An anti-interference laser radar and ranging method based on quantum noise

Abstract

The present invention discloses an anti-interference laser radar and ranging method based on quantum noise, belonging to the field of laser radar technology. A coherent state light signal is generated by a laser and split into signal light and local oscillator light by a beam splitter; the signal light is randomly phase modulated according to a true random number sequence, so that the phase difference between adjacent signal lights is less than the vacuum shot noise; the signal light after random phase modulation is expanded by a transmitting telescope to illuminate the target object, and after being reflected, it forms an echo signal light and enters the receiving telescope; the echo signal light is coherently detected by a coherent detection module and the local oscillator light, and the initial data is generated by collecting the output electrical signal; the initial data is phase calculated to generate demodulated data and perform shift cross-correlation operation with a true random number sequence to obtain the target distance. The present invention only needs to perform random phase modulation, and does not need to perform random amplitude modulation, thus eliminating the amplitude modulator and reducing the cost and complexity of the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radars, and in particular relates to an anti-interference laser radar and a ranging method based on quantum noise. Background Art

[0002] Laser radar has a wide range of applications in target detection, unmanned driving, surveying and mapping, etc. Traditional laser radar uses classical signals, which are easily intercepted and accurately measured by jammers, making the radar system susceptible to deception interference. Applying quantum technology to the radar field, using the characteristics of entangled quantum states, uncertainty of continuous variable quantum states, and measurement collapse to detect deception interference, can effectively identify interception and retransmission attacks, and improve the security and reliability of detection. In the prior art (publication number CN116381643B, CN116400323B), it is proposed to use Gaussian modulated coherent states to detect targets. Since Gaussian coherent states naturally have quantum noise, their two regular components cannot be accurately measured at the same time. The jammer intercepts, measures and forwards the signal, which will inevitably introduce additional noise. By measuring the noise of the radar receiver, it can be determined whether there is deception interference. However, it is necessary to randomly modulate the amplitude and phase of the coherent state at the same time, requiring the modulated signal to present a two-dimensional Gaussian distribution centered on the origin in the phase space, and the generation rate of random numbers is relatively high. Moreover, only discrete modulation can be performed during implementation, and true continuous modulation cannot be achieved, which makes the actual anti-spoofing performance of the radar system different from the theory. In order to approach continuous modulation, more sophisticated discrete amplitude and phase modulation is required, which places higher requirements on the bandwidth of multiple electro-optic modulators and the number of bits and accuracy of the digital-to-analog conversion module, increasing the difficulty and complexity of implementation. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides an anti-interference laser radar and ranging method based on quantum noise, which does not require very fine discrete amplitude and phase modulation to approach the continuous modulation required by the anti-interference theoretical basis, thereby reducing the requirements on the bandwidth of the electro-optical modulator and the number of bits and accuracy of the digital-to-analog conversion module.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] An anti-interference laser radar based on quantum noise, comprising:

[0006] A random number generator, used to generate a true random number sequence;

[0007] A laser for generating a coherent optical signal;

[0008] A beam splitter, used for splitting the coherent state optical signal into signal light and local oscillator light;

[0009] A phase modulation module, used for performing random phase modulation on the signal light according to a true random number sequence, so that the phase difference between adjacent signal lights is smaller than the vacuum shot noise;

[0010] A transmitting telescope is used to expand the signal light after random phase modulation and illuminate the target object;

[0011] A receiving telescope, used for receiving the echo signal light reflected by the target object;

[0012] A coherent detection module, used to measure the phase of the echo signal light in combination with the local oscillator light;

[0013] A data acquisition module, used to collect the electrical signal output by the coherent detection module and generate initial data;

[0014] The data processing module is used to calculate the phase of the initial data, generate demodulated data and perform shift cross-correlation operation with the true random number sequence to obtain the target distance; and is used to count the bit error rate of the demodulated data when the cross-correlation operation reaches a peak value. When the bit error rate exceeds a threshold, it is determined that deception interference exists.

[0015] On the other hand, the present invention provides a quantum noise-based anti-interference laser radar ranging method, which is applied to the aforementioned quantum noise-based anti-interference laser radar, and the method comprises the following steps:

[0016] Step S1: The laser generates a coherent light signal which is split into signal light and local oscillator light by a beam splitter;

[0017] Step S2: the phase modulation module performs random phase modulation on the signal light according to the true random number sequence generated by the random number generator, so that the phase difference between adjacent signal lights is smaller than the vacuum shot noise;

[0018] Step S3: The signal light subjected to random phase modulation is expanded by the transmitting telescope and illuminates the target object, and after being reflected, it forms an echo signal light and enters the receiving telescope;

[0019] Step S4: using the coherent detection module and the local oscillator light to perform coherent detection on the echo signal light, and collecting the electrical signal output by the coherent detection module through the data acquisition module to generate initial data;

[0020] Step S5: Use the data processing module to perform phase calculation on the initial data, generate demodulated data, and perform shift cross-correlation operation with the true random number sequence to obtain the target distance;

[0021] Step S6: Count the bit error rate of the demodulated data when the cross-correlation operation reaches a peak value, and determine that there is deception interference on the target when the bit error rate exceeds a threshold.

[0022] In a third aspect, the present invention provides an electronic device comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned quantum noise-based anti-interference lidar ranging method.

[0023] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned quantum noise-based anti-interference lidar ranging method.

[0024] The beneficial effects of the present invention are:

[0025] The present invention only needs to perform random phase modulation, and does not need to perform random amplitude modulation, thus eliminating the need for an amplitude modulator and reducing the cost and complexity of the system; at the same time, the signal is distributed on a circular ring centered on the origin in the phase space, and there is no distribution within the circle, and the demand for random numbers is greatly reduced. There is no need to perform very fine discrete amplitude and phase modulation to approach the continuous modulation required by the theoretical basis of anti-interference, which reduces the requirements for the bandwidth of the electro-optic modulator and the number of bits and accuracy of the digital-to-analog conversion module, thereby reducing the difficulty and complexity of implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of an anti-interference laser radar based on quantum noise according to the present invention;

[0027] Figure 2 Schematic diagram of phase distribution of signal light in phase space;

[0028] Figure 3 This is a structural diagram of an anti-interference laser radar based on quantum noise according to the first embodiment of the present invention;

[0029] Figure 4 This is a structural diagram of an anti-interference laser radar based on quantum noise according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] like Figure 1 As shown, an anti-interference laser radar based on quantum noise is characterized by comprising:

[0032] A random number generator, used to generate a true random number sequence;

[0033] A laser for generating a coherent optical signal;

[0034] A beam splitter, used for splitting the coherent state optical signal into signal light and local oscillator light;

[0035] A phase modulation module, used for performing random phase modulation on the signal light according to a true random number sequence, so that the phase difference between adjacent signal lights is smaller than the vacuum shot noise;

[0036] A transmitting telescope is used to expand the signal light after random phase modulation and illuminate the target;

[0037] A receiving telescope, used for receiving the echo signal light reflected by the target;

[0038] A coherent detection module, used to measure the phase of the echo signal light in combination with the local oscillator light;

[0039] A data acquisition module, used to collect the electrical signal output by the coherent detection module and generate initial data;

[0040] The data processing module is used to calculate the phase of the initial data, generate demodulated data and perform shift cross-correlation operation with the true random number sequence to obtain the target distance; and is used to count the bit error rate of the demodulated data when the cross-correlation operation reaches a peak value. When the bit error rate exceeds a threshold, it is determined that deception interference exists.

[0041] The specific working process and principle are as follows:

[0042] The laser generates a coherent light signal, which is split into signal light and local oscillator light by a beam splitter. The signal light can be expressed as , where X and P are the two canonical components of the coherent state in the phase space, i represents the imaginary unit, and they satisfy and ,in and They represent the photon annihilation operator and the photon production operator respectively. According to Heisenberg's uncertainty principle, the X and P components cannot be accurately measured at the same time. The uncertainty of the two is equal to the shot noise caused by vacuum fluctuations. That is, in the shot noise unit, the uncertainty relationship between the two is .like Figure 2 As shown in the enlarged area in , a dotted circular area represents the distribution of a coherent state in the phase space, and the radius of the circle represents the standard deviation of the shot noise.

[0043] The signal light enters the phase modulation module, and the signal light is randomly phase modulated according to the true random number sequence generated by the random number generator, so that the phase distribution of the signal light in the phase space is a circle with the origin as the center and the radius as the amplitude of the signal light. , and ensure that the phase difference between adjacent signal lights is less than the vacuum shot noise.

[0044] Subsequently, the signal light after random phase modulation is expanded through the transmitting telescope and illuminates the target object, and after being reflected, it forms an echo signal light and enters the receiving telescope. A fiber amplifier can be set before the transmitting telescope. The echo signal light is coherently detected using the coherent detection module and the local oscillator light, and the output photocurrent is:

[0045] ,

[0046] in, is the responsivity of the photodetector in coherent detection, They are the quantum efficiency, elementary charge, Planck constant, and signal frequency of the photodetector; and are the power (angular frequency) of the signal light and the local oscillator light respectively, is the modulation phase.

[0047] The data acquisition module collects the electrical signal output by the coherent detection module to obtain the initial data; the data processing module processes the initial data to obtain the phase demodulation data of the signal light, which is the receiving sequence. The receiving sequence is subjected to shift cross-correlation operation with the transmitting sequence obtained according to the true random number sequence, and the target distance can be obtained when the cross-correlation peak is reached.

[0048] The shot noise variance of coherent detection is:

[0049] ,

[0050] in, is the elementary charge, is the electrical signal bandwidth. The phase angle uncertainty caused by shot noise is like Figure 2 As shown, it can be calculated by the above two formulas:

[0051] ,

[0052] Assume that the minimum angle between two adjacent signals of random phase modulation is , we can calculate the number of phases modulated in a shot noise:

[0053] ,

[0054] When N is larger, the number of signal light codes contained in a shot noise is larger, which makes it more difficult for the target to distinguish the phase of the signal light emitted by the laser radar. Therefore, when the target intercepts and measures the signal light emitted by the laser radar, it cannot accurately copy it, which makes the deception signal it emits very different from the original signal emitted by the laser radar. After being measured by the laser radar receiver, a large bit error rate will be obtained, so that the laser radar can determine whether the target has deception interference by counting the bit error rate of the received signal through the data processing module to see whether it exceeds the set threshold.

[0055] like Figure 3 As shown, embodiment 1:

[0056] The random number generator is a quantum random number generator.

[0057] The random number generator generates a first true random number sequence {x} of L bits and M A second true random number sequence {y} of L bits;

[0058] The phase modulation module includes a first driving module and a first phase modulator;

[0059] The first driving module divides the second true random number sequence {y} into L M-bit sub-blocks {z}, and combines the first true random number sequence {x} to construct a phase modulation sequence { } and generate a first driving signal to drive the first phase modulator to perform phase modulation on the signal light, wherein , represents the decimal operation on sub-block z, and .

[0060] The coherent detection module includes a 90° optical mixer and two balanced detectors.

[0061] The specific working process and principle are as follows:

[0062] The laser generates a coherent light signal, which is split into signal light and local oscillator light by a beam splitter. The quantum random number generator generates a true random number sequence. Due to the inherent true randomness and unpredictability of quantum effects, it is impossible to infer subsequent signals through interception and analysis.

[0063] The quantum random number generator generates the first true random number sequence {x} and M of L bits The first driving module divides the second true random number sequence {y} into L M-bit sub-blocks {z}, and combines the first true random sequence {x} to construct a phase modulation sequence { } and generate a first driving signal to drive the first phase modulator to perform phase modulation on the signal light, wherein , represents the decimal operation on z, and Therefore, the phase distribution of the signal light in the phase space is a circle with the origin as the center and the radius as the amplitude of the signal light. , and the angle (phase difference) between two adjacent signal lights is satisfied Smaller than vacuum shot noise.

[0064] Subsequently, the signal light after random phase modulation is expanded through the transmitting telescope and illuminates the target object, and after being reflected, it forms an echo signal light and enters the receiving telescope. The echo signal light and the local oscillator light enter the 90° optical mixer and two balanced detectors for coherent detection, and the output photocurrent is:

[0065] ,

[0066] in, is the responsivity of the photodetector, They are the quantum efficiency, elementary charge, Planck constant, and signal frequency of the photodetector; and are the powers (angular frequencies) of the signal light and the local oscillator light respectively.

[0067] The data acquisition module collects the electrical signal output by the coherent detection module to obtain the initial data; the data processing module processes the initial data to obtain the phase demodulation data of the signal light, which is the receiving sequence. The receiving sequence is subjected to shift cross-correlation operation with the transmitting sequence obtained according to the true random number sequence, and the target distance can be obtained when the cross-correlation peak is reached.

[0068] The shot noise variance of coherent detection is:

[0069] ,

[0070] in, is the elementary charge, is the electrical signal bandwidth. The phase angle uncertainty caused by shot noise is like Figure 2 As shown, it can be calculated by the above two formulas:

[0071] ,

[0072] Assume that the minimum angle between two adjacent signals of random phase modulation is , we can calculate the number of phases modulated in a shot noise:

[0073] ,

[0074] When N is larger, the number of signal light codes contained in a shot noise is larger, which makes it more difficult for the target to distinguish the phase of the signal light emitted by the laser radar. Therefore, when the target intercepts and measures the signal light emitted by the laser radar, it cannot accurately copy it, which makes the deception signal it emits very different from the original signal emitted by the laser radar. After being measured by the laser radar receiver, a large bit error rate will be obtained, so that the laser radar can determine whether the target has deception interference by counting the bit error rate of the received signal through the data processing module to see whether it exceeds the set threshold.

[0075] like Figure 4 As shown, Example 2:

[0076] The random number generator is a quantum random number generator.

[0077] The random number generator generates a first true random number sequence {x} of L bits and M A second true random number sequence {y} of L bits;

[0078] The phase modulation module includes a second driving module, a third driving module, a Mach-Zehnder modulator and a second phase modulator;

[0079] The second driving module generates a second driving signal according to the first true random number sequence {x}, driving the Mach-Zehnder modulator to perform binary phase modulation on the signal light;

[0080] The third driving module divides the second true random number sequence {y} into L M-bit sub-blocks {z} to construct a phase rotation base sequence { } and generate a third driving signal to drive the second phase modulator to perform phase modulation on the signal light, wherein , represents the decimal operation on z, and .

[0081] The coherent detection module includes a 90° optical mixer and two balanced detectors.

[0082] The specific working process and principle of the second embodiment are as follows:

[0083] The laser generates a coherent light signal, which is split into signal light and local oscillator light by a beam splitter. The quantum random number generator generates a true random number sequence. Due to the inherent true randomness and unpredictability of quantum effects, it is impossible to infer subsequent signals through interception and analysis.

[0084] The quantum random number generator generates the first true random number sequence {x} and M of L bits The second true random sequence {y} of L bits, the second driving module generates a second driving signal according to the first true random number sequence {x}, and drives the Mach-Zehnder modulator to perform binary phase modulation on the signal light; the third driving module divides the second true random sequence {y} into L M-bit sub-blocks {z}, and constructs a phase rotation base sequence { } and generate a third driving signal to drive the second phase modulator to perform phase modulation on the signal light, wherein , represents the decimal operation on z, and Therefore, the phase distribution of the signal light in the phase space is a circle with the origin as the center and the radius as the amplitude of the signal light. , and the phase difference between two adjacent signal lights is satisfied Smaller than vacuum shot noise.

[0085] Subsequently, the signal light after random phase modulation is expanded through the transmitting telescope and illuminates the target object, and after being reflected, it forms an echo signal light and enters the receiving telescope. The echo signal light and the local oscillator light enter the 90° optical mixer and two balanced detectors for coherent detection, and the output photocurrent is:

[0086] ,

[0087] in, is the responsivity of the photodetector, They are the quantum efficiency, elementary charge, Planck constant, and signal frequency of the photodetector; and are the powers (angular frequencies) of the signal light and the local oscillator light respectively.

[0088] The data acquisition module collects the electrical signal output by the coherent detection module to obtain the initial data; the data processing module processes the initial data to obtain the phase demodulation data of the signal light, which is the receiving sequence. The receiving sequence is subjected to shift cross-correlation operation with the transmitting sequence obtained according to the true random number sequence, and the target distance can be obtained when the cross-correlation peak is reached.

[0089] The shot noise variance of coherent detection is:

[0090] ,

[0091] in, is the elementary charge, is the electrical signal bandwidth. The phase angle uncertainty caused by shot noise is like Figure 2 As shown, it can be calculated by the above two formulas:

[0092] ,

[0093] Assume that the minimum angle between two adjacent signals of random phase modulation is , we can calculate the number of phases modulated in a shot noise:

[0094] ,

[0095] When N is larger, the number of signal light codes contained in a shot noise is larger, which makes it more difficult for the target to distinguish the phase of the signal light emitted by the laser radar. Therefore, when the target intercepts and measures the signal light emitted by the laser radar, it cannot accurately copy it, which makes the deception signal it emits very different from the original signal emitted by the laser radar. After being measured by the laser radar receiver, a large bit error rate will be obtained, so that the laser radar can determine whether the target has deception interference by counting the bit error rate of the received signal through the data processing module to see whether it exceeds the set threshold.

[0096] On the other hand, the present invention provides a quantum noise-based anti-interference laser radar ranging method, which is applied to the aforementioned quantum noise-based anti-interference laser radar, and the method comprises the following steps:

[0097] Step S1: The laser generates a coherent light signal which is split into signal light and local oscillator light by a beam splitter;

[0098] Step S2: the phase modulation module performs random phase modulation on the signal light according to the true random number sequence generated by the random number generator, so that the phase difference between adjacent signal lights is smaller than the vacuum shot noise;

[0099] Step S3: The signal light subjected to random phase modulation is expanded by the transmitting telescope and illuminates the target object, and after being reflected, it forms an echo signal light and enters the receiving telescope;

[0100] Step S4: using the coherent detection module and the local oscillator light to perform coherent detection on the echo signal light, and collecting the electrical signal output by the coherent detection module through the data acquisition module to generate initial data;

[0101] Step S5: Use the data processing module to perform phase calculation on the initial data, generate demodulated data, and perform shift cross-correlation operation with the true random number sequence to obtain the target distance;

[0102] Step S6: Count the bit error rate of the demodulated data when the cross-correlation operation reaches a peak value, and determine that there is deception interference on the target when the bit error rate exceeds a threshold.

[0103] In a third aspect, the present invention provides an electronic device comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned quantum noise-based anti-interference lidar ranging method.

[0104] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned quantum noise-based anti-interference lidar ranging method.

[0105] In summary, the present invention only needs to perform random phase modulation, and no random amplitude modulation is required; the demand for random numbers is greatly reduced, and only phase modulation is required, so that the signal is distributed on a circular ring centered on the origin in the phase space, and there is no distribution within the circle; the theoretical basis for anti-deception interference is discrete phase modulation, and discrete phase modulation is achieved by two-phase modulation plus phase rotation.

[0106] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An anti-interference laser radar based on quantum noise, characterized in that: include: A random number generator, used to generate a true random number sequence; A laser for generating a coherent optical signal; A beam splitter, used for splitting the coherent state optical signal into signal light and local oscillator light; A phase modulation module, used for performing random phase modulation on the signal light according to a true random number sequence, so that the phase difference between adjacent signal lights is smaller than the vacuum shot noise; A transmitting telescope is used to expand the signal light after random phase modulation and illuminate the target object; A receiving telescope, used for receiving the echo signal light reflected by the target object; A coherent detection module, used to measure the phase of the echo signal light in combination with the local oscillator light; A data acquisition module, used to collect the electrical signal output by the coherent detection module and generate initial data; The data processing module is used to calculate the phase of the initial data, generate demodulated data and perform shift cross-correlation operation with the true random number sequence to obtain the target distance; and is used to count the bit error rate of the demodulated data when the cross-correlation operation reaches a peak value. When the bit error rate exceeds a threshold, it is determined that deception interference exists.

2. The anti-interference laser radar based on quantum noise according to claim 1, characterized in that: The random number generator generates a first true random number sequence {x} of L bits and M A second true random number sequence {y} of L bits.

3. The anti-interference laser radar based on quantum noise according to claim 2, characterized in that: The phase modulation module includes a first driving module and a first phase modulator; The first driving module divides the second true random number sequence {y} into L M-bit sub-blocks {z}, and combines the first true random number sequence {x} to construct a phase modulation sequence { } and generates a first driving signal to drive the first phase modulator to phase modulate the signal light.

4. The anti-interference laser radar based on quantum noise according to claim 2, characterized in that: The phase modulation module includes a second driving module, a third driving module, a Mach-Zehnder modulator and a second phase modulator; The second driving module generates a second driving signal according to the first true random number sequence {x}, driving the Mach-Zehnder modulator to perform binary phase modulation on the signal light; The third driving module divides the second true random number sequence {y} into L M-bit sub-blocks {z} to construct a phase rotation base sequence { } and generates a third driving signal to drive the second phase modulator to phase modulate the signal light.

5. The anti-interference laser radar based on quantum noise according to any one of claims 1 to 4, characterized in that: The random number generator is a quantum random number generator.

6. The anti-interference laser radar based on quantum noise according to any one of claims 1 to 4, characterized in that: An optical fiber amplifier is arranged before the transmitting telescope.

7. The anti-interference laser radar based on quantum noise according to any one of claims 1 to 4, characterized in that: The coherent detection module includes a 90° optical mixer and two balanced detectors. The echo signal light and the local oscillator light sequentially enter the 90° optical mixer and the two balanced detectors for coherent detection.

8. A quantum noise-based anti-interference laser radar ranging method, applied to a quantum noise-based anti-interference laser radar according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: Step S1: The laser generates a coherent light signal which is split into a signal light and a local oscillator light by a beam splitter; Step S2: the phase modulation module performs random phase modulation on the signal light according to the true random number sequence generated by the random number generator, so that the phase difference between adjacent signal lights is smaller than the vacuum shot noise; Step S3: The signal light subjected to random phase modulation is expanded by the transmitting telescope and illuminates the target object, and after being reflected, it forms an echo signal light and enters the receiving telescope; Step S4: using the coherent detection module and the local oscillator light to perform coherent detection on the echo signal light, and collecting the electrical signal output by the coherent detection module through the data acquisition module to generate initial data; Step S5: Use the data processing module to perform phase calculation on the initial data, generate demodulated data, and perform shift cross-correlation operation with the true random number sequence to obtain the target distance; Step S6: Count the bit error rate of the demodulated data when the cross-correlation operation reaches a peak value, and when the bit error rate exceeds a threshold, determine that there is deception interference on the target.

9. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; Wherein, when one or more programs are executed by the one or more processors, the one or more processors implement the quantum noise-based anti-interference lidar ranging method as described in claim 8.

10. A computer-readable storage medium, characterized in that: Executable instructions are stored thereon, which, when executed by a processor, enable the processor to implement a quantum noise-based anti-interference laser radar ranging method as described in claim 8.

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