Microwave quantum radar receiver based on low-temperature superconducting Josephson junction device

Abstract

The invention provides a microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device, and aims to solve the problem of receiving and detecting a large-dynamic-range signal by a microwave quantum radar, and the microwave quantum radar receiver based on the low-temperature superconducting Josephson junction device is obtained by utilizing the ultrahigh sensitivity characteristic of the low-temperature superconducting Josephson junction device. By designing the receiver with either the microwave single-photon detector or the parametric amplifier, the dynamic range of the receiver is widened, extremely weak signals to common signals can be effectively received and detected, the receiver can be well matched with a transmitter of a traditional radar, and the reliability and practicability of the microwave quantum radar are improved.

Description

Technical Field

[0001] The present invention belongs to the field of microwave quantum radar, and specifically relates to a microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device. Background Art

[0002] Quantum radar is a new type of radar that combines radar technology with quantum technology. It makes full use of the quantum characteristics of electromagnetic waves to break through the performance limits of classical detection and has broad application prospects. An important feature of quantum radar over traditional radar is that it has higher sensitivity and can detect farther distances at the same transmission power and antenna size.

[0003] Quantum radars in the optical frequency band, especially laser quantum radars based on single-photon detection, have been fully studied, but research on microwave quantum radars is still in its infancy. The document "Vortex Microwave Quantum Radar" (Journal of Radar, Issue 05, 2021) discloses a microwave quantum radar system based on the quantum state of orbital angular momentum (OAM) of electromagnetic waves. The OAM quantum state has a strong reflection coefficient for traditional absorbing materials, resulting in an increase in the radar scattering cross-section (RCS), which can improve the received signal power and detection probability of the target echo. When the same polarization mode is used at both the transmitting and receiving ends, the echo power in the experiment is increased by about 9dB compared with traditional radars. The disadvantage is that this type of microwave quantum radar needs to use gyrotrons and other equipment at the transmitting end to prepare the OAM quantum state, which is very different from the transmitter idea of ​​conventional microwave radars, especially phased array radars. The life and reliability of gyrotrons are not as good as solid-state devices, which brings obstacles to the further application of microwave quantum radars. Summary of the invention

[0004] In view of the above technical problems, the purpose of the present invention is to propose a microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device, which utilizes the ultra-high sensitivity characteristics of the low-temperature superconducting Josephson junction device to effectively receive and detect extremely weak signals to ordinary signals, and can be well matched with the transmitter of a traditional radar, thereby improving the reliability and practicality of the microwave quantum radar.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device, by comprehensively utilizing a microwave single-photon detector and a parametric amplifier based on a low-temperature superconducting Josephson junction at the receiving end, performing receiving link selection for echo signals of different intensities, thereby realizing ultra-high sensitivity microwave signal reception and detection.

[0006] Specifically, it includes: a low-temperature switch and two parallel receiving channels. The first receiving channel is a microwave single-photon detector receiving link, including an attenuator, a microwave single-photon detector, a readout signal amplifier, and a readout signal reading device arranged in sequence. The second receiving channel is a parametric amplifier receiving link, including a parametric amplifier, a post-amplifier, a signal sampling device, and a signal processing device arranged in sequence.

[0007] The function of the attenuator is to attenuate the external noisy echo signal to avoid the influence of excessive input noise on signal detection; the function of the microwave single-photon detector is to receive the echo signal and output the readout signal containing the detection result; the function of the readout signal amplifier is to further amplify the readout signal to facilitate the reading of subsequent equipment; the function of the readout signal reading device is to read and analyze the amplified readout signal.

[0008] The attenuator attenuates the noisy echo signal input from the outside to the microwave quantum radar receiver, in order to keep the false alarm probability of single photon detection within the radar design requirements. The false alarm probability is

[0009]

[0010] Among them, P fa,1 is the false alarm probability of the microwave single photon detector receiving link, N n is the average noise photon number of the input microwave single photon detector, C d is the microwave single photon detector dark count rate, B is the receiver bandwidth, N n The expression is

[0011]

[0012] Where k is the Boltzmann constant, T a is the noise temperature of the external input, τ is the pulse time, h is the Planck constant, f is the receiver frequency, and L is the attenuation of the attenuator.

[0013] Radars generally give an upper limit on the false alarm probability, assuming this upper limit is P fa,0 , that is

[0014] P fa,1 ≤P fa,0

[0015] When other parameters are given, the required attenuation L of the attenuator can be calculated according to the above formula.

[0016] The microwave single-photon detector is a signal detection device based on a superconducting Josephson junction. It can determine whether there are photons in the input signal, that is, output "1" (photon) or "0" (no photon).

[0017] The function of the parametric amplifier is to amplify the echo signal with ultra-low noise to ensure the performance of the receiving link; the function of the post-amplifier is to further amplify the signal to facilitate subsequent sampling and processing; the function of the signal sampling device is to digitally sample the signal; the function of the signal processing device is to detect the signal through calculation based on the results of the digital sampling of the signal.

[0018] The microwave quantum radar receiver of the present invention first uses a microwave single-photon detector receiving link to receive an echo signal, and analyzes whether the false alarm probability meets the requirements by pre-receiving environmental noise. When the false alarm probability meets the requirements, the microwave single-photon detector receiving link is continued to be used for signal reception and detection; when the false alarm probability does not meet the requirements, a low-temperature switch is used to switch to a parameter amplifier receiving link for signal reception and detection.

[0019] The method for determining the false alarm probability is:

[0020] Using a cryogenic switch, the microwave single-photon detector receiving link is selected. Before the radar officially works, the echo reception detection is first performed according to the radar parameters without detecting a target. At this time, the microwave single-photon detector outputs "1" which represents a false alarm caused by noise. According to the number of "1" counted, the actual false alarm probability is calculated as:

[0021]

[0022] Among them, P fa,1 ' is the actual false alarm probability, K is the number of false alarm "1" occurrences, τ K It is the statistical duration.

[0023] The actual false alarm probability P fa,1 ' and the upper limit of false alarm probability P designed by radar fa,0 In contrast, if P fa,1 '≤P fa,0 , then it meets the requirements if P fa,1 '>P fa,0 , it does not meet the requirements.

[0024] The principle of microwave single-photon detector receiving link signal detection is: when the result output by the microwave single-photon detector is "1", it is judged that the target signal exists; when the result output by the microwave single-photon detector is "0", it is judged that the target signal does not exist.

[0025] The detection principle of the parametric amplifier receiving link is: first, calculate the detection threshold voltage by pre-receiving the environmental noise: before the radar officially works, in the absence of a detected target, perform echo reception detection according to the radar parameters, and the average power received by the radar is the noise power Pn;

[0026] The parametric amplifier is a signal detection device based on superconducting Josephson junction, which can amplify the input signal with ultra-low noise. The device indicators include amplifier noise T. Considering the external noise Ta, the total noise received by the parametric amplifier is T+Ta, the noise power is Pn=k(T+Ta)B, and the false alarm probability is:

[0027]

[0028] Where Pfa,2 is the false alarm probability of the parametric amplifier receiving link, VT is the detection threshold voltage, and exp() is the e exponential function;

[0029] Assume that the upper limit of the radar's given false alarm probability is Pfa,0, that is:

[0030] Pfa,2≤Pfa,0

[0031] When other parameters are given, the detection threshold voltage VT is calculated according to the above formula:

[0032]

[0033] Then, when the output voltage exceeds the detection threshold voltage VT, it is determined that the target signal exists; otherwise, it is determined that the target signal does not exist.

[0034] Compared with the prior art, the beneficial effects of the technical solution adopted by the present invention are as follows: the present invention can effectively receive and detect large-scale signals ranging from extremely weak energy to conventional echo energy. When the signal and noise are extremely weak, the use of a microwave single-photon detector receiving link can effectively detect signals at the single photon level; when the signal and noise exceed the allowable range of the microwave single-photon detector, the use of a parametric amplifier receiving link can achieve large dynamic signal detection, and at the same time can be compatible with the transmitter and working system of conventional microwave radars, thereby improving the reliability and practicality of microwave quantum radars. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the structure of the microwave quantum radar receiver in this embodiment. DETAILED DESCRIPTION

[0036] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and examples.

[0037] like Figure 1 As shown, this embodiment discloses a microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device, which uses a microwave single-photon detector and a parametric amplifier based on a low-temperature superconducting Josephson junction to build a two-choice switching receiver.

[0038] The main purpose is to build a microwave quantum radar receiver with two receiving channels. The core components of the two receiving channels are microwave single-photon detectors and parametric amplifiers based on low-temperature superconducting Josephson junctions. The two channels target different signal and noise dynamic ranges.

[0039] The microwave single-photon detector receiving link includes: attenuator, microwave single-photon detector, readout signal amplifier, and readout signal reading device. The attenuator is used to attenuate the echo signal with external noise to avoid the influence of excessive input noise on signal detection; the microwave single-photon detector is used to receive the echo signal and output the readout signal containing the detection result; the readout signal amplifier is used to further amplify the readout signal to facilitate the reading of subsequent equipment; the readout signal reading device is used to read and analyze the amplified readout signal.

[0040] The attenuator attenuates the noisy echo signal input from the outside to the microwave quantum radar receiver, in order to keep the false alarm probability of single photon detection within the radar design requirements. The false alarm probability is

[0041]

[0042] Among them, P fa,1 is the false alarm probability of the microwave single photon detector receiving link, N n is the average noise photon number of the input microwave single photon detector, C d is the microwave single photon detector dark count rate, B is the receiver bandwidth, N n The expression is

[0043]

[0044] Where k is the Boltzmann constant, T a is the noise temperature of the external input, τ is the pulse time, h is the Planck constant, f is the receiver frequency, and L is the attenuation of the attenuator.

[0045] Radars generally give an upper limit on the false alarm probability, assuming this upper limit is P fa,0 , that is

[0046] P fa,1 ≤P fa,0

[0047] When other parameters are given, the required attenuation L of the attenuator can be calculated according to the above formula.

[0048] In the example, we set the following parameters:

[0049] External input noise temperature T a 30K;

[0050] The pulse time τ is 10us;

[0051] The receiver frequency f is 10 GHz;

[0052] Microwave single photon detector dark count rate C d 1cps (cps: count per second, counts per second);

[0053] The receiver bandwidth B is 10MHz;

[0054] Upper limit of false alarm probability P fa,0 For 10 -6 .

[0055] At the same time, there are the following physical constants:

[0056] The Boltzmann constant k is 1.38×10 -23 J / K;

[0057] Planck's constant h is 6.63×10 -34 J.S.

[0058] According to the above parameters, P fa,1 ≤P fa,0 , that is

[0059]

[0060] The attenuation of the attenuator that can be used is L=88.4dB.

[0061] The microwave single-photon detector is a signal detection device based on a superconducting Josephson junction. It can determine whether there are photons in the input signal, that is, output "1" (photon) or "0" (no photon).

[0062] The parametric amplifier receiving link includes: parametric amplifier, post-stage amplifier, signal sampling device, and signal processing device. The function of the parametric amplifier is to amplify the echo signal with ultra-low noise to ensure the performance of the receiving link; the function of the post-stage amplifier is to further amplify the signal to facilitate subsequent sampling and processing; the function of the signal sampling device is to digitally sample the signal; the function of the signal processing device is to detect the signal through calculation based on the result of the digital sampling of the signal.

[0063] Using a cryogenic switch, the microwave single photon detector receiving link and the parametric amplifier receiving link are connected in parallel to build a two-choice microwave quantum radar receiver, such as Figure 1 shown.

[0064] In this embodiment, the microwave quantum radar receiver first uses a microwave single-photon detector receiving link to receive an echo signal, and by pre-receiving environmental noise, analyzes whether the false alarm probability meets the requirements. When the false alarm probability meets the requirements, the microwave single-photon detector receiving link continues to be used for signal reception and detection; when the false alarm probability does not meet the requirements, a low-temperature switch is used to switch to a parametric amplifier receiving link for signal reception and detection.

[0065] The method for determining the false alarm probability is:

[0066] Using a cryogenic switch, the microwave single-photon detector receiving link is selected. Before the radar officially works, the echo reception detection is first performed according to the radar parameters without detecting a target. At this time, the microwave single-photon detector outputs "1" which represents a false alarm caused by noise. According to the number of "1" counted, the actual false alarm probability is calculated as:

[0067]

[0068] Among them, P fa,1 ' is the actual false alarm probability, K is the number of false alarm "1" occurrences, τ K It is the statistical duration.

[0069] The actual false alarm probability P fa,1 ' and the upper limit of false alarm probability P designed by radar fa,0 In contrast, if P fa,1 '≤P fa,0 , then it meets the requirements if P fa,1 '>P fa,0 , it does not meet the requirements.

[0070] In an embodiment, two cases are considered:

[0071] Case A, requirement P fa,0 =10 -6 . In the statistical time τ K =10s, receiver bandwidth B=10MHz, the number of false alarm "1" occurrences K=10, then P fa,1 '=10 -7 , P fa,1 '≤P fa,0 , so continue to use the microwave single photon detector receiving link for signal reception and detection.

[0072] Case B, requirement P fa,0 =10 -6 . In the statistical time τ K =10s, receiver bandwidth B=10MHz, the number of false alarm "1" occurrences K=1000, then P fa,1'=10 -5 , P fa,1 '>P fa,0 Therefore, a cryogenic switch is used to switch to the parametric amplifier receiving link for signal reception detection.

[0073] If the false alarm probability meets the requirement, the microwave single photon detector receiving link is continued to be used for signal reception detection.

[0074] The detection principle is that when the result output by the microwave single-photon detector is "1", it is determined that the target signal exists; when the result output by the microwave single-photon detector is "0", it is determined that the target signal does not exist.

[0075] For case A of the embodiment, this step is performed without switching to the parametric amplifier receiving link.

[0076] If the false alarm probability does not meet the requirements, a cryogenic switch is used to switch to the parametric amplifier receiving link.

[0077] This step is performed for case B of the embodiment.

[0078] The purpose of this step is mainly to use a parametric amplifier to receive and detect signals for echo signals that require large dynamic range of the receiver instead of using a microwave single-photon detector to ensure the detection of echo signals of normal intensity.

[0079] By pre-receiving the environmental noise, the detection threshold voltage is calculated.

[0080] Before the radar officially works, firstly, in the absence of a detected target, the radar receives echoes according to the radar parameters for detection. The average power received by the radar is the noise power P. n .

[0081] The parametric amplifier is a signal detection device based on a superconducting Josephson junction, which can amplify the input signal with ultra-low noise. The device indicators include the amplifier noise T. Considering the external noise T a , the total noise received by the parametric amplifier is T+T a , the noise power is P n = k(T + T a ) B, the false alarm probability is

[0082]

[0083] Among them, P fa,2 is the false alarm probability of the parametric amplifier receiving link, V T is the detection threshold voltage, and exp(x) is the e exponential function.

[0084] Radars generally give an upper limit on the false alarm probability, assuming this upper limit is P fa,0, that is

[0085] P fa,2 ≤P fa,0

[0086] When other parameters are given, the detection threshold voltage V can be calculated according to the above formula. T for

[0087]

[0088] In the example, we set the following parameters:

[0089] The amplifier noise T is 1K;

[0090] External noise T a 50K;

[0091] The receiver bandwidth B is 10MHz;

[0092] Upper limit of false alarm probability P fa,0 For 10 -6 .

[0093] At the same time, there are the following physical constants:

[0094] The Boltzmann constant k is 1.38×10 -23 J / K.

[0095] According to the above parameters, we can get: V T =-127.1dBV / Ω 1 / 2 The unit Ω is because the above calculation is based on unit resistance.

[0096] A parametric amplifier receiving link is used to perform signal reception detection. The detection principle is that when the output voltage exceeds the detection threshold voltage, it is determined that the target signal exists; otherwise, it is determined that the target signal does not exist.

[0097] In the embodiment, assuming that the link matching resistance is 50Ω, the actual detection threshold voltage is V T = -110.1dBV. When the signal processing device analyzes the voltage result given by the signal sampling device, the output voltage exceeds V T When , it is determined that the target signal exists; otherwise, it is determined that the target signal does not exist.

[0098] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device, characterized in that: It includes a cryogenic switch and two parallel receiving channels. The first receiving channel is a microwave single-photon detector receiving link, including an attenuator, a microwave single-photon detector, a readout signal amplifier, and a readout signal reading device arranged in sequence. The second receiving channel is a parametric amplifier receiving link, including a parametric amplifier, a post-amplifier, a signal sampling device, and a signal processing device arranged in sequence.

2. A microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device according to claim 1, characterized in that: In the first receiving channel, the attenuator is used to attenuate the external noisy echo signal to avoid the influence of excessive input noise on signal detection; the microwave single-photon detector is used to receive the echo signal and output a readout signal containing the detection result; the readout signal amplifier is used to further amplify the readout signal to facilitate reading by subsequent equipment; the readout signal reading device is used to read and analyze the amplified readout signal.

3. The microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device according to claim 1, characterized in that: The attenuator attenuates the noisy echo signal input from the outside to the microwave quantum radar receiver in order to keep the false alarm probability of single photon detection within the radar design requirements. The false alarm probability is: Among them, P fa,1 is the false alarm probability of the microwave single photon detector receiving link, N n is the average noise photon number of the input microwave single photon detector, C d is the microwave single photon detector dark count rate, B is the receiver bandwidth, N n The expression is: Where k is the Boltzmann constant, T a is the noise temperature of the external input, τ is the pulse time, h is the Planck constant, f is the receiver frequency, and L is the attenuation of the attenuator. Assume that the upper limit of the false alarm probability of the radar is P fa,0 , that is: P fa,1 ≤P fa,0 When other parameters are given, the required attenuation L of the attenuator can be calculated according to the above formula.

4. The microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device according to claim 3, characterized in that: The microwave single-photon detector is a signal detection device based on a superconducting Josephson junction. It can determine whether there are photons in the input signal, that is, output "1" or "0", "1" represents the presence of photons, and "0" represents the absence of photons.

5. The microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device according to claim 1, characterized in that: In the second receiving channel, the parametric amplifier is used to amplify the echo signal with ultra-low noise to ensure the performance of the receiving link; the post-amplifier is used to further amplify the signal to facilitate subsequent sampling and processing; the signal sampling device is used to digitally sample the signal; and the signal processing device is used to detect the signal through calculation based on the results of the digital sampling of the signal.

6. A microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device according to any one of claims 1 to 5, characterized in that: A microwave single-photon detector receiving link is used to receive the echo signal. By pre-receiving the environmental noise, the false alarm probability is analyzed to see whether it meets the requirements. When the false alarm probability meets the requirements, the microwave single-photon detector receiving link is continued to be used for signal reception and detection. When the false alarm probability does not meet the requirements, a low-temperature switch is used to switch to the parametric amplifier receiving link for signal reception and detection.

7. A microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device according to claim 6, characterized in that: The method for determining the false alarm probability is: Using a cryogenic switch, the microwave single-photon detector receiving link is selected. Before the radar officially works, the echo reception detection is first performed according to the radar parameters without detecting a target. At this time, the microwave single-photon detector output "1" represents a false alarm caused by noise. According to the number of "1" counted, the actual false alarm probability is calculated as: Among them, P fa,1 ' is the actual false alarm probability, K is the number of false alarm "1" occurrences, τ K It is the statistical duration. The actual false alarm probability P fa,1 ' and the upper limit of false alarm probability P designed by radar fa,0 In contrast, if P fa,1 '≤P fa,0 , then it meets the requirements if P fa,1 '>P fa,0 , it does not meet the requirements.

8. The microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device according to claim 6, characterized in that: The principle of microwave single-photon detector receiving link signal detection is: when the result output by the microwave single-photon detector is "1", it is judged that the target signal exists; when the result output by the microwave single-photon detector is "0", it is judged that the target signal does not exist.

9. A microwave quantum radar receiver based on a low-temperature superconducting Josephson junction device according to claim 6, characterized in that: The detection principle of the parametric amplifier receiving link is: First, the detection threshold voltage is calculated by pre-receiving the environmental noise: before the radar officially works, in the absence of a detected target, echo reception detection is performed according to the radar parameters, and the average power received by the radar is the noise power P n ; The parametric amplifier is a signal detection device based on superconducting Josephson junction, which can amplify the input signal with ultra-low noise. The device indicators include amplifier noise T; considering the external noise T a , the total noise received by the parametric amplifier is T+T a , the noise power is P n = k(T + T a ) B, the false alarm probability is: Among them, P fa,2 is the false alarm probability of the parametric amplifier receiving link, V T is the detection threshold voltage, exp() is the e exponential function; Assume that the upper limit of the false alarm probability of the radar is P fa,0 , that is: P fa,2 ≤P fa,0 When other parameters are given, the detection threshold voltage V is calculated according to the above formula. T for: Then, when the output voltage exceeds the detection threshold voltage VT, it is determined that the target signal exists; otherwise, it is determined that the target signal does not exist.

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