CN114594462A - Broadband light-controlled beam forming network based on double-optical frequency comb and phased array radar - Google Patents

Broadband light-controlled beam forming network based on double-optical frequency comb and phased array radar Download PDF

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CN114594462A
CN114594462A CN202210204709.8A CN202210204709A CN114594462A CN 114594462 A CN114594462 A CN 114594462A CN 202210204709 A CN202210204709 A CN 202210204709A CN 114594462 A CN114594462 A CN 114594462A
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optical
signal
frequency
comb
frequency comb
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王棉
薛晓晓
郑小平
李尚远
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Tsinghua University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/292—Extracting wanted echo-signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S2013/0236—Special technical features
    • G01S2013/0245—Radar with phased array antenna
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
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  • General Physics & Mathematics (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

The application discloses a broadband light-controlled beam forming network and method based on a double-optical frequency comb and a phased array radar, wherein the network comprises: a light source for outputting continuous light; the first optical frequency comb generation module is used for generating a first optical frequency comb signal with a first repetition frequency by using continuous light; the second optical frequency comb generation module is used for generating a second optical frequency comb signal of a second repetition frequency by using continuous light; the electro-optical modulation module is used for modulating a linear frequency modulation wave signal with a preset pulse width to a first optical frequency comb signal to generate a first modulation signal; and the output module is used for coupling the first modulation signal and the second optical frequency comb signal, filtering and performing photoelectric detection so as to perform frequency shift and phase shift on the linear frequency modulation wave signal and output a delay microwave signal after broadband light-controlled beam forming. The method and the device do not use an optical delay line, and solve the problems of large system and difficult delay regulation of a broadband light-controlled beam forming network.

Description

Broadband light-controlled beam forming network based on double-optical frequency comb and phased array radar
Technical Field
The application relates to the technical field of light-operated beam forming, in particular to a broadband light-operated beam forming network and method based on a double-optical-frequency comb and a phased array radar.
Background
The traditional mechanical scanning radar is not suitable for the requirement of a novel detection task due to the reasons of low scanning speed, large volume, poor stability and the like, and replaces the traditional mechanical scanning radar with a phased array radar which has the advantages of high scanning speed, conformality with a radar platform, high stability, strong waveform agility and the like. The flexible and changeable detection capability of the phased array radar enables the phased array radar to be widely applied.
The radar detection mainly comprises four dimensions of azimuth, elevation, longitudinal and Doppler. Wherein the detection resolution of azimuth and elevation, together with the target distance, determines the lateral resolution of radar detection. The transverse detection resolution range and the Doppler resolution of the radar are mainly increased by long-time irradiation of the target, the longitudinal detection resolution range of the radar is inversely proportional to the bandwidth of the transmitted signal, and the longitudinal resolution and the longitudinal detection precision of the radar can be improved by increasing the bandwidth of the transmitted signal. Therefore, the use of broadband radar signals is very beneficial for radar ranging and imaging.
In order to integrate the flexible detection capability of the phased array radar and the high-resolution detection capability of the broadband radar, researchers begin to carry out intensive research on the broadband phased array radar. However, the conventional phased array radar is a narrow-band system, and the aperture effect influences the instantaneous bandwidth and beam direction of a transmitted signal and is not suitable for transmitting a broadband radar signal. Therefore, the technical route of the broadband phased array radar cannot be directly applied to the technical route of the traditional phased array radar. At present, two types of related technical routes exist, namely a real-time delay compensation technology and an adaptive beam forming technology. At present, many implementations of real-time delay compensation technology exist, such as digital delay line, fractional delay filter, optical delay line, and frequency shift and phase shift delay method for chirp wave. The optical delay line scheme has the advantages of low loss, light weight, electromagnetic interference resistance and the like, and becomes a research hotspot. However, in the existing optical delay line schemes, the large delay amount scheme can only realize discrete adjustment, and the scheme capable of realizing continuous adjustment of the delay amount can only provide a smaller delay amount, and a practical optical delay line scheme is still under search. The adaptive beam forming technology is mainly used in a receiver, can adjust the shape of a spatial beam in real time, and is suitable for occasions with strong interference and weak targets, but the adaptive beam forming scheme has the problem of overlarge calculation amount when the array size is enlarged.
Therefore, how to develop a broadband light-controlled beamforming network scheme with a simple structure and easy expansion still is a problem to be solved urgently.
Disclosure of Invention
The application provides a broadband light-controlled beam forming network based on a double-optical-frequency comb, a method and a phased array radar, and aims to solve the problems of large system and difficulty in delay regulation and control of the broadband light-controlled beam forming network in the related technology.
An embodiment of a first aspect of the present application provides a broadband light-controlled beam forming network based on a dual optical frequency comb, including the following modules: a light source for outputting continuous light; a first optical frequency comb generation module for generating a first optical frequency comb signal of a first repetition frequency using the continuous light; a second optical frequency comb generation module for generating a second optical frequency comb signal of a second repetition frequency using the continuous light; the electro-optical modulation module is used for modulating a linear frequency modulation wave signal with a preset pulse width onto the first optical frequency comb signal to generate a first modulation signal; and the output module is used for coupling the first modulation signal and the second optical frequency comb signal, filtering and performing photoelectric detection so as to shift frequency and phase of the linear frequency modulation wave signal and output a delay microwave signal after broadband light-controlled beam forming.
Optionally, in an embodiment of the present application, the method further includes: and the linear frequency modulation wave source is used for generating the linear frequency modulation wave signal with the preset pulse width and inputting the linear frequency modulation wave signal with the preset pulse width to the electro-optical modulation module.
Optionally, in an embodiment of the present application, the method further includes: and the phase compensation module is connected with the output end of the second optical frequency comb generation module and is used for adding a phase shift amount to each comb tooth of the second optical frequency comb signal so as to obtain a phase required by the chirp signal.
Optionally, in an embodiment of the present application, the output module includes: a coupler for coupling the first modulated signal and the second optical-frequency comb signal; the optical filter bank is used for filtering the coupled signals; and the photoelectric detector group is used for carrying out photoelectric detection on the filtered signals.
Optionally, in an embodiment of the present application, the optical filter bank is composed of a plurality of optical filters with different center frequencies, wherein the number of the optical filters is consistent with the number of the beam forming network channels, and the center frequencies of the optical filters are aligned with the center frequencies of the first optical-frequency comb signal and the second optical-frequency comb signal.
Optionally, in an embodiment of the present application, the photodetector group includes a plurality of photodetectors, and the plurality of photodetectors are respectively connected to output ends of the filters of the optical filter group, and down-convert the optical carrier chirp to a baseband, so as to obtain a delayed chirp component.
Optionally, in an embodiment of the present application, the method further includes: and the beam splitter is connected with the light source output end and used for splitting the continuous light and respectively inputting the split continuous light to the first optical frequency comb generating module and the second optical frequency comb generating module.
The embodiment of the second aspect of the present application provides a broadband light-controlled beam forming method based on a dual optical frequency comb, including: generating a first optical frequency comb signal of a first repetition frequency and a second optical frequency comb signal of a second repetition frequency using the continuous light, respectively; carrying a preset broadband linear frequency modulation wave signal on the first optical frequency comb signal to modulate and generate a first modulation signal; and coupling the first modulation signal and the second optical frequency comb signal, and then filtering and performing photoelectric detection to perform frequency shift and phase shift on the linear frequency modulation wave signal and output a delay microwave signal after broadband light-operated beam forming.
Optionally, in an embodiment of the present application, before the coupling of the first modulation signal and the second optical-frequency comb signal, the method further includes: and adding a phase shift amount to each comb tooth of the second optical frequency comb signal to obtain a phase required by the chirp signal.
An embodiment of a third aspect of the present application provides a phased array radar, including: the broadband light-controlled beam forming network based on the double optical frequency comb is described in the embodiment of the application.
The embodiment of the application utilizes a linear frequency modulation wave frequency shift phase shift method realized in an optical domain to replace an optical true delay network, realizes a simple multi-channel beam forming network, and has the characteristics of low system complexity, quick delay adjustment, capability of supporting broadband phased array application and the like. Therefore, the problems of large system and difficult delay regulation of a broadband light-controlled beam forming network are solved.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic diagram of a broadband optically controlled beam forming network based on a dual optical frequency comb according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a broadband optically controlled beamforming network based on a dual-optical-frequency comb according to an embodiment of the present application;
FIG. 3 is a diagram illustrating optical frequency comb fingers and filter pass bands according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a multi-channel broadband optical beamforming network based on a dual-optical-frequency comb according to an embodiment of the present application;
FIG. 5 is a diagram of simulation results provided according to an embodiment of the present application;
fig. 6 is a schematic diagram of a radar simulation of a broadband light-controlled beamforming method based on a dual-optical-frequency comb according to an embodiment of the present application;
fig. 7 is a schematic flow chart of a method of a broadband optically controlled beam forming network based on a dual optical frequency comb according to an embodiment of the present application.
Detailed Description
Reference will now be made in detail to the embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present application and should not be construed as limiting the present application.
The following describes a broadband light-controlled beamforming network based on a dual-optical-frequency comb, a method and a phased array radar according to an embodiment of the present application with reference to the drawings. Aiming at the problems of huge system and difficult delay regulation of a broadband light-operated beam forming network in the related technology mentioned in the background technology center, the application provides a broadband light-operated beam forming network based on a double-optical-frequency comb, which utilizes the free spectral width difference of the double-optical-frequency comb, simultaneously provides frequency shift for multiple paths of linear frequency modulation waves, and then simultaneously shifts the phases of the multiple paths of linear frequency modulation waves to realize the true delay of the multiple paths of linear frequency modulation waves, has continuously adjustable delay difference and simple operation, can obtain large-range delay regulation without using a long delay line or other delay methods, has simple network structure, few required devices, can easily realize large-scale expansion, has small delay error and high channel consistency, and is favorable for accurate beam forming. Therefore, the problems of large system and difficult delay regulation of the broadband light-controlled beam forming network in the related technology are solved.
Specifically, fig. 1 is a schematic diagram of a broadband optically controlled beamforming network based on a dual-optical-frequency comb according to an embodiment of the present application.
As shown in fig. 1, the broadband optically controlled beamforming network 10 based on the dual-optical-frequency comb includes: the optical system comprises a light source 100, a first optical-frequency comb generating module 200, a second optical-frequency comb generating module 300, an electro-optical modulation module 400 and an output module 500.
The light source 100 may be a laser, which stably outputs continuous light.
The first optical-frequency comb generating module 200 is configured to generate a first optical-frequency comb signal with a first repetition frequency using continuous light.
The second optical-frequency comb generating module 300 is configured to generate a second optical-frequency comb signal of a second repetition frequency using the continuous light.
It is understood that the optical-frequency comb generating module can stably generate a flat optical-frequency comb having a certain free spectral width, and in the embodiment of the present application, two optical-frequency comb generating modules are included to generate a first optical-frequency comb signal having a first spectral width (i.e., a first repetition frequency) and a second optical-frequency comb signal having a second spectral width (i.e., a second repetition frequency), respectively.
The electro-optical modulation module 400 is configured to modulate the chirp signal with a preset pulse width to the first optical frequency comb signal to generate a first modulation signal.
It is understood that in the embodiment of the present application, one input terminal of the electro-optical modulation module 400 is connected to the first optical-frequency comb generating module 200 to receive the first optical-frequency comb signal, and the other input terminal inputs the chirp signal. In practical implementation, the connection relationship of the electro-optical modulation module 400 may be adjusted according to practical requirements, such as connecting the electro-optical modulation module 400 with the second optical-frequency comb generating module 300.
The output module 500 is configured to couple the first modulation signal and the second optical frequency comb signal, and then perform filtering and photoelectric detection, so as to perform frequency shift and phase shift on the linear frequency modulated wave signal, and output a delayed microwave signal after broadband light-controlled beam forming.
It can be understood that continuous light output by the light source passes through the first optical frequency comb generating module 200 and the second optical frequency comb generating module 300 to generate two optical signals, wherein one optical frequency comb signal is modulated by a chirp signal and then output, and then is coupled with the other optical frequency comb signal, so that frequency shift and phase shift of the chirp signal are realized, equivalent delay of the chirp signal is realized, and a delayed microwave signal after broadband light-controlled beam forming is output.
Further, the first optical frequency comb generating module and the second optical frequency comb generating module of the embodiment of the present application generate two optical frequency combs with different repetition frequencies, that is, the frequency intervals between the comb teeth of the optical combs are different, the difference between the repetition frequencies of the two optical combs is related to the delay difference between the adjacent channels that the beamforming network needs to provide, and the delay difference between the adjacent channels determines the beam direction of the phased array. The repetition frequency of the optical frequency comb is at least two times greater than the highest frequency of the chirp signal, so that aliasing of sidebands of adjacent modulated comb teeth is prevented.
Optionally, in an embodiment of the present application, the broadband optically controlled beamforming network 10 based on a dual-optical-frequency comb further includes: and the beam splitter is connected with the light source output end and used for splitting the continuous light and respectively inputting the split continuous light into the first optical frequency comb generation module and the second optical frequency comb generation module.
It is understood that, in order to input the continuous light to the first optical-frequency comb generating module 200 and the second optical-frequency comb generating module 300 respectively, in the embodiments of the present application, a beam splitter may be disposed behind the light source 100 to split the continuous light into two beams, and input the two beams to the first optical-frequency comb generating module 200 and the second optical-frequency comb generating module 300 respectively.
Optionally, in an embodiment of the present application, the broadband optically controlled beamforming network 10 based on a dual-optical-frequency comb further includes: and the linear frequency modulation wave source is used for generating a linear frequency modulation wave signal with a preset pulse width and inputting the linear frequency modulation wave signal with the preset pulse width to the electro-optical modulator.
The embodiment of the present application modulates the optical frequency comb signal by using a chirp signal with a preset pulse width, and optionally, a chirp source is provided in a network structure in the embodiment of the present application to generate a chirp signal required in the embodiment of the present application.
It will be appreciated that the parameters of the chirp generated by the chirp source need not be varied according to the parameters of the phased array, and that the pulse width is not varied according to a predetermined delay. The difference between the repetition frequencies of the two optical frequency combs is adjusted according to the chirp rate K of the chirp wave.
As shown in fig. 2, one input end of the electro-optical modulation module is connected to the first optical-frequency comb generation module, and the other input end is connected to the chirp source, so that the first optical-frequency comb signal is modulated by the chirp signal output by the chirp source.
In particular, the chirp source is one capable of producing a chirpA waveform generator of frequency waves. A chirp signal is a signal whose frequency varies linearly with time, and the time domain expression is written as s (t) cos (2 pi f)0t+πKt2) And K is the chirp rate of the chirp wave. After the time delay Δ τ is performed on the chirp wave, the time domain expression of the time-delayed chirp wave is written as:
s′(t)＝cos(2πf0(t-Δτ)+πK(t-Δτ)2)＝cos(2π(f0+Δf)t+Δφ+πKt2) (1)
wherein f is0Is the initial frequency of the chirp, Δ f-K Δ τ is an equivalent frequency shift, Δ φ -2 π f0Δτ+ πKΔτ2Is an equivalent phase shift quantity. It can be seen from the formula (1) that the frequency and the phase of the chirp are shifted, and when the frequency shift amount and the phase shift amount satisfy the condition, the effect is the same as the time delay of the chirp. Therefore, a linear frequency modulation wave frequency shift phase shift method is realized in an optical domain, an optical true delay network is replaced, and a simple multi-channel beam forming network is realized.
In one embodiment of the present application, two pairs of optical-frequency combs with different free spectral widths are used, as shown in fig. 2, the optical-frequency comb generated by the optical-frequency comb generating module 1 is used to carry a broadband chirp signal, and for convenience of description, it is referred to as a signal optical comb; the optical frequency comb generated by the optical frequency comb generation module 2 is used as a local signal to be mixed with the signal optical comb, and is called a local optical comb. If the number of channels of the light-controlled beam forming network is M, the number of comb teeth of the signal optical comb and the local optical comb is also M. The free spectral width of the signal optical comb is slightly different from that of the local optical comb. And numbering the comb teeth of the local optical comb and the signal optical comb respectively, wherein the number value M is increased from 0 to M-1, and the optical comb teeth with the same number are defined as the mth group of optical comb teeth. Assuming that the optical combs with the number m equal to 0 are frequency aligned, the frequency difference between the optical combs can be expressed as m Δ FSR equal to m (FSR) due to the difference in free spectral width between the signal optical comb and the local optical comb1-FSR2) Wherein, FSR1Free spectral width, FSR, of signal optical comb2The free spectral width of the local optical comb.
Optionally, in an embodiment of the present application, the broadband optically controlled beamforming network 10 based on a dual-optical-frequency comb further includes: and the phase compensation module is connected with the output end of the first optical frequency comb generation module or the output end of the second optical frequency comb generation module and is used for adding a phase shift amount to each comb tooth of the second optical frequency comb signal or the first optical frequency comb signal so as to obtain a phase required by the linear frequency modulation wave signal.
In fig. 2, the electro-optical modulation module is connected to the first optical-frequency comb generating module, and in the second optical-frequency comb generating module, a phase compensation module may be disposed in an embodiment of the present application, and configured to perform phase compensation on the second optical-frequency comb signal.
Specifically, on the basis of the above-described embodiment, the phase compensation module adds a phase shift amount to each comb tooth of the local optical comb (i.e., the second optical-frequency comb signal). The phase shift quantity applied to the optical comb is a linear frequency modulation signal transmitted to the side band of the signal optical comb during photoelectric detection, and the phase shift quantity applied to the optical comb teeth with the number m by the phase shift module is as follows:
Δφm＝2πf0mΔτ+πKm2Δτ2,m＝0,1,..,M-1 (2)
in the embodiment of the application, after the frequency shift and the phase shift of the chirp are performed, the effect is equivalent to that of delaying the chirp, so that the embodiment of the application can set the size of the frequency shift amount and the phase shift amount according to the mainly realized delay amount.
Optionally, in an embodiment of the present application, the output module 500 includes: a coupler for coupling the first modulated signal and the second optical frequency comb signal; the optical filter bank is used for filtering the coupled signals; and the photoelectric detector group is used for carrying out photoelectric detection on the filtered signals.
In one embodiment of the present application, the function of the output module 500 can be realized by an optical filter bank and a photodetector bank, as shown in fig. 2. The multi-channel delayed microwave signal is output through the optical filter bank and the photoelectric detector, and can be used for supporting a multi-channel array antenna and realizing the function of a phased array radar.
Optionally, in an embodiment of the present application, the optical filter bank is composed of a plurality of optical filters with different center frequencies, wherein the number of the optical filters is consistent with the number of the beam forming network channels, and the center frequencies of the optical filters are aligned with the center frequencies of the first optical-frequency comb signal and the second optical-frequency comb signal.
Optionally, in an embodiment of the present application, the photodetector group includes a plurality of photodetectors, and the plurality of photodetectors are respectively connected to output ends of the filters of the optical filter group, and down-convert the optical carrier chirp to a baseband to obtain a delayed chirp component.
As shown in fig. 2, the Electro-optical modulation module includes an Electro-optical Modulator (EOM) for modulating a chirp signal with a preset pulse width, and modulating the chirp signal to the signal optical comb through Electro-optical modulation. The optical filter group is a group of filters with the same passband width and the passband center frequency distributed at equal intervals, and the number of the filters is the same as the number of channels of the beam forming network, namely M. As shown in fig. 3, the comb teeth with the same serial number (close frequency) as the signal optical comb and the local optical comb are divided into a group, and are filtered out by the group through the optical filter bank. The photoelectric detector module comprises M photoelectric detectors which are respectively connected with the output ends of the M optical filters of the optical filter bank and used for carrying out photoelectric detection on optical signals to obtain down-conversion chirp signals, and phase shift quantities added to each comb tooth of the local optical comb are transmitted to chirp signals.
After the optical comb group output by the optical filter is subjected to photoelectric detection, the initial frequency of the obtained down-conversion chirp signal is increased by the difference delta FSR of the free spectral width, namely the initial frequency of the chirp signal of the mth channel is
fm＝f0+Δfm＝f0+mΔFSR, m＝0,1,2,…,M-1 (3)
To support array element spacing of d, the target pointing angle is θBThe delay time interval between each array element of the phased array radar is delta taud＝dsinθBAnd c, the ratio of the total weight to the total weight of the product. See formula (1), the frequency shift quantity of each channel of the optically-controlled beam-forming network should satisfy Δ fm＝mKΔτd＝ mKdsinθBAnd c, the ratio of the total weight to the total weight of the product. Due to the fact thatTherefore, the difference Δ FSR between the free spectral widths of the signal comb and the local comb should satisfy
ΔFSR＝KdsinθB/c (4)
In summary, after passing through the light-controlled beam forming network provided by the present application, the expression of the m-th channel of the light-controlled beam forming network for outputting the chirped wave time domain is as follows
sm(t)＝cos(2πf0(t-mΔτd)+πK(t-mΔτd)2) (5)
Therefore, the multichannel light-operated beamforming is realized through frequency shift and phase shift, the link structure is simple, a delay line and a delay device are not needed, the network complexity is greatly simplified, and the multichannel delay amount can be continuously changed in a program-controlled manner.
The following describes in detail a broadband optically controlled beam forming network based on a dual optical frequency comb according to the present application with reference to the accompanying drawings and specific embodiments.
The network structure shown in fig. 4 can realize a 16-channel optically controlled beam forming network and support a 16-array element phased array radar transmitter. The specific structure is described as follows:
an Arbitrary Waveform Generator (AWG) generates a chirp signal of 8-12 GHz with a time width of 20us and a chirp rate K of 2 × 1014. The array element spacing of the phased array antenna array supported by the beamforming network is d ═ lambda12GHz1.25cm and the target beam pointing angle thetaB60 deg.. A 1550nm laser was used as the light source. Generating comb frequency interval of omega by cascading phase modulator and intensity modulatorRF1And ωRF2The electro-optical frequency comb of, wherein ωRF1＝30GHz,ωRF1-ωRF27.22kHz, the frequencies of two single-frequency microwave signals generated by the microwave signal source are respectively injected into the two optical frequency comb generating modules.
After being generated, the signal optical combs are injected into a double parallel Mach-Zehnder modulator (DPMZM) to carry out single-side modulation on each optical comb by restraining a carrier. After the local optical combs are generated, each optical comb is respectively subjected to phase shifting by using a wave former (Waveshaper), and the phase shifting quantity meets the following requirements:
Δφm＝2πf0mΔτ+πKm2Δτ2,m＝0,1,..,M-1
wherein the delay difference Δ τ between adjacent channels is dsin θBC 20.8ps, the initial frequency f of the chirp0＝8GHz。
Accordingly, the embodiments of the present application calculate the received signals at different azimuth angles of the far field by simulation, and obtain the result as shown in fig. 5, where (1) - (4) of fig. 5 are the received signals at azimuth angles of the far field of 60 °,45 °,30 °, and 0 °, respectively: at the designed 60 ° target direction (as in (1) of fig. 5), the same chirp signal as the transmitted signal can be received, and although distortion occurs at the edge of the window, such distortion is almost negligible due to the wide time width of the chirp. At 45 °,30 °, and 0 ° which are not the design target direction, as shown in (2) of fig. 5 to (4) of fig. 5, the correct chirp signal cannot be received.
As shown in fig. 6, a wideband phased array radar receiver capable of implementing 16-element arrays is shown. The basic working principle is as follows: laser generated by a narrow linewidth laser is divided into two parts, two pairs of optical combs with unequal repetition frequencies are generated respectively, the upper branch is a signal optical comb, and the lower branch is a local optical comb. The method comprises the steps of modulating received signals of each array element of the phased array radar to an optical comb by a carrier suppression single-side single modulation method, and combining the signals into an optical comb with a carrier signal through a wavelength division multiplexer. The signal optical comb and the local optical comb are coupled into a path of optical signal, comb teeth with the same serial number (close to frequency) in the signal optical comb and the local optical comb are divided into a group, and the group is filtered out through wavelength division multiplexing. And beating frequency between each group of optical combs to obtain a received linear frequency modulation wave signal which completes delay compensation. The output linear frequency modulation wave signals of each group are aligned in time and can be coherently superposed, and finally the signals are combined and sent to a rear-end data processing unit to realize phased array radar reception.
According to the broadband light-operated beam forming network based on the double optical frequency combs, a linear frequency modulation wave frequency shift phase shifting method realized in an optical domain is utilized to replace an optical true delay network, the simple multi-channel beam forming network is realized, and the broadband light-operated beam forming network has the characteristics of low system complexity, quick delay adjustment, capability of supporting application of a broadband phased array and the like. Therefore, the problems of large system and difficult delay regulation of the broadband light-controlled beam forming network are solved.
Next, a broadband optical control beam forming method based on a dual optical frequency comb according to an embodiment of the present application is described with reference to the drawings.
Fig. 7 is a schematic flow chart of a method of a broadband optically controlled beam forming network based on a dual optical frequency comb according to an embodiment of the present application.
As shown in fig. 7, the broadband light-controlled beamforming method based on the dual-optical-frequency comb includes the following steps:
in step S101, a first optical frequency comb signal of a first repetition frequency and a second optical frequency comb signal of a second repetition frequency are generated using continuous light, respectively.
In step S102, a preset wideband chirp signal is loaded on the first optical frequency comb signal and modulated to generate a first modulation signal.
In step S103, the first modulation signal and the second optical frequency comb signal are coupled and then filtered and subjected to photoelectric detection, so as to perform frequency shift and phase shift on the linear frequency modulated wave signal, and output a delayed microwave signal after broadband light-controlled beam forming.
Optionally, in an embodiment of the present application, before coupling the first modulation signal and the second optical-frequency comb signal, the method further includes: and adding a phase shift amount to each comb tooth of the second optical frequency comb signal to obtain a phase required by the chirp signal.
It should be noted that, the foregoing explanation on the embodiment of the broadband light-controlled beam forming network based on the dual-optical frequency comb is also applicable to the broadband light-controlled beam forming method based on the dual-optical frequency comb in the embodiment, and details are not described here.
According to the broadband light-operated beam forming method based on the double optical frequency combs, a linear frequency modulation wave frequency shift phase shifting method realized in an optical domain is utilized to replace an optical true delay network, a simple multi-channel beam forming network is realized, and the broadband light-operated beam forming method has the characteristics of low system complexity, quick delay adjustment, capability of supporting application of a broadband phased array and the like. Therefore, the problems of large system and difficult delay regulation of the broadband light-controlled beam forming network are solved.
In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or N embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "N" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more N executable instructions for implementing steps of a custom logic function or process, and alternate implementations are included within the scope of the preferred embodiment of the present application in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of implementing the embodiments of the present application.
It should be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
It will be understood by those skilled in the art that all or part of the steps carried out in the method of implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and the program, when executed, includes one or a combination of the steps of the method embodiments.

Claims (10)

1. A broadband light-operated beam forming network based on a double-optical frequency comb is characterized by comprising:
a light source for outputting continuous light;
a first optical frequency comb generation module for generating a first optical frequency comb signal of a first repetition frequency using the continuous light;
a second optical frequency comb generation module for generating a second optical frequency comb signal of a second repetition frequency using the continuous light;
the electro-optical modulation module is used for modulating a linear frequency modulation wave signal with a preset pulse width onto the first optical frequency comb signal to generate a first modulation signal;
and the output module is used for filtering and photoelectric detection after the first modulation signal and the second optical frequency comb signal are coupled so as to shift the frequency and the phase of the linear frequency modulation wave signal and output a delay microwave signal after broadband light-controlled beam forming.
2. The dual-optical-frequency-comb-based broadband optically-controlled beamforming network of claim 1, further comprising:
and the linear frequency modulation wave source is used for generating the linear frequency modulation wave signal with the preset pulse width and inputting the linear frequency modulation wave signal with the preset pulse width to the electro-optical modulation module.
3. The dual-optical-frequency-comb-based broadband optically-controlled beamforming network of claim 1, further comprising:
and the phase compensation module is connected with the output end of the second optical frequency comb generation module and is used for adding a phase shift amount to each comb tooth of the second optical frequency comb signal so as to obtain a phase required by the chirp signal.
4. The dual-optical-frequency-comb-based broadband optically-controlled beamforming network of claim 1, wherein the output module comprises:
a coupler for coupling the first modulated signal and the second optical-frequency comb signal;
the optical filter bank is used for filtering the coupled signals;
and the photoelectric detector group is used for carrying out photoelectric detection on the filtered signals.
5. The dual-optical-frequency-comb-based broadband optically-controlled beamforming network of claim 4, wherein the optical filter bank is composed of a plurality of optical filters with different center frequencies, wherein the number of the optical filters is consistent with the number of channels of the beamforming network, and the center frequencies of the optical filters are aligned with the center frequencies of the first optical-frequency comb signal and the second optical-frequency comb signal.
6. The dual-optical-frequency-comb-based broadband light-controlled beam-forming network as claimed in claim 5, wherein the photo detector set comprises a plurality of photo detectors, and the photo detectors are respectively connected to output ends of the filters of the optical filter set to down-convert the optical carrier chirp to a baseband to obtain a delayed chirp component.
7. The dual-optical-frequency-comb-based broadband optically-controlled beamforming network of claim 1, further comprising:
and the beam splitter is connected with the light source output end and used for splitting the continuous light and respectively inputting the split continuous light to the first optical frequency comb generating module and the second optical frequency comb generating module.
8. A method for broadband optical control beamforming based on dual optical frequency comb, wherein the system of any one of claims 1 to 7 is utilized, wherein the method comprises the following steps:
generating a first optical frequency comb signal of a first repetition frequency and a second optical frequency comb signal of a second repetition frequency using the continuous light, respectively;
carrying a preset broadband linear frequency modulation wave signal on the first optical frequency comb signal to modulate and generate a first modulation signal;
and coupling the first modulation signal and the second optical frequency comb signal, and then filtering and performing photoelectric detection to perform frequency shift and phase shift on the linear frequency modulation wave signal and output a delay microwave signal after broadband light-operated beam forming.
9. The method of claim 8, wherein prior to said coupling said first modulated signal and said second optical-frequency comb signal, further comprising:
and adding a phase shift amount to each comb tooth of the second optical frequency comb signal to obtain a phase required by the chirp signal.
10. A phased array radar, comprising: the dual-optical-frequency comb-based broadband optically controlled beamforming network of any of claims 1-7.
CN202210204709.8A 2022-03-03 2022-03-03 Broadband light-controlled beam forming network based on double-optical frequency comb and phased array radar Pending CN114594462A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116337777A (en) * 2023-05-29 2023-06-27 之江实验室 Broadband photoacoustic spectrum measurement system and method based on single optical comb
WO2024036521A1 (en) * 2022-08-17 2024-02-22 华为技术有限公司 Optical phased array circuit, transmitting device and signal transmission system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024036521A1 (en) * 2022-08-17 2024-02-22 华为技术有限公司 Optical phased array circuit, transmitting device and signal transmission system
CN116337777A (en) * 2023-05-29 2023-06-27 之江实验室 Broadband photoacoustic spectrum measurement system and method based on single optical comb
CN116337777B (en) * 2023-05-29 2023-08-29 之江实验室 Broadband photoacoustic spectrum measurement system and method based on single optical comb

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