CN114460562A - Radar signal generation system based on injection locking Fourier mode locking optoelectronic oscillator - Google Patents
Radar signal generation system based on injection locking Fourier mode locking optoelectronic oscillator Download PDFInfo
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- CN114460562A CN114460562A CN202210072340.XA CN202210072340A CN114460562A CN 114460562 A CN114460562 A CN 114460562A CN 202210072340 A CN202210072340 A CN 202210072340A CN 114460562 A CN114460562 A CN 114460562A
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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
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/484—Transmitters
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S1/00—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range
Abstract
The invention discloses a radar signal generating system based on an injection locking Fourier mode locking optoelectronic oscillator, which comprises: a laser for generating a single frequency optical signal; the first electro-optical modulator is used for converting the microwave signal into an optical signal; the second electro-optical modulator is used for converting the electric signal fed back by the electric power beam splitter into an optical signal; the delay optical fiber is used for providing enough delay and reducing the phase noise of the optical signal; the photoelectric detector is used for converting the optical signal subjected to noise reduction into an electric signal; an amplifier for amplifying an input electrical signal; the electric power beam splitter is used for splitting an input electric signal into two parts, wherein one part is used as output to obtain a microwave signal, and the other part is fed back to the second electro-optical modulator again; and the electric signal source is used for injecting an external microwave signal into the first electro-optical modulator. The invention changes the parameters of the external injection signal through the electric signal source, can realize the reconstruction of the output waveform, and has simple adjusting method and quick response.
Description
Technical Field
The invention relates to the technical field of photoelectrons, in particular to a radar signal generating system based on an injection locking Fourier mode locking photoelectric oscillator.
Background
With the development of science and technology, the existing systems of radar, communication, electronic warfare and the like are developed in the direction of multiple functions. For example, in a radar system, in order to meet the requirements of the system for various functions such as target detection, identification, imaging, etc., a radar transmitter is required to have the capability of generating and switching various waveforms. On the other hand, at the present stage, the space electromagnetic environment tends to be complicated, and radar detection targets tend to be diversified, so that higher requirements are also put on the operating frequency and bandwidth of a radar system.
The transmitted signal of the conventional radar is usually generated by an electronic technology, and although the conventional radar has the advantages of being tunable and reconfigurable, indexes such as the center frequency, the bandwidth and the phase noise of the generated signal are limited by the bottleneck of an electronic system, so that the conventional radar is difficult to adapt to the requirements of the radar, the electronic warfare and other systems at the present stage. With the development of microwave photonics, signal generation based on the microwave photon technology has the advantages of low loss, large bandwidth and the like, and is widely applied. The photoelectric oscillator is a main mode for generating high-quality microwave signals based on the microwave photon technology at present, and generates reference signals with phase noise as low as-160 dBc/Hz @10kHz by utilizing the photoelectric oscillator with a high Q value, so that the performances of systems such as radars and the like are greatly improved. On the other hand, with the development of the technology, the existing photoelectric oscillator can not only generate a single-frequency continuous microwave signal, but also generate various microwave signals of different types, such as a broadband signal, a pulse signal and the like, by utilizing technologies such as fourier domain mode locking, injection locking, active mode locking and the like. However, the signal generated by the conventional optoelectronic oscillator still has a single form, and the waveform reconstruction performance is not good.
Research on a fourier domain mode-locked optoelectronic oscillator begins in recent years, for example, chinese patent application CN110176709A discloses an integrated fourier domain mode-locked optoelectronic oscillator and an application and communication system, the integrated fourier domain mode-locked optoelectronic oscillator includes an optoelectronic chip and an electronic chip, the optoelectronic chip includes a laser, a modulator, an optical notch filter and a photodetector connected by an optical waveguide; the electronic chip comprises an electric amplifier and a power divider which are connected through coplanar microwave waveguides. After the broadband microwave signal generation realized by the concept of Fourier domain mode locking is reported in sequence by Beijing post and telecommunications university and semiconductor research institute of Chinese academy, research on Fourier domain mode locking photoelectric oscillators is rapidly developed. Then, based on the Fourier domain mode locking concept, researchers at home and abroad successively realize the generation of various broadband signals such as double chirp signals, frequency variable signals, phase coding signals and the like, and the functions of the Fourier domain mode locking photoelectric oscillator are greatly enriched. On the other hand, an injection locking technique that is often used in microwave oscillators has also been introduced into optoelectronic oscillators in recent years. By using the injection locking technology, mode competition can be effectively inhibited, the side mode inhibition ratio and the system stability are improved, and the method becomes another mainstream research direction. However, at present, neither the injection-locked optoelectronic oscillator nor the fourier domain mode-locked optoelectronic oscillator can achieve microwave signal generation with tunable and reconfigurable performance and switchable waveform. Therefore, the research on a signal generation method capable of meeting the requirement of the multifunctional radar on the emission waveform at the present stage is a problem which needs to be solved urgently at present.
Disclosure of Invention
The invention aims to provide a radar signal generating system based on an injection locking Fourier mode locking optoelectronic oscillator, and aims to solve the problem that the existing radar signal generating system cannot generate tunable and reconfigurable microwave signals with switchable waveforms.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the invention relates to a radar signal generating system based on an injection locking Fourier mode locking photoelectric oscillator, which comprises a photoelectric oscillator and an electric signal source; the optoelectronic oscillator comprises:
the laser is used for generating a single-frequency optical signal and outputting the single-frequency optical signal to the first electro-optical modulator;
the first electro-optical modulator is used for receiving the optical signal from the laser and the microwave signal from the electric signal source, converting the microwave signal into an optical signal and outputting the modulated optical signal to the second electro-optical modulator;
the second electro-optical modulator is used for receiving the modulated optical signal from the first electro-optical modulator and the electric signal fed back by the electric power beam splitter, converting the electric signal into an optical signal and outputting the optical signal to the delay optical fiber;
the delay optical fiber is used for providing enough delay and reducing the phase noise of the optical signal;
the photoelectric detector is used for converting the optical signal subjected to noise reduction into an electric signal and outputting the electric signal to the amplifier;
an amplifier for amplifying the input electrical signal and outputting the amplified electrical signal to the electrical power splitter;
the electric power beam splitter is used for splitting an input electric signal into two parts, wherein one part is used as output to obtain a microwave signal, and the other part is fed back to the second electro-optical modulator again;
the second electro-optical modulator, the delay optical fiber, the photoelectric detector, the amplifier and the electric power beam splitter form a loop;
and the electric signal source is used for injecting an external microwave signal into the first electro-optical modulator.
Preferably, the delay fiber makes the signal transmit in the loop for a period equal to an integral multiple of the signal's own period, that is
T＝nTs (1)
Wherein T is the time of one week of signal transmission in the ring cavity, TSN is a positive integer for the period of the signal itself.
Preferably, the laser is a semiconductor laser or a fiber laser.
Preferably, the first electro-optic modulator and the second electro-optic modulator are broadband modulators or polarization modulators.
Preferably, the first electro-optical modulator and the second electro-optical modulator are mach-zehnder electro-optical intensity modulators.
Preferably, the delay fiber is a single mode fiber or a zero dispersion fiber.
Preferably, the bandwidth of the photodetector is 1-100 GHz.
Preferably, the bandwidth of the amplifier is 50kHz-100GHz, and the gain is more than 10 dB.
Preferably, the operating bandwidth of the electrical power splitter is 1-100 GHz.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
1. the radar signal generating system based on the injection locking Fourier mode locking photoelectric oscillator is characterized in that an electric signal source used for injecting external microwave signals into the second photoelectric modulator is connected to the photoelectric oscillator, the output waveform can be reconfigured by changing parameters of the external injection signals through the electric signal source, and the radar signal generating system has the advantages of simple adjusting method, quick response and the like.
2. The photoelectric oscillator used in the radar signal generating system based on the injection locking Fourier mode locking photoelectric oscillator can generate tunable and reconfigurable broadband microwave signals, and high-frequency broadband signal output can be realized only by a low-frequency narrow-band signal source.
3. The signal output by the radar signal generating system based on the injection locking Fourier mode locking photoelectric oscillator combines the hyperfine regulation and control of the traditional microwave signal generation and the low phase noise characteristic of the photoelectric oscillator, can be widely applied to the fields of radar, communication, electronic warfare and the like, and has wide application range.
Drawings
FIG. 1 is a block schematic diagram of a radar signal generating system based on an injection-locked Fourier-mode locked optoelectronic oscillator according to the present invention;
FIG. 2 is a spectral plot of a chirp signal generated based on the system of FIG. 1;
FIG. 3 is a graph of the results of a partial amplification of a chirp signal generated based on the system of FIG. 1;
FIG. 4 is a time domain waveform of a chirp signal generated based on the system of FIG. 1;
fig. 5 is a graph of the phase noise of a chirp signal generated based on the system of fig. 1.
Detailed Description
For further understanding of the present invention, the present invention will be described in detail with reference to examples, which are provided for illustration of the present invention but are not intended to limit the scope of the present invention.
Referring to fig. 1, the radar signal generating system based on the injection locking fourier mode locking optoelectronic oscillator according to the present invention includes an optoelectronic oscillator and an electrical signal source 8.
The optoelectronic oscillator comprises a laser 1, a first electro-optical modulator 2, a second electro-optical modulator 3, a time delay optical fiber 4, a photoelectric detector 5, an amplifier 6 and an electric power beam splitter 7. The output end of the laser 1 is connected with the optical input end of the first electro-optical modulator 2, the optical output end of the first electro-optical modulator 2 is connected with the optical input end of the second electro-optical modulator 3, the optical output end of the second electro-optical modulator 3 is connected with the input end of the delay optical fiber 4, the output end of the delay optical fiber 4 is connected with the input end of the photoelectric detector 5, and the optical fibers are used for connection among the devices; after the photoelectric conversion is completed by the photoelectric detector 5, the output end of the photoelectric detector is connected with the input end of the amplifier 6 through a cable, the output end of the amplifier 6 is connected with the input end of the electric power beam splitter 7 through a cable, one of two output ports of the electric power beam splitter 7 is connected with the electric input port of the second electro-optical modulator 3, and the other port is used for outputting signals, so that the second electro-optical modulator 3, the delay optical fiber 4, the photoelectric detector 5, the amplifier 6 and the electric power beam splitter 7 form a loop. The output of the electrical signal source 8 is connected to the electrical input port of the first electro-optical modulator 2. The connection between the electric signal source 8 and the first electro-optical modulator 2, the connection between the photoelectric detector 5 and the amplifier 6, and the connection between the amplifier 6 and the electric power beam splitter 7 are all connected by cables.
The radar signal generating system has the following functions:
the laser 1 is used for generating a single-frequency optical signal and outputting the single-frequency optical signal to the first electro-optical modulator 2;
the first electro-optical modulator 2 is used for receiving the optical signal from the laser 1 and the microwave signal from the electric signal source 8, converting the microwave signal into an optical signal, and outputting the modulated optical signal to the second electro-optical modulator 3;
the second electro-optical modulator 3 is used for receiving the modulated optical signal from the first electro-optical modulator 2 and the electric signal fed back by the electric power beam splitter 7, converting the electric signal into an optical signal, and outputting the optical signal to the delay optical fiber 4;
the delay fiber 4 is used to provide sufficient delay to reduce the phase noise of the optical signal, and in order to realize fourier domain mode locking, the signal must be transmitted in the loop for a period equal to an integral multiple of the period of the signal itself, that is, the time of one cycle of the signal must be equal to the integral multiple of the period of the signal itself
T＝nTs (1)
Wherein T is the time of one week of signal transmission in the ring cavity, TSIs the signal period, n is a positive integer;
a photodetector 5 for converting the optical signal after noise reduction into an electrical signal and outputting the electrical signal to an amplifier 6;
the amplifier 6 is configured to amplify an input electrical signal and output the amplified electrical signal to the electrical power splitter 7;
the electric power beam splitter 7 is used for splitting the input electric signal into two parts, one part is used as output to obtain a microwave signal, and the other part is fed back to the second electro-optical modulator 3 again;
the electrical signal source 8 is used to inject an external microwave signal into the first electro-optical modulator 2.
In this embodiment, the laser 1 is a semiconductor laser or a fiber laser; the first electro-optical modulator 2 and the second electro-optical modulator 3 are broadband modulators or polarization modulators, preferably Mach-Zehnder electro-optical intensity modulators; the delay optical fiber 4 is a single mode optical fiber or a zero dispersion optical fiber; the bandwidth of the photoelectric detector is 1-100 GHz; the bandwidth of the amplifier is 50kHz-100GHz, and the gain is more than 10 dB; the working bandwidth of the electric power beam splitter is 1-100 GHz.
The process of the radar signal generation system based on the injection locking Fourier mode locking optoelectronic oscillator to generate the radar transmission signal comprises the following steps:
when no external microwave signal is injected, the system is equivalent to a common photoelectric oscillator structure, and after the microwave signal is injected into the photoelectric oscillator by using an external electric signal source, the generated optical sideband is used as a light source of the photoelectric oscillator to be input into the oscillator, so that signal frequency multiplication is realized. If the injection signal is a broadband signal, the input signal changes with time, and injection locking of the broadband signal can be realized by adjusting the power, the frequency and the like of the input signal. In order to ensure that the broadband signal stably oscillates in the ring cavity, the condition that the delay of the ring cavity is equal to integral multiple of the period of the input signal, namely the condition of mode locking in a Fourier domain, is met, and the generation of various radar waveforms can be realized by changing the waveform of the injected signal.
Fig. 2 and 3 are a system output spectrum and its partial amplification when the injection signal is a wideband chirp signal according to an embodiment of the present invention. The center frequency of the injected signal is 14.06GHz, the bandwidth is 200MHz, and as can be seen from FIGS. 2 and 3, the signal-to-noise ratio is close to 80dB under the condition of 3kHz resolution. Fig. 4 is a corresponding time domain waveform, from which it can be seen that the signal period is 2.3 mus, corresponding to the oscillation loop delay, the amount of which can be adjusted by varying the delay unit length. Fig. 5 shows a phase noise plot of the resulting signal, which is seen to be below-120 dBc/Hz near 10kHz frequency offset due to the low phase noise characteristics of the oscillator.
Furthermore, the above definitions of the various elements and methods are not limited to the specific structures, shapes or modes mentioned in the embodiments, and those skilled in the art may simply well-know substitutions for their structures, such as: the positions of the electric power splitter and the electric amplifier can be interchanged; an optical amplifier can be added at any position of the optical path part in the ring cavity to amplify the signal; the light path can be added with a dimmable delay line or a filter or a phase shifter and the like to meet the delay requirement. Also, the number, shape and size of the devices shown in the drawings may be modified depending on the actual situation.
The present invention has been described in detail with reference to the embodiments, but the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Claims (9)
1. A radar signal generation system based on an injection locking Fourier mode locking optoelectronic oscillator is characterized in that:
it comprises an optoelectronic oscillator and an electrical signal source; the optoelectronic oscillator comprises:
the laser is used for generating a single-frequency optical signal and outputting the single-frequency optical signal to the first electro-optical modulator;
the first electro-optical modulator is used for receiving the optical signal from the laser and the microwave signal from the electric signal source, converting the microwave signal into an optical signal and outputting the modulated optical signal to the second electro-optical modulator;
the second electro-optical modulator is used for receiving the modulated optical signal from the first electro-optical modulator and the electric signal fed back by the electric power beam splitter, converting the electric signal into an optical signal and outputting the optical signal to the delay optical fiber;
the delay optical fiber is used for providing enough delay and reducing the phase noise of the optical signal;
the photoelectric detector is used for converting the optical signal subjected to noise reduction into an electric signal and outputting the electric signal to the amplifier;
an amplifier for amplifying the input electrical signal and outputting the amplified electrical signal to the electrical power splitter;
the electric power beam splitter is used for splitting an input electric signal into two parts, wherein one part is used as output to obtain a microwave signal, and the other part is fed back to the second electro-optical modulator again;
the second electro-optical modulator, the delay optical fiber, the photoelectric detector, the amplifier and the electric power beam splitter form a loop;
and the electric signal source is used for injecting an external microwave signal into the first electro-optical modulator.
2. The injection-locked fourier-mode-locked optoelectronic oscillator-based radar signal generating system of claim 1, wherein: the time delay optical fiber ensures that the time of one circle of signal transmission in the loop is equal to integral multiple of the period of the signal, namely
T＝nTs (1)
Wherein T is the signal transmitted in the ring cavity for one cycleTime, TsN is a positive integer for the period of the signal itself.
3. The injection-locked fourier-mode-locked optoelectronic oscillator-based radar signal generating system of claim 1, wherein: the laser is a semiconductor laser or a fiber laser.
4. The injection-locked fourier-mode-locked optoelectronic oscillator-based radar signal generating system of claim 1, wherein: the first electro-optic modulator and the second electro-optic modulator are broadband modulators or polarization modulators.
5. The injection-locked fourier-mode-locked optoelectronic oscillator-based radar signal generating system of claim 4, wherein: the first electro-optical modulator and the second electro-optical modulator are Mach-Zehnder electro-optical intensity modulators.
6. The injection-locked fourier-mode-locked optoelectronic oscillator-based radar signal generating system of claim 1, wherein: the delay fiber is a single mode fiber or a zero dispersion fiber.
7. The injection-locked fourier-mode-locked optoelectronic oscillator-based radar signal generating system of claim 1, wherein: the bandwidth of the photoelectric detector is 1-100 GHz.
8. The injection-locked fourier-mode-locked optoelectronic oscillator-based radar signal generating system of claim 1, wherein: the bandwidth of the amplifier is 50kHz-100GHz, and the gain is larger than 10 dB.
9. The injection-locked fourier-mode-locked optoelectronic oscillator-based radar signal generating system of claim 1, wherein: the working bandwidth of the electric power beam splitter is 1-100 GHz.
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