A chirp phase compensation method and device

Abstract

This invention discloses a chirped phase compensation method and apparatus for a photonic millimeter-wave sensing integrated system. Addressing the problem of communication data randomness disrupting the chirped phase of the LFM signal, a small number of subcarriers in the OFDM signal are set to constant values ​​as sensing subcarriers, while the rest carry communication data, forming an I-OFDM signal. This I-OFDM-LFM waveform is then synthesized with the LFM signal, preserving the chirped phase structure. Two coding schemes are provided: one in the digital domain and one in the optical domain. The radar receiver obtains the peak range through chirped dechirping; the communication receiver uses the sensing subcarriers to estimate the propagation delay, assisting in synchronization and channel compensation, and reducing training overhead. Simulation results show that under 16QAM, with an SNR of -10dB, the EVM ≤ 8%, meeting the 5G NR requirements. This invention achieves deep sensing fusion with almost no sacrifice in communication spectrum efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication and radar sensing technology, specifically relating to a chirped phase compensation method and device, which can be applied to an integrated photonic millimeter-wave communication and sensing system. Background Technology

[0002] With the development of B5G / 6G applications, future wireless systems need to possess both high-speed data communication and high-precision environmental sensing capabilities. Millimeter-wave bands, with their large bandwidth potential, have become an ideal carrier for achieving deep integration of communication and sensing. Against this backdrop, integrated millimeter-wave sensing waveform design becomes the core factor determining system performance.

[0003] Linear frequency modulation (LFM) signals are ideal sensing waveforms due to their superior distance and velocity resolution. However, their nature is deterministic, while the communication data carrying information has inherent randomness. If communication data is directly modulated onto the phase of an LFM signal, the randomness of the data will disrupt the critical chirp structure of the LFM phase, leading to a sharp decline in sensing performance. This constitutes the fundamental contradiction in integrated sensing design.

[0004] To reconcile this contradiction, existing technical solutions mainly revolve around the idea of ​​isolation, but all have significant limitations: Time-division / frequency-division multiplexing avoids interference by separating communication and sensing signals in the time or frequency dimension. Although this method is simple, it sacrifices valuable time and frequency resources, makes it difficult to achieve true synchronous sensing, and has low spectral efficiency; Orthogonal multiplexing uses coding theory to distinguish sensing signals, which is complex to design, and under actual conditions such as multipath channels and high-speed movement, orthogonality is difficult to maintain, and the system robustness faces challenges.

[0005] In summary, none of the existing solutions have fundamentally solved the problem of communication randomness disrupting the determinism of sensing waveforms. This makes it difficult to balance sensing accuracy, communication rate, and implementation complexity, thus hindering further performance improvements in the integrated sensing system. Summary of the Invention

[0006] The technical problem to be solved by this invention is that in an integrated communication and sensing system, the randomness of communication data will destroy the chirped phase structure of the LFM signal, resulting in a decrease in sensing performance; existing time division, frequency division or orthogonal multiplexing schemes are difficult to balance communication rate, sensing accuracy and resource efficiency.

[0007] To address the aforementioned technical problems, this invention proposes an improved OFDM-LFM (I-OFDM-LFM) integrated communication sensing waveform and its chirped phase compensation method.

[0008] A chirped phase compensation method, applied to a photonic millimeter-wave communication and sensing integrated system, includes the following steps:

[0009] Step S1: Generate a baseband-improved orthogonal frequency division multiplexing (I-OFDM) signal, wherein the total number of subcarriers is... OFDM signals Each subcarrier is configured as a sensing subcarrier, and each sensing subcarrier carries a constant value. ,the remaining Each subcarrier is a communication subcarrier, carrying a random communication sequence. The baseband I-OFDM signal is represented as:

[0010] in, For the first The frequency of each communication subcarrier, For the first The frequency of a sensing subcarrier;

[0011] Step S2: Generate a baseband linear frequency modulated (LFM) signal, represented as:

[0012] in, The starting frequency, To adjust the frequency, Duration;

[0013] Step S3: Combine the baseband I-OFDM signal and the baseband LFM signal into an I-OFDM-LFM signal; Step S4: Upconvert the I-OFDM-LFM signal to the millimeter wave frequency band to generate a millimeter wave integrated sensing signal.

[0014] This invention provides two optional encoding implementation schemes, the core difference of which lies in the fact that the synthesis point of the I-OFDM signal and the LFM signal is located in different physical domains of the signal generation link, namely the digital domain and the optical domain.

[0015] In the digital domain coding scheme, the synthesis in step S3 is a digital domain multiplication synthesis, that is, the baseband I-OFDM-LFM signal is:

[0016]

[0017] The upconversion in step S4 includes: converting the baseband I-OFDM-LFM signal into an analog signal via a digital-to-analog converter; using the analog signal to drive an I / Q modulator to perform electro-optic modulation on the signal optical carrier provided by the optical frequency comb and wavelength selection switch to obtain an optical baseband sensing signal; combining the optical baseband sensing signal with the optical local oscillator carrier provided by the same optical frequency comb and wavelength selection switch; and generating the millimeter-wave sensing integrated signal by photoelectric conversion after combining the optical signal.

[0018] In the optical domain coding scheme, the synthesis in step S3 is optical domain synthesis, specifically including: performing digital-to-analog conversion on the baseband I-OFDM signal and the baseband LFM signal respectively to obtain an analog I-OFDM signal and an analog LFM signal; driving the analog I-OFDM signal to drive a first I / Q modulator to perform electro-optic modulation on a first optical carrier to obtain a first optical signal; driving the analog LFM signal to drive a second I / Q modulator to perform electro-optic modulation on a second optical carrier to obtain a second optical signal; combining the first optical signal and the second optical signal to obtain a combined optical signal; the up-conversion in step S4 includes: generating the millimeter-wave inductive integrated signal by photoelectric conversion of the combined optical signal.

[0019] Both schemes share the same radar receiver processing and communication receiver processing architecture.

[0020] Radar reception processing includes the following steps: Step R1: Receive the echo signal after the millimeter-wave inductive integrated signal is reflected by the target; Step R2: Mix the echo signal with a reference signal to obtain an intermediate frequency signal, wherein the reference signal is the millimeter-wave inductive integrated signal coupled from the output of the power amplifier before transmission; Step R3: Integrate the intermediate frequency signal, and during the integration time... Peak frequencies extracted from the internal spectrum Step R4: Based on the peak frequency Calculate target distance :

[0021] in At the speed of light, The frequency modulation is mentioned.

[0022] The communication reception and processing includes the following steps: Step C1: Receive the millimeter-wave integrated sensing signal and down-convert it to an intermediate frequency signal; Step C2: Perform a dechirping operation on the intermediate frequency signal, i.e., multiply it by the conjugate signal of the baseband LFM signal. Step C3: Estimate the signal propagation delay based on the peak frequency corresponding to the sensing subcarrier in the dechirped signal. Step C4: Utilize the aforementioned delay Time delay compensation is performed on the dechirped signal to recover the baseband I-OFDM signal.

[0023] The present invention also provides a transmitter for implementing the above method, comprising:

[0024] The baseband signal generation module is used to generate baseband I-OFDM signals and baseband LFM signals, wherein the baseband I-OFDM signals contain sensing subcarriers carrying constant values. The communication subcarrier carries a random communication sequence; a waveform synthesis module is used to synthesize the baseband I-OFDM signal and the baseband LFM signal into an I-OFDM-LFM signal; an up-conversion module is used to up-convert the I-OFDM-LFM signal to the millimeter-wave frequency band; and a power amplifier is used to amplify the up-converted millimeter-wave inductive integrated signal and radiate it through the antenna.

[0025] Corresponding to the digital domain scheme, the waveform synthesis module is a digital domain multiplier, and the upconversion module includes a digital-to-analog converter, an I / Q modulator, an optical signal combining module, and a photoelectric conversion unit connected in sequence; the I / Q modulator is used to perform electro-optic modulation on the signal optical carrier, and the optical signal combining module is used to combine the modulated optical baseband inductive signal with the optical local oscillator carrier.

[0026] Corresponding to the optical domain scheme, the waveform synthesis module includes a first digital-to-analog converter (DAC), a second DAC, a first I / Q modulator, a second I / Q modulator, and an optical signal combining module. The first DAC converts the baseband I-OFDM signal into an analog I-OFDM signal, and the first I / Q modulator modulates the analog I-OFDM signal onto a first optical carrier to obtain a first optical signal. The second DAC converts the baseband LFM signal into an analog LFM signal, and the second I / Q modulator modulates the analog LFM signal onto a second optical carrier to obtain a second optical signal. The optical signal combining module combines the first optical signal and the second optical signal, and the combined optical signal is converted into the millimeter-wave integrated sensing signal via photoelectric conversion.

[0027] The present invention also provides a radar receiver, comprising:

[0028] Antenna, used to receive the echo signal of the millimeter-wave integrated sensing signal after it is reflected by the target;

[0029] A low-noise amplifier, connected to the antenna, is used for noise processing and power compensation of the echo signal;

[0030] A mixer, connected to the low-noise amplifier, is used to mix the processed echo signal with a reference signal and output an intermediate frequency (IF) signal. The reference signal is obtained from the power amplifier of the transmitter. An analog-to-digital converter (ADC) is used to digitize the IF signal. A radar digital signal processing unit is used to integrate the digitized IF signal and extract the peak frequency of the spectrum. And according to the formula Calculate target distance ,in At the speed of light, To adjust the frequency.

[0031] The present invention also provides a communication receiver, comprising: an antenna for receiving the millimeter-wave inductive signal; a down-conversion unit connected to the antenna for down-converting the received signal to an intermediate frequency (IF) signal; an analog-to-digital converter for digitizing the IF signal; and a communication digital signal processing unit for performing dechirping, delay estimation, and delay compensation on the digitized IF signal to recover the baseband I-OFDM signal.

[0032] This invention provides a photonic millimeter-wave communication and sensing integrated system, including a transmitter, a radar receiver, and a communication receiver; the communication receiver includes: an antenna for receiving the millimeter-wave integrated communication and sensing signal; a down-conversion unit connected to the antenna for down-converting the received signal to an intermediate frequency (IF) signal; an analog-to-digital converter for digitizing the IF signal; and a communication digital signal processing unit for performing dechirping, delay estimation, and delay compensation on the digitized IF signal to recover the baseband I-OFDM signal.

[0033] Beneficial Effects: LFM signals are characterized by a large time-width-bandwidth product, while OFDM communication signals possess extremely high spectral efficiency. When simply using time-division or frequency-division multiplexing to couple LFM sensing signals and OFDM communication signals, the time width or bandwidth of both LFM and OFDM signals is reduced, decreasing radar sensing performance and communication spectral efficiency. This invention proposes an improved OFDM-LFM (I-OFDM-LFM) integrated communication and sensing waveform. Before inductive coding, a small portion of OFDM subcarriers (e.g., less than 1% of the total number of subcarriers) are designated as sensing subcarriers, and the communication data they carry is set to a constant value, forming the improved OFDM (I-OFDM) signal. Based on the orthogonal nature of OFDM signal subcarriers, the data setting of the sensing subcarriers does not affect the data transmission of the remaining communication subcarriers. Due to the constant characteristics of the OFDM sensing subcarriers, the I-OFDM-LFM signal retains the chirped phase characteristics of the LFM signal, making it compatible with existing LFM sensing architectures and algorithms. Therefore, this invention can acquire accurate sensing data with almost no loss of communication spectrum efficiency. In addition, by adjusting the bandwidth of I-OFDM and LFM, when the LFM bandwidth is greater than the I-OFDM bandwidth, the communication spread spectrum gain can be achieved, which effectively improves the signal-to-noise ratio of communication and is suitable for the future network's need for high-capacity and high-precision communication sensing.

[0034] This invention provides two optional encoding schemes, the core difference being that the synthesis point of the I-OFDM signal and the LFM chirped signal is located in different physical domains of the signal generation link: the digital domain and the optical domain, respectively. The digital domain encoding scheme completes waveform synthesis in baseband digital signal processing, offering advantages such as algorithmic flexibility and ease of implementation; however, its performance is limited by the sampling rate of the digital-to-analog converter (DAC) and the electro-optic modulation bandwidth. The optical domain encoding scheme utilizes the optical heterodyne principle to achieve signal synthesis and up-conversion in the optical link, overcoming the bandwidth limitations of devices such as DACs and modulators, and directly generating high-spectral-purity millimeter-wave signals. Both schemes share the same waveform design principles and receiver processing architecture, allowing for the optimal choice between performance, cost, and implementation complexity based on specific application scenarios. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0036] Figure 1 The diagram shows a photonic millimeter-wave communication and sensing integrated system, where (a) is a photonic millimeter-wave communication and sensing integrated system based on digital domain I-OFDM-LFM coding, and (b) is a photonic millimeter-wave communication and sensing integrated system based on optical domain I-OFDM-LFM coding.

[0037] Figure 2 This is a spectrum diagram of a baseband I-OFDM signal;

[0038] Figure 3 This is the time-frequency diagram of the baseband LFM signal;

[0039] Figure 4 This is the time-frequency diagram of the baseband I-OFDM-LFM at the transmitting end;

[0040] Figure 5 The spectrum diagrams are for dechirped signals, where (a) is the dechirped spectrum diagram of the millimeter-wave I-OFDM-LFM at the sensing receiver, and (b) is the dechirped spectrum diagram of the millimeter-wave conventional OFDM-LFM at the sensing receiver.

[0041] Figure 6 The I-OFDM-LFM time-frequency diagram after down-conversion at the communication receiver;

[0042] Figure 7 The spectrum diagrams are shown at the communication receiver before and after dechirping following downconversion. (a) is the spectrum before dechirping (subcarrier broadening and overlap), and (b) is the spectrum after dechirping (recovering clear I-OFDM subcarriers).

[0043] Figure 8The simulation results of I-OFDM-LFM communication after dechirping at the communication receiver are shown in the figure. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0045] In this invention, an "optical frequency comb" is used to generate multiple coherent optical carriers; a "wavelength selection switch" is used to select a specific optical carrier with a target millimeter-wave frequency spacing from the optical frequency comb; and a "dechirping operation" refers to multiplying the received signal with the local LFM conjugate signal to eliminate the effects of LFM modulation.

[0046] The concept of this invention is to encode LFM signals using I-OFDM communication sequences to generate I-OFDM-LFM waveforms with chirped phase, thereby providing more flexible design and higher robustness for integrated communication and sensing waveform design. OFDM subcarriers for sensing are selected, and the data they carry is set to a constant value, so that the combination of I-OFDM and LFM signals has sensing capabilities. By loading I-OFDM signals onto the LFM signals of traditional radar, a sensing-integrated signal is formed. Based on the I-OFDM-LFM waveform design, this invention provides an improved photonic millimeter-wave communication and sensing integrated system, achieving high spectral efficiency, large capacity, and high precision photonic millimeter-wave sensing integration. Based on the above inventive concept, as... Figure 1 As shown, the photonic millimeter-wave communication and sensing integrated system provided in this embodiment includes a sensing integrated signal generation module, a radar receiving module, and a communication receiving module. The sensing integrated signal generation module generates a millimeter-wave sensing integrated signal; the communication receiving module receives the millimeter-wave integrated signal and demodulates it to recover communication information; and the radar receiving module receives the millimeter-wave integrated echo and processes it to obtain sensing information.

[0047] The present invention provides a chirped phase compensation method, applied to a photonic millimeter-wave communication and sensing integrated system, comprising the following steps (steps S1 to S4):

[0048] Step S1: Generate a baseband-modified orthogonal frequency division multiplexing (I-OFDM) signal.

[0049] In the baseband signal generation module, a baseband I-OFDM signal with a bandwidth of 20GHz is generated (e.g., ...). Figure 2 As shown, the I-OFDM signal is split into two parts: one part carries random data for communication, and the other part is set as a constant sequence for sensing. Specifically, the total number of subcarriers is... OFDM signals Each subcarrier is configured as a sensing subcarrier, and each sensing subcarrier carries a constant value. ,the remaining Each subcarrier is a communication subcarrier, carrying a random communication sequence. The baseband I-OFDM signal can be represented as:

[0050]

[0051]

[0052]

[0053] in, For signals used in communication, For signals used for sensing, Represents the number of communication sub-channels. Represents the number of sensing sub-channels. For the first Communication sequences in each sub-channel For a constant sequence amplitude loaded onto the sub-channel, For the first The frequency of each communication subcarrier, For the first The frequency of each sensing subcarrier.

[0054] In this embodiment, to maximize the utilization of communication resources, sensing subcarriers are used. The number is much smaller than the number of communication subcarriers. Select the total number of subcarriers. For 1000, of which Set as one subcarrier and carry the data Set it to a known constant value. For example... Figure 2 As shown, the data transmitted on the first subcarrier, at 0.02 GHz, is set to a constant sequence for sensing operations, while the other subcarriers still carry random communication sequences. This design ensures that over 99% of the spectrum resources are still used for high-speed data transmission with minimal sacrifice to communication.

[0055] Step S2: Generate a baseband linear frequency modulated (LFM) signal.

[0056] Baseband LFM signal such as Figure 3 As shown (bandwidth 10GHz), it is represented as:

[0057] in, The starting frequency of the LFM signal. To adjust the frequency, Duration.

[0058] Step S3: Combine the baseband I-OFDM signal and the baseband LFM signal into an I-OFDM-LFM signal.

[0059] Step S4: Upconvert the I-OFDM-LFM signal to the millimeter wave band to generate a millimeter wave integrated sensing signal.

[0060] Based on the fact that the physical domain of the synthesis and up-conversion of I-OFDM signal and baseband LFM signal is different, this invention provides two optional encoding schemes: a digital domain encoding scheme and an optical domain encoding scheme.

[0061] (a) Digital field coding scheme

[0062] like Figure 1 As shown in (a), in the baseband signal generation module, the baseband I-OFDM signal is first loaded onto the baseband LFM signal to generate a digital baseband I-OFDM-LFM signal. The synthesis in step S3 is a digital domain multiplication synthesis, that is:

[0063]

[0064] in, The starting frequency of the LFM signal. For the chirping rate, Duration.

[0065] from Figure 4 In the time-frequency diagram of the baseband I-OFDM-LFM signal at the transmitting end, it can be clearly observed that there is a component with a frequency that increases linearly with time at the center of the signal, which is consistent with the typical time-frequency characteristics of LFM signals.

[0066] The digital signal is then fed into a digital-to-analog converter (DAC), which generates an analog I-OFDM-LFM signal. This signal then drives the I / Q modulator in the optical modulation module to achieve electro-optic modulation. In the optical modulation module, multiple coherent optical carriers generated by the optical frequency comb are first injected into a wavelength selective switch. This switch selects coherent optical carriers with target millimeter-wave frequency spacing: one, after power compensation by an optical amplifier, serves as the signal optical carrier for electro-optic modulation; the other serves as the optical local oscillator carrier for subsequent optical signal combining. The analog I-OFDM-LFM signal drives the I / Q modulator to electro-optically modulate the signal optical carrier, generating an optical baseband inductive signal.

[0067] After passing through the I / Q modulator, the optical signal combining module combines the optical baseband sensing signal with the optical local oscillator carrier. The combined signal can be written as...

[0068]

[0069] in, and These are the frequencies of the signal optical carrier and the optical local oscillator carrier, respectively. This represents the amplitude ratio between the modulated signal and the optical local oscillator carrier.

[0070] The combined optical signal is converted into a millimeter-wave sensing and communication integrated signal via photoelectric conversion. The generated millimeter-wave signal is first amplified by a power amplifier and then radiated into free space through an antenna. Considering the passband frequency on the radio frequency device, the generated target millimeter-wave sensing and communication integrated signal can be represented as...

[0071]

[0072]

[0073]

[0074] The first component is the communication component, which carries the majority of the communication data on the OFDM subcarriers, enabling high-speed data transmission. The second component is the sensing component, consisting of a few subcarriers carrying constant sequence data. It is used to protect the critical chirped phase structure of the linear frequency modulated waveform from damage, thereby providing the system with high-precision distance and velocity measurement capabilities. These two components enable a single set of hardware and the same time-frequency resources to simultaneously complete both communication and sensing tasks.

[0075] (II) Optical Domain Coding Scheme

[0076] like Figure 1 As shown in (b), the waveform synthesis process is transferred to the optical domain. The synthesis in step S3 is optical domain synthesis. The baseband I-OFDM signal and the baseband LFM signal are generated in the baseband signal generation module and converted into analog signals by independent digital-to-analog converters. Two coherent optical carriers with the target millimeter-wave frequency spacing are selected by an optical frequency comb and a wavelength selection switch: the first optical carrier is used for electro-optic modulation of the I-OFDM signal, and the second optical carrier is used for electro-optic modulation of the LFM signal. The signals obtained after the two analog signals (I-OFDM and LFM) independently drive the I / Q modulator to achieve electro-optic modulation are as follows:

[0077]

[0078]

[0079] The two signals are reassembled by an optical signal combining module, and the combined signal is...

[0080]

[0081] The signal is converted into a millimeter-wave integrated sensing and communication signal through photoelectric conversion, amplified by a power amplifier, and then radiated into free space through an antenna. Due to the passband frequency limitation of the radio frequency equipment, the generated target millimeter-wave signal is:

[0082]

[0083] With formula The results are consistent, indicating that both the digital domain coding scheme and the optical domain coding scheme can generate the required millimeter-wave I-OFDM-LFM signal.

[0084] Digital domain coding schemes offer centralized signal processing and high flexibility, but they require high digital processing capabilities, DAC sampling rates, and electro-optic modulation bandwidth. Optical domain coding schemes, on the other hand, can directly generate radio frequency signals with extremely high frequency and spectral purity, greatly alleviating the bandwidth bottleneck of electrical devices such as digital-to-analog converters and electro-optic modulators.

[0085] Both schemes share the same radar receiver processing and communication receiver processing architecture.

[0086] (III) Radar Reception Processing

[0087] The radar receiver module includes an antenna, a low-noise amplifier, a mixer, and a radar signal processing module connected in sequence. Radar receiver processing includes the following steps R1 to R4:

[0088] Step R1: After receiving the signal, the antenna first performs noise processing and power compensation using a low-noise amplifier.

[0089] Step R2: The mixing operation is then performed. The electrical signal used for mixing is the pre-radiation signal, coupled from the output of the transmitter's power amplifier, and can be represented as follows:

[0090]

[0091] The mixing process can be represented as

[0092]

[0093]

[0094] in Indicates conjugate transformation. This is the time delay between the echo and the reference signal. Because high-frequency components are filtered out by the low-sampling-rate analog-to-digital converter, only the target's intermediate-frequency photocurrent is collected.

[0095]

[0096]

[0097]

[0098]

[0099]

[0100] Due to the orthogonality of the sub-channels of OFDM signals, Integrating within a given time, the formula is... The first and third terms are integrated in the time domain because the communication channel and the sensing channel are different sub-channels on the OFDM signal. It will then become In the second item, the energy of the communication channel is weaker than the constant value set in the sensing channel (which can be determined by...). Figure 2 (As seen in the magnified view), the energy of the sensing channel in the fourth term is more concentrated and easier to observe in the spectrum, thus exhibiting dominance. In step R3, during the integration time... Peak frequencies extracted from the internal spectrum In the simulation, the sensing delay was set to 6 ns, the duration of the entire periodic signal was 2.85 μs, and the chirp rate was... Hz / s, from Figure 5 In the dechirped spectrum diagram of (a) millimeter wave I-OFDM-LFM, a peak can be seen at 21.053 MHz, which is obtained by the superposition of constant values ​​in the sensing channel.

[0101] Step R4: Based on the peak frequency Calculate target distance :

[0102]

[0103] in It is the distance between the target and the radar. It is the speed of light (approximately) m / s), It is the peak frequency observed near zero frequency. It is the chirp rate of the linear frequency modulated signal. According to formula (14), the target delay is calculated to be 6 ns, and the distance is 0.9 m, which is consistent with the preset sensing delay in the simulation. And... Figure 5 In (b), no peak is observed in the dechirped spectrum of the traditional millimeter-wave OFDM-LFM. This indicates that the I-OFDM-LFM waveform design method based on constant sequence sensing subcarriers proposed in this invention successfully protects the chirped phase of the LFM signal, enabling the system to achieve high-precision distance measurement using LFM dechirping processing. Furthermore, the measurement results are highly consistent with the preset target parameters, verifying the effectiveness and reliability of this method in achieving high-precision sensing in a sensor-integrated system.

[0104] (iv) Communication Reception Processing

[0105] In the communication receiving module, the signal received by the antenna is first down-converted to an intermediate frequency (IF), and then digitized by an analog-to-digital converter (ADC) for subsequent digital signal processing. The communication receiving process includes the following steps C1 to C4:

[0106] Step C1: Receive the millimeter-wave integrated sensing signal and down-convert it to an intermediate frequency (IF) signal. The time-frequency diagram of the obtained IF signal is as follows: Figure 6 As shown in the figure. A clear band can be seen in the figure, and it shows a certain displacement (due to...). Figure 6 (As can be seen from the enlarged view), this represents the time-frequency characteristics of the sensing subcarrier being loaded onto the LFM signal and experiencing a time delay.

[0107] Step C2: After digital down-conversion, a dechirping operation is performed, i.e., multiplied by the conjugate signal of the baseband LFM signal. , can be represented as:

[0108]

[0109]

[0110]

[0111]

[0112] Comparing equations (3) and (15), it can be found that the dechirped baseband signal, compared with the original signal, contains a time-dependent variable in the output signal. Proportional linear phase term This proves that the received signal In this process, the original LFM's chirped phase structure is completely preserved, with only a time delay introduced during propagation. The first term of equation (15) is existent. The frequency offset communication sequence, the second term is A constant sensing sequence with frequency offset.

[0113] Step C3: Estimate the signal propagation delay based on the peak frequency corresponding to the sensing subcarrier in the chirped signal. .from Figure 2 It is known that the amplitude of a constant-sequence sensing channel in the spectrum is significantly higher than that of a communication channel. Therefore, we only need to focus on the frequency of the peak values ​​in the spectrum, given that... Under the premise of constant sequence sensing channel frequency calculation, the frequency offset can be obtained, and thus the signal propagation delay can be obtained. This delay information can be further used for pilot-assisted phase deflection compensation to achieve high-precision signal synchronization and reconstruction.

[0114] Step C4: Utilize the aforementioned delay Delay compensation is performed on the dedicated signal to recover the baseband I-OFDM signal. After achieving precise communication synchronization, delay compensation and dechirping are performed on the received signal to obtain the I-OFDM baseband component.

[0115]

[0116]

[0117] It can be seen that after dechirping, the interference of LFM signal and communication delay on I-OFDM signal is completely eliminated, thus successfully reconstructing I-OFDM signal to baseband.

[0118] Figure 7 In (a), the I-OFDM subcarriers are broadened and overlapped due to LFM modulation; after dechirping and delay compensation operations, the LFM components are canceled out, resulting in... Figure 7 (b) shows a clear I-OFDM spectrum. This result demonstrates that the original I-OFDM signal was effectively recovered, the effects of LFM modulation were eliminated, and the I-OFDM signal was successfully reconstructed to baseband.

[0119] Finally, the results are evaluated for performance. Figure 8 For EVM / SNR in 16QAM modulation, by Figure 8 It is evident that this solution recovers the baseband I-OFDM communication signal without distortion, eliminates the interference of LFM modulation on the communication signal, and enables the demodulated signal to still meet the stringent requirements of 5G NR for modulation accuracy (EVM≤8%) even when the SNR is 10dB.

[0120] (v) Transmitters, radar receivers, communication receivers and systems

[0121] The present invention also provides a transmitter for implementing the above method, comprising: a baseband signal generation module for generating a baseband I-OFDM signal and a baseband LFM signal, wherein the baseband I-OFDM signal carries a constant value in the sensing subcarrier. The communication subcarrier carries a random communication sequence; a waveform synthesis module is used to synthesize the baseband I-OFDM signal and the baseband LFM signal into an I-OFDM-LFM signal; an up-conversion module is used to up-convert the I-OFDM-LFM signal to the millimeter-wave frequency band; and a power amplifier is used to amplify the up-converted millimeter-wave inductive integrated signal and radiate it through the antenna.

[0122] Corresponding to the digital domain scheme, the waveform synthesis module is a digital domain multiplier, and the up-conversion module includes a digital-to-analog converter, an I / Q modulator, an optical signal combining module, and a photoelectric conversion unit connected in sequence. The I / Q modulator is used to electro-optically modulate the signal optical carrier provided by the optical frequency comb and wavelength selective switch. The optical signal combining module is used to combine the modulated optical baseband inductive signal with the optical local oscillator carrier provided by the same optical frequency comb and wavelength selective switch. The combined optical signal is then converted into the millimeter-wave inductive integrated signal by the photoelectric conversion unit.

[0123] Corresponding to the optical domain scheme, the waveform synthesis module includes a first digital-to-analog converter (DAC), a second DAC, a first I / Q modulator, a second I / Q modulator, and an optical signal combining module. The first DAC converts a baseband I-OFDM signal into an analog I-OFDM signal, and the first I / Q modulator modulates the analog I-OFDM signal onto a first optical carrier to obtain a first optical signal. The second DAC converts a baseband LFM signal into an analog LFM signal, and the second I / Q modulator modulates the analog LFM signal onto a second optical carrier to obtain a second optical signal. The optical signal combining module combines the first optical signal and the second optical signal, and the combined optical signal is then photoelectrically converted to generate the millimeter-wave integrated sensing signal.

[0124] The present invention also provides a radar receiver, comprising: an antenna for receiving echo signals; a low-noise amplifier connected to the antenna; a mixer connected to the low-noise amplifier for mixing the processed echo signal with a reference signal, wherein the reference signal is a millimeter-wave inductively coupled signal coupled from the output of a power amplifier of a transmitter; an analog-to-digital converter for digitizing the intermediate frequency signal; and a radar digital signal processing unit for integrating the digitized intermediate frequency signal to extract the peak frequency of the spectrum. And according to the formula Calculate target distance .

[0125] The present invention also provides a communication receiver, comprising: an antenna for receiving the millimeter-wave inductive signal; a low-noise amplifier connected to the antenna; a down-conversion unit connected to the antenna for down-converting the received signal to an intermediate frequency (IF) signal; an analog-to-digital converter for digitizing the IF signal; and a communication digital signal processing unit for performing dechirping, delay estimation, and delay compensation on the digitized IF signal to recover the baseband I-OFDM signal.

[0126] Furthermore, the present invention provides a photonic millimeter-wave communication and sensing integrated system, including the aforementioned transmitter, radar receiver, and communication receiver.

[0127] Thanks to the preservation of the chirped phase in LFM (Low-Frequency Mode), the communication receiver can skip the complex delay estimation steps when processing signals. It can perform accurate delay estimation and time shift compensation for the received signal through simple dechirping, aligning symbol boundaries. Furthermore, the determinism of the chirped phase can be used to assist in channel equalization of communication signals, thereby reducing the training overhead of the communication subsystem itself for estimating parameters such as delay and channel distortion. This means that the communication receiver can significantly reduce the training sequence overhead for channel estimation, using fewer symbol resources to track channel changes, thus freeing up more time-frequency resources to carry effective communication data, improving the system's communication spectral efficiency and effective throughput, and reducing communication delay.

[0128] This example has at least the following advantages:

[0129] (1) The orthogonality of OFDM signal sub-channels is utilized, and the data between different sub-channels will not interfere with each other. Therefore, only a few sub-channels need to be selected for sensing operations, and the communication signal transmission of other sub-channels will not be affected, which greatly reduces the loss of communication performance.

[0130] (2) Sensing can be achieved by setting the OFDM signal sub-channels to constant values. This can be achieved by making simple improvements on the basis of the original OFDM communication, and can be well integrated into the existing communication system, saving costs.

[0131] (3) The frequency of the LFM signal increases linearly with time. When the bandwidth of I-OFDM and LFM is adjusted to the point that the bandwidth of LFM is greater than that of I-OFDM, the communication spread spectrum gain can be achieved. This method of increasing the signal bandwidth improves the communication signal-to-noise ratio and increases the tolerance to communication interference.

[0132] (4) By using linear frequency modulation signals, the chirped phase characteristics of LFM are fully preserved, thereby achieving ultra-high precision measurement of target distance and improving the perception interference tolerance.

[0133] (5) By protecting the LFM chirped phase, the communication receiver can utilize the inherent sensing capability of the integrated waveform to measure the signal propagation delay with high precision before demodulation. This delay information can be used as prior knowledge for precise synchronization and timing compensation of communication symbols, thereby significantly reducing or even eliminating the overhead of dedicated training sequences used for delay estimation in traditional communication systems. This not only improves synchronization accuracy and reliability but also frees up more time-frequency resources to carry effective data, increasing net throughput and spectral efficiency at the system level and realizing perception-assisted communication.

Claims

1. A chirped phase compensation method, applied to a photonic millimeter-wave communication and sensing integrated system, characterized in that, Includes the following steps: Step S1: Generate a baseband-improved orthogonal frequency division multiplexing (I-OFDM) signal, wherein the total number of subcarriers is... OFDM signals Each subcarrier is configured as a sensing subcarrier, and each sensing subcarrier carries a constant value. ,the remaining Each subcarrier is a communication subcarrier, carrying a random communication sequence. The baseband I-OFDM signal is represented as: ,in, For the first The frequency of each communication subcarrier, For the first The frequency of a sensing subcarrier; Step S2: Generate a baseband linear frequency modulated (LFM) signal, represented as: ,in, The starting frequency, To adjust the frequency, Duration; Step S3: Combine the baseband I-OFDM signal and the baseband LFM signal into an I-OFDM-LFM signal; Step S4: Upconvert the I-OFDM-LFM signal to the millimeter wave band to generate a millimeter wave integrated sensing signal.

2. The method according to claim 1, characterized in that, The synthesis in step S3 is a digital domain multiplication synthesis, that is, the baseband I-OFDM-LFM signal is: ， The upconversion in step S4 includes: converting the baseband I-OFDM-LFM signal into an analog signal via a digital-to-analog converter; using the analog signal to drive an I / Q modulator to perform electro-optic modulation on the signal optical carrier provided by the optical frequency comb and wavelength selection switch to obtain an optical baseband sensing signal; combining the optical baseband sensing signal with the optical local oscillator carrier provided by the same optical frequency comb and wavelength selection switch; and generating the millimeter-wave sensing integrated signal by photoelectric conversion after combining the optical signal.

3. The method according to claim 1, characterized in that, The synthesis in step S3 is optical domain synthesis, specifically including: performing digital-to-analog conversion on the baseband I-OFDM signal and the baseband LFM signal respectively to obtain an analog I-OFDM signal and an analog LFM signal; driving the analog I-OFDM signal to drive a first I / Q modulator to perform electro-optic modulation on a first optical carrier to obtain a first optical signal; driving the analog LFM signal to drive a second I / Q modulator to perform electro-optic modulation on a second optical carrier to obtain a second optical signal; combining the first optical signal and the second optical signal to obtain a combined optical signal; the up-conversion in step S4 includes: generating the millimeter-wave inductive integrated signal by photoelectric conversion of the combined optical signal.

4. The method according to any one of claims 1 to 3, characterized in that, It also includes radar receiving and processing steps: Step R1: Receive the echo signal after the millimeter-wave integrated sensing signal is reflected by the target; Step R2: Mix the echo signal with a reference signal to obtain an intermediate frequency signal, wherein the reference signal is the millimeter-wave integrated sensing signal coupled from the output of the power amplifier before transmission; Step R3: Integrate the intermediate frequency signal during the integration time. Peak frequencies extracted from the internal spectrum Step R4: Based on the peak frequency Calculate target distance : ,in At the speed of light, The frequency modulation is mentioned.

5. The method according to any one of claims 1 to 3, characterized in that, It also includes communication reception and processing steps: Step C1: Receive the millimeter-wave integrated sensing signal and down-convert it to an intermediate frequency signal; Step C2: Perform a dechirping operation on the intermediate frequency signal, i.e., multiply it by the conjugate signal of the baseband LFM signal. ; Step C3: Estimate the signal propagation delay based on the peak frequency corresponding to the sensing subcarrier in the chirped signal. ; Step C4: Utilize the aforementioned delay Time delay compensation is performed on the dechirped signal to recover the baseband I-OFDM signal.

6. A transmitter implementing the method of claim 1, characterized in that, include: The baseband signal generation module is used to generate baseband I-OFDM signals and baseband LFM signals, wherein the baseband I-OFDM signals contain sensing subcarriers carrying constant values. The communication subcarrier carries a random communication sequence; a waveform synthesis module is used to synthesize the baseband I-OFDM signal and the baseband LFM signal into an I-OFDM-LFM signal; an up-conversion module is used to up-convert the I-OFDM-LFM signal to the millimeter-wave frequency band; and a power amplifier is used to amplify the up-converted millimeter-wave inductive integrated signal and radiate it through the antenna.

7. The transmitter according to claim 6, characterized in that, The waveform synthesis module is a digital domain multiplier, and the upconversion module includes a digital-to-analog converter, an I / Q modulator, an optical signal combining module, and a photoelectric conversion unit connected in sequence. The I / Q modulator is used to electro-optically modulate the signal optical carrier provided by the optical frequency comb and wavelength selection switch. The optical signal combining module is used to combine the modulated optical baseband sensing signal with the optical local oscillator carrier provided by the same optical frequency comb and wavelength selection switch. The combined optical signal is then converted into the millimeter-wave sensing integrated signal by the photoelectric conversion unit.

8. The transmitter according to claim 6, characterized in that, The waveform synthesis module includes a first digital-to-analog converter (DAC), a second DAC, a first I / Q modulator, a second I / Q modulator, and an optical signal combining module. The first DAC converts a baseband I-OFDM signal into an analog I-OFDM signal, and the first I / Q modulator modulates the analog I-OFDM signal onto a first optical carrier to obtain a first optical signal. The second DAC converts a baseband LFM signal into an analog LFM signal, and the second I / Q modulator modulates the analog LFM signal onto a second optical carrier to obtain a second optical signal. The optical signal combining module is used to combine the first optical signal and the second optical signal, and the combined optical signal is converted into the millimeter-wave integrated sensing signal by photoelectric conversion.

9. A radar receiver implementing the method of claim 4, characterized in that, include: Antenna, used to receive the echo signal of the millimeter-wave integrated sensing signal after it is reflected by the target; A low-noise amplifier, connected to the antenna, is used for noise processing and power compensation of the echo signal; A mixer, connected to the low-noise amplifier, is used to mix the processed echo signal with a reference signal and output an intermediate frequency signal. The reference signal is a millimeter-wave inductive integrated signal coupled from the output of the transmitter's power amplifier. An analog-to-digital converter is used to digitize the intermediate frequency signal; The radar digital signal processing unit is used to integrate the digitized intermediate frequency signal and extract the peak frequency of the spectrum. And according to the formula Calculate target distance ,in At the speed of light, To adjust the frequency.

10. A photonic millimeter-wave communication and sensing integrated system, characterized in that, The system includes the transmitter of claim 6, the radar receiver of claim 9, and a communication receiver; the communication receiver includes: an antenna for receiving the millimeter-wave integrated sensing signal; a down-conversion unit connected to the antenna for down-converting the received signal to an intermediate frequency (IF) signal; an analog-to-digital converter for digitizing the IF signal; and a communication digital signal processing unit for performing dechirping, delay estimation, and delay compensation on the digitized IF signal to recover the baseband I-OFDM signal.

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