CN111128217B - Distributed multi-channel coherent laser radar voice interception method and device - Google Patents
Distributed multi-channel coherent laser radar voice interception method and device Download PDFInfo
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Abstract
The invention discloses a distributed multi-channel coherent laser radar voice interception method and a device, wherein a light beam of a laser light source in a radar platform is divided into N output light beams by a 1 XN beam splitter, wherein N is larger than or equal to 2; each output light beam is subjected to frequency shift through a frequency shifter and then divided into a local oscillation light beam and an emission light beam through a 1 multiplied by 2 beam splitter; the emission light beams are directionally emitted to a target through beam control to form an array topological structure, the echo light beams of the target are received, N echo light beams and corresponding local oscillator light beams are subjected to coherent reception to obtain N signal data, the N signal data are transmitted to a digital signal processing system, and the data processing system obtains high-definition voice information through demodulation and enhancement of the voice information. The invention can flexibly obtain a plurality of sound source information by forming an array topological structure by a plurality of output light beams, has good space selectivity, and also has the characteristics of strong anti-noise interference capability, long interception distance, high precision and clear voice.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a distributed multichannel coherent laser radar voice interception method and device.
Background
The laser voice interception radar detects nanometer level weak vibration signals on the surface of an object caused by sound pressure in a real-time non-contact manner by emitting laser beams to the target and the periphery, demodulates the signals and acquires object micro-vibration information, thereby realizing the acquisition of remote passive voice signals, having the advantages of high sensitivity, strong anti-interference performance, non-contact type, long detection distance, safety, secrecy and the like, effectively making up the defects of the traditional electronic interception means, and having important application value in the fields of national safety, criminal investigation and case solving, military information and the like.
At present, laser voice interception radars can be roughly divided into three types according to detection system division: a regular reflection type laser intensity detection method, a speckle image detection method, and a coherent laser detection method. The positive reflection type laser intensity detection method has the advantages of complex operation, single target type, low detection sensitivity and weak environmental interference resistance, so that the positive reflection type laser intensity detection method cannot play a good role in voice information acquisition; the speckle image detection method utilizes the intensity change of speckle interference to acquire voice information, and although the method is simple to operate and high in sensitivity, the method has high emitted laser power, can cause certain damage to a human body and has weak environmental interference resistance; the coherent laser detection method comprises a homodyne system and a heterodyne system, has the advantages of high sensitivity, high measurement range, quick real-time response, multiple target object types, simplicity in operation and the like, and becomes the current main technical means.
Although coherent laser speech interception radar can realize highly sensitive speech interception, atmospheric interference noise, environmental noise and speckle noise can seriously reduce the signal-to-noise ratio of a received speech signal, room reverberation and speech interference of other speakers while acquiring speech, and the quality of speech communication is also reduced due to the existence of the noise, the reverberation and the interference, speech intelligibility is seriously affected, and the performance of a system is sharply deteriorated. Reducing noise in laser listening signals has become an urgent issue facing current laser listening techniques. Lutao et al (one of the prior arts, see Lutao, zhang Hecourage, guo jin, yanchui, laser coherent acquisition and enhancement of long-distance speech, optical precision engineering, 2017, vol.25, no. 3, 569-575) adopt an all-fiber laser coherent heterodyne vibration measurement system, and combine with a wiener-filter-based speech enhancement algorithm to improve the signal-to-noise ratio, but this algorithm needs to perform noise judgment in the frequency domain first and then perform filtering and noise reduction, and has poor effect under the condition of low received signal-to-noise ratio, and is difficult to apply to real-time high-precision speech acquisition. Rui Li et al (see Rui Li, nichlas Madampouos, zhuing Zhu, and Liangping Xie, performance composition of an all-fiber-based laser Doppler transducer for remote optical signal detection using short and long coherent lasers, applied Optics,2012, vol.51, no.21, 5011-5018) propose to suppress noise during heterodyne detection using a tunable optical delay line compensation method, but this method is not applicable for remote detection. Shi-song Wu et al (three of the prior art, see Shi-song Wu, tao Lv, xi-yu Han, chun-hui Yan, he-yong Zhang, remote audio signals detection using a partial-fiber laser Doppler splitter, applied Acoustics,2018,130, 216-221) propose to suppress crosstalk noise introduced by fiber circulators using a free space-fiber mixing scheme, but the coupling efficiency of the signal light decreases and the system complexity increases.
In summary, although the existing speech enhancement techniques can improve the quality of the noisy speech to a certain extent, because these techniques are all based on single-channel detection, the noise in the received signal is directly superimposed on the speech signal, so the performance of the techniques inevitably decreases with the enhancement of the environmental noise, and especially in a strong noise environment, the existing speech enhancement techniques still hardly achieve a good effect, which causes the low detection precision, the poor anti-noise interference capability, and the unclear speech of the existing speech interception laser radar, so that the application prospect is severely limited.
Disclosure of Invention
The invention aims to provide a distributed multi-channel coherent laser radar voice interception method and a distributed multi-channel coherent laser radar voice interception device. The invention can flexibly obtain the information of a plurality of sound sources by forming an array topological structure by a plurality of output light beams, has good space selectivity, and also has the characteristics of strong anti-noise interference capability, long interception distance, high precision and clear voice; in addition, the invention can filter and process crosstalk signals among different output light beams, and effectively improves the voice detection precision of a single output light beam.
The technical scheme of the invention is as follows: the distributed multi-channel coherent laser radar voice interception method is characterized by comprising the following steps: dividing a light beam of a laser light source in the radar platform into N output light beams by a 1 XN beam splitter, wherein N is not less than 2; each output light beam is subjected to frequency shift through a frequency shifter and then divided into a local oscillation light beam and an emission light beam through a 1 multiplied by 2 beam splitter; the emission light beams are directionally emitted to a target to form an array topological structure, the echo light beams of the target are received, the N echo light beams and the corresponding local oscillator light beams are subjected to coherent reception to obtain N signal data, the N signal data are transmitted to a digital signal processing system, and the data processing system obtains high-definition voice information through demodulation and voice enhancement of the voice information.
In the voice interception method of the distributed multichannel coherent laser radar, the transmission of the echo light beam is to transmit the emission light beam to the optical circulator, then to transmit the emission light beam to the target through the optical telescope and the light beam director, and to receive the echo light beam of the target through the optical telescope, and finally to transmit the echo light beam to the optical bridge through the optical circulator.
In the voice interception method of the distributed multichannel coherent laser radar, the echo light beam and the local oscillator light beam enter a 2 × 4 90 ° optical bridge for orthogonal coherent reception, and the light field is expressed as:
wherein R is N (t) is the object surface weak vibration amplitude caused by sound pressure sensed by the Nth echo beam, f 0 Is the carrier frequency of the laser, f N Is the amount of frequency shift of the Nth output beam, c is the speed of light, phi S Is the noise phase of the emitted beam, phi LO Is the noise phase of the local oscillator beam;t is time; e S_N Is the echo beam amplitude; e LO_N Is the local oscillator beam amplitude;
the four outputs after being mixed by the 2 × 4 90 ° optical bridge are respectively:
wherein phi N_noise Is the noise phase; I.C. A S Is a direct current quantity related to the echo beam; i is 0 Is the direct current quantity related to the local oscillator beam;
the in-phase signal and the orthogonal signal with the orthogonal characteristic output by the optical bridge are respectively received by the photoelectric balance detector, and the in-phase signal and the orthogonal signal output by the photoelectric balance detector are respectively:
wherein k is in Photoelectric balance detector response rate, k, of in-phase signal qu Is the photoelectric balance detector responsivity of the quadrature signal;
if the response rates of the photodetectors of the in-phase signal and the quadrature signal are consistent, the weak vibration phase of the surface of the object can be obtained by arctan solution phase:
wherein phi is N_noise Is the noise phase of the nth output beam;
finally, reconstructing the voice signal R of the Nth output beam through the unwrapping algorithm N (t)。
In the distributed multi-channel coherent laser radar voice interception method, coherent reception is performed on the nth echo light beam and the corresponding local oscillator light beam to obtain nth signal data, where crosstalk signals generated by coherent reception of the local oscillator light beams corresponding to the nth echo light beam and other echo light beams are contained in the nth signal data, and the crosstalk signals are represented as follows:
E S_M expressed as other echo beam amplitudes, E LO_N The local oscillation beam amplitude corresponding to the Nth echo beam is represented;
the data of the crosstalk signal generated by coherent reception contains the frequency of | f N -f M And the item is filtered through low-pass filtering, so that crosstalk signals are eliminated, and the voice detection precision of a single output light beam is improved.
In the distributed multichannel coherent laser radar voice interception method, the array topological structure comprises a one-dimensional linear array, a two-dimensional area array and a three-dimensional array; the one-dimensional linearity comprises an equidistant array, a nested linear array and a non-equidistant array; the two-dimensional area array comprises a uniform and non-uniform circular array and a square array; the array topological structure utilizes the space sampling theorem to inhibit space aliasing and adopts an array detection speech enhancement algorithm to realize noise reduction.
The device for realizing the distributed multichannel coherent laser radar voice interception method comprises a laser light source, wherein the laser light source is connected with a plurality of frequency shifters through 1 × N beam splitters, and each frequency shifter is sequentially connected with a 1 × 2 beam splitter and an optical circulator;
the output end of the optical circulator is sequentially connected with an optical telescope and a light beam director; the optical circulator and the 1 x 2 beam splitter are connected with an optical bridge together, and the optical bridge is a 2 x 4 90-degree optical bridge; the optical bridge is connected with filters through a photoelectric balance detector, the filters are connected with an analog-to-digital converter together, and the analog-to-digital converter is connected with a main control computer through a digital signal processing system; the main control computer is also connected with the beam director.
In the foregoing apparatus, a polarizer and a laser amplifier are further disposed between the laser light source and the 1 × N beam splitter.
Compared with the prior art, the invention has the following beneficial effects:
1. the method adopts directional emission of distributed multi-output light beams to form an array topological structure at a target, frequency shift is carried out on each output light beam through a frequency shifter, then, coherent reception of local oscillator light beams and echo light beams is carried out, a plurality of sound source information is flexibly obtained, and high-definition voice information is obtained through demodulation and voice enhancement of the voice information; in addition, the invention can effectively inhibit the noise problem caused by crosstalk of different output light beams through filtering processing, thereby further improving the speech definition.
2. The array detection voice enhancement algorithm can effectively inhibit noise, and inhibit spatial aliasing through the spatial sampling theorem, so that the array detection voice enhancement algorithm has good spatial selectivity, and has the characteristics of strong anti-noise interference capability, long interception distance, high precision and clear voice.
3. The invention realizes the receiving and sending coaxiality through the optical circulator, the optical telescope and the beam director, the emitted laser is emitted to the target to be measured in a directional way through the beam director under the condition of not rotating the radar, and no external speed/acceleration measuring device is arranged, thereby being beneficial to the integration miniaturization and reducing the complexity of the system; the coherent receiving technology based on the 2 multiplied by 4 90-degree optical bridge can inhibit image frequency interference and reduce production cost.
Drawings
FIG. 1 is a schematic diagram of the present invention.
The labels in the figures are: 1. a laser light source; 2. a 1 XN beam splitter; 3. a frequency shifter; 4. a 1 × 2 beam splitter; 5. an optical circulator; 6. an optical telescope; 7. a beam director; 8. an optical bridge; 9. a photoelectric balance detector; 10. a filter; 11. an analog-to-digital converter; 12. a digital signal processing system; 13. a main control computer; 14. a polarizer; 15. and a laser amplifier.
Detailed Description
The invention is further illustrated by the following figures and examples, which are not to be construed as limiting the invention.
Example 1: a distributed multi-channel coherent laser radar voice interception method is characterized in that light beams of a laser light source in a radar platform are divided into 4 output light beams through a 1 x 4 beam splitter; each output light beam is subjected to frequency shift through a frequency shifter and then divided into a local oscillation light beam and an emission light beam through a 1 multiplied by 2 beam splitter; the emission light beam is directionally emitted to a target to form an array topological structure, the echo light beam of the target is received, 4 echo light beams and corresponding local oscillator light beams are coherently received to obtain 4 signal data, then the 4 signal data are transmitted to a digital signal processing system, and the data processing system obtains voice information through the demodulation of the voice information.
Example 2: a distributed multi-channel coherent laser radar voice listening method device, as shown in fig. 1, including a laser light source 1, where the laser light source 1 is a 1550nm single-mode narrow-linewidth continuous fiber laser safe to human eyes, the linewidth of the laser is 10kHz, the output power is 20mW, the output of the optical fiber has isolation protection, a polarizer 14 and a laser amplifier 15 are further arranged between the laser light source 1 and a 1 × 4 beam splitter 2, a light beam of the laser light source 1 passes through the polarizer 14 to ensure that the polarization extinction ratio is greater than 25dB, and is amplified to 600mW by the laser amplifier, the laser light source 1 is connected with a plurality of frequency shifters 3 through the 1 × 4 beam splitter 2, 4 output light beams are emitted through the 1 × 4 beam splitter, and in consideration of insertion loss, the power of each output light beam is about 100mW, each output light beam is subjected to frequency shift by the frequency shifter 3, and the frequency shift amounts are 48MHz, 49MHz, 50MHz and 51MHz respectively; each frequency shifter 3 is connected with a 1 × 2 beam splitter 4 and an optical circulator 5 in sequence; the output end of the optical circulator 5 is sequentially connected with an optical telescope 6 and a beam director 7; output light beam is through 1X 2 beam splitter 4 output two way light, and intensity is 1 99, and the small part energy is as local oscillator signal, and most energy is as the transmission signal, through optics circulator 5, and rethread optical telescope 6 and light beam director 7 (rotatory two optical wedge scanners) are launched to the target, and the transmission light bore is 20mm, and the facula diameter of distance 100 meters department is about 20mm, and the topological structure of facula array is the equidistance linear array, and facula interval 10mm.
The optical circulator 5 and the 1 × 2 beam splitter 4 are connected together with an optical bridge 8, and the optical bridge 8 is a 2 × 4 90 ° optical bridge; the echo light beam and the local oscillator light beam enter a 2 x 4 90-degree optical bridge for orthogonal coherent reception, and the optical field is expressed as:
wherein R is N (t) the object surface weak vibration caused by sound pressure sensed by the Nth echo beam
Amplitude, f 0 Is the laser carrier frequency, f N Is the amount of frequency shift of the Nth output beam, c is the speed of light, phi S Is the noise phase of the emitted light beam, phi LO Is the noise phase of the local oscillator beam;t is time; e S_N Is the echo beam amplitude; e LO_N Is the local oscillator beam amplitude;
the four outputs after being mixed by the 2 × 4 90 ° optical bridge are respectively:
wherein phi N_noise Is a mixing noise phase; I.C. A S Is a direct current quantity related to the echo beam; i is 0 Is the direct current quantity related to the local oscillator beam;
the in-phase signal and the quadrature signal with the quadrature characteristic output by the optical bridge 8 are respectively received by the photoelectric balanced detector 9, the bandwidth is 100MHz, and the dc coupling is performed, where the in-phase signal and the quadrature signal output by the photoelectric balanced detector 9 are respectively:
wherein k is in Photoelectric balance detector response rate, k, of in-phase signal qu Is the photoelectric balance detector responsivity of the quadrature signal;
coherent reception is carried out on the Nth echo light beam and the corresponding local oscillator light beam to obtain Nth signal data, wherein crosstalk signals generated by coherent reception of other echo light beams and the local oscillator light beam corresponding to the Nth echo light beam are contained in the Nth signal data, and the crosstalk signals are represented as follows:
E S_M expressed as other echo beam amplitudes, E LO_N The local oscillation beam amplitude corresponding to the Nth echo beam;
The data of the crosstalk signal generated by coherent reception contains the frequency of | f N -f M The filter 10 filters the light beams to remove signals above 1MHz, so as to eliminate crosstalk signals and improve the voice detection accuracy of a single output light beam.
The method comprises the following steps of using a 4-channel 14-bit 100KHz analog-to-digital converter 11 to realize synchronous data acquisition of target signals output by 4 photoelectric balanced detectors 9, then processing the obtained 4 sampled data by using a digital signal processing system 12 (DSP), and if the response rates of the photoelectric detectors 9 of in-phase signals and orthogonal signals are consistent, obtaining the weak vibration phase of the object surface through arc tangent phase splitting:
wherein phi is N_noise Is the noise phase of the nth output signal.
Reconstructing the speech signal R of the Nth output beam by the unwrapping algorithm N (t), thus obtain the voice information of 4 passways in real time, meanwhile, the digital signal processing system 12 connects with the main control computer 13; the main control computer 13 is also connected with the light beam director 7, the main control computer 13 is used for controlling and obtaining the information of the array topological structure, and finally, combining the equidistant linear array topological structure and the voice signal, the noise reduction is realized through the array detection voice enhancement algorithm processing, and the voice precision is improved.
In summary, the present invention employs directional emission of distributed multiple output beams to form an array topology at a target, and then obtains multiple sound source information flexibly by coherent reception of local oscillator beams and echo beams, and obtains voice information by a data processing system through demodulation and voice enhancement of the voice information. Therefore, the invention has the advantages of good space selectivity, strong anti-noise interference capability, long interception distance, high precision and clear voice.
Claims (6)
1. The distributed multichannel coherent laser radar voice interception method is characterized by comprising the following steps: dividing a light beam of a laser light source in the radar platform into N output light beams by a 1 XN beam splitter, wherein N is not less than 2; each output light beam is subjected to frequency shift through a frequency shifter and then divided into a local oscillation light beam and an emission light beam through a 1 multiplied by 2 beam splitter; the emission light beams are directionally emitted to a target to form an array topological structure, the echo light beams of the target are received, N echo light beams and corresponding local oscillator light beams are coherently received to obtain N signal data, the N signal data are transmitted to a digital signal processing system, and the data processing system obtains high-definition voice information through the demodulation and voice enhancement of the voice information;
the echo light beam and the local oscillator light beam enter a 2 x 4 90-degree optical bridge for orthogonal coherent reception, and the optical field is expressed as:
wherein R is N (t) is the object surface weak vibration amplitude caused by sound pressure sensed by the Nth echo beam, f 0 Is the carrier frequency of the laser, f N Is the amount of frequency shift of the Nth output beam, c is the speed of light, phi S Is the noise phase of the emitted light beam, phi LO Is the noise phase of the local oscillator beam;t is time; e S_N Is the echo beam amplitude; e LO_N Is the local oscillator beam amplitude;
the four outputs after being mixed by the 2 × 4 90 ° optical bridge are respectively:
wherein phi N_noise Is the noise phase; i is s Is a direct current quantity related to the echo beam; i is o Is the direct current quantity related to the local oscillator beam;
the in-phase signal and the orthogonal signal with the orthogonal characteristic output by the optical bridge are respectively received by the photoelectric balance detector, and the in-phase signal and the orthogonal signal output by the photoelectric balance detector are respectively:
wherein k is in Photoelectric balance detector response rate, k, of in-phase signal qu Is the photoelectric balance detector responsivity of the quadrature signal;
if the response rates of the photodetectors of the in-phase signal and the quadrature signal are consistent, the weak vibration phase of the surface of the object can be obtained by arctan solution phase:
wherein phi is N_noise Is the noise phase of the nth output beam;
finally, reconstructing the voice signal R of the Nth output beam through the unwrapping algorithm N (t)。
2. The distributed multichannel coherent lidar voice listening method according to claim 1, characterized in that: the transmission of the echo light beam is realized by transmitting the emission light beam to the optical circulator, transmitting the emission light beam to a target through the optical telescope and the light beam director, receiving the echo light beam of the target by the optical telescope, and finally transmitting the echo light beam to the optical bridge through the optical circulator.
3. The distributed multi-channel coherent laser radar voice interception method according to claim 1, characterized in that: coherent reception is carried out on the Nth echo light beam and the corresponding local oscillator light beam to obtain Nth signal data, wherein crosstalk signals generated by coherent reception of other echo light beams and the local oscillator light beam corresponding to the Nth echo light beam are contained in the Nth signal data, and the crosstalk signals are represented as follows:
E S_M expressed as other echo beam amplitudes, E LO_N The amplitude is expressed as the local oscillation beam amplitude corresponding to the Nth echo beam;
the data of the crosstalk signal generated by coherent reception contains the frequency of | f N -f M And the I term is subjected to filtering processing through low-pass filtering, so that crosstalk signals are eliminated, and the voice detection precision of a single output light beam is improved.
4. The distributed multi-channel coherent laser radar voice interception method according to claim 1, characterized in that: the array topological structure comprises a one-dimensional linear array, a two-dimensional area array and a three-dimensional array; the one-dimensional linearity comprises an equidistant array, a nested linear array and a non-equidistant array; the two-dimensional area array comprises a uniform and non-uniform circular array and a square array; the array topological structure utilizes the space sampling theorem to inhibit space aliasing and adopts an array detection speech enhancement algorithm to realize noise reduction.
5. Apparatus for implementing a distributed multi-channel coherent lidar voice listening method according to any of claims 1-4, wherein: the laser frequency shifter comprises a laser light source (1), wherein the laser light source (1) is connected with a plurality of frequency shifters (3) through a 1 × N beam splitter (2), and each frequency shifter (3) is sequentially connected with a 1 × 2 beam splitter (4) and an optical circulator (5);
the output end of the optical circulator (5) is sequentially connected with an optical telescope (6) and a beam director (7); the optical circulator (5) and the 1 x 2 beam splitter (4) are connected with an optical bridge (8), and the optical bridge (8) is a 2 x 4 90-degree optical bridge; the optical bridge (8) is connected with filters (10) through a photoelectric balance detector (9), the filters (10) are connected with an analog-to-digital converter (11) together, and the analog-to-digital converter (11) is connected with a main control computer (13) through a digital signal processing system (12); the main control computer (13) is also connected with the beam director (7).
6. The apparatus of claim 5, wherein: a polarizer (14) and a laser amplifier (15) are also arranged between the laser light source (1) and the 1 XN beam splitter (2).
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