodiments adopt a multi-frequency point radio frequency center frequency + variable intermediate frequency linkage frequency modulation system, abandoning the traditional single variable frequency modulation mode, taking into account multi-frequency point switching and multi-level bandwidth adaptation, and constraining the intermediate frequency in the high-quality range under all operating conditions, thus solving the problem of ultra-wideband signal spectrum distortion. Without changing the hardware system, it realizes the rapid switching of the spaceborne SAR operating frequency, effectively reducing the impact of unintentional ground interference signals on the spaceborne SAR imaging capability. It adopts a pulse leading-edge out-of-band offset frequency preset pre-stabilization transmission mechanism, and achieves physical isolation and non-interference between the imaging main signal and the interference spectrum through waveform timing reconstruction and spectrum partitioning planning. Ground-based interference detection equipment generates additional independent spectral peaks in the spectrum, causing multi-frequency confusion during wideband jamming, making it impossible to accurately lock onto the true operating frequency and transmission timing of the spaceborne SAR, significantly reducing the reliability and hit rate of targeted jamming. Furthermore, the transient abrupt change at the time-domain junction between the out-of-band preset signal and the main LFM signal causes feature confusion in the jammer's modulation recognition algorithm based on intra-pulse feature extraction, making it difficult to correctly extract key parameters such as modulation slope and pulse width, increasing the difficulty of intra-pulse modulation recognition and monitoring efficiency. Therefore, by actively countering ground-based jamming equipment through waveform design at the transmitting end, the anti-interception and anti-targeting jamming capabilities of the spaceborne SAR are significantly improved. This approach is implemented without changing the original system architecture or increasing hardware complexity, only through parameter linkage configuration and timing waveform optimization, making it easy to implement in engineering and ensuring high on-orbit reliability. The preset out-of-band signal does not occupy the imaging spectrum and does not reduce the normal imaging quality of the spaceborne SAR. The frequency offset, duration, and amplitude of the out-of-band signal can be flexibly adjusted to adapt to different interference scenarios, creating multiple suppression effects on ground-based jammers, including deflection, loss of lock, and missynchronization.

[0059] This disclosure provides a method for transmitting spaceborne radar signals. Figure 2 A flowchart 200 illustrates an embodiment of a spaceborne radar signal transmission method, which includes the following steps: Step 201: Receive radar reflected echo signals from the target area via the antenna.

[0060] In this embodiment, the radar reflected echo signal is the signal after the transmitted signal obtained by the above-mentioned spaceborne radar signal transmission method is reflected by the target. Specifically, the radar reflected echo signal can be an electromagnetic wave signal formed after reflection by the regional surface or ground objects.

[0061] In this embodiment, radar reflected echo signals from the target area are received via an antenna. Specifically, the spaceborne receiving antenna captures the weak electromagnetic wave echoes in space and converts them into radio frequency electrical signals. These signals are then pre-amplified by a low-noise amplifier (LNA) at the front end of the receiving channel to improve the signal-to-noise ratio of the echo signal without introducing excessive additional noise, thus providing high-quality radio frequency echo input for subsequent down-conversion processing.

[0062] Step 202: Using the same radio frequency local oscillator frequency as the transmitter, the radar reflected echo signal is down-converted to obtain an analog intermediate frequency echo signal.

[0063] Step 202 above includes: mixing the radar echo signal with the same fixed radio frequency local oscillator signal as the transmitter, downconverting it to the same target intermediate frequency signal frequency as the transmitter, and obtaining a simulated intermediate frequency echo signal.

[0064] Optionally, step 202 above includes: the mixer of the receiving channel uses a fixed radio frequency local oscillator frequency (e.g., a 12.8 GHz high-precision local oscillator signal uniformly provided by the on-board phase-locked loop) that is exactly the same as that of the transmitting end to perform a mixing operation with the amplified radar reflected echo signal. Since the transmitting and receiving ends share the same fixed local oscillator source, there is no need to add additional dynamically tuned local oscillator hardware at the receiving end, and the X-band radio frequency echo signal can be directly and accurately down-converted to obtain an analog intermediate frequency echo signal containing target information.

[0065] Step 203: At the target intermediate frequency signal frequency, the analog intermediate frequency echo signal is filtered and converted from analog to digital to obtain the digital baseband echo signal.

[0066] In this embodiment, the target intermediate frequency signal frequency is the intermediate frequency dynamically calculated by the transmitter based on the current imaging bandwidth (such as 3.00GHz or 3.45GHz).

[0067] In this embodiment, the intermediate frequency bandpass filter of the control receiving channel is switched to a passband state that matches the frequency of the target intermediate frequency signal, filtering out image frequency interference and out-of-band thermal noise generated by mixing in the analog intermediate frequency echo signal. Subsequently, the analog intermediate frequency echo signal is sent to the analog-to-digital converter after the dynamic range is adjusted by the variable gain amplifier. The analog-to-digital converter samples, quantizes and quadratures the filtered analog signal at a rate not lower than the signal Nyquist sampling rate, and finally converts it into a digital baseband echo signal (i.e., I / Q dual-channel data).

[0068] Step 204: Based on the bandwidth and frequency parameters of the main imaging signal, filter out the echo components corresponding to the out-of-band preset signal from the digital baseband echo signal, and extract the effective echo data corresponding to the main imaging signal.

[0069] In this embodiment, step 204 includes: constructing a bandpass filter in the digital domain based on the known bandwidth and center frequency of the main imaging signal; the passband of the bandpass filter covers the frequency range of the main imaging signal, and the stopband of the bandpass filter covers the bias frequency range of the out-of-band preset signal; passing the digital baseband echo signal through the bandpass filter to isolate and filter out the echo components corresponding to the out-of-band preset signal and the accompanying ground interference signals in the frequency domain, and outputting clean and effective echo data.

[0070] In this embodiment, a digital bandpass filter is first designed based on the center frequency and bandwidth parameters of the main imaging signal. The digital baseband echo signal is input into the filter to filter out the corresponding echo components generated by the out-of-band preset signal and out-of-band noise interference, and only retain the effective echo data within the frequency band of the main imaging signal, thereby extracting the effective echo data of the main imaging signal for subsequent imaging processing.

[0071] Optionally, since the transmitted signal contains out-of-band preset signals for anti-interference purposes, these must be removed in the digital domain to avoid affecting SAR imaging quality. Specifically, in step 204, a high-order digital bandpass filter can be constructed in the digital signal processor based on the known center frequency and bandwidth parameters of the main imaging signal. The passband of this filter strictly covers the frequency range of the main imaging signal, while its stopband precisely covers the offset frequency range of the out-of-band preset signals. By passing the digital baseband echo signal through this digital bandpass filter, the echo components corresponding to the out-of-band preset signals are completely isolated and filtered out in the frequency domain, achieving perfect decoupling between the anti-interference camouflage signal and the main imaging signal, ultimately outputting clean and effective echo data.

[0072] Optionally, step 204 includes: determining the frequency domain position of the out-of-band preset signal in the digital baseband echo signal based on the frequency offset and bandwidth parameters of the out-of-band preset signal configured at the transmitter; filtering out the echo components corresponding to the frequency domain position of the out-of-band preset signal using a digital band-stop filter, and retaining the effective echo data within the frequency domain range of the main imaging signal.

[0073] Step 205: Perform synthetic aperture radar imaging processing using the effective echo data.

[0074] In this embodiment, the effective echo data undergoes pulse compression, motion compensation, and clutter suppression. The effective echo data obtained after pulse compression, motion compensation, and clutter suppression is then coherently accumulated according to the relative motion trajectory between the radar platform and the target. Range-direction pulse compression, range-travel correction, and Doppler azimuth focusing processing are then performed sequentially (using range-Doppler algorithms, chirped scaling algorithms, or back projection algorithms, etc.). Finally, a high-resolution two-dimensional or three-dimensional radar image of the target scene is reconstructed. Because the preceding steps successfully avoid ground interference and filter out out-of-band preset signals, this step can output a high signal-to-noise ratio, high-quality ground feature image without sidelobe distortion.

[0075] The spaceborne radar signal receiving method provided in the embodiments of this disclosure firstly receives radar reflected echo signals from a target area via an antenna. The radar reflected echo signals are signals formed after the transmitted signals obtained by the spaceborne radar information transmission method of the above embodiments are reflected by the target. Secondly, the radar reflected echo signals are down-converted using the same radio frequency local oscillator frequency as the transmitter to obtain analog intermediate frequency echo signals. Thirdly, the analog intermediate frequency echo signals are filtered and analog-to-digital converted at the target intermediate frequency signal frequency to obtain digital baseband echo signals. Then, based on the bandwidth and frequency parameters of the main imaging signal, the echo components corresponding to the out-of-band preset signals are filtered out from the digital baseband echo signals to extract the effective echo data corresponding to the main imaging signal. Finally, synthetic aperture radar imaging processing is performed using the effective echo data. Therefore, by using the same fixed RF local oscillator frequency and target intermediate frequency signal frequency at the receiving end for down-conversion and filtering as at the transmitting end, a high degree of consistency in the radar transceiver link system is maintained. This eliminates the need for additional frequency conversion hardware or dynamic tuning equipment in the receiving channel, reducing the system's engineering complexity and ensuring on-orbit reliability. Simultaneously, during the digital baseband echo signal processing stage, the echo components corresponding to out-of-band preset signals are precisely filtered out, achieving complete decoupling between the anti-jamming signal and the main imaging signal. This asymmetric processing mechanism—superimposing camouflage at the transmitting end and filtering and restoring at the receiving end—ensures that the preset signals used to counter ground jammers do not encroach on the main imaging spectrum, nor do they cause any attenuation or interference to the normal pulse compression and imaging quality of the spaceborne SAR system. Thus, while achieving strong electromagnetic countermeasure capabilities, it perfectly guarantees the purity and accuracy of the spaceborne SAR ultra-high resolution imaging data.

[0076] Further reference Figure 3 As an implementation of the methods shown in the above figures, this disclosure provides an embodiment of a spaceborne radar signal transmitting device, which is similar to... Figure 1 Corresponding to the method embodiments shown, this device can be specifically applied to various electronic devices.

[0077] like Figure 3As shown, the spaceborne radar signal transmitting device 300 provided in this embodiment includes: a determining unit 301, a calculating unit 302, a generating unit 303, an embedding unit 304, a obtaining unit 305, and a transmitting unit 306. The determining unit 301 can be configured to determine the radio frequency (RF) operating center frequency of the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar. The calculating unit 302 can be configured to calculate the target intermediate frequency (IF) signal frequency based on the RF operating center frequency and a fixed RF local oscillator frequency. The generating unit 303 can be configured to generate an out-of-band preset signal based on anti-interference requirement information. The frequency band of the out-of-band preset signal deviates from the bandwidth of the main imaging signal of the current imaging mission by a preset ratio, the duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal, and it is embedded in the pulse leading edge of the main imaging signal. The embedding unit 304 can be configured to generate a digital waveform of the main imaging signal and superimpose the digital waveform of the out-of-band preset signal onto the pulse leading edge of the main imaging signal to generate a composite digital baseband signal. The aforementioned unit 305 can be configured to convert the composite digital baseband signal into an analog signal, perform intermediate frequency filtering on the analog signal at the target intermediate frequency signal frequency, up-convert the signal to the radio frequency carrier band, and then amplify the power to obtain the transmitted signal. The aforementioned transmitting unit 306 can be configured to radiate the transmitted signal to the target area through an antenna.

[0078] In this embodiment, the specific processing of the determination unit 301, calculation unit 302, generation unit 303, embedding unit 304, obtaining unit 305, and transmission unit 306 in the spaceborne radar signal transmitting device, and the resulting technical effects, can be found in reference to [reference needed]. Figure 1 The relevant descriptions of steps 101, 102, 103, 104, 105, and 106 in the corresponding embodiments will not be repeated here.

[0079] In one embodiment of this disclosure, the determining unit 301 is configured to: determine the radio frequency (RF) working center frequency of the current imaging task based on the operating band capability range of the spaceborne synthetic aperture radar (SAR), including: determining the signal bandwidth required for the current imaging task based on the imaging mode, resolution requirements, and operating band capability range of the SAR; and selecting the RF working center frequency corresponding to the signal bandwidth based on a preset hierarchical bandwidth matching rule; wherein the hierarchical bandwidth matching rule is formed by a plurality of preset discrete RF working center frequencies and their configured maximum support bandwidths; in the hierarchical bandwidth matching rule, the RF working center frequency located at the center of the operating band is configured with the maximum support bandwidth, and the RF working center frequency located at the edge of the operating band is configured with a smaller support bandwidth.

[0080] In one embodiment of this disclosure, the calculation unit 302 is configured to calculate the target intermediate frequency signal frequency based on the radio frequency operating center frequency and the fixed radio frequency local oscillator frequency, including: subtracting the fixed radio frequency local oscillator frequency from the radio frequency operating center frequency to obtain the target intermediate frequency signal frequency.

[0081] In one embodiment of this disclosure, the generation unit 303 is configured to: determine the out-of-band center frequency based on anti-interference requirement information, so that the start and end frequency bands of the initial preset signal deviate from the bandwidth of the main imaging signal by a preset ratio; set the duration of the initial preset signal to be less than the pulse width of the main imaging signal, and limit the initial preset signal to the leading edge period of the main signal pulse; set the intensity of the initial preset signal to be lower than the intensity of the main imaging signal, and generate the out-of-band preset signal.

[0082] In one embodiment of this disclosure, the embedding unit 304 is configured to: superimpose the digital waveform of the out-of-band preset signal onto the pulse leading edge of the main imaging signal to generate a composite digital baseband signal, including: setting the trigger time of the digital waveform of the main imaging signal as the initial reference time; controlling the digital waveform of the out-of-band preset signal to start outputting from the initial reference time and ending outputting after the duration of the out-of-band preset signal; compensating for the path delay difference between the out-of-band preset signal and the main imaging signal in the generation link through a digital delay line; and linearly superimposing the digital sampled value of the timing-synchronized out-of-band preset signal with the digital sampled value of the leading edge of the main imaging signal to obtain a composite digital baseband signal.

[0083] The spaceborne radar signal transmitting device provided in the embodiments of this disclosure firstly determines the radio frequency (RF) center frequency of the current imaging task based on the operating band capability range of the spaceborne synthetic aperture radar (SAR). Secondly, the calculation unit 302 calculates the target intermediate frequency (IF) signal frequency based on the RF center frequency and a fixed RF local oscillator frequency. Thirdly, the generation unit 303 generates an out-of-band preset signal based on anti-interference requirements. The frequency band of the out-of-band preset signal deviates from the bandwidth of the main imaging signal of the current imaging task by a preset ratio, the duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal, and it is embedded in the pulse leading edge of the main imaging signal. Next, the embedding unit 304 generates a digital waveform of the main imaging signal and superimposes and embeds the digital waveform of the out-of-band preset signal into the pulse leading edge of the main imaging signal to generate a composite digital baseband signal. Then, the obtaining unit 305 converts the composite digital baseband signal into an analog signal, performs IF filtering on the analog signal at the target IF signal frequency, up-converts it to the RF carrier band, and amplifies it to obtain the transmitted signal. Finally, the transmitting unit 306 radiates the transmitted signal to the target area through an antenna. Therefore, flexible frequency switching and precise embedding of preset signals can be achieved through digital domain signal processing without modifying the RF link hardware, balancing system flexibility and functional scalability. This enables multi-frequency, multi-bandwidth adaptation in the X-band and distortion-free transmission after ultra-wideband signal transitions, solving the electronic interference problem caused by unintentional co-frequency interference signals from fixed ground-based sources in local areas for spaceborne SAR satellites. Simultaneously, by superimposing an anti-interference transmission waveform of an out-of-band preset signal at the leading edge of the main pulse, and through joint camouflage in the frequency and time domains, the carrier frequency detection, pulse synchronization, and modulation identification of ground jammers are disrupted, effectively countering ground jamming equipment. This prevents ground jamming equipment from quickly and accurately obtaining the main imaging parameters of the spaceborne SAR, thus causing ground jamming to malfunction or reduce its interference effect.

[0084] Further reference Figure 4 As an implementation of the methods shown in the above figures, this disclosure provides an embodiment of a spaceborne radar signal receiving device, which is similar to... Figure 2 Corresponding to the method embodiments shown, this device can be specifically applied to various electronic devices.

[0085] like Figure 4As shown, the spaceborne radar signal receiving device 400 provided in this embodiment includes: a receiving unit 401, a frequency conversion unit 402, a conversion unit 403, an extraction unit 404, and a processing unit 405. The receiving unit 401 can be configured to receive radar reflected echo signals from a target area via an antenna. The radar reflected echo signals are signals formed after the transmitted signal obtained by the device is reflected by the target. The frequency conversion unit 402 can be configured to down-convert the radar reflected echo signals using the same radio frequency local oscillator frequency as the transmitter to obtain analog intermediate frequency echo signals. The conversion unit 403 can be configured to filter and perform analog-to-digital conversion on the analog intermediate frequency echo signals at the target intermediate frequency signal frequency to obtain digital baseband echo signals. The extraction unit 404 can be configured to filter out echo components corresponding to out-of-band preset signals from the digital baseband echo signals based on the main imaging signal bandwidth and frequency parameters, extracting the effective echo data corresponding to the main imaging signal. The aforementioned processing unit 405 can be configured to perform synthetic aperture radar imaging processing using effective echo data.

[0086] In this embodiment, the specific processing of the receiving unit 401, frequency conversion unit 402, conversion unit 403, extraction unit 404, and processing unit 405 in the spaceborne radar signal receiving device, and the resulting technical effects, can be found in reference to [reference needed]. Figure 2 The relevant descriptions of steps 101, 102, 103, 104, and 105 in the corresponding embodiments will not be repeated here.

[0087] The spaceborne radar signal receiving device provided in the embodiments of this disclosure firstly receives radar reflected echo signals from a target area via an antenna by a receiving unit 401. The radar reflected echo signals are signals formed after the transmitted signal obtained by the device is reflected by the target. Secondly, a frequency conversion unit 402 performs down-conversion processing on the radar reflected echo signals using the same radio frequency local oscillator frequency as the transmitter to obtain analog intermediate frequency echo signals. Thirdly, a conversion unit 403 performs filtering and analog-to-digital conversion on the analog intermediate frequency echo signals at the target intermediate frequency signal frequency to obtain digital baseband echo signals. Then, an extraction unit 404 uses the main imaging signal bandwidth and frequency parameters to filter out the echo components corresponding to the out-of-band preset signals from the digital baseband echo signals and extracts the effective echo data corresponding to the main imaging signal. Finally, a processing unit 405 performs synthetic aperture radar imaging processing using the effective echo data. Therefore, by using the same fixed RF local oscillator frequency and target intermediate frequency signal frequency at the receiving end for down-conversion and filtering as at the transmitting end, a high degree of consistency in the radar transceiver link system is maintained. This eliminates the need for additional frequency conversion hardware or dynamic tuning equipment in the receiving channel, reducing the system's engineering complexity and ensuring on-orbit reliability. Simultaneously, during the digital baseband echo signal processing stage, the echo components corresponding to out-of-band preset signals are precisely filtered out, achieving complete decoupling between the anti-jamming signal and the main imaging signal. This asymmetric processing mechanism—superimposing camouflage at the transmitting end and filtering and restoring at the receiving end—ensures that the preset signals used to counter ground jammers do not encroach on the main imaging spectrum, nor do they cause any attenuation or interference to the normal pulse compression and imaging quality of the SAR system. Thus, while achieving strong electromagnetic countermeasure capabilities, it perfectly guarantees the purity and accuracy of the spaceborne SAR ultra-high resolution imaging data.

[0088] According to embodiments of this disclosure, this disclosure also provides an electronic device, a readable storage medium, and a computer program product.

[0089] Figure 5 A schematic block diagram of an example electronic device 500 that can be used to implement embodiments of the present disclosure is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their patterns are merely examples and are not intended to limit the implementation of the present disclosure described and / or claimed herein.

[0090] like Figure 5As shown, the electronic device 500 includes a computing unit 501, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 502 or a computer program loaded from a storage unit 508 into a random access memory (RAM) 503. The RAM 503 may also store various programs and data required for the operation of the electronic device 500. The computing unit 501, ROM 502, and RAM 503 are interconnected via a bus 504. An input / output (I / O) interface 505 is also connected to the bus 504.

[0091] Multiple components in electronic device 500 are connected to I / O interface 505, including: input unit 506, such as keyboard, mouse, etc.; output unit 507, such as various types of monitors, speakers, etc.; storage unit 508, such as disk, optical disk, etc.; and communication unit 509, such as network card, modem, wireless transceiver, etc. Communication unit 509 allows electronic device 500 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0092] The computing unit 501 can be various general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 501 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. The computing unit 501 performs the various methods and processes described above, such as a spaceborne radar signal transmission method or a spaceborne radar signal reception method. For example, in some embodiments, the spaceborne radar signal transmission method or the spaceborne radar signal reception method can be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as storage unit 508. In some embodiments, part or all of the computer program can be loaded and / or installed on the electronic device 500 via ROM 502 and / or communication unit 509. When the computer program is loaded into RAM 503 and executed by the computing unit 501, one or more steps of the spaceborne radar signal transmission or reception method described above can be performed. Alternatively, in other embodiments, the computing unit 501 may be configured in any other suitable manner (e.g., by means of firmware) as a method for transmitting or receiving spaceborne radar signals.

[0093] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), payload-programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0094] The program code used to implement the methods of this disclosure may be written in any combination of one or more programming languages. This program code may be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable spaceborne radar signal transmitter or receiver, such that when executed by the processor or controller, the patterns / operations specified in the flowcharts and / or block diagrams are implemented. The program code may be executed entirely on a machine, partially on a machine, as a standalone software package partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0095] In the context of this disclosure, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium can be, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0096] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device for displaying information to the user (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor); and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0097] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as a data server), or computing systems that include middleware components (e.g., an application server), or computing systems that include frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), and the Internet.

[0098] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this disclosure can be achieved, and this is not limited herein.

[0099] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for transmitting spaceborne radar signals, characterized in that, The method includes: Based on the operating band capability range of the spaceborne synthetic aperture radar, determine the radio frequency center point of the current imaging mission; Calculate the target intermediate frequency signal frequency based on the radio frequency operating center frequency and the fixed radio frequency local oscillator frequency; Based on the anti-interference requirement information, an out-of-band preset signal is generated. The frequency band of the out-of-band preset signal deviates from the bandwidth of the main imaging signal of the current imaging task by a preset ratio. The duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal and is embedded in the pulse leading edge of the main imaging signal. The digital waveform of the main imaging signal is generated, and the digital waveform of the out-of-band preset signal is superimposed and embedded into the pulse leading edge of the main imaging signal to generate a composite digital baseband signal; The composite digital baseband signal is converted into an analog signal. The analog signal is then filtered at the target intermediate frequency signal frequency and up-converted to the radio frequency carrier band. After power amplification, the transmitted signal is obtained. The transmitted signal is radiated to the target area via an antenna; The step of determining the radio frequency center point of the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar includes: Based on the imaging mode, resolution requirements, and operating band capability range of the spaceborne synthetic aperture radar, determine the signal bandwidth required for the current imaging mission. Based on a preset hierarchical bandwidth matching rule, a radio frequency operating center frequency corresponding to the signal bandwidth is selected; wherein, the hierarchical bandwidth matching rule is formed by a plurality of preset discrete radio frequency operating center frequencies and their configured maximum support bandwidth; in the hierarchical bandwidth matching rule, the radio frequency operating center frequency located at the center of the operating band is configured with the maximum support bandwidth, and the radio frequency operating center frequency located at the edge of the operating band is configured with a smaller support bandwidth.

2. The method according to claim 1, characterized in that, The step of calculating the target intermediate frequency signal frequency based on the radio frequency operating center frequency and the fixed radio frequency local oscillator frequency includes: The target intermediate frequency signal frequency is obtained by subtracting the fixed RF local oscillator frequency from the RF operating center frequency.

3. The method according to claim 1, characterized in that, The step of generating out-of-band preset signals based on anti-interference requirements includes: Based on the anti-interference requirements, the out-of-band center frequency is determined so that the start and end frequency bands of the initial preset signal deviate from the preset bandwidth of the main imaging signal by a predetermined ratio. The duration of the initial preset signal is set to be less than the pulse width of the main imaging signal, and the initial preset signal is limited to the leading edge period of the main signal pulse; The intensity of the initial preset signal is set to be lower than the intensity of the main imaging signal to generate an out-of-band preset signal.

4. The method according to claim 1, characterized in that, The step of superimposing and embedding the digital waveform of the out-of-band preset signal onto the pulse leading edge of the main imaging signal to generate a composite digital baseband signal includes: The trigger time of the digital waveform of the main imaging signal is set as the initial reference time; The digital waveform of the out-of-band preset signal is controlled to start outputting from the initial reference time and end outputting after the duration of the out-of-band preset signal; The path delay difference between the out-of-band preset signal and the main imaging signal in the generation link is compensated by a digital delay line; The digital sampled value of the out-of-band preset signal after timing synchronization is linearly superimposed with the digital sampled value of the leading edge of the main imaging signal to obtain the composite digital baseband signal.

5. A method for receiving spaceborne radar signals, characterized in that, The method includes: The antenna receives radar reflected echo signals from the target area, wherein the radar reflected echo signals are signals formed after the transmitted signal obtained by the method described in any one of claims 1-4 is reflected by the target. Using the same radio frequency local oscillator frequency as the transmitter, the radar reflected echo signal is down-converted to obtain an analog intermediate frequency echo signal; At the target intermediate frequency signal frequency, the analog intermediate frequency echo signal is filtered and converted from analog to digital to obtain a digital baseband echo signal; Based on the bandwidth and frequency parameters of the main imaging signal, the echo component corresponding to the out-of-band preset signal is filtered out from the digital baseband echo signal, and the effective echo data corresponding to the main imaging signal is extracted. The effective echo data is used for synthetic aperture radar imaging processing.

6. A spaceborne radar signal transmitting device, characterized in that, The device includes: The determining unit is configured to determine the radio frequency (RF) operating center frequency for the current imaging mission based on the operating band capability range of the spaceborne synthetic aperture radar (SAR). The determining unit is further configured to: determine the signal bandwidth required for the current imaging mission based on the imaging mode, resolution requirements, and operating band capability range of the spaceborne SAR; and select the RF operating center frequency corresponding to the signal bandwidth based on a preset hierarchical bandwidth matching rule. The hierarchical bandwidth matching rule is formed by a plurality of preset discrete RF operating center frequencies and their configured maximum support bandwidths. In the hierarchical bandwidth matching rule, the RF operating center frequency located at the center of the operating band is configured with the maximum support bandwidth, while the RF operating center frequency located at the edge of the operating band is configured with a smaller support bandwidth. The calculation unit is configured to calculate the target intermediate frequency signal frequency based on the radio frequency operating center frequency and the fixed radio frequency local oscillator frequency; The generation unit is configured to generate an out-of-band preset signal based on anti-interference requirement information. The frequency band of the out-of-band preset signal deviates from the bandwidth of the main imaging signal of the current imaging task by a preset ratio. The duration of the out-of-band preset signal is shorter than the pulse width of the main imaging signal and is embedded in the pulse leading edge of the main imaging signal. An embedding unit is configured to generate a digital waveform of the main imaging signal and superimpose and embed the digital waveform of the out-of-band preset signal onto the pulse leading edge of the main imaging signal to generate a composite digital baseband signal. The unit is configured to convert the composite digital baseband signal into an analog signal, perform intermediate frequency filtering on the analog signal at the target intermediate frequency signal frequency, up-convert the signal to the radio frequency carrier band, and amplify the signal to obtain the transmitted signal. The transmitting unit is configured to radiate the transmitted signal to the target area via an antenna.

7. A spaceborne radar signal receiving device, characterized in that, The device includes: The receiving unit is configured to receive radar reflected echo signals from a target area via an antenna, wherein the radar reflected echo signals are signals formed after the transmitted signal obtained by the method described in any one of claims 1-4 is reflected by the target. The frequency conversion unit is configured to use the same radio frequency local oscillator frequency as the transmitter to perform down-conversion processing on the radar reflected echo signal to obtain an analog intermediate frequency echo signal. The conversion unit is configured to filter and perform analog-to-digital conversion on the analog intermediate frequency echo signal at the target intermediate frequency signal frequency to obtain a digital baseband echo signal; The extraction unit is configured to filter out the echo component corresponding to the out-of-band preset signal from the digital baseband echo signal based on the bandwidth and frequency parameters of the main imaging signal, and extract the effective echo data corresponding to the main imaging signal. The processing unit is configured to perform synthetic aperture radar imaging processing using the effective echo data.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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