Microwave photon phased array radar detection method and system based on optical domain true time delay

Abstract

The application discloses a microwave photon phased array radar detection method and system based on optical domain true delay, and realizes optical domain true delay on different wavelength laser signals through an optical delay module, controls the beam emission angle by combining the wavelength division multiplexing technology and the transmitting / receiving antenna array, modulates the target echo signal to another different wavelength laser signal as a carrier to obtain a receiving optical signal, and again passes through the optical delay module to make different wavelength components reach the coherent receiving module at the same time, realizes coherent fusion with the reference optical signal in the optical domain, and obtains target information through algorithm processing. The application realizes wideband scanning and real-time signal processing of the phased array radar based on the optical domain true delay technology, avoids the problem of beam tilting, has a compact system, low loss, strong anti-interference capability, and can effectively reduce the complexity and manufacturing cost.

Description

Technical Field

[0001] This invention relates to a radar detection method, and more particularly to a microwave photonic phased array radar detection method and system based on optical domain true time delay technology. Background Technology

[0002] Phased array technology, implemented using microwave technology, has been widely used in radar systems to replace mechanical scanning and control the radar beam emission angle. However, there are still many problems in implementing the all-electronic control system of phased array antenna elements using microwave components in traditional phased array radars (see [Brookner E. Practical Phased-Array Antenna System [M]. Norwood. MA: Artech House, 1991.]). For example, the large weight and high loss of the phase shifter itself restrict the radar performance. Furthermore, since the control of the phase is related to the signal frequency, there are problems such as beam pointing tilt under wide bandwidth angle signals, which seriously restrict the wide bandwidth, high precision, and high resolution scanning of phased array radars. In recent years, thanks to the rapid development of microwave photonics technology, based on the characteristics of photonics such as large bandwidth, low transmission loss, and resistance to electromagnetic interference, microwave photonics technology has provided new technical support for overcoming the electronic bottlenecks of traditional radar and improving its technical performance, and has become a key technology for the next generation of radar (see [J. Yao, "Microwave PhotoMics," JourMal of Lightwave Technology, vol. 27, Mo. 3, pp. 314-335, 2009.]). In particular, optical domain true-time delay phased arrays based on high-dispersion photonic crystal fibers, fiber Bragg gratings, and other technologies have been reported, for example (see [Chen MYHybrid photonic true-time delay modules for quasi-continuous steering of 2-D phased-array antennas[J].Journal of Lightwave Technology,2013,31(6):910-917.]). Although this method solves the beam tilt problem of traditional phased array radar and improves the scanning bandwidth, the currently reported methods only realize independent control of the beam emission angle or only transmit the received signal carrying target information. The system is discrete and still requires further photoelectric conversion and complex acquisition processing of the signal. This invention adopts a new microwave photonic phased array radar architecture to realize broadband radar scanning and real-time signal processing based on optical domain true time delay. The system is simple and compact, effectively reducing system complexity and manufacturing cost. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a microwave photonic phased array radar detection method and system based on optical domain true delay technology. This method achieves true optical domain delay for laser signals of different wavelengths through an optical delay module. Combined with wavelength division multiplexing (WDM) technology and a transmit / receive antenna array, it controls the beam emission angle. The target echo signal is further optically delayed, allowing different wavelength components to simultaneously reach the coherent receiving module and reference signal for coherent reception. This achieves wide bandwidth and wide angle scanning of the phased array while integrating system transmission and reception with real-time signal processing. It solves the problems of high phase shifter loss and beam tilt in traditional phased array radars, effectively reducing system complexity and manufacturing costs.

[0004] The objective of this invention is achieved through the following technical solution: a microwave photonic phased array radar detection method based on true time delay in the optical domain. First, a multi-wavelength light source generates an optical signal containing M frequency (wavelength) components and divides it into two paths. One path is demultiplexed into M optical signals, which are then sent as optical carrier signals to sub-electro-optic modulators in M ​​transmitting / receiving units. The other path is modulated by a baseband linear frequency modulation signal generated by a baseband signal source to obtain a modulated optical signal containing M frequency (wavelength) components. The modulated optical signal is then divided into two paths. One path is sent as a reference optical signal to one port of a coherent receiving module, and the other path is sent to an optical delay module through an optical circulator so that adjacent frequency (wavelength) components are sequentially increased by an equal time delay to obtain a transmitted optical signal. This transmitted optical signal is then demultiplexed into M transmitted optical signals and sent to M transmitting / receiving units. After photoelectric conversion and amplification, a radar detection signal is obtained and transmitted into the target space through an antenna.

[0005] The radar detection signal transmitted into the target space is reflected after encountering the target and received by the antenna of the transmit / receive unit to obtain the target echo signal. After being amplified, the target echo signal is modulated into the optical carrier signal sent to the sub-electro-optic modulator to obtain M received optical signals. The M received optical signals are combined into one and sent to the optical delay module, so that adjacent frequency (wavelength) components are successively increased by equal time delays and then simultaneously sent to another port of the coherent receiving module through the optical circulator. The combined received optical signal and the reference optical signal are coherently received in the coherent receiving module to obtain M intermediate frequency signals. The intermediate frequency signals are processed by the signal acquisition and processing module to obtain the target information.

[0006] Furthermore, the multi-wavelength light source is an optical frequency comb generator, a multi-wavelength laser, or multiple lasers with different wavelengths that can generate light signals containing M different frequency components.

[0007] Furthermore, the optical delay module consists of N+1 optical switches and dispersive optical fibers of different lengths connecting adjacent optical switches; the length of the dispersive optical fiber between the nth and (n+1)th optical switches is 2. n-1ΔL, where 1≤n≤N; the delay τ generated by adjacent frequency components of the modulated optical signal. d =Δλ·D·L, where Δλ is the wavelength interval, D is the dispersion coefficient, and L is the total length of the dispersive fiber through which the delayed modulated optical signal passes.

[0008] Furthermore, the pointing angle of the radar detection signal beam is θ = arcsin(τ). d ·c / d), the delay of the M-channel optical carrier signals increases by τ sequentially. d = dsinθ / c, where c is the speed of light in the atmosphere and d is the distance between adjacent transmitting / receiving antennas.

[0009] A microwave photonic phased array radar detection system based on true optical domain delay includes:

[0010] A multi-wavelength light source is used to generate the light signal containing M frequency (wavelength) components;

[0011] Baseband signal source, used to generate baseband linear frequency modulated signals;

[0012] The first optical coupler is used to split the generated optical signal containing M frequency (wavelength) components into two paths, one of which is sent to the second optical wavelength division multiplexer and the other is sent to the electro-optic modulator.

[0013] An electro-optic modulator is used to modulate a baseband linear frequency modulated signal onto an optical signal containing M frequency components output from a first optical coupler to obtain a modulated optical signal.

[0014] The second optical coupler (OC2) is used to split the modulated optical signal into two paths: one path is sent as a reference optical signal to one port of the coherent receiver module, and the other path is sent to the optical circulator.

[0015] An optical circulator is used to send the modulated optical signal output from the second optical coupler into the optical delay module, and to send the combined and delayed received optical signal returned from the optical delay module into another port of the coherent receiving module.

[0016] The optical delay module is used to sequentially add equal time delays to adjacent frequency (wavelength) components of the modulated optical signal output from the optical circulator to obtain the transmitted optical signal, and to sequentially add equal time delays to adjacent frequency (wavelength) components of the received optical signal that is combined into one channel.

[0017] The first optical wavelength division multiplexer is used to demultiplex the transmitted optical signal into M transmitted optical signals and then send them into M transmit / receive units.

[0018] The second optical wavelength division multiplexer is used to demultiplex the optical signal containing M frequency (wavelength) components output from the first optical coupler into M optical signals as optical carrier signals, and send them into M transmit / receive units.

[0019] There are M transmit / receive units. Each transmit / receive unit is used to convert and amplify one of the M paths of the demultiplexed optical signal into a radar detection signal and then transmit it as a radar detection signal. It also receives the target echo signal and modulates it onto the optical carrier signal to obtain the received optical signal and sends it into the first optical wavelength division multiplexer.

[0020] A coherent receiving module is used to coherently receive the combined and delayed received optical signal and the reference optical signal to obtain M intermediate frequency signals; the coherent receiving module is provided with at least two ports;

[0021] The signal acquisition and processing module is used to perform analog-to-digital conversion on the intermediate frequency signal and process the obtained digital signal carrying target information to obtain the target detection information.

[0022] Furthermore, each of the M transmit / receive units includes:

[0023] The sub-optical circulator is used to send the transmitted optical signal into the photodetector and the received optical signal into the first optical wavelength division multiplexer.

[0024] A photodetector is used to convert emitted light signals into radar detection signals through photoelectric conversion.

[0025] A power amplifier is used to amplify the radar detection signal output by the photodetector.

[0026] An electrical circulator is used to send the radar detection signal amplified by the power amplifier to the antenna and the target echo signal to the low-noise amplifier.

[0027] The antenna is used to transmit amplified radar detection signals and receive target echo signals.

[0028] A low-noise amplifier is used to amplify the echo signal received by the receiving antenna with low noise.

[0029] The sub-electro-optic modulator is used to modulate the low-noise amplified target echo signal onto the optical carrier signal to obtain the received optical signal.

[0030] Furthermore, the multi-wavelength light source is an optical frequency comb generator, a multi-wavelength laser, or multiple lasers with different wavelengths that can generate light signals containing M different frequency (wavelength) components.

[0031] Furthermore, the electro-optic modulator and the sub-electro-optic modulator are Mach-Zehnder or dual parallel Mach-Zehnder electro-optic modulators.

[0032] Furthermore, the optical delay module consists of N+1 optical switches and dispersive optical fibers of different lengths connecting adjacent optical switches, with the length of the dispersive optical fiber between the nth and (n+1th)th optical switches being 2. n-1 ΔL, where 1≤n≤N.

[0033] Furthermore, the target echo signal is obtained by the radar detection signal transmitted into the target space being reflected after encountering the target and received by the antenna of the transmitting / receiving unit.

[0034] The beneficial effects of this invention are as follows: Based on optical domain true delay technology, this invention delays laser signals of different wavelengths through an optical delay module to control the beam emission angle, thereby improving the scanning accuracy and scanning angle of the phased array system and simplifying system control; compared with microwave phase shifters, it significantly reduces the phase shifter's own losses and complexity, avoids beam tilting problems, and achieves wide bandwidth and wide angle scanning of the phased array radar; combined with integrated transmit / receive unit array and wavelength division multiplexing technology, it can effectively reduce the complexity and manufacturing cost of the radar system. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the microwave photonic phased array radar detection system based on true optical domain delay according to the present invention;

[0036] Figure 2 This is a schematic diagram of a specific embodiment of the microwave photonic phased array radar detection system based on true optical domain delay of the present invention.

[0037] Figure 3 This is a schematic diagram of the transmitting / receiving unit in a specific embodiment of the microwave photonic phased array radar detection system based on true optical domain delay of the present invention;

[0038] Figure 4 This is a schematic diagram of the optical delay module in a specific embodiment of the microwave photonic phased array radar detection system based on true optical domain delay of the present invention;

[0039] Figure 5 This is a schematic diagram showing the relationship between the delay of M transmitted optical signals and the beam emission angle in the microwave photonic phased array radar detection method based on true optical domain delay of the present invention.

[0040] Figure 6 This is a schematic diagram illustrating the relative relationship between the time and space of the M-channel transmitted optical signals and the antenna array and equiphase surface of the radar detection signal in the microwave photonic phased array radar detection method based on true optical domain delay of the present invention.

[0041] Figure 7 This is a schematic diagram illustrating the relative relationship between the time and space of the M-channel received optical signals and the antenna array and equiphase surface of the target echo signal in the microwave photonic phased array radar detection method based on true optical domain delay of the present invention.

[0042] Figure 8 This is a temporal and spatial diagram of the received optical signal after being combined into one channel and delayed in the microwave photonic phased array radar detection method based on true optical domain delay of the present invention. Detailed Implementation

[0043] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0044] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0045] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of this invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0046] The present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise specified, the features of the following embodiments and implementations can be combined with each other.

[0047] The present invention aims to achieve phase control of laser signals of different wavelengths by using true optical domain dispersion delay, thereby controlling the beam emission angle to achieve wide bandwidth angle scanning of phased array radar. By using true optical domain delay of the received optical signal to achieve coherent reception with the reference optical signal and real-time signal processing, the high loss and beam tilt problems of traditional phased array radar are solved. It has strong anti-interference ability and can effectively reduce complexity and manufacturing cost.

[0048] This invention provides a microwave photonic phased array radar detection method based on true optical domain delay, such as... Figure 1As shown, it includes a multi-wavelength light source, a baseband signal source, an electro-optic modulator, an optical circulator, an optical delay module, a first optical wavelength division multiplexer, a second optical wavelength division multiplexer, M transmit / receive units, a coherent receive module, and a signal acquisition and processing module.

[0049] First, a multi-wavelength light source generates an optical signal containing M frequency target echo signal components, which is then split into two paths. One path is demultiplexed into M optical signals, which are then sent as optical carrier signals to the sub-electro-optic modulators in the M transmitting / receiving units. The other path is modulated by a baseband linear frequency modulation signal generated by a baseband signal source to obtain a modulated optical signal containing M frequency target echo signal components. The modulated optical signal is then split into two paths. One path is sent as a reference optical signal to one port of a coherent receiving module, and the other path is sent through an optical circulator to an optical delay module so that adjacent frequency target echo signal components are sequentially increased by an equal time delay to obtain a transmitted optical signal. This transmitted optical signal is then demultiplexed into M transmitted optical signals and sent to the M transmitting / receiving units. After photoelectric conversion and amplification, a radar detection signal is obtained and transmitted to the target space through an antenna.

[0050] The radar detection signal transmitted into the target space is reflected upon encountering the target and received by the antenna of the transmit / receive unit to obtain the target echo signal. After being amplified, the target echo signal modulates the optical carrier signal sent to the sub-electro-optic modulator to obtain M received optical signals. The M received optical signals are combined into one and sent to the optical delay module, so that the target echo signal components of adjacent frequencies are successively increased by equal time delays and then simultaneously sent to another port of the coherent receiving module through the optical circulator. The combined received optical signal and the reference optical signal are coherently received in the coherent receiving module to obtain M intermediate frequency signals. The intermediate frequency signals are processed by the signal acquisition and processing module to obtain the target information.

[0051] In some embodiments, the multi-wavelength light source may be an optical frequency comb generator, a multi-wavelength laser, or multiple lasers with different wavelengths to generate a light source containing M different frequency components.

[0052] In some embodiments, specifically, both the electro-optic modulator and the sub-electro-optic modulator can be Mach-Zehnder or dual parallel Mach-Zehnder electro-optic modulators.

[0053] To facilitate public understanding, the technical solution of the present invention will be further described in detail below through a specific embodiment:

[0054] like Figure 2As shown, the radar detection system of this invention includes: a multi-wavelength laser, a first optical coupler (OC1), a second optical coupler (OC2), a Mach-Zehnder modulator (MZM), a baseband signal source, an optical delay module, an optical circulator, a first optical wavelength division multiplexer, a second optical wavelength division multiplexer, M transmit / receive units, a coherent receiving module, and a signal acquisition and processing module.

[0055] It should be noted that the multi-wavelength light source can employ various existing technologies, preferably, such as... Figure 2 As shown, the multi-wavelength light source is realized by a multi-wavelength laser.

[0056] like Figure 3 As shown, each of the M transmit / receive units includes:

[0057] One optical circulator, one photodetector (PD), one power amplifier, one electrical circulator, one antenna, one low-noise amplifier, and one sub-Mach-Zehnder modulator (MZMm).

[0058] like Figure 4 As shown, the optical delay module includes:

[0059] There are N+1 optical switches and dispersive optical fibers of different lengths connecting adjacent optical switches. The length of the dispersive optical fiber between the nth and (n+1th)th optical switches is 2. n ΔL.

[0060] First, a multi-wavelength light source generates wavelengths f1, f2, ... f M An optical signal with M frequency components is fed into port 1 of the first optical coupler and split into two paths. One path is output from port 3 and fed into the second optical wavelength division multiplexer. The other path is output from port 2 and fed into a Mach-Zehnder modulator. A baseband linear frequency modulated signal is generated by the baseband signal source and then subjected to double-sideband modulation by the first Mach-Zehnder modulator to obtain a modulated optical signal. The instantaneous frequency f of the baseband linear frequency modulated signal is... LFM (t) is:

[0061] f LFM (t)=f0+kt(0≤t≤T)

[0062] Where f0 is the starting frequency of the baseband linear frequency modulated signal, T is its period, and k is its modulation slope. At this time, the modulated optical signal S... OM The time domain of (t) can be represented as:

[0063]

[0064] Where A OMm- A OMm A OMm+Let fm represent the center wavelength of the modulated optical signal and the amplitudes of the positive and negative first-order sideband signals, respectively, where m = 1, 2, ..., M, j is an imaginary number, and fm is the amplitude of the multi-wavelength light source containing f1, f2, ..., fm. M The optical signal of the m-th frequency component in a total of M frequency components.

[0065] A modulated optical signal containing M different frequency components is fed into port 1 of the second optical coupler and split into two paths. One path outputs from port 3 of the second optical coupler as a reference optical signal and is sent to one port of the coherent receiving module. The other path outputs from port 2 of the second optical coupler and is sent to port 1 of the optical circulator. Then, it is output from port 2 of the optical circulator and sent to the optical delay module. The optical delay module contains N+1 optical switches and dispersive optical fibers connecting adjacent optical switches. The length of the dispersive optical fiber between adjacent optical switches is 2. n-1 ΔL, M light signals of different frequencies (i.e., different wavelengths) are delayed to varying degrees in the dispersive ray to produce the emitted light signal. The delay between adjacent wavelengths is: τ d =Δλ·D·L, where Δλ is the wavelength spacing and D is the fiber dispersion coefficient. Different degrees of delay can be achieved by controlling the total length L of the dispersive fiber through which the modulated optical signal passes via optical switches; in an optical delay module containing N+1 optical switches, L can have 2... N The possible values ​​are L = 0, ΔL, 2ΔL…2 N ΔL, emitted optical signal S OMd The time domain of (t) can be expressed as:

[0066]

[0067] Where A OMdm- A OMdm A OMdm+ The center wavelength and positive and negative first-order sideband signal amplitudes of the transmitted optical signal are respectively represented. The transmitted optical signal is sent to the first optical wavelength division multiplexer for demultiplexing into M channels. The M different frequency components are respectively sent to the M transmit / receive units. Each transmitted optical signal is sent to port 2 of the sub-optical circulator and output from port 3 of the sub-optical circulator. The m-th transmitted optical signal S OTdm The time domain of (t) can be expressed as:

[0068] S OTdm (t)=A OTdm- exp[j2π(f m -f0)(t-(m-1)τ d )-0.5k(t-(m-1)τ d ) 2 )]+A OTdm+ exp[j2π(f m +f0)(t-(m-1)τ d)+0.5k(t-(m-1)τ d ) 2 )]+A OTdm exp[j2πf m (t-(m-1)τ d (0≤t≤T)

[0069] Where A OTdm- A OTdm A OTdm+ Let λ represent the center wavelength and the amplitude of the positive and negative first-order sideband signals of the m-th transmitted optical signal, respectively. Therefore, the m-th transmitted optical signal has a time delay (m-1)τ relative to the 1st transmitted optical signal. d That is, the spatial positions of the emitted optical signals in the optical fiber are sequential, such as Figure 6 As shown. The m-th transmitted optical signal is sent to a photodetector (PD), where it is converted into a photoelectric signal and then sent to a power amplifier. After amplification, the radar detection signal is obtained and sent to port 1 of an electric circulator. The signal is output from port 2 of the electric circulator and transmitted to the target space by the antenna. The time domain S of the radar detection signal is shown. Tm (t) can be represented as:

[0070] S Tm (t)=A Tm exp[j2π(f0(t-(m-1)τ d )+0.5k(t-(m-1)τ d ) 2 (0≤t≤T)

[0071] Where A Tm Let θ be the amplitude of the radar detection signal. From this, it can be deduced that at the same time, adjacent transmitting / receiving units emit radar signals with equal phase differences between their detected targets. This means that the equiphase surface and the antenna array have an angle θ between them. Figure 6 As shown, m radar detection signals interfere in space to form a beam, and the included angle θ is the beam emission angle. The beam emission angle θ of the radar detection signal is related to the delay τ. d Relevant, such as Figure 5 As shown, it can be specifically represented as:

[0072] θ = arcsin(τ) d ·c / d)

[0073] Where c is the speed of light in the atmosphere, and d is the spacing between antennas in adjacent transmitting / receiving units. The radar detection signal radiated into the target space is reflected upon encountering the target and received by the antennas of the transmitting / receiving unit to obtain the target echo signal, whose time domain S... Rm (t) can be represented as:

[0074] S Rm (t)=ARm exp[j2π(f0(t-τ-(2M-m-1)τ d )+0.5k(t-τ-(2M-m-1)τ d ) 2 (0≤t≤T)

[0075] Where A Rm Let τ be the amplitude of the target echo signal, and τ be the time delay of the target echo signal relative to the radar detection signal. Therefore, it can be concluded that there is an equal phase difference between adjacent channels of the target echo signals arriving at m transmitting / receiving units at the same time; that is, the equiphase surface still has an angle θ with the antenna array surface. Figure 7 As shown. The target echo signal is received by the antenna and sent to port 2 of the circulator, and output from port 3 of the circulator to a low-noise amplifier. After amplification, it is loaded onto a sub-Mach-Zehnder modulator (MZMm). At this time, the optical carrier signal output from port 3 of the first optical coupler is sent to the second optical wavelength division multiplexer and demultiplexed into M channels. The time domain S of the m-th optical carrier signal... OCm (t) can be represented as:

[0076] S OCm (t)=A OCm exp(j2πf m t) (0≤t≤T)

[0077] Where A OCm The input terminals of the sub-Mach-Zehnder modulators (MZMm) fed into the M transmit / receive units are used to adjust the operating point of the sub-Mach-Zehnder modulators so that the amplified target echo signal is double-sideband modulated onto the optical carrier signal, resulting in M ​​received optical signals. The time domain S of the m-th received optical signal is given. ORm (t) can be represented as:

[0078]

[0079] Where A ORm- A ORm A ORm+ Let be the center wavelength of the received optical signal and the amplitudes of the positive and negative first-order sideband signals, respectively. Therefore, the first received optical signal has a time delay of (m-1)τ relative to the m-th received optical signal. d That is, the spatial positions of the emitted optical signals in the optical fiber are sequential, such as Figure 7 As shown. The received optical signal is fed into port 1 of the sub-optical circulator and output from port 2 to the first optical wavelength division multiplexer. After wavelength division multiplexing, it is combined into one signal and then sent to the optical delay module so that different frequency components are simultaneously sent to port 2 of the optical circulator. The signal is then output from port 3 of the optical circulator and sent to another input port of the coherent receiving module. The time domain S of the combined and delayed received optical signal is shown. OR(t) can be represented as:

[0080]

[0081] Where A ORdm- A ORdm A ORdm+ These are the center wavelength and the amplitudes of the positive and negative first-order sideband signals of the received optical signal after being combined and delayed, respectively. Therefore, it can be concluded that the delay differences of the m components in the received optical signal after being combined and delayed are compensated, achieving temporal and spatial alignment, as shown below. Figure 8 As shown. The positive first-order sideband of the received optical signal, after being combined and delayed, and the positive first-order sideband of the reference optical signal are coherently fused and detected in the optical domain. The relative instantaneous frequency difference f between the overlapping portions of the two signals, which contain target information, is given by f. IF =kτt, after the received optical signal and the reference optical signal are coherently received in the coherent receiving unit, two orthogonal intermediate frequency (IF) signals are obtained at the two outputs of the coherent receiving unit. The IF signals are expressed as:

[0082]

[0083] That is, the two orthogonal components SI(t) and SQ(t) of the intermediate frequency signal carrying target information, where φ is the phase information of the intermediate frequency signal, and the corresponding complex form of the signal is:

[0084] S IF (t)=S I (t)+jS Q (t)=Cexp[j2πkτt+jφ] (0≤t≤T)

[0085] Where C is the amplitude of the intermediate frequency signal. After the intermediate frequency signal is converted from analog to digital by the acquisition and processing unit, the target's range, azimuth angle, relative scattering intensity and other information can be obtained by processing this signal through radar-related algorithms.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0087] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

[0088] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only.

[0089] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A microwave photonic phased array radar detection method based on true optical domain delay, characterized in that, First, a multi-wavelength light source generates an optical signal containing M frequency components, which is then split into two paths. One path is demultiplexed into M optical signals, which are then used as optical carrier signals and fed into the sub-electro-optic modulators in the M transmitting / receiving units. The other path is modulated by a baseband linear frequency modulation signal generated by a baseband signal source to obtain a modulated optical signal containing M frequency components. The modulated optical signal is then split into two paths. One path is used as a reference optical signal and fed into one port of a coherent receiving module. The other path is fed into an optical delay module through an optical circulator, which increases the time delay of adjacent frequency components by an equal amount to obtain a transmitted optical signal. This transmitted optical signal is then demultiplexed into M transmitted optical signals and fed into the M transmitting / receiving units. After photoelectric conversion and amplification, a radar detection signal is obtained and transmitted to the target space through an antenna. The radar detection signal transmitted into the target space is reflected after encountering the target and received by the antenna of the transmit / receive unit to obtain the target echo signal. After being amplified, the target echo signal is modulated into the optical carrier signal sent to the sub-electro-optic modulator to obtain M received optical signals. The M received optical signals are combined into one and sent to the optical delay module, so that adjacent frequency components are successively increased by equal time delays. Then, they are simultaneously sent to another port of the coherent receiving module through the optical circulator. The combined received optical signal and the reference optical signal are coherently received in the coherent receiving module to obtain M intermediate frequency signals. The intermediate frequency signals are processed by the signal acquisition and processing module to obtain the target information. The optical delay module consists of N+1 optical switches and dispersive optical fibers of different lengths connecting adjacent optical switches; the length of the dispersive optical fiber between the nth and (n+1th)th optical switches is 2. n-1 ΔL, where 1≤n≤N; the delay τ generated by adjacent frequency components of the modulated optical signal. d =Δλ·D·L, where Δλ is the wavelength interval, D is the dispersion coefficient, and L is the total length of the dispersive fiber through which the delayed modulated optical signal passes.

2. The microwave photonic phased array radar detection method based on true optical domain delay as described in claim 1, characterized in that, The multi-wavelength light source is an optical frequency comb generator, a multi-wavelength laser, or multiple lasers with different wavelengths that can generate light signals containing M different frequency components.

3. The microwave photonic phased array radar detection method based on true optical domain delay as described in claim 1, characterized in that, The pointing angle of the radar detection signal beam is θ = arcsin(τ) d ·c / d), the delay of the M-channel optical carrier signals increases by τ sequentially. d = dsinθ / c, where c is the speed of light in the atmosphere and d is the distance between adjacent transmitting / receiving antennas.

4. A microwave photonic phased array radar detection system based on true optical domain delay, characterized in that, include: A multi-wavelength light source is used to generate the optical signal containing M frequency components; Baseband signal source, used to generate baseband linear frequency modulated signals; The first optical coupler is used to split the generated optical signal containing M frequency components into two paths, one of which is sent to the second optical wavelength division multiplexer and the other is sent to the electro-optic modulator. An electro-optic modulator is used to modulate a baseband linear frequency modulated signal onto an optical signal containing M frequency components output from a first optical coupler to obtain a modulated optical signal. The second optical coupler is used to split the modulated optical signal into two paths: one path is sent as a reference optical signal to one port of the coherent receiving module, and the other path is sent to the optical circulator. An optical circulator is used to send the modulated optical signal output from the second optical coupler into the optical delay module, and to send the combined and delayed received optical signal returned from the optical delay module into another port of the coherent receiving module. The optical delay module is used to sequentially add equal delays to adjacent frequency components of the modulated optical signal output from the optical circulator to obtain the transmitted optical signal, and to sequentially add equal delays to adjacent frequency components of the received optical signal that has been combined into one channel. The first optical wavelength division multiplexer is used to demultiplex the transmitted optical signal into M transmitted optical signals and then send them into M transmit / receive units. The second optical wavelength division multiplexer is used to demultiplex the optical signal containing M frequency components output from the first optical coupler into M optical signals as optical carrier signals, and send them into M transmit / receive units. There are M transmit / receive units. Each transmit / receive unit is used to convert and amplify one of the M paths of the demultiplexed optical signal and then transmit it as a radar detection signal. The target echo signal is received and modulated onto the optical carrier signal to obtain the received optical signal, which is then sent to the first optical wavelength division multiplexer. The coherent receiving module is used to coherently receive the combined and delayed received optical signal and the reference optical signal to obtain M intermediate frequency signals; The signal acquisition and processing module is used to perform analog-to-digital conversion on the intermediate frequency signal and process the obtained digital signal carrying target information to obtain the target detection information; The optical delay module consists of N+1 optical switches and dispersive optical fibers of different lengths connecting adjacent optical switches; the length of the dispersive optical fiber between the nth and (n+1th)th optical switches is 2. n-1 ΔL, where 1≤n≤N; the delay τ generated by adjacent frequency components of the modulated optical signal. d =Δλ·D·L, where Δλ is the wavelength interval, D is the dispersion coefficient, and L is the total length of the dispersive fiber through which the delayed modulated optical signal passes.

5. A microwave photonic phased array radar detection system based on true optical domain delay as described in claim 4, characterized in that, The M transmitting / receiving units, each transmitting / receiving unit includes: The sub-optical circulator is used to send the transmitted optical signal into the photodetector and the received optical signal into the first optical wavelength division multiplexer. A photodetector is used to convert emitted light signals into radar detection signals through photoelectric conversion. A power amplifier is used to amplify the radar detection signal output by the photodetector. An electrical circulator is used to send the radar detection signal amplified by the power amplifier to the antenna and the target echo signal to the low-noise amplifier. The antenna is used to transmit amplified radar detection signals and receive target echo signals. A low-noise amplifier is used to amplify the echo signal received by the receiving antenna with low noise. The sub-electro-optic modulator is used to modulate the low-noise amplified target echo signal onto the optical carrier signal to obtain the received optical signal.

6. The microwave photonic phased array radar detection system based on true optical domain delay as described in claim 4, characterized in that, The multi-wavelength light source is an optical frequency comb generator, a multi-wavelength laser, or multiple lasers with different wavelengths that can generate light signals containing M different frequency components.

7. The microwave photonic phased array radar detection system based on true optical domain delay as described in claim 5, characterized in that, The electro-optic modulator and sub-electro-optic modulator are Mach-Zehnder or dual parallel Mach-Zehnder electro-optic modulators.

8. A microwave photonic phased array radar detection system based on true optical domain delay as described in claim 4, characterized in that, The target echo signal is obtained by the radar detection signal transmitted into the target space being reflected after encountering the target and received by the antenna of the transmitting / receiving unit.

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