OFDM-NLFM (Orthogonal Frequency Division Multiplexing-Non-Linear Frequency Modulation) inductance integrated signal design method for free space light inductance and application

Abstract

The invention belongs to the technical field of communication and radar sensing integration, and discloses an OFDM-NLFM (Orthogonal Frequency Division Multiplexing-Non-Linear Frequency Modulation) sensing integrated signal design method for free space light sensing and an application of the OFDM-NLFM sensing integrated signal design method. Controllable nonlinear frequency modulation spectrum shaping is introduced into an OFDM frequency domain, a sidelobe adjustable window is adopted to construct a target amplitude spectrum, nonlinear instantaneous frequency is generated through cumulative distribution mapping, continuous phase NLFM modulation of multi-carrier OFDM is achieved, and therefore a communication and inductance integrated signal with the communication modulation capacity and the high-resolution radar detection capacity at the same time is obtained. The invention also provides an OFDM-NLFM (Orthogonal Frequency Division Multiplexing-Non-Local Frequency Modulation) inductance integration method, and effective separation of communication data recovery and radar echo parameter extraction is realized through dechirp correction, OFDM demodulation and NLFM matched filtering. Compared with the traditional sine subcarrier OFDM, the OFDM-NLFM signal provided by the invention has obvious advantages in the aspects of distance sidelobe, weak target detection, distance resolution and dynamic range, and can improve the sensing performance while keeping the communication rate.

Description

Technical Field

[0001] This invention belongs to the field of communication and radar sensing integration technology, and more specifically, relates to an OFDM-NLFM integrated sensing signal design method and application for free space optical sensing. Background Technology

[0002] With the development of applications such as mobile communications, intelligent transportation, and unmanned systems, the demand for spectrum and hardware resources for communication and radar sensing systems is constantly increasing. The traditional approach is to configure independent frequency bands and hardware platforms for communication and radar respectively. This not only causes spectrum redundancy but also increases system size and cost, making it unsuitable for deployment in space-constrained scenarios such as vehicle platforms and drone platforms.

[0003] To improve spectrum utilization and reduce system complexity, integrated sensing and communication (ISAC) has gradually become a research hotspot, which integrates communication and detection functions by sharing bandwidth and waveforms. Among them, orthogonal frequency division multiplexing (OFDM) has advantages such as high spectral efficiency and flexible modulation, while linear frequency modulation (LFM) or nonlinear frequency modulation (NLFM) signals have good pulse compression characteristics and are commonly used waveforms in high-resolution radar.

[0004] Some existing schemes attempt to combine LFM and OFDM to form an integrated OFDM-LFM signal, such as replacing sinusoidal subcarriers with LFM subcarriers or superimposing LFM phases onto OFDM signals, achieving a certain degree of waveform co-firing between communication and radar. However, such schemes are designed for linear frequency modulation (LFM), resulting in high range sidelobes, and weak target echoes are easily overwhelmed by strong target sidelobes. Furthermore, many schemes independently superimpose LFM phases within each OFDM symbol, leading to phase discontinuities between adjacent symbols and introducing additional sidelobes at symbol boundaries, affecting range pulse compression performance. Compared to LFM signals, NLFM signals have a lower peak-to-sidelobe ratio. Existing technologies for integrated OFDM-NLFM sensing in optical communication scenarios are relatively few, and there is a lack of a unified sensing signal and processing method that balances communication performance and radar detection performance and is applicable to both fiber optic links and free-space optical links. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a design method and application for an OFDM-NLFM integrated sensing signal for free-space optical sensing, aiming to provide an OFDM-NLFM integrated sensing signal that combines high-speed communication modulation capabilities with high-resolution radar pulse compression capabilities.

[0006] To achieve the above objectives, this invention provides an OFDM-NLFM integrated sensing signal design method for free-space optical sensing, comprising: The original communication data stream is mapped to QAM symbols, and the QAM symbols are then modulated using OFDM to generate an OFDM baseband signal. ; Within the preset NLFM sweep bandwidth Within the range, a frequency domain window function whose sidelobe height satisfies the radar's requirement for weak target resolution is selected as the target amplitude spectrum for NLFM. The frequency domain window function is then shaped to obtain the target nonlinear frequency modulated amplitude spectrum. ;right Sample along the frequency axis to obtain each frequency point. Sample value at , , The total number of sampling points; calculate from the start of the frequency sweep. Integrate to each frequency point Normalized cumulative energy at the location ;Will With normalized time parameters on the time axis Numerically corresponding, we obtain the values ​​from each frequency point. With time The instantaneous frequency sequence that varies with time, formed by the mapping relationship between them. , The desired NLFM phase sequence duration; Integrating, we obtain the desired NLFM phase sequence. ; Using the NLFM phase sequence For the OFDM baseband signal Continuous phase nonlinear frequency modulation is performed to obtain the OFDM-NLFM integrated inductive baseband signal. ; Will The signal is processed into a transmittable OFDM-NLFM integrated sensing signal; wherein the OFDM-NLFM integrated sensing signal is divided into two paths, one path serving as a radar reference signal, and the other path being transmitted via a transmitting antenna to an optical fiber link or free space.

[0007] Furthermore, the normalized cumulative energy The calculation method is as follows:

[0008] in, For at frequency point The sampled value at that location.

[0009] Further, the frequency domain window function is any one of a Taylor window, a rectangular window, and a Kaiser window; or it is a combined window function formed by superimposing two or more of the Taylor window, rectangular window, and Kaiser window according to a preset weight. 4. The OFDM-NLFM integrated sensing signal design method according to any one of claims 1-3, characterized in that the QAM symbol is OFDM modulated to generate an OFDM baseband signal. ,include: After the QAM symbols are converted from serial to parallel, they are loaded onto multiple OFDM subcarriers according to a preset subcarrier mapping rule to form frequency domain symbols; the frequency domain symbols are then subjected to IFFT transformation to obtain the time-domain OFDM baseband signal; a cyclic prefix is ​​added to the beginning of each OFDM symbol of the time-domain OFDM baseband signal to form the OFDM baseband signal. .

[0010] Furthermore, Processed into an transmittable OFDM-NLFM integrated sensing signal, including: Will After up-conversion and digital-to-analog conversion, optical carrier modulation is performed. The signal modulated by the optical carrier is then amplified to obtain an transmittable OFDM-NLFM integrated sensing signal.

[0011] The present invention also provides an OFDM-NLFM integrated sensing signal for free space optical sensing, wherein the OFDM-NLFM integrated sensing signal is designed by any of the OFDM-NLFM integrated sensing signal design methods described above.

[0012] This invention also provides an OFDM-NLFM inductive integration method, comprising: At the communication receiving end, after down-conversion and analog-to-digital conversion of the received signal, it is processed according to a preset NLFM phase sequence. After deskewing, the restored OFDM signal is obtained. The restored OFDM signal is then demodulated using OFDM to recover the original communication data stream. The received signal is the received signal after the OFDM-NLFM integrated sensing signal designed using any of the above-described OFDM-NLFM integrated sensing signal design methods is transmitted from the transmitting antenna to the optical fiber link or free space. At the radar receiver, the reflected signal of the target is received, and the reflected signal is matched and filtered or correlated with the radar transmitted signal to obtain a range pulse compression output; target information is extracted from the range pulse compression output to realize radar perception processing; wherein, the radar transmitted signal is the radar reference signal in any of the OFDM-NLFM integrated sensing signal design methods described above.

[0013] The present invention also provides an electronic device, including a computer-readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read executable instructions stored in the computer-readable storage medium to execute the OFDM-NLFM integrated sensing signal design method described above, or / and execute the OFDM-NLFM integrated sensing method described above.

[0014] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the OFDM-NLFM integrated sensing signal design method as described above, or / and implements the OFDM-NLFM integrated sensing method as described above.

[0015] The present invention also provides a computer program product, including a computer program that, when the computer program is run on a computer, causes the computer to execute the OFDM-NLFM integrated sensing signal design method described above, or / and execute the OFDM-NLFM integrated sensing method described above.

[0016] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: (1) This invention introduces NLFM spectrum shaping based on window function on the basis of traditional OFDM, and sets the frequency sweep bandwidth of NLFM according to the radar's requirements for weak target resolution. Constructing the target nonlinear frequency modulation amplitude spectrum using a frequency domain window function with controllable sidelobes. By mapping between the normalized cumulative energy ratio on the frequency axis and the normalized time ratio on the time axis, the frequency domain is... The designed energy distribution is converted into a time-varying instantaneous frequency sequence, which is then used to construct the required NLFM phase sequence. The NLFM phase sequence is then continuously phase-modulated with the OFDM baseband signal using NLFM, essentially embedding NLFM features into the multi-carrier OFDM signal. This constructs an OFDM-NLFM integrated signal that combines high-speed communication modulation capabilities with high-resolution radar pulse compression capabilities. Compared to existing OFDM-NLFM integrated signals, it exhibits lower range sidelobes, enhancing weak target detection capabilities and improving spectral efficiency. Simultaneously, the NLFM phase sequence is continuously phase-modulated within the OFDM frame, ensuring continuous frequency modulation phase at symbol boundaries between adjacent OFDM symbols. This reduces additional sidelobes caused by symbol boundaries and mitigates the impact on range pulse compression performance.

[0017] (2) The OFDM-NLFM integrated sensing method of the present invention is compatible with existing OFDM communication modulation and demodulation structures, and can be used in optical fiber or free space optical links to realize optical domain communication-sensing integration, which has good engineering application value.

[0018] Overall, this invention enables high-speed communication and precise detection within the same bandwidth, reduces system complexity, improves spectrum utilization efficiency, and is applicable to sensor fusion scenarios such as optical communication, free-space optical radar, and optical millimeter-wave radar. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of OFDM-NLFM integrated sensing signal generation according to an embodiment of the present invention; Figure 2 This is a block diagram of an OFDM-NLFM integrated sensing system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the NLFM target power spectrum of the combined window in an embodiment of the present invention; Figure 4 for Figure 3 The cumulative distribution function corresponding to the NLFM target power spectrum of the combined window Schematic diagram; Figure 5 This is a schematic diagram of the range pulse compression result of the OFDM-NLFM signal matched filtering output in a single-target scenario according to an embodiment of the present invention. Figure 6 A comparison of the range pulse compression results between linear LFM and combined window NLFM in the embodiment of the present invention in a strong and weak dual-target scenario; Figure 7 The BER–SNR performance comparison curves are shown for traditional OFDM, OFDM-LFM, and OFDM-NLFM integrated sensing signals. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Example 1 like Figure 1 As shown, this embodiment of the invention provides a method for designing an integrated OFDM-NLFM sensing signal for free-space optical sensing, comprising the following steps: Step 1: Communication Baseband Signal Generation Steps: Acquire the raw communication data stream information and map it into QAM symbols; perform OFDM modulation on the QAM symbols to generate the OFDM baseband signal. The OFDM modulation module performs OFDM modulation on the QAM symbols, including: converting the QAM symbols from serial to parallel, loading them onto multiple OFDM subcarriers according to a preset subcarrier mapping rule to form frequency domain symbols, performing IFFT on the frequency domain symbols to obtain the time-domain OFDM baseband signal, and adding a cyclic prefix to each OFDM symbol of the time-domain OFDM baseband signal to form the transmit OFDM baseband signal. :

[0022] in, This refers to the QAM data carried by the Lth OFDM symbol on the qth subcarrier in the time-domain OFDM baseband signal. For forming pulses, For OFDM symbol period, For the q-th subcarrier frequency, For the overall OFDM symbol, This represents the total number of OFDM subcarriers. It is the imaginary unit.

[0023] Step 2, NLFM Phase Sequence Design Steps: Within the preset NLFM sweep bandwidth... A frequency domain window function with controllable sidelobes is selected, where the sidelobe height of the frequency domain window function is lower than a preset value to meet the radar's requirements for weak target resolution. The frequency domain window function is then used as the target amplitude spectrum for NLFM (Non-Low Frequency Modulation), and shaping of the frequency domain window function yields the target's non-linear frequency modulated amplitude spectrum. ,right At discrete frequency points Upsampling is used to obtain each discrete frequency point. Sample value at , , For the first Each sample value. (By) , Given the total number of sampling points, calculate the frequency sweep starting point. Integrate to the current discrete frequency point Normalized cumulative energy over time This forms a normalized cumulative distribution sequence. ;in, , This is the end point of the frequency sweep. The normalized cumulative distribution sequence forms a normalized cumulative distribution function that monotonically increases from 0 to 1. Using the cumulative distribution function The monotonicity establishes a one-to-one mapping between frequency variables and normalized time variables: the normalized cumulative energy on the frequency axis is calculated. With normalized time parameters on the time axis Numerically corresponding to ( = ), to establish the current discrete frequency point With time The mapping relationship between them, each discrete frequency point With time The mapping relationship between them constitutes a time-varying instantaneous frequency sequence. This mapping relationship characterizes a one-to-one mapping from the cumulative energy ratio to the normalized time ratio, that is, when the cumulative energy reaches a certain ratio... At that time, it is considered that the NLFM signal is in time. The instantaneous frequency at that point falls on the corresponding frequency. Using this monotonic mapping relationship, the frequency domain can be mapped according to... The designed energy distribution is converted into a time-varying instantaneous frequency sequence. ;in, , The desired time length of the NLFM phase sequence. Integrating, we obtain the desired NLFM phase sequence. .

[0024] Step 3: OFDM-NLFM Integrated Inductive Baseband Signal Generation Steps: Using the NLFM phase sequence obtained in Step 2 The OFDM baseband signal obtained in step one Continuous phase NLFM (nonlinear frequency modulation) modulation is performed according to absolute time to obtain the OFDM-NLFM integrated inductive baseband signal. Among them, based on the designed NLFM phase sequence, continuous phase modulation is performed in absolute time within the OFDM frame, so that the frequency modulation phase of adjacent OFDM symbols remains continuous at the symbol boundary, thereby reducing the impact of phase abrupt changes between symbols on the range pulse compression performance.

[0025] Step 4: After up-converting and digital-to-analog conversion of the integrated inductive baseband signal, optical carrier modulation and amplification are performed to form an integrated inductive transmission signal. The signal is then split into two paths by a power divider. One path serves as a radar reference signal, while the other path is amplified and transmitted to an optical fiber link or free space by the transmitting antenna.

[0026] In step two, the frequency domain window function can be any type of window function such as Taylor window, rectangular window, or Kaiser window, or a combination window of two or more window functions superimposed with preset weights. By selecting the weights and sidelobe heights of each frequency domain window function in the combination window, the requirements of different radar applications for range resolution, sidelobe level, and weak target detection capability can be adapted.

[0027] Waveform shaping of the combined window can be represented by the following amplitude spectrum: , =1 in, Let m be the frequency domain window function. Here are the corresponding weighting coefficients, and M is the total number of frequency domain window functions in the combined window.

[0028] Example 2 This invention provides an OFDM-NLFM inductive integration method, comprising: At the communication receiving end, the received signal undergoes down-conversion and analog-to-digital conversion, and is processed according to a preset NLFM phase sequence. Deskewing is performed to restore the integrated inductive signal to an OFDM signal, remove the cyclic prefix, and perform FFT demodulation and channel equalization to recover the communication data information; wherein, the received signal is the signal received after the integrated inductive transmission signal designed in Example 1 is transmitted to the optical fiber link or free space through the transmitting antenna.

[0029] Radar reception and range pulse compression steps: At the radar receiver, the signal reflected back from the target is received. The returned signal is matched and filtered or correlated with a reference signal. The resulting range pulse compressed output can be expressed as follows: ,in, For reference signal, For the returned signal, For time delay; reference signal The returned signal is the reference signal transmitted via the integrated sensing signal designed in Example 1. As a radar-transmitted signal, and the signal reflected back from the target. According to The target distance information and weak target echoes are extracted from the main lobe position and amplitude of the signal to achieve radar perception processing. In this way, communication-sensing integration is realized in the optical communication system.

[0030] Example 3 like Figure 2As shown, this embodiment of the invention provides an OFDM-NLFM integrated sensing optical system, including an optical transmitter, a communication receiver, and a radar receiver. The optical transmitter includes a laser, an external modulator, an arbitrary waveform generator (AWG), an optical power divider, an optical amplifier (EDFA), and a transmission collimator. The OFDM-NLFM integrated sensing baseband signal output by the AWG drives the external modulator to modulate a continuous optical carrier. The modulated optical signal is split into two paths by the optical power divider. One path is amplified by the EDFA and then transmitted into free space by the transmission collimator to form an integrated sensing transmission waveform. The other path serves as a reference optical path and is sent to the radar receiver.

[0031] The communication receiver consists of a receiving collimator, a photodetector (PD), a high-speed oscilloscope (OSC), a de-chirping module, and an OFDM demodulation module. The receiving collimator gathers the optical signal from the transmitting end, converts it into an electrical signal by the PD, and then samples and digitizes it by the OSC. The de-chirping module uses the known NLFM phase to perform phase compensation on the sampled signal, restoring the OFDM-NLFM signal to an equivalent OFDM signal. The OFDM demodulation module performs cyclic prefix removal, FFT demodulation, and QAM demapping to recover the original data information.

[0032] The radar receiver includes an avalanche photodiode (APD), a high-speed oscilloscope, and a cross-correlation or range calculation module. The APD receives the reflected light signal from the target and converts it into an electrical signal, which is then simultaneously fed into the OSC for sampling along with the reference optical path signal. The cross-correlation or range calculation module performs digital cross-correlation calculations on the reference signal and the echo signal, and obtains sensing parameters such as the target distance based on the position of the correlation peak, thereby realizing radar ranging under the same OFDM-NLFM waveform.

[0033] like Figure 3 As shown, the target amplitude spectrum of NLFM obtained based on window function shaping is presented. The window function is a hybrid window of Taylor window and rectangular window function, and the combination coefficients are given. . Figure 4 The corresponding Normalized Cumulative Distribution (CDF) curve shows that the CDF value monotonically increases with frequency. This CDF value is used to establish a one-to-one mapping between frequency and normalized time, thereby determining the instantaneous frequency and NLFM phase. In the time domain, the NLFM phase is applied to the OFDM baseband signal, i.e., in... Figure 2 Implementation at the multiplication node shown This yields an OFDM-NLFM integrated inductive baseband signal, which is used to drive an optical external modulator or an RF transmission link.

[0034] In a specific embodiment of the present invention, the OFDM system parameters of the transmitting end are set as follows: the number of used subcarriers N=128, the subcarrier modulation method is 16QAM, and the corresponding subcarrier spacing is approximately The cyclic prefix length is configured as 10% of the symbol length, and the superimposed NLFM sweep bandwidth is 500MHz.

[0035] To demonstrate the ranging function of the waveform in this embodiment of the invention, a single target is preset in front of the transmitter, and the actual distance between the target and the transmitter is set to... =2m. The transmitted OFDM-NLFM signal propagates in free space and is scattered by the target before returning to the receiver. The echo signal is superimposed with Gaussian white noise through an additive white Gaussian noise channel. The receiver first amplifies and filters the echo signal, and then performs matched filtering or cross-correlation processing with the reference OFDM-NLFM baseband signal to obtain the range echo envelope, such as... Figure 5 As shown. The distance estimate is obtained by converting the location of the main peak in the figure. Distance from reality Basically consistent, measured under a set of typical parameters =2.02m, with a relative error of about 1%, proving that the waveform of the embodiment of the present invention can achieve high-precision distance measurement in a single-target scenario.

[0036] To visually demonstrate the advantages of the combined window NLFM in this embodiment of the invention in a dual-target scenario (strong and weak), this embodiment constructs an echo signal containing one strong target and one weak target. The strong target is located at... The weak target is located at... Among them The range cell is selected near the first sidelobe of the linear LFM autocorrelation function; the amplitude of the weak target is attenuated by 30 dB compared to the strong target. Matched filtering is performed on the linear LFM and the NLFM pulse of this embodiment, respectively, to obtain a comparison of the range profiles of the two waveforms, as shown below. Figure 6 As shown. It can be seen that in the case of traditional linear LFM ( Figure 6 In the above figure, the sidelobe level near the distance of the weak target is comparable to the main peak of the weak target, and the peak of the weak target is obviously submerged by the sidelobes of the strong target, making it difficult to reliably distinguish; when using the combined window NLFM of Taylor window function and rectangular window function in the embodiments of the present invention ( Figure 6 (See the image below). The overall sidelobe level is significantly reduced, and the weak target peak stands out from the sidelobe background. It can still be clearly detected when a strong target is present, thus effectively improving the detection capability of weak targets.

[0037] Regarding communication performance, the embodiments of this invention perform BER simulations on three waveforms: traditional OFDM waveform, OFDM-LFM waveform, and OFDM-NLFM waveform in this embodiment. Under additive white Gaussian noise (AGN) channel, the signal-to-noise ratio (SNR) is progressively scanned from low to high. After completing timing synchronization, frequency offset estimation, channel estimation, and equalization according to standard procedures, the uncoded bit error rate (BER) is calculated, and the BER–SNR curve is plotted. Figure 7 As shown, the BER curves of the three waveforms basically overlap or have only minor differences, indicating that under reasonable parameter configuration, neither superimposing the linear LFM phase nor the NLFM phase in this embodiment will significantly degrade the bit error rate performance of the OFDM system. This embodiment of the invention significantly improves range sidelobe suppression and weak target detection capabilities while essentially maintaining the original OFDM system's communication performance, achieving true integration of communication and sensing.

[0038] In summary, the embodiments of this invention introduce a nonlinear frequency-modulated (NLFM) target amplitude spectrum based on an adjustable window function and a combined window design into the OFDM frequency domain, and use normalized cumulative distribution mapping to generate nonlinear instantaneous frequency and continuous phase NLFM, thereby constructing an OFDM-NLFM integrated sensing signal that simultaneously carries communication data and high-resolution radar detection information within the same bandwidth. This integrated sensing baseband signal can be up-converted and transmitted in RF / microwave links, or used as a modulated baseband signal for optical fiber links and / or free-space optical links. At the receiving end, communication data is recovered through deskewing and OFDM demodulation, and target range information and weak target echoes are extracted through matched filtering or correlation processing with a reference signal, thus solving the problems mentioned in the background art.

[0039] Example 4 This invention provides an electronic device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the methods in Embodiments 1 and 2 above.

[0040] The relevant technical solutions are the same as above, and will not be repeated here.

[0041] Example 5 This invention provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the methods in Embodiments 1 and 2 above.

[0042] Specifically, the memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital (SD) cards, flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0043] The relevant technical solutions are the same as above, and will not be repeated here.

[0044] Example 6 This invention provides a computer program product, including a computer program that, when run on a computer, causes the computer to perform the steps of the methods in Embodiments 1 and 2 described above.

[0045] The relevant technical solutions are the same as above, and will not be repeated here.

[0046] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for designing an integrated OFDM-NLFM sensing signal for free-space optical sensing, characterized in that, include: The original communication data stream is mapped to QAM symbols, and the QAM symbols are then modulated using OFDM to generate an OFDM baseband signal. ; Within the preset NLFM sweep bandwidth Within the range, a frequency domain window function whose sidelobe height satisfies the radar's requirement for weak target resolution is selected as the target amplitude spectrum for NLFM. The frequency domain window function is then shaped to obtain the target nonlinear frequency modulated amplitude spectrum. ;right Sample along the frequency axis to obtain each frequency point. Sample value at , , This represents the total number of sampling points; Calculation from the start of the frequency sweep Integrate to each frequency point Normalized cumulative energy at the location ;Will With normalized time parameters on the time axis Numerically corresponding, we obtain the values ​​from each frequency point. With time The instantaneous frequency sequence that varies with time, formed by the mapping relationship between them. , The desired NLFM phase sequence duration; Integrating, we obtain the desired NLFM phase sequence. ; Using the NLFM phase sequence For the OFDM baseband signal Continuous phase nonlinear frequency modulation is performed to obtain the OFDM-NLFM integrated inductive baseband signal. ; Will The signal is processed into a transmittable OFDM-NLFM integrated sensing signal; wherein the OFDM-NLFM integrated sensing signal is divided into two paths, one path serving as a radar reference signal, and the other path being transmitted via a transmitting antenna to an optical fiber link or free space.

2. The OFDM-NLFM integrated inductive signal design method according to claim 1, characterized in that, The normalized cumulative energy The calculation method is as follows: in, For at frequency point The sampled value at that location.

3. The OFDM-NLFM integrated inductive signal design method according to claim 1, characterized in that, The frequency domain window function is any one of the Taylor window, rectangular window, and Kaiser window; or it is a combination window function formed by superimposing two or more of the Taylor window, rectangular window, and Kaiser window according to a preset weight.

4. The OFDM-NLFM integrated inductive signal design method according to any one of claims 1-3, characterized in that, The QAM symbols are modulated using OFDM to generate an OFDM baseband signal. ,include: After the QAM symbols are converted from serial to parallel, they are loaded onto multiple OFDM subcarriers according to a preset subcarrier mapping rule to form frequency domain symbols; the frequency domain symbols are then subjected to IFFT transformation to obtain the time-domain OFDM baseband signal; a cyclic prefix is ​​added to the beginning of each OFDM symbol of the time-domain OFDM baseband signal to form the OFDM baseband signal. .

5. The OFDM-NLFM integrated inductive signal design method according to claim 1, characterized in that, Will Processed into an transmittable OFDM-NLFM integrated sensing signal, including: Will After up-conversion and digital-to-analog conversion, optical carrier modulation is performed. The signal modulated by the optical carrier is then amplified to obtain an transmittable OFDM-NLFM integrated sensing signal.

6. An OFDM-NLFM integrated sensing signal for free-space optical sensing, characterized in that, The OFDM-NLFM integrated sensing signal is designed by the OFDM-NLFM integrated sensing signal design method according to any one of claims 1-5.

7. An OFDM-NLFM inductive integration method, characterized in that, include: At the communication receiving end, after down-conversion and analog-to-digital conversion of the received signal, it is processed according to a preset NLFM phase sequence. After deskewing, the restored OFDM signal is obtained. The restored OFDM signal is then demodulated using OFDM to recover the original communication data stream. The received signal is the received signal after the OFDM-NLFM integrated sensing signal designed using the OFDM-NLFM integrated sensing signal design method according to any one of claims 1-5 is transmitted by the transmitting antenna to the optical fiber link or free space. At the radar receiver, the reflected signal of the target is received, and the reflected signal is matched and filtered or correlated with the radar transmitted signal to obtain a range pulse compression output; target information is extracted from the range pulse compression output to realize radar perception processing; wherein, the radar transmitted signal is the radar reference signal in the OFDM-NLFM integrated sensing signal design method according to any one of claims 1-5.

8. An electronic device, characterized in that, Includes computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is used to read executable instructions stored in the computer-readable storage medium to execute the OFDM-NLFM integrated sensing signal design method according to any one of claims 1-5, or / and execute the OFDM-NLFM integrated sensing method according to claim 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the OFDM-NLFM integrated sensing signal design method as described in any one of claims 1-5, or / and implements the OFDM-NLFM integrated sensing method as described in claim 7.

10. A computer program product, characterized in that, Includes a computer program that, when run on a computer, causes the computer to execute the OFDM-NLFM integrated sensing signal design method according to any one of claims 1-5, or / and execute the OFDM-NLFM integrated sensing method according to claim 7.

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