CN113691321B - Low-power microwave signal integrated processing method and integrated receiver - Google Patents

Low-power microwave signal integrated processing method and integrated receiver Download PDF

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CN113691321B
CN113691321B CN202110979626.1A CN202110979626A CN113691321B CN 113691321 B CN113691321 B CN 113691321B CN 202110979626 A CN202110979626 A CN 202110979626A CN 113691321 B CN113691321 B CN 113691321B
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洪俊
贺卫
邓元祥
王小虎
严亚周
彭志强
李新瑞
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Hunan Institute of Technology
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Abstract

The invention relates to a micro-low power microwave signal integrated processing method and an integrated receiver, wherein firstly, the invention realizes the extraction and amplification of low power microwave signals through a photoelectric mixed loop, modulates optical carriers, and extracts modulated optical signals by utilizing phase shift fiber bragg gratings; meanwhile, generating a photoelectric mixed oscillation signal through another photoelectric mixed loop to obtain a local oscillation optical signal coherent with the modulated optical signal; then, the envelope detection function of the photoelectric detector is used for realizing the frequency mixing of the modulated optical signal and the local oscillator optical signal and realizing the down-conversion function of the microwave signal; and finally, suppressing out-of-band noise through a low-pass filter to realize intermediate frequency signal output. The invention is based on the advantages of large bandwidth, low loss, anti-electromagnetic interference and the like of the optical fiber, completes the receiving of low-power microwave signals in the optical domain, has the anti-electromagnetic interference function while ensuring extremely low introduced noise, effectively inhibiting image signals and simplifying system complexity, and realizes the integrated receiving of integrating amplification, filtering and down-conversion functions.

Description

Low-power microwave signal integrated processing method and integrated receiver
Technical Field
The invention relates to the crossing field of microwave technology and optical communication technology, in particular to a low-power microwave signal integrated processing method and an integrated receiver.
Background
The detection of microwave signals in complex electromagnetic environments has important application in the fields of remote sensing and remote measuring, radio frequency communication, radars, electronic warfare systems and the like.
In a complex electronic environment, useful low-power microwave signals may coexist with a complex noise environment, and the detection of weak microwave signals has certain difficulty. The traditional microwave signal receiving mainly comprises three parts of amplification, filtering and down-conversion: the method comprises the steps of receiving microwave signals through an antenna, amplifying the microwave signals, performing down-conversion processing after filtering, finally realizing intermediate frequency output, directly performing analog/digital conversion on the intermediate frequency output signals, converting the intermediate frequency output signals into digital signals, and finishing the signal processing process through a digital signal processor. In a traditional microwave signal receiving system, a microwave amplifier is required to be introduced for realizing an amplification function, belongs to a typical active device, and can introduce relatively large noise; the Q value of the filter in a microwave frequency band is low, the bandwidth is large, and out-of-band noise cannot be effectively inhibited; meanwhile, the down-conversion process needs a mixer and a local oscillator to complete, and also generates additional noise, image signals and other interference factors.
Disclosure of Invention
The invention aims to provide a low-power microwave signal integrated processing method, which aims to break through the limitation of the traditional electronic microwave receiving technology, realize the integrated processing of the amplification, filtering and down-conversion processes, ensure extremely low introduced noise, effectively inhibit image signals, simplify the complexity of a system and simultaneously have anti-electromagnetic interference performance.
In order to achieve the purpose, the invention adopts the following technical scheme: a low-power microwave signal integrated processing method comprises the following steps:
firstly, extracting and amplifying low-power microwave signals through a photoelectric hybrid loop, modulating optical carriers, and extracting modulated optical signals by using phase-shift fiber gratings; meanwhile, a photoelectric mixed oscillation signal is generated through another photoelectric mixed loop based on self-oscillation of a loop, and a local oscillation optical signal coherent with the modulated optical signal is extracted by utilizing a phase-shift fiber grating;
then, the envelope detection function of the photoelectric detector is used for realizing the frequency mixing of the modulated optical signal and the local oscillator optical signal and realizing the down-conversion function of the microwave signal;
and finally, suppressing out-of-band noise through a low-pass filter to realize intermediate frequency signal output.
Specifically, an upper photoelectric hybrid loop and a lower photoelectric hybrid loop are constructed, a tunable laser is used for generating an optical carrier signal, and the optical carrier signal is shunted to the upper photoelectric hybrid loop and the lower photoelectric hybrid loop after passing through an optical coupler 1; receiving a low-power microwave signal to be processed through an antenna and inputting the low-power microwave signal to the upper photoelectric mixed loop, completing extraction and amplification of the low-power microwave signal to be processed through the upper photoelectric mixed loop, modulating an optical carrier, extracting a modulated optical signal through a phase-shift fiber grating 1 and outputting the modulated optical signal; the lower photoelectric hybrid loop generates a photoelectric hybrid oscillation signal, and then the photoelectric hybrid oscillation signal is extracted by the phase fiber grating 2 and outputs a local oscillation optical signal coherent with the modulated optical signal.
Further, in the upper photoelectric hybrid loop, a to-be-processed low-power microwave signal received by an antenna is introduced through the electric coupler 2, phase modulation of an optical carrier is achieved through the electro-optical phase modulator 1, then the optical carrier enters the optical amplifier 1 to be amplified, the amplified optical signal enters the phase-shifting fiber grating 1 through the circulator 1, the reflected optical signal is restored into an electric signal through the photoelectric detector 1, a main channel electric signal returns to the electro-optical phase modulator 1 to be circulated for the next time, the circulating electric signal achieves partial output through the electric coupler 1, original frequency signal output is completed, meanwhile, phase modulation of the microwave signal on the optical carrier is achieved in the upper photoelectric hybrid loop, narrow-band filtering is achieved on one sideband through the phase-shifting fiber grating 1, and a modulated optical signal is output.
Furthermore, in the lower photoelectric hybrid loop, an optical signal output by the optical coupler 1 is used as an optical carrier of the loop through the electro-optic phase modulator 2, a point noise signal of the loop is subjected to phase modulation on the optical carrier through the electro-optic phase modulator 2 and then enters the optical amplifier 2 to be amplified, one sideband of the point noise signal is suppressed through the circulator 2 and then enters the optical fiber delay line to realize optical delay, the point noise signal is restored into an electric signal through the photoelectric detector 2, and single-frequency output is realized through the narrow-band filter and then returns to the electro-optic phase modulator 2 to perform the next round of circulation; in the process, for some specific frequency point signals, if the specific frequency point signals meet the Barkhausen condition, the signals of the frequency point can realize positive feedback to generate oscillation, and finally, local oscillation optical signal output coherent with the modulated optical signals is realized through the phase-shifting fiber grating 2.
Wherein, the wavelength of the tunable laser is adjusted to ensure that
Figure BDA0003228561400000031
The signal in the upper photoelectric mixed loop is continuously amplified and enhanced by the optical amplifier 1 in the photoelectric-photoelectric conversion process, so that the original frequency signal is output, and one side band signal is transmitted through the phase-shift fiber grating 1Discharging; in the above formula, λ1For adjusted laser wavelength, lambda2The phase shift fiber grating 1 is used for trapping wave length, omega is the frequency of receiving microwave, and n is the refractive index of the fiber;
obtaining a single-frequency oscillation signal by adjusting the optical fiber delay amount and a narrow-band filter in the lower photoelectric hybrid loop, and modulating an optical carrier by using the signal to realize local oscillation optical signal output;
the modulated optical signal output by the phase-shift fiber grating 1 and the local oscillator optical signal which is coherent with the modulated optical signal output by the phase-shift fiber grating 2 are input into the optical coupler 2 together, beat frequency is carried out by the photoelectric detector 3, down-conversion of the microwave signal is realized through optical difference frequency, and finally out-of-band noise is suppressed through the low-pass filter, so that intermediate frequency output is realized.
In addition, the invention also relates to a low-power microwave signal integrated receiver for processing the received low-power microwave signal by adopting the low-power microwave signal integrated processing method.
Specifically, the low-power microwave signal integrated receiver comprises an antenna, a tunable laser, an optical coupler 1, an upper photoelectric hybrid loop, a lower photoelectric hybrid loop, a phase-shift fiber grating 1, a phase-shift fiber grating 2, an optical coupler 2, a photoelectric detector 3 and a low-pass filter;
the tunable laser generates an optical carrier signal, and the optical carrier signal is shunted to the upper photoelectric mixed loop and the lower photoelectric mixed loop after passing through the optical coupler 1; the antenna receives a low-power microwave signal to be processed and inputs the low-power microwave signal into the upper photoelectric hybrid loop, the upper photoelectric hybrid loop extracts and amplifies the low-power microwave signal to be processed, an optical carrier is modulated, and then a modulated optical signal is extracted and output by using the phase-shifted fiber grating 1; the lower photoelectric hybrid loop generates a photoelectric hybrid oscillation signal, and then a local oscillation optical signal coherent with the upper loop is extracted and output through the phase fiber grating 2;
the modulated optical signal output by the phase-shift fiber grating 1 and the local oscillator optical signal output by the phase-shift fiber grating 2 are input into the optical coupler 2 together, beat frequency is carried out by the photoelectric detector 3, down-conversion of the microwave signal is realized through optical difference frequency, and finally out-of-band noise is suppressed through the low-pass filter, so that intermediate frequency output is realized.
The upper photoelectric hybrid loop comprises an electro-optic phase modulator 1, an optical amplifier 1, an optical circulator 1, a photoelectric detector 1, an electric coupler 1 and an electric coupler 2 which are sequentially connected end to end, wherein the electro-optic phase modulator 1 is connected with one output port of the optical coupler 1, the electric coupler 2 is connected with an antenna, and the optical circulator 1 is also connected with a phase-shifting fiber grating 1;
the low-power microwave signal to be processed received by the antenna is introduced into an upper photoelectric mixed loop through an electric coupler 2, the phase modulation of an optical carrier is realized through an electro-optical phase modulator 1 and then enters an optical amplifier 1 to be amplified, the amplified optical signal enters a phase-shifting optical fiber grating 1 through a circulator 1, the reflected optical signal is restored into an electric signal through a photoelectric detector 1, a main channel electric signal returns to the electro-optical phase modulator 1 to be circulated for the next time, the circulating electric signal realizes partial output through the electric coupler 1, the phase modulation of the microwave signal on the optical carrier is realized in the upper photoelectric mixed loop, and finally, the narrow-band filtering is realized on one sideband through the phase-shifting optical fiber grating 1, so that the output of a modulated optical signal is realized.
The lower photoelectric hybrid loop comprises an electro-optic phase modulator 2, an optical amplifier 2, an optical circulator 2, an optical fiber delay line, a photoelectric detector 2 and a narrow-band filter which are sequentially connected end to end, wherein the electro-optic phase modulator 2 is connected with the other output port of the optical coupler 1, and the optical circulator 2 is also connected with a phase-shifting fiber grating 2;
an optical signal output by the optical coupler 1 is used as an optical carrier of a lower photoelectric hybrid loop through the electro-optic phase modulator 2, a point noise signal of the lower photoelectric hybrid loop is subjected to phase modulation on the optical carrier through the electro-optic phase modulator 2 and then enters the optical amplifier 2 to be amplified, one sideband of the point noise signal is inhibited through the circulator 2 and then enters the optical fiber delay line to realize optical delay, then the point noise signal is restored into an electric signal through the photoelectric detector 2, single-frequency output is realized through the narrow-band filter, and then the single-frequency output returns to the electro-optic phase modulator 2 to perform the next round of circulation; in the process, for some specific frequency point signals, if the specific frequency point signals meet the Barkhausen condition, the signals of the frequency point can realize positive feedback to generate oscillation, and finally, narrow-band filtering is realized on one sideband through the phase-shifting fiber grating 2, so that local oscillation optical signal output coherent with the modulated optical signal is realized.
Further, in the low-power microwave signal integrated receiver, the tunable laser wavelength is adjusted so that
Figure BDA0003228561400000051
The signal in the upper photoelectric mixed loop is continuously amplified and enhanced by the optical amplifier 1 in the photoelectric-photoelectric conversion process, so that the original frequency signal is output, and one side band signal enters the optical coupler 2 through the phase-shifted fiber grating 1; in the above formula, λ1For adjusted laser wavelength, λ2The phase shift fiber grating 1 is used for trapping wave length, omega is the frequency of receiving microwave, and n is the refractive index of the fiber; a single-frequency oscillation signal is obtained by adjusting the optical fiber delay amount and the narrow-band filter in the lower photoelectric hybrid loop, and the local oscillation optical signal output can be realized after the signal modulates the optical carrier.
Compared with the prior art, the invention has at least the following beneficial effects: the invention breaks through the 'electronic bottleneck' of the traditional channelized receiving system, completes the receiving of low-power microwave signals in the optical domain based on the advantages of large bandwidth, low loss, electromagnetic interference resistance and the like of optical fibers, has electromagnetic interference resistance while ensuring extremely low introduced noise, effectively inhibiting image signals and simplifying system complexity, and realizes the integrated processing of integrating amplification, filtering and down-conversion functions.
Drawings
FIG. 1 is a low power microwave signal processing flow diagram;
FIG. 2 is a block diagram of a low power microwave signal integral receiver;
fig. 3 is a diagram of a single sideband modulation signal analysis implemented based on a phase-shifted fiber grating.
Detailed Description
To facilitate a better understanding of the present invention as compared to the prior art by those skilled in the art, the present invention is further described below in conjunction with the accompanying drawings, it being understood that the following detailed description is provided for illustration only and not for the purpose of limiting the invention specifically.
Fig. 1 is a flowchart of integrated processing of low-power microwave signals according to the present invention, which includes three processes of generating modulated optical signals + generating modulated local oscillator light sources, and implementing down-conversion and low-pass filtering by optical domain mixing, specifically:
firstly, extracting and amplifying a low-power microwave signal based on an opto-electric hybrid loop, modulating an optical carrier, and extracting a modulated optical signal by using the optical characteristics of a phase-shift fiber grating (for simplification, the modulated optical signal is uniformly referred to as a "modulated optical signal"); meanwhile, another photoelectric hybrid loop is constructed, a photoelectric hybrid oscillation signal is generated based on the self-oscillation of the loop, and a local oscillation light source (namely a local oscillation light signal coherent with the modulated light signal) is extracted based on the optical characteristics of the phase-shift fiber grating.
Then, mixing is performed on the modulated optical signal and the local oscillator optical signal (i.e., the modulated oscillating optical signal) based on the envelope detection characteristic of the photodetector, so as to achieve down-conversion output.
And finally, passing the down-conversion output signal through a low-pass filter to realize intermediate frequency output.
The signals output by the intermediate frequency are converted into digital signals through an analog-to-digital converter, and then the digital signals are further processed by using the existing digital signal processing method.
The specific structure and principle of the low power microwave signal integrated receiver implementing the above-mentioned process will be described in detail below.
Fig. 2 is a block diagram of an integrated receiver according to the present invention. As shown in fig. 2, the low-power microwave signal integrated receiver includes an antenna, a tunable laser, an optical coupler 1, an upper opto-electric hybrid loop (hereinafter, referred to as "upper loop"), a lower opto-electric hybrid loop (hereinafter, referred to as "lower loop"), a phase-shifted fiber grating 1, a phase-shifted fiber grating 2, an optical coupler 2, a photodetector 3, and a low-pass filter. The tunable laser generates an optical carrier signal, and the optical carrier signal is shunted to the upper loop and the lower loop after passing through the optical coupler 1. Receiving a low-power microwave signal to be processed through an antenna and inputting the low-power microwave signal to be processed into an upper loop, finishing extraction and amplification of the low-power microwave signal to be processed by the upper loop, modulating an optical carrier, and extracting and outputting a modulated optical signal by using a phase-shift fiber grating 1; the lower loop aims to generate an optical-electric mixed oscillation signal, and then a local oscillation optical signal coherent with the upper loop is extracted and output through the phase fiber grating 2. The modulated optical signal output by the phase-shift fiber grating 1 and the local oscillator optical signal output by the phase-shift fiber grating 2 are input into the optical coupler 2 together, beat frequency is carried out by the photoelectric detector 3, down-conversion of the microwave signal is realized through optical difference frequency, and finally out-of-band noise is suppressed through the low-pass filter, so that intermediate frequency output is realized.
Specifically, in fig. 2, the upper loop is composed of an electro-optical phase modulator 1, an optical amplifier 1, an optical circulator 1, a photodetector 1, an electric coupler 1, and an electric coupler 2, which are sequentially connected end to end. In addition, the electro-optical phase modulator 1 is also connected with one output port of the optical coupler 1, the electric coupler 2 is connected with an antenna, and the optical circulator 1 is also connected with the phase-shifting fiber grating 1. After receiving a low-power microwave signal to be processed, the antenna introduces an upper loop through the electric coupler 2, realizes phase modulation on an optical carrier through the electro-optic phase modulator 1, then enters the optical amplifier 1 to be amplified, and the amplified optical signal enters the phase-shifting fiber grating 1 through the circulator 1. The reflected optical signal enters the photoelectric detector 1 to be reduced into an electric signal, and the main trunk electric signal returns to the electro-optic phase modulator 1 to be circulated for the next time; and partial output of the partial circulating electric signal is realized through the electric coupler 1, namely, the original frequency signal output is finished. Meanwhile, the phase modulation of the microwave signal on the optical carrier is realized based on the photoelectric hybrid loop, and the phase-shift fiber grating can realize narrow-band filtering on one sideband, so that the output of the modulated optical signal is realized.
As mentioned before, the purpose of the lower loop is to generate an opto-electric hybrid oscillator signal and output a local oscillator optical signal coherent with the upper loop. In fig. 2, the lower loop is composed of an electro-optical phase modulator 2, an optical amplifier 2, an optical circulator 2, an optical fiber delay line, a photodetector 2, and a narrow-band filter, which are sequentially connected end to end. In addition, the electro-optical phase modulator 2 is also connected with the other output port of the optical coupler 1, and the optical circulator 2 is also connected with the phase-shifting fiber grating 2. An optical signal output by the optical coupler 1 is used as an optical carrier of a loop through the electro-optic phase modulator 2, a point noise signal of the loop is subjected to phase modulation on the optical carrier through the electro-optic phase modulator 2 and then enters the optical amplifier 2 to be amplified, then enters an optical fiber delay line to realize optical delay after being inhibited on one sideband through the circulator 2, is reduced into an electric signal through the photoelectric detector 2, and finally is subjected to single-frequency output through the narrow-band filter and then returns to the electro-optic phase modulator 2 to perform next round of circulation. For some specific frequency point signals, if the frequency point signals meet the Barkhausen condition (the open loop gain is larger than 1, and the phase difference is an integral multiple of 2 pi), the frequency point signals can realize positive feedback to generate oscillation. Based on the optical characteristics of the phase-shift fiber grating, the local oscillator optical signal output can be realized in the phase-shift fiber grating 2. The modulated optical signal output by the upper loop through the phase-shifting fiber bragg grating 1 and the local oscillator optical signal output by the lower loop through the phase-shifting fiber bragg grating 2 are subjected to wave combination through the optical coupler 2, enter the photoelectric detector 3 to realize envelope detection, then are subjected to optical frequency mixing and are reduced into electric signals; and finally, realizing the output of the intermediate frequency signal through a low-pass filter.
The principle of generating the original frequency signal and outputting the modulated optical signal by the upper loop is as follows: the optical carrier passes through a phase modulator, and a signal V (t) is added0cosωt(V0For signal amplitude, ω for signal circle frequency), the electric field of the output optical signal can be expressed as:
Eout(t)＝Ein(t)ej(mcosωt) (1)；
wherein m is pi V0/VπIs a modulation factor, VπFor the half-wave voltage of the modulator, Jacobi-Anger expansion of equation (1) can be obtained:
Figure BDA0003228561400000091
in the formula (2), Jn(m) is n-order Bessel function of the first kind, and it can be seen that the phase modulation signal generates multiple pairs of frequency spectrum components in the optical domain, namely, sidebands, which are symmetrically distributed in the optical domainOn both sides of the optical carrier, only 0 and ± 1 order modulation signals are considered under the condition of small signal approximation, and equation (2) can be simplified as follows:
Eout(t)＝Ein(t)[J0(m)+j-1J-1(m)e-jωt+jJ1(m)ejωt] (3)；
and J is-n(m)＝(-1)nJn(m), so the above formula (3) can be simplified as:
Eout(t)＝Ein(t)[J0(m)-j-1J1(m)e-jωt+jJ1(m)ejωt] (4)：
therefore, the phase difference of the +/-1 order sidebands is pi, and if the phase modulation signal directly passes through the beat frequency of the photoelectric detector, the output photocurrent is as follows:
i∝[J0(m)2+2J1(m)2+2J1(m)2cos2ωt] (5)；
as can be seen from the above equation, the phase modulation signal directly passes through the photodetector, and the spectrum component of the original signal cannot be recovered. The original signal frequency can be generated by suppressing one sideband through a phase-shifted fiber grating and beating the remaining carrier with the other sideband, as shown in fig. 3: when a microwave signal carries out phase modulation on an optical carrier, two sidebands with opposite phases are generated; after the modulated light signal passes through the phase-shifting fiber grating, one sideband (the sideband frequency is equal to the suppression peak) is suppressed, and only the other sideband and the carrier wave are left, so that single-sideband modulation is realized; the single-sideband modulated signal can realize the original signal output after being subjected to beat frequency by the photoelectric detector. The principle is as follows: after phase modulation, the signal passes through a phase-shifting fiber grating, one of the signals is suppressed, and the signal after realizing single-sideband modulation can be expressed as:
Eout(t)’＝Ein(t)[J0(m)-J1(m)ejωt] (6)；
the beat frequency of the signal by a photoelectric detector is as follows:
i’∝[J0(m)2+J1(m)2-J0(m)J1(m)cosωt] (7)；
as can be seen from the above equation, the direct current term and the signal term output signal are generated after the beat frequency.
In summary, a low-power microwave signal received by the antenna enters the upper loop, and the electro-optical phase modulator 1 modulates an optical carrier; by adjusting the laser wavelength so that
Figure BDA0003228561400000101
(λ1For the tuned laser wavelength, λ2In order to shift the notch wavelength of the fiber grating, omega is the frequency of receiving microwaves, n is the refractive index of the fiber), the signal is amplified and enhanced by the optical amplifier 1 in the process of continuously realizing photoelectric/electro-optical conversion, and finally the output of the original frequency signal is realized, wherein a sideband signal (E)in(t)J1(m)ejωt) Is transmitted through the phase-shifting fiber grating 1 into the optical coupler 2.
The principle of the lower loop generating the photoelectric mixed oscillation signal and outputting the local oscillation optical signal coherent with the upper loop is as follows: the carrier optical signal is modulated by the electric noise of the loop through the electro-optic phase modulator 2, then is amplified through the optical amplifier 2, enters the phase-shifting fiber grating 2 through the optical ring circulator 2, is delayed through an optical fiber delay line after being reflected, is reduced into an electric signal through the photoelectric detector 2, completes the single-sideband modulation process, and then enters the electro-optic phase modulator 2 to circulate next time after filtering is completed through the narrow-band filter. For some specific frequency point signals, if the specific frequency point signals meet the Barkhausen condition (the open-loop gain is greater than 1, and the phase difference is an integral multiple of 2 pi), the signals of the frequency points can realize positive feedback to generate oscillation, and local oscillation optical signal output can be realized in the phase-shifting fiber grating 2 based on the optical characteristics of the phase-shifting fiber grating. In the lower loop, the system oscillation originates from the in-loop noise, which is set to
Figure BDA0003228561400000111
(A is the signal amplitude, ω0Signal circle frequency) after the first cycle
Figure BDA0003228561400000112
Secondary circulationIs composed of
Figure BDA0003228561400000113
n cycles of
Figure BDA0003228561400000114
Wherein alpha is the open loop amplitude gain of the system and tau is the delay; the electrical signal after multiple superposition can be expressed as
Figure BDA0003228561400000115
Calculated from the summation of geometric series
Figure BDA0003228561400000116
The amplitude of the signal is:
Figure BDA0003228561400000117
easily deriving omega from the above formula0When τ is n · 2 pi (n is an integer), the amplitude value obtains the maximum value and is in periodic distribution, a single-frequency oscillation signal can be obtained by adjusting the delay τ and the narrow-band filter, and the local oscillation optical signal output is realized after the signal modulates the optical carrier.
Then, the modulated optical signal output by the upper loop and the local oscillator optical signal output by the lower loop are simultaneously input into the optical coupler 2, and then optical frequency mixing is realized through beat frequency of the photoelectric detector 3. The principle is as follows: the modulated optical signal output by the upper ring and the local oscillator optical signal output by the lower ring are respectively shown as follows: sOn the upper part＝Ein(t)ejωt，
Figure BDA0003228561400000118
The beat frequency of the photoelectric detector 3 is reduced into an electric signal, and the generated photocurrent is as follows:
ip＝(Son the upper part+SLower part)·(SOn the upper part+SLower part)*＝2ρ|Ein(t)|2[1+cos(ω0-ω)t] (10)；
In the above equation, ρ is the responsivity of the photodetector. The formula comprises a direct current term and a down-conversion signal term, namely down-conversion of the microwave signal is realized through optical difference frequency, and finally out-of-band noise is suppressed through a low-pass filter to realize intermediate frequency output.
By combining the above analysis, it can be known that the low-power microwave signal integrated receiver adopted in the embodiment breaks through the "electronic bottleneck" of the traditional channelized receiving system, and the receiver completes the reception of the low-power microwave signal in the optical domain based on the advantages of the optical fiber, such as large bandwidth, low loss, and anti-electromagnetic interference, thereby ensuring that the introduced noise is extremely low, effectively inhibiting the image signal, simplifying the system complexity, and simultaneously having anti-electromagnetic interference, and realizing the integrated reception integrating the functions of amplification, filtering and down-conversion.
The above embodiments are preferred implementations of the present invention, and the present invention can be implemented in other ways without departing from the spirit of the present invention.
Some of the drawings and descriptions of the present invention have been simplified to facilitate the understanding of the improvements over the prior art by those skilled in the art, and some other elements have been omitted from this document for the sake of clarity, and it should be appreciated by those skilled in the art that such omitted elements may also constitute the subject matter of the present invention.

Claims (7)

1. The low-power microwave signal integrated processing method is characterized by comprising the following steps of:
firstly, constructing an upper photoelectric mixed loop and a lower photoelectric mixed loop, generating an optical carrier signal by using a tunable laser, and shunting the optical carrier signal to the upper photoelectric mixed loop and the lower photoelectric mixed loop after the optical carrier signal passes through an optical coupler 1; the low-power microwave signal to be processed is received by the antenna and input into the upper photoelectric hybrid loop, in the upper photoelectric hybrid loop, the low-power microwave signal to be processed received by the antenna is introduced through the electric coupler 2, the electro-optical phase modulator 1 is used for realizing the phase modulation of optical carriers, the optical carriers enter the optical amplifier 1 for amplification, the amplified optical signals enter the phase-shifting fiber grating 1 through the circulator 1, the reflected optical signals are restored into electric signals through the photoelectric detector 1, the main trunk electric signals return to the electro-optical phase modulator 1 for next circulation, the circulating electric signals are partially output through the electric coupler 1, the original frequency signals are output, meanwhile, phase modulation of microwave signals on optical carriers is realized based on the upper photoelectric hybrid loop, narrow-band filtering is realized on one sideband through the phase-shifting fiber grating 1, and modulated optical signals are output; in the lower photoelectric hybrid loop, an optical signal output by the optical coupler 1 is used as an optical carrier of the loop through the electro-optic phase modulator 2, a point noise signal of the loop is subjected to phase modulation on the optical carrier through the electro-optic phase modulator 2 and then enters the optical amplifier 2 to be amplified, one sideband of the point noise signal is inhibited by the circulator 2 and then enters the optical fiber delay line to realize optical delay, then the point noise signal is restored into an electric signal through the photoelectric detector 2, and single-frequency output is realized through the narrow-band filter and then returns to the electro-optic phase modulator 2 to perform the next round of circulation; in the process, for some specific frequency point signals, if the specific frequency point signals meet the Barkhausen condition, the signals of the frequency point can realize positive feedback to generate oscillation, and finally local oscillation optical signals coherent with the modulated optical signals are extracted and output through the phase-shifting fiber bragg grating 2;
then, the envelope detection function of the photoelectric detector is used for realizing the frequency mixing of the modulated optical signal and the local oscillator optical signal and realizing the down-conversion function of the microwave signal;
and finally, suppressing out-of-band noise through a low-pass filter to realize intermediate frequency signal output.
2. The integrated processing method of low-power microwave signals according to claim 1, characterized in that:
by adjusting the wavelength of the tunable laser so that
Figure DEST_PATH_IMAGE002
The signal in the upper photoelectric mixed loop is continuously amplified and enhanced by the optical amplifier 1 in the photoelectric-to-photoelectric conversion process, so that the output of the original frequency signal is realized, and one side band signal is output through the phase-shifted fiber grating 1; in the above formula, the first and second carbon atoms are,
Figure DEST_PATH_IMAGE004
for the purpose of the adjusted laser wavelength,
Figure DEST_PATH_IMAGE006
in order to trap the wavelength of the phase-shifted fiber grating 1,
Figure DEST_PATH_IMAGE008
in order to receive the frequency of the microwaves,nis the refractive index of the optical fiber;
obtaining a single-frequency oscillation signal by adjusting the optical fiber delay amount and a narrow-band filter in the lower photoelectric hybrid loop, and modulating an optical carrier by using the signal to realize local oscillation optical signal output;
the modulated optical signal output by the phase-shift fiber grating 1 and the local oscillator optical signal which is coherent with the modulated optical signal output by the phase-shift fiber grating 2 are input into the optical coupler 2 together, beat frequency is carried out by the photoelectric detector 3, down-conversion of the microwave signal is realized through optical difference frequency, and finally out-of-band noise is suppressed through the low-pass filter, so that intermediate frequency output is realized.
3. A low power microwave signal integrated receiver, characterized by: processing the received low power microwave signal using the integrated low power microwave signal processing method of claim 1.
4. A low power microwave signal-integrated receiver as claimed in claim 3, wherein: the device comprises an antenna, a tunable laser, an optical coupler 1, an upper photoelectric hybrid loop, a lower photoelectric hybrid loop, a phase-shifted fiber grating 1, a phase-shifted fiber grating 2, an optical coupler 2, a photoelectric detector 3 and a low-pass filter;
the tunable laser generates an optical carrier signal, and the optical carrier signal is shunted to the upper photoelectric mixed loop and the lower photoelectric mixed loop after passing through the optical coupler 1; the antenna receives a low-power microwave signal to be processed and inputs the low-power microwave signal into the upper photoelectric hybrid loop, the upper photoelectric hybrid loop extracts and amplifies the low-power microwave signal to be processed, an optical carrier is modulated, and then a modulated optical signal is extracted and output by using the phase-shifted fiber grating 1; the lower photoelectric mixed loop generates a photoelectric mixed oscillation signal, and then the photoelectric mixed oscillation signal is extracted by the phase fiber grating 2 and outputs a local oscillation optical signal which is coherent with the upper loop;
the modulated optical signal output by the phase-shift fiber grating 1 and the local oscillator optical signal output by the phase-shift fiber grating 2 are input into the optical coupler 2 together, beat frequency is carried out by the photoelectric detector 3, down-conversion of the microwave signal is realized through optical difference frequency, and finally out-of-band noise is suppressed through the low-pass filter, so that intermediate frequency output is realized.
5. The low power microwave signal-integrated receiver of claim 4, wherein: the upper photoelectric hybrid loop comprises an electro-optic phase modulator 1, an optical amplifier 1, an optical circulator 1, a photoelectric detector 1, an electric coupler 1 and an electric coupler 2 which are sequentially connected end to end, wherein the electro-optic phase modulator 1 is connected with one output port of the optical coupler 1, the electric coupler 2 is connected with an antenna, and the optical circulator 1 is also connected with a phase-shifting fiber grating 1;
the low-power microwave signal to be processed received by the antenna is introduced into an upper photoelectric mixed loop through an electric coupler 2, the phase modulation of an optical carrier is realized through an electro-optical phase modulator 1 and then enters an optical amplifier 1 to be amplified, the amplified optical signal enters a phase-shifting optical fiber grating 1 through a circulator 1, the reflected optical signal is restored into an electric signal through a photoelectric detector 1, a main channel electric signal returns to the electro-optical phase modulator 1 to be circulated for the next time, the circulating electric signal realizes partial output through the electric coupler 1, the phase modulation of the microwave signal on the optical carrier is realized in the upper photoelectric mixed loop, and finally, the narrow-band filtering is realized on one sideband through the phase-shifting optical fiber grating 1, so that the output of a modulated optical signal is realized.
6. The low power microwave signal integral receiver of claim 5, characterized in that: the lower photoelectric hybrid loop comprises an electro-optic phase modulator 2, an optical amplifier 2, an optical circulator 2, an optical fiber delay line, a photoelectric detector 2 and a narrow-band filter which are sequentially connected end to end, wherein the electro-optic phase modulator 2 is connected with the other output port of the optical coupler 1, and the optical circulator 2 is also connected with a phase-shifting fiber grating 2;
an optical signal output by the optical coupler 1 is used as an optical carrier of a lower photoelectric hybrid loop through the electro-optic phase modulator 2, an electrical noise signal of the lower photoelectric hybrid loop is subjected to phase modulation on the optical carrier through the electro-optic phase modulator 2 and then enters the optical amplifier 2 to be amplified, one sideband of the electrical noise signal is inhibited through the circulator 2 and then enters an optical fiber delay line to realize optical delay, the electrical signal is restored through the photoelectric detector 2, a narrow-band filter is used for realizing single-frequency output, and the single-frequency output returns to the electro-optic phase modulator 2 to perform next round of circulation; in the process, for some specific frequency point signals, if the specific frequency point signals meet the Barkhausen condition, the signals of the frequency point can realize positive feedback to generate oscillation, and finally, narrow-band filtering is realized on one sideband through the phase-shifting fiber grating 2, so that local oscillation optical signal output coherent with the modulated optical signal is realized.
7. The low power microwave signal-integrated receiver of claim 6, wherein: adjusting the tunable laser wavelength such that
Figure 242230DEST_PATH_IMAGE002
The signal in the upper photoelectric hybrid loop is continuously amplified and enhanced by the optical amplifier 1 in the photoelectric-to-photoelectric conversion process, so that the original frequency signal is output, and one sideband signal enters the optical coupler 2 through the phase-shift fiber grating 1; in the above formula, the first and second carbon atoms are,
Figure 159370DEST_PATH_IMAGE004
for the purpose of the adjusted laser wavelength,
Figure 752157DEST_PATH_IMAGE006
in order to trap the wavelength of the phase-shifted fiber grating 1,
Figure 147366DEST_PATH_IMAGE008
in order to receive the microwave frequency,nis the refractive index of the optical fiber; a single-frequency oscillation signal is obtained by adjusting the optical fiber delay amount and the narrow-band filter in the lower photoelectric hybrid loop, and the local oscillation optical signal output can be realized after the signal modulates the optical carrier.
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