Extremely narrow electromagnetic pulse time domain alignment method, unit and detection system

Abstract

The invention belongs to the field of radar signal processing, and discloses an extremely narrow electromagnetic pulse time domain alignment method and unit and a detection system. According to the ultra-narrow electromagnetic pulse time domain alignment method, optical wavelength scanning is converted into microwave frequency scanning based on photonics regulation and control, higher measurement resolution is achieved, the microwave frequency is low (GHz magnitude), the phase of a microwave signal is conveniently measured and processed, and then time delay is accurately measured. The method is a parallel measurement mechanism, the measurement efficiency is higher, and the precision is higher. The delay error between the extremely narrow electromagnetic pulse transmitting channel and the extremely narrow electromagnetic pulse receiving channel is compensated, so that the extremely narrow electromagnetic pulses can be effectively synthesized in space, and the detection efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of radar signal processing, specifically to a method, unit, and detection system for aligning extremely narrow electromagnetic pulses in the time domain. Background Technology

[0002] Ultra-wideband detection systems utilize extremely narrow pulse electromagnetic waves (pulse widths on the order of hundreds of picoseconds) for detection, offering an extremely wide instantaneous bandwidth (greater than 1 GHz). They are suitable for applications such as through-wall detection, geological exploration, and biological monitoring. However, due to the extremely narrow pulse signal's very small time-domain width (on the order of hundreds of picoseconds), an accuracy of less than ten picoseconds is required to achieve time-domain alignment; otherwise, effective spatial synthesis and accumulation of the signal is difficult. This technical bottleneck forces existing ultra-wideband detection systems to adopt a single-channel transceiver mode, limiting further improvements in overall detection efficiency.

[0003] Solving the time-domain alignment problem requires measuring the signal transmission delay, calculating the corresponding compensation value based on the delay, and finally achieving time-domain alignment by applying the compensation value. Existing technologies for measuring signal transmission delay employ radio frequency (RF) measurement methods, which are susceptible to electromagnetic interference from high-power pulses. Furthermore, these methods use a serial measurement mechanism, meaning they involve multiple measurements by changing the frequency of the measurement signal, resulting in low measurement accuracy and efficiency, and failing to meet the time-domain alignment requirements of extremely narrow electromagnetic pulses. Summary of the Invention

[0004] To address the existing technical problems and achieve time-domain alignment of extremely narrow pulse signals, this paper provides a method, unit, and detection system for time-domain alignment of extremely narrow electromagnetic pulses.

[0005] Firstly, a method for aligning the time domain of extremely narrow electromagnetic pulses is provided, comprising the following steps:

[0006] The delay measurement signal is loaded by optical domain modulation, and the delay measurement signal is an optical carrier double-sideband sine wave signal;

[0007] The delay measurement signal is used to perform reflection measurement on each radar channel to obtain the reference delay amount of each radar channel;

[0008] The reflected signal of the delay measurement signal is demodulated in the optical domain and read out to obtain the time domain response of each radar channel;

[0009] The time-domain response of each radar channel is converted into a phase response, phase calculation is performed, the calibration delay of each radar channel is obtained, and delay compensation is performed based on the calibration delay.

[0010] Furthermore, when loading a delay measurement signal using optical domain modulation, the specific steps are as follows:

[0011] The signal generator produces a sinusoidal signal with a fixed frequency, which is transmitted to the laser diode controller to modulate the amplitude of the distributed feedback laser. The optical signal modulated by the distributed feedback laser enters the Mach-Zehnder modulator, where it is intensity modulated by a microwave sweep signal generated by a microwave source. The modulated signal is the delay measurement signal, which is a double-sideband sine wave signal with an optical carrier.

[0012] Furthermore, the delay measurement signal Represented as:

[0013]

[0014] in, Indicates the amplitude of the delayed measurement signal; Indicates the modulation coefficient; Indicates the frequency of the microwave sweep signal; Indicates time; It is an exponential function; Indicates the center frequency of the coherent optical carrier; It is the imaginary unit.

[0015] Furthermore, when using the delay measurement signal to perform reflection measurements on each radar channel to obtain the reference delay amount for each radar channel, the specific steps are as follows:

[0016] The delay measurement signal passes sequentially through the circulator and beam splitter before entering each radar channel. After reaching the reflection point of each channel, it returns, and the reflected signal... Represented as:

[0017]

[0018] in, Indicates the total number of channels. It is an integer, and ; Indicates the channel index. It is an integer, and ; Indicates the first The amplitude of the reflected signal in each channel; Indicates the modulation coefficient; Indicates the frequency of the microwave sweep signal; Indicates time; It is an exponential function; Indicates the center frequency of the coherent optical carrier; The imaginary unit; Indicates the first The delay of the reflected signal from each channel is denoted as the reference delay.

[0019] Furthermore, when optically demodulating and reading out the reflected signal of the delay measurement signal to obtain the time-domain response of each radar channel, the specific steps are as follows:

[0020] The reflected signal passes sequentially through an erbium-doped fiber amplifier, an optical bandpass filter, and a photodetector before entering a vector network analyzer. The photocurrent carrying the microwave sweep frequency component is represented in the frequency domain as:

[0021]

[0022] in, This represents the vector sum of the frequency responses of the reflection points in each radar channel; This represents the response coefficient of the photodetector; This represents the amplification factor of the erbium-doped fiber amplifier. Indicates the total number of channels. It is an integer, and ; Indicates the channel index. It is an integer, and ; Indicates the first The amplitude of the reflected signal in each channel; Indicates the modulation coefficient; It is an exponential function; Indicates the frequency of the microwave sweep signal; The imaginary unit; Indicates the first The delay of the reflected signal in each channel, i.e., the reference delay;

[0023] right Perform an inverse Fourier transform to obtain the time-domain response of each radar channel's optical link. , means as follows:

[0024]

[0025] in, This represents the response coefficient of the photodetector; This represents the amplification factor of the erbium-doped fiber amplifier. Indicates the total number of channels. It is an integer, and ; Indicates the channel index. It is an integer, and ; Indicates the first The amplitude of the reflected signal in each channel; Indicates the modulation coefficient; For Dirac function; Indicates time; Indicates the first The delay of the reflected signal in each channel, i.e., the reference delay.

[0026] Furthermore, when converting the time-domain response of each radar channel into a phase response, performing phase calculation, and obtaining the calibration delay of each channel, the specific steps are as follows:

[0027] The time-domain response of each radar channel is windowed and Fourier transformed to convert it into a phase response;

[0028] Perform phase calculations to restore the wrapped phase to a continuous absolute phase;

[0029] The slope of the absolute phase is calculated, and then the calibration delay of each radar channel is obtained. :

[0030]

[0031] in, The slope of the absolute phase; The frequency of the difference frequency signal is the instantaneous frequency difference between the delayed measurement signal and the reflected signal.

[0032] Furthermore, when performing phase calculations to restore the wrapped phase to a continuous absolute phase, the specific steps are as follows:

[0033] First, select a frequency point with minimal and no integer cycle ambiguity. Starting from this frequency point, check the phase relationship between each subsequent frequency point and the previous frequency point. If the phase difference is greater than one cycle, add a phase adjustment to the frequency point. Eliminate blur, among which It is an integer.

[0034] Furthermore, a univariate linear regression analysis method is used to calculate the slope of the absolute phase.

[0035] In a second aspect, an ultra-narrow electromagnetic pulse time-domain alignment unit is provided to implement the ultra-narrow electromagnetic pulse time-domain alignment method as described in the first aspect. The ultra-narrow electromagnetic pulse time-domain alignment unit includes a signal modulation module, a delay measurement module, a delay calibration module, and a delay compensation module, wherein:

[0036] The signal modulation module is used to load a delay measurement signal by optical domain modulation, wherein the delay measurement signal is an optical carrier double-sideband sine wave signal;

[0037] The delay measurement module is used to perform reflective measurements on each channel of the radar using the delay measurement signal to obtain the reference delay amount of each channel;

[0038] The delay calibration module is used to demodulate and read out the reflected signal of the delay measurement signal in the optical domain to obtain the time domain response of each channel; convert the time domain response of each channel into the phase response, perform phase calculation, and obtain the calibration delay amount of each channel.

[0039] The delay compensation module is used to perform delay compensation based on the calibration delay amount.

[0040] Thirdly, a detection system is provided, which is an ultrawideband detection system based on extremely narrow pulse electromagnetic waves, including a transmitter and a receiver, wherein the transmitter and receiver of the detection system have an extremely narrow electromagnetic pulse time-domain alignment unit as described in the second aspect.

[0041] The beneficial effects of this invention are as follows:

[0042] In existing technologies, the radio frequency measurement method is used to measure time delay. This method is susceptible to electromagnetic interference from high-power pulses and is a serial measurement mechanism, which involves changing the frequency of the measurement signal multiple times. This results in low measurement accuracy and efficiency, and cannot meet the time-domain alignment requirements of extremely narrow pulse signals. Therefore, ultra-wideband detection systems have to adopt a single-channel transceiver mode, which limits detection efficiency.

[0043] This application presents an ultra-narrow electromagnetic pulse time-domain alignment method based on photonics manipulation, converting optical wavelength scanning into microwave frequency scanning. This method offers higher measurement resolution, and the relatively low microwave frequency (GHz level) facilitates the measurement and processing of microwave signal phase. Simultaneously, it avoids high-power electromagnetic interference found in traditional RF measurement methods, resulting in higher measurement accuracy. This application employs a parallel measurement mechanism to improve measurement efficiency. By compensating for the delay error between the ultra-narrow electromagnetic pulse transmission and reception channels, it enables effective spatial coherent synthesis, thereby enhancing detection efficiency. Attached Figure Description

[0044] Figure 1 This is a flowchart of the ultra-narrow electromagnetic pulse time-domain alignment method according to Embodiment 1 of the present invention;

[0045] Figure 2 This is a block diagram illustrating the principle of the multi-channel optical delay measurement technology according to Embodiment 1 of the present invention.

[0046] Figure 3 This refers to an extremely narrow electromagnetic pulse that has not been aligned using the method described in this application.

[0047] Figure 4 For extremely narrow electromagnetic pulses aligned by the method of this application;

[0048] Figure 5 This describes the transmitting end working mechanism of the detection system in Embodiment 3 of the present invention;

[0049] Figure 6This describes the working mechanism of the receiving end of the detection system in Embodiment 3 of the present invention. Detailed Implementation

[0050] The present invention will now be described in further detail.

[0051] Example 1:

[0052] This invention provides a time-domain alignment method for extremely narrow electromagnetic pulses. Based on photonics manipulation, it utilizes microwave (electromagnetic waves with frequencies between 300MHz and 3000GHz) photonic multi-channel amplitude and phase precision measurement and feedback technology to compensate for the delay error between the transmitting and receiving channels of extremely narrow electromagnetic pulses. This enables effective spatial coherent synthesis, improving the detection efficiency of ultra-wideband detection systems. The term "multi-channel" refers to a channel count greater than one.

[0053] This application employs multi-channel optical delay measurement technology, and the principle block diagram of the multi-channel optical delay measurement technology with time-domain resolution is shown below. Figure 2 As shown, a signal source generates a fixed-frequency sine wave signal, which is transmitted to the external input of the laser diode controller to modulate the amplitude of the distributed feedback laser. The optical signal modulated by the distributed feedback laser enters the Mach-Zehnder modulator, where it is intensity modulated by a microwave sweep signal generated by a microwave source. The modulated signal is a double-sideband sine wave signal with an optical carrier, which serves as the delay measurement signal. The delay measurement signal passes through a circulator and a beam splitter before entering the radar channel. The reflected signal is then demultiplexed, passed through a circulator, and amplified by an erbium-doped fiber amplifier to increase the signal-to-noise ratio. An optical bandpass filter removes out-of-band spurious signals, and a photodetector converts it into photocurrent. This photocurrent is then received by a vector network analyzer, which calculates the calibration delay and determines the delay compensation value required for the time-domain alignment of the extremely narrow electromagnetic pulse. The feedback control of the delay devices in the optical channel performs precise compensation.

[0054] The present invention provides a method for time-domain alignment of extremely narrow electromagnetic pulses, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps:

[0055] Step 1: Load the delay measurement signal by optical domain modulation. The delay measurement signal is an optical carrier double-sideband sine wave signal.

[0056] A signal generator produces a sinusoidal signal at a fixed frequency, which is transmitted to a laser diode controller to modulate the amplitude of a distributed feedback laser. The optical signal modulated by the distributed feedback laser then enters a Mach-Zehnder modulator, where it is intensity modulated by a microwave sweep signal generated by a microwave source. The modulated signal is the delay measurement signal, i.e., a double-sideband sine wave signal with an optical carrier. Details are as follows:

[0057] The signal generator produces a sine wave signal with a fixed frequency. In this embodiment, the fixed frequency produced by the signal generator is 500MHz.

[0058] A fixed-frequency sine wave signal generated by a signal generator is transmitted to the external input terminal of the laser diode controller to modulate the amplitude of the distributed feedback laser.

[0059] The optical signal modulated by the distributed feedback laser enters the Mach-Zehnder modulator, where it is intensity modulated by a microwave sweep signal generated by a microwave source. The modulated signal is a double-sideband sine wave signal with an optical carrier, which is used as the delay measurement signal. Represented as:

[0060]

[0061] in, Indicates the amplitude of the delayed measurement signal; Indicates the modulation coefficient; Indicates the frequency of the microwave sweep signal; Indicates time; It is an exponential function; Indicates the center frequency of the coherent optical carrier; The imaginary unit ( In this embodiment, , , , .

[0062] By utilizing microwave photonics, specifically employing a double-sideband sine wave signal with an optical carrier, measurements are performed, avoiding the high-power electromagnetic interference found in traditional RF measurement methods. This results in more accurate and stable measurement data. The delay measurement signal is a double-sideband sine wave signal carried on an optical wave. The microwave frequency scans over time, providing a highly precise microwave frequency scan with higher measurement resolution compared to coarse-grained optical wavelength scanning.

[0063] Step 2: Use the delay measurement signal to perform reflection measurement on each radar channel to obtain the reference delay of each radar channel.

[0064] The delay measurement signal passes sequentially through the circulator and beam splitter before entering each radar channel. After reaching the reflection point of each channel, it returns, as detailed below:

[0065] The total number of radar channels is ( It is an integer, and The delay measurement signal is input from port 1 of the circulator and output from port 2 to the beam splitter, which splits the delay measurement signal into two parts. In this embodiment, the number of radar channels to be measured is 4. After the delay measurement signal passes through the circulator, it is split into 4 paths by the beam splitter.

[0066] The decoupled delay measurement signal enters each radar channel for reflection measurement, and returns after reaching the reflection point of each radar channel. The reflected signal is then demultiplexed and returned to port 2 of the circulator, and then output from port 3. Because each radar channel has a different reflection point, the reflected signal has different intensity and time delay depending on the location of the reflection point. Represented as:

[0067]

[0068] in, Indicates the total number of channels ( It is an integer, and ); For channel index ( It is an integer, and ); Indicates the modulation coefficient; Indicates the first The amplitude of the reflected signal in each channel; Indicates the frequency of the microwave sweep signal; Indicates time; It is an exponential function; Indicates the center frequency of the coherent optical carrier; The imaginary unit ( ); Indicates the first The delay amount of the reflected signal from each channel is denoted as the reference delay amount. In this embodiment, , , , , , , , , , .

[0069] Since the delay measurement signal is a double-sideband sine wave signal with an optical carrier, modulated by a microwave frequency sweep signal, the microwave frequency scans over time. Therefore, the delay measurement signal contains multiple frequencies; in this embodiment, it contains four. Thus, a single measurement is equivalent to four measurements in a traditional RF measurement method, reducing the measurement time to one-quarter of the traditional method and increasing measurement efficiency. Using microwave interferometry instead of the traditional optical interferometry architecture improves the stability of the measurement system.

[0070] Step 3: Perform optical domain demodulation and readout on the reflected signal of the delay measurement signal to obtain the time domain response of each radar channel.

[0071] The reflected signal passes sequentially through an erbium-doped fiber amplifier, an optical bandpass filter, and a photodetector before entering a vector network analyzer. This analyzer acquires the frequency domain response of the photocurrent for each radar channel, performs an inverse Fourier transform, and then obtains the time domain response of the optical link for each radar channel. Multiple frequencies are measured simultaneously on one channel, and the delay is determined through deambiguation. The details are as follows:

[0072] Reflected signal The signal-to-noise ratio is first amplified by an erbium-doped fiber amplifier after output from port 3 of the circulator. Then, it is filtered by an optical bandpass filter to remove out-of-band spurious signals. Finally, it is converted into photocurrent by a photodetector and received by a vector network analyzer, carrying microwave sweep frequency components. The photocurrent in the frequency domain is expressed as:

[0073]

[0074] in, Indicates radar The vector sum of the frequency responses at the reflection points of the road channel; Indicates the total number of channels ( It is an integer, and ); Indicates channel index ( It is an integer, and ); This represents the response coefficient of the photodetector; Indicates the modulation coefficient; This represents the amplification factor of the erbium-doped fiber amplifier. Indicates the first The amplitude of the reflected signal in each channel; It is an exponential function; Indicates the frequency of the microwave sweep signal; The imaginary unit ( ); Indicates the first The delay amount of the reflected signal from each channel, i.e., the reference delay amount. In this embodiment, , , , , , , , , , , , .

[0075] right Perform an inverse Fourier transform to obtain the time-domain response of each radar channel's optical link. , Represented as:

[0076]

[0077] in, Indicates the total number of channels ( It is an integer, and ); Indicates channel index ( It is an integer, and ); This represents the response coefficient of the photodetector; Indicates the modulation coefficient; This represents the amplification factor of the erbium-doped fiber amplifier. Indicates the first The amplitude of the reflected signal in each channel; For Dirac function; Indicates time; Indicates the first The delay of the reflected signal in each channel, i.e., the reference delay.

[0078] Step 4: Convert the time domain response of each radar channel into a phase response, perform phase calculation, obtain the calibration delay of each radar channel, and perform delay compensation based on the calibration delay.

[0079] The time-domain response of each radar channel is converted into a phase response, and then phase calculation is performed to restore the wrapped phase to a continuous absolute phase. Finally, the slope of the absolute phase is calculated. This allows us to obtain the calibration delay of each radar channel. And delay compensation is performed based on the calibration delay amount. Specifically:

[0080] The time domain response of each radar channel Windowing and Fourier transform are performed to convert the signal into a phase response. Then, the phase expansion method is used to restore the wrapped phase to a continuous absolute phase. Since the delay measurement signal contains multiple frequencies, phase deambiguity can be performed to determine the delay amount, resulting in higher measurement accuracy.

[0081] Specifically as follows:

[0082] First, select a frequency point with minimal and no integer cycle ambiguity. Starting from this frequency point, check the phase relationship between each subsequent frequency point and the previous frequency point. If the phase difference is greater than one cycle, add a phase adjustment to the frequency point. Eliminate blur, among which It should be an integer to ensure correct phase expansion.

[0083] Then, the slope of the expanded absolute phase is calculated using univariate linear regression analysis. Alternatively, the slope of the absolute phase expansion can be calculated using the total least squares method. .

[0084] Obtain the slope of the absolute phase Then, the calibration delay of each radar channel can be obtained. .

[0085]

[0086] in, The slope of the absolute phase; The frequency of the difference frequency signal is the instantaneous frequency difference between the delayed measurement signal and the reflected signal.

[0087] In this implementation, the calibration delay of each radar channel is... , , , .

[0088] In this implementation, the reference delay and the calibration delay are consistent, indicating that the measurement of the reference delay is accurate and the measurement method is effective and meets expectations.

[0089] Based on the calibration delay, the delay compensation value required for the time-domain alignment of the extremely narrow electromagnetic pulse is determined, and the delay device in the optical channel is controlled by feedback for precise compensation.

[0090] In this application, microwave photonics are used, specifically a double-sideband optical carrier sine wave signal for measurement, avoiding the high-power electromagnetic interference found in traditional radio frequency (RF) measurement methods, thus resulting in more accurate and stable measurement data. Since the delay measurement signal is a double-sideband optical carrier sine wave signal modulated by a microwave frequency sweep signal, it contains multiple frequencies (four in this embodiment). Therefore, a single measurement is equivalent to four measurements in a traditional RF method, reducing the measurement time to one-quarter of the traditional method, resulting in higher measurement efficiency.

[0091] Furthermore, when converting the time-domain response of each radar channel into the phase response, since the delay measurement signal contains multiple frequencies, phase deambiguity can be achieved through methods such as phase expansion, thereby determining the delay amount and achieving higher measurement accuracy.

[0092] To more intuitively evaluate the performance of this method, the waveforms of extremely narrow electromagnetic pulse sequences before and after time-domain alignment processing during the transmission phase are compared. Multiple extremely narrow electromagnetic pulses not aligned using the method described in this application are shown below. Figure 3As shown, due to inherent delay differences in the hardware of each transmission channel (such as power amplifiers and modulators) and clock distribution errors, there is a significant deviation in the pulse transmission timing, with a maximum difference of approximately 2 ns. The pulse leading edges are scattered along the time axis, and the peak power points cannot be aligned. This misalignment means that the extremely narrow electromagnetic pulse signal cannot be synchronously radiated in the antenna element, thus preventing effective synthesis in the far field and leading to a decrease in detection efficiency. Multiple extremely narrow electromagnetic pulses aligned using the method described in this application are shown below. Figure 4 As shown, the pulses from each channel are transmitted in strict synchronization, with their waveforms highly overlapping on the time axis. This ensures precise alignment between the leading edge and peak point of the transmitted pulses, thereby enabling effective synthesis in the far field and improving detection efficiency.

[0093] Example 2:

[0094] The present invention also provides an ultra-narrow electromagnetic pulse time-domain alignment unit for implementing the ultra-narrow electromagnetic pulse time-domain alignment method of Embodiment 1 of this application. The ultra-narrow electromagnetic pulse time-domain alignment unit includes the following modules:

[0095] The signal modulation module is used to load a delay measurement signal through optical domain modulation. The delay measurement signal is an optical carrier double-sideband sine wave signal; specifically as follows:

[0096] A signal generator produces a fixed-frequency sine wave signal, which is then transmitted to the external input of the laser diode controller to modulate the amplitude of the distributed feedback laser. The optical signal modulated by the distributed feedback laser enters a Mach-Zehnder modulator, where it is intensity-modulated by a microwave sweep signal generated by a microwave source. The modulated signal is a double-sideband optical carrier sine wave signal, which serves as the delay measurement signal. Represented as:

[0097]

[0098] in, Indicates the amplitude of the signal; Indicates the modulation coefficient; Indicates the frequency of the microwave sweep signal; Indicates time; It is an exponential function; Indicates the center frequency of the coherent optical carrier; The imaginary unit ( The delay measurement signal is a double-sideband sine wave signal carried on light waves. The microwave frequency is scanned over time, which is a high-precision microwave frequency scan and has a higher measurement resolution compared to the coarse-grained optical wavelength.

[0099] The delay measurement module is used to perform reflective measurements on each channel of the radar using the delay measurement signal to obtain the reference delay amount of each channel; specifically as follows:

[0100] The delay measurement signal is input from port 1 of the circulator and output from port 2 to the beam splitter, which splits the delay measurement signal into two parts. road( It is an integer, and The decoupled delay measurement signal enters each radar channel for reflection measurement, and returns after reaching the reflection point of each radar channel. The reflected signal is then demultiplexed and returned to port 2 of the circulator, and then output from port 3. Because each radar channel has a different reflection point, the reflected signal has different intensity and time delay depending on the location of the reflection point. Represented as:

[0101]

[0102] in, Indicates the total number of channels ( It is an integer, and ); Indicates channel index ( It is an integer, and ); Indicates the modulation coefficient; Indicates the first The amplitude of the reflected signal in each channel; Indicates the frequency of the microwave sweep signal; Indicates time; It is an exponential function; Indicates the center frequency of the coherent optical carrier; The imaginary unit ( ); Indicates the first The delay of the reflected signal from each channel is denoted as the reference delay. The delay measurement signal is a double-sideband optical carrier sine wave signal, with the microwave frequency scanning over time. Microwave interferometry is used to replace the traditional optical interferometry architecture, improving the stability of the measurement system.

[0103] The delay calibration module is used to optically demodulate and read out the reflected signal of the delay measurement signal to obtain the time domain response of each radar channel; it then converts the time domain response into a phase response, performs phase calculation, and obtains the calibration delay amount of each radar channel; specifically as follows:

[0104] Reflected signal The output from port 3 of the circulator passes through an erbium-doped fiber amplifier, an optical bandpass filter, a photodetector, and is then received by a vector network analyzer, carrying microwave sweep frequency components. The photocurrent in the frequency domain is expressed as:

[0105]

[0106] in, The vector sum of the frequency responses of the reflection points of each radar channel; Indicates the total number of channels ( It is an integer, and ); Indicates channel index ( It is an integer, and ); This represents the response coefficient of the photodetector; Indicates the modulation coefficient; This represents the amplification factor of the erbium-doped fiber amplifier. Indicates the first The amplitude of the reflected signal in each channel; It is an exponential function; Indicates the frequency of the microwave sweep signal; The imaginary unit ( ); Indicates the first The delay of the reflected signal in each channel, i.e., the reference delay.

[0107] right Perform inverse Fourier transform to obtain radar data. Time domain response of optical link in the path channel , Represented as:

[0108]

[0109] in, Indicates the total number of channels ( It is an integer, and ); Indicates channel index ( It is an integer, and ); This represents the response coefficient of the photodetector; Indicates the modulation coefficient; This represents the amplification factor of the erbium-doped fiber amplifier. Indicates the first The amplitude of the reflected signal in each channel; For Dirac function; Indicates time; Indicates the first The delay of the reflected signal in each channel, i.e., the reference delay.

[0110] The time-domain response of each channel is converted into a phase response, phase calculation is performed, the calibration delay of each channel is obtained, and delay compensation is performed based on the calibration delay.

[0111] Will Time-domain response of the road channel Windowing and Fourier transform are performed to convert the phase response. Then, the phase unwrapping method is used to restore the wrapped phase to a continuous absolute phase. Specifically, the following steps are taken: First, a frequency point with minimal and no integer cycle ambiguity is selected. Starting from this frequency point, the phase relationship between subsequent frequency points and previous frequency points is checked one by one. If the phase difference is greater than one cycle, the phase of that frequency point is added. Eliminate blur, among which The values ​​are integers to ensure correct phase expansion. Then, the slope of the expanded absolute phase is calculated using univariate linear regression or total least squares analysis. This allows us to obtain the calibration delay of each radar channel. .

[0112]

[0113] in, The slope of the absolute phase; The frequency of the difference frequency signal is the instantaneous frequency difference between the delayed measurement signal and the reflected signal.

[0114] The delay compensation module is used to perform delay compensation based on the calibration delay amount. Based on the calibration delay amount obtained by the delay calibration module, the delay compensation value required for electromagnetic pulse time-domain alignment is determined, and feedback control is used to perform precise compensation on the delay devices in the optical channel.

[0115] Example 3:

[0116] This invention also provides a detection system, which is an ultra-wideband detection system based on extremely narrow pulse electromagnetic waves, including a transmitter and a receiver. The transmitter and receiver of the detection system have the extremely narrow electromagnetic pulse time-domain alignment unit of Embodiment 2. The working mechanism of the transmitter of the detection system is as follows: Figure 5 As shown: During the transmission phase, the extremely narrow pulse trigger signal generated by the transient waveform is precisely measured and fed back through delay feedback control (delay control accuracy improved to the picosecond level). This ensures that the trigger signal of each channel simultaneously reaches the corresponding high-power pulse source (peak power reaching the megawatt level), thereby ensuring that the hundreds of picosecond-level extremely narrow pulse signal emitted by the high-power pulse source is synchronously radiated in the antenna element, thus achieving effective synthesis in the far field. The working mechanism of the receiver of the detection system is as follows: Figure 6As shown: During the receiving phase, the extremely narrow pulse echo signal reaches the filtering and amplification module through the antenna unit of the receiving end. After delay feedback control, it is ensured that the signal of each channel arrives at the transient signal receiving and sampling module at the same time for transient signal receiving and sampling, thereby realizing effective signal synthesis. The synthesized extremely narrow pulse signal is sampled and sent to the transient signal processing unit to complete transient signal processing.

[0117] While the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the invention. Any equivalent changes or modifications made without departing from the spirit and scope of the invention are also within the scope of protection of the invention. Therefore, the scope of protection of the present invention should be determined by the claims of this application.

Claims

1. A method for time-domain alignment of extremely narrow electromagnetic pulses, characterized in that, Includes the following steps: The delay measurement signal is loaded by optical domain modulation, and the delay measurement signal is an optical carrier double-sideband sine wave signal; The delay measurement signal is used to perform reflection measurement on each radar channel to obtain the reference delay amount of each radar channel; The reflected signal of the delay measurement signal is demodulated in the optical domain and read out to obtain the time domain response of each radar channel; The time-domain response of each radar channel is converted into a phase response, phase calculation is performed, the calibration delay of each radar channel is obtained, and delay compensation is performed based on the calibration delay.

2. The method for aligning the time domain of an extremely narrow electromagnetic pulse according to claim 1, characterized in that, When using optical domain modulation to load a time-delayed measurement signal, the specific steps are as follows: The signal generator produces a sinusoidal signal with a fixed frequency, which is transmitted to the laser diode controller to modulate the amplitude of the distributed feedback laser. The optical signal modulated by the distributed feedback laser enters the Mach-Zehnder modulator, where it is intensity modulated by a microwave sweep signal generated by a microwave source. The modulated signal is the delay measurement signal, which is a double-sideband sine wave signal with an optical carrier.

3. The method for aligning the time domain of an extremely narrow electromagnetic pulse according to claim 2, characterized in that, Delay measurement signal Represented as: in, Indicates the amplitude of the delayed measurement signal; Indicates the modulation coefficient; Indicates the frequency of the microwave sweep signal; Indicates time; It is an exponential function; Indicates the center frequency of the coherent optical carrier; It is the imaginary unit.

4. The method for aligning the time domain of an extremely narrow electromagnetic pulse according to claim 1, characterized in that, When using the aforementioned delay measurement signal to perform reflection-based measurements on each radar channel to obtain the reference delay value for each radar channel, the specific steps are as follows: The delay measurement signal passes sequentially through the circulator and beam splitter before entering each radar channel. After reaching the reflection point of each channel, it returns, and the reflected signal... Represented as: in, Indicates the total number of channels. It is an integer, and ; Indicates the channel index. It is an integer, and ; Indicates the first The amplitude of the reflected signal in each channel; Indicates the modulation coefficient; Indicates the frequency of the microwave sweep signal; Indicates time; It is an exponential function; Indicates the center frequency of the coherent optical carrier; The imaginary unit; Indicates the first The delay of the reflected signal from each channel is denoted as the reference delay.

5. The method for aligning the time domain of an extremely narrow electromagnetic pulse according to claim 1, characterized in that, When performing optical domain demodulation and readout on the reflected signal of the delay measurement signal to obtain the time domain response of each radar channel, the specific steps are as follows: The reflected signal passes sequentially through an erbium-doped fiber amplifier, an optical bandpass filter, and a photodetector before entering a vector network analyzer. The photocurrent carrying the microwave sweep frequency component is represented in the frequency domain as: in, This represents the vector sum of the frequency responses of the reflection points in each radar channel; This represents the response coefficient of the photodetector; This represents the amplification factor of the erbium-doped fiber amplifier. Indicates the total number of channels. It is an integer, and ; Indicates the channel index. It is an integer, and ; Indicates the first The amplitude of the reflected signal in each channel; Indicates the modulation coefficient; It is an exponential function; Indicates the frequency of the microwave sweep signal; The imaginary unit; Indicates the first The delay of the reflected signal in each channel, i.e., the reference delay; right Perform an inverse Fourier transform to obtain the time-domain response of each radar channel's optical link. , means as follows: in, This represents the response coefficient of the photodetector; This represents the amplification factor of the erbium-doped fiber amplifier. Indicates the total number of channels. It is an integer, and ; Indicates the channel index. It is an integer, and ; Indicates the first The amplitude of the reflected signal in each channel; Indicates the modulation coefficient; For Dirac function; Indicates time; Indicates the first The delay of the reflected signal in each channel, i.e., the reference delay.

6. The method for aligning the time domain of an extremely narrow electromagnetic pulse according to claim 1, characterized in that, When converting the time-domain response of each radar channel into a phase response, performing phase calculation, and obtaining the calibration delay of each channel, the specific steps are as follows: The time-domain response of each radar channel is windowed and Fourier transformed to convert it into a phase response; Perform phase calculations to restore the wrapped phase to a continuous absolute phase; The slope of the absolute phase is calculated, and then the calibration delay of each radar channel is obtained. : in, The slope of the absolute phase; The frequency of the difference frequency signal is the instantaneous frequency difference between the delayed measurement signal and the reflected signal.

7. The method for aligning the time domain of an extremely narrow electromagnetic pulse according to claim 6, characterized in that, When performing phase resolution to restore the wrapped phase to a continuous absolute phase, the specific steps are as follows: First, select a frequency point with minimal and no integer cycle ambiguity. Starting from this frequency point, check the phase relationship between each subsequent frequency point and the previous frequency point. If the phase difference is greater than one cycle, add a phase adjustment to the frequency point. Eliminate blur, among which It is an integer.

8. The method for aligning the time domain of an extremely narrow electromagnetic pulse according to claim 7, characterized in that, The slope of the absolute phase is calculated using a univariate linear regression analysis method.

9. A time-domain alignment unit for extremely narrow electromagnetic pulses, used to implement the time-domain alignment method for extremely narrow electromagnetic pulses as described in claim 1, characterized in that, The ultra-narrow electromagnetic pulse time-domain alignment unit includes a signal modulation module, a delay measurement module, a delay calibration module, and a delay compensation module, wherein: The signal modulation module is used to load a delay measurement signal by optical domain modulation, wherein the delay measurement signal is an optical carrier double-sideband sine wave signal; The delay measurement module is used to perform reflective measurements on each channel of the radar using the delay measurement signal to obtain the reference delay amount of each channel; The delay calibration module is used to demodulate and read out the reflected signal of the delay measurement signal in the optical domain to obtain the time domain response of each channel; convert the time domain response of each channel into the phase response, perform phase calculation, and obtain the calibration delay amount of each channel. The delay compensation module is used to perform delay compensation based on the calibration delay amount.

10. A detection system, said detection system being an ultra-wideband detection system based on extremely narrow pulse electromagnetic waves, comprising a transmitter and a receiver, characterized in that, The transmitting and receiving ends of the detection system have an ultra-narrow electromagnetic pulse time-domain alignment unit as described in claim 9.

Images