Broadband signal detection method based on reflective narrowband JPA

Abstract

The invention relates to a broadband signal detection method based on a reflective narrowband JPA, and the method comprises the following steps: S1, determining the frequency band range of a to-be-detected signal, and selecting an appropriate narrowband JPA group; s2, establishing a signal high-sensitivity amplification link in an extremely low temperature environment by using a narrowband JPA group and a corresponding number of circulators; s3, using an amplifier and an ADC (Analog to Digital Converter) to build a signal post-amplification and sampling link at normal temperature; and S4, processing an ADC sampling result to complete signal detection. According to the broadband signal detection method based on the reflective narrowband JPA, the problem that the working bandwidth is narrow although the sensitivity of the JPA is extremely high can be solved by using a reflective JPA cascade mode, extremely weak energy signals in a broadband range can be effectively received and detected, and the practicability of the type of signal detection equipment is improved.

Description

Technical Field

[0001] This invention relates to the field of radar detection technology, and in particular to a broadband signal detection method based on reflective narrowband JPA. Background Technology

[0002] In 1962, Josephson proposed that electron pairs can still pass through a thin insulating layer between two superconductors separated by a thin insulating layer, even without a potential difference, thus exhibiting superconductivity. This is the Josephson junction. When two identical Josephson junctions are connected in parallel to form a superconducting closed-loop circuit, the quantization of magnetic flux within the superconducting ring establishes a relationship with the phase of the two Josephson junctions due to the superconducting ring flux quantization effect, resulting in a macroscopic quantum interference effect. This effect can be used to create various superconducting quantum interference devices (SQUIDs). On the other hand, in the microwave band, there exists a simple, stable, and dissipation-free component: the Josephson tunnel junction. Its nonlinearity can dominate the linear operation of circuits at the single microwave photon level, enabling various quantum signal processing functions. In particular, the Josephson parametric amplifier (JPA) has the ability to amplify signals with low noise or even zero noise.

[0003] Due to the rapid development of quantum computing technology, Josephson junction devices, such as amplifiers and detectors, have been extensively studied. However, there is a lack of research on using JPAs for broadband signal detection. The paper "Research on Superconducting Josephson Parametric Amplifiers" (Nanjing University, Lu Yapeng, Doctoral Dissertation) provides a detailed analysis of the principles, fabrication, and testing of JPAs. In fact, most existing high-performance JPAs operate within a narrow bandwidth, typically on the order of a few MHz, classifying them as narrowband amplifiers. Broadband JPAs, on the other hand, suffer from lower gain and larger gain fluctuations within the bandwidth. In the field of radar detection, radar typically operates with a wider bandwidth to meet requirements such as multifunctionality, anti-interference, and high resolution. Therefore, the practical application of narrowband JPAs in radar faces obstacles. Summary of the Invention

[0004] To address the existing technical problems, this invention provides a broadband signal detection method based on reflective narrowband JPA, comprising the following steps:

[0005] S1, determine the frequency band range of the signal to be detected and select a suitable narrowband JPA group;

[0006] S2 uses a narrowband JPA group and a corresponding number of circulators to build a high-sensitivity signal amplification link in an extremely low temperature environment;

[0007] S3 uses an amplifier and ADC to build a signal post-amplification and sampling link at room temperature;

[0008] S4 processes the ADC sampling results to complete signal detection.

[0009] Furthermore, in S1, the frequency band range is determined based on the source and characteristics of the signal to be detected. If the radar signal is being received and detected, the operating frequency band range of the radar transmitter is referenced; if the communication signal is being intercepted and detected, the frequency band used by the communication equipment is referenced.

[0010] Furthermore, in S1, the union of the operating frequency bands of the selected narrowband JPA group can cover the frequency band range of the signal to be detected, and the gain of the JPA can ensure that the amplified level meets the requirements of the ADC.

[0011] Furthermore, S2 includes:

[0012] S21, Pair the narrowband JPA with the circulator one by one: Based on the number of narrowband JPA groups in S1, prepare the same number of circulators, and connect the ports of the JPAs to the B ports of the circulators one by one to form several combinations of narrowband JPA-circulators.

[0013] S22, connect multiple narrowband JPA-circulators end to end to form a link: connect the C port of the circulator in the previous narrowband JPA-circulator combination to the A port of the circulator in the next narrowband JPA-circulator combination, and so on; the A port of the circulator in the first narrowband JPA-circulator combination is connected to the input signal, and the C port of the circulator in the last narrowband JPA-circulator combination is connected to the room temperature amplifier.

[0014] Furthermore, in S3, a room-temperature amplifier covering the frequency band of the signal to be detected is selected to further amplify the signal after JPA amplification, and an ADC is used to digitally sample the signal further amplified by the room-temperature amplifier to obtain sampling level data.

[0015] Furthermore, S4 includes:

[0016] S41, according to the format of the ADC data, use data processing software to read the data;

[0017] S42 processes the data, selects a segment of data outside the detection signal frequency band, calculates the average value as the noise reference, sets the detection level threshold according to the signal detection accuracy requirements, and checks whether there is data exceeding the threshold within the detection signal frequency band.

[0018] The broadband signal detection method based on reflective narrowband JPA of the present invention can effectively receive and detect extremely weak energy signals over a wide bandwidth, thereby improving the practicality of this type of signal detection equipment. Attached Figure Description

[0019] The invention will be further explained below with reference to the accompanying drawings.

[0020] Figure 1 This is a schematic diagram of the pairing of the narrowband JPA and the circulator of the present invention;

[0021] Figure 2 This is a schematic diagram of a low-temperature, high-sensitivity signal amplification link.

[0022] Figure 3 This is a schematic diagram of room temperature amplification and digital sampling. Detailed Implementation

[0023] Combination Figures 1-3 The broadband signal detection method based on reflective narrowband JPA of the present invention includes the following steps: (1) determining the frequency band range of the signal to be detected and selecting a suitable narrowband JPA group; (2) using the narrowband JPA group and the corresponding number of circulators to build a high-sensitivity signal amplification link in an extremely low temperature environment; (3) using an amplifier and an analog-to-digital converter (ADC) to build a signal post-amplification and sampling link at room temperature; (4) using a computer or other equipment to process the ADC sampling results and complete the signal detection.

[0024] Specifically as follows:

[0025] (1) Determine the frequency band range of the signal to be detected and select a suitable narrowband JPA group.

[0026] The main purpose of this step is to determine the number of JPA devices required for the narrowband JPA group based on the relationship between the frequency band of the signal to be detected and the capability of the narrowband JPA.

[0027] 1) Determine the frequency band range of the signal to be detected.

[0028] Based on the source and characteristics of the signal to be detected, its possible frequency band range is determined. For example, if the detection is to receive radar signals, then the operating frequency band range of the radar transmitter must be known; if the detection is to intercept and intercept communication signals, then the frequency band used by the communication equipment must be known.

[0029] In this embodiment, the radar signal is received and detected. The frequency range of the radar transmitted signal is 4000MHz~4100MHz, and the operating bandwidth is 100MHz.

[0030] 2) Select a suitable narrowband JPA group

[0031] A suitable set of JPAs should have an operating frequency band union that covers the frequency range of the signal to be detected; at the same time, the number of JPAs used should be minimized to save costs and simplify the link. In addition, the gain of the JPAs needs to be high enough to ensure that the amplified level meets the requirements of the ADC.

[0032] First, the possible operating bandwidth of the narrowband JPA needs to be determined based on the required JPA gain. For example, for radar signal reception and detection, the gain of the preamplifier is generally required to be at least 25dB. This is because the wider the operating bandwidth, the lower the JPA gain will be. Therefore, a 25dB gain requires that the JPA operating bandwidth cannot be too wide. In this embodiment, we assume that the selected narrowband JPA has an operating bandwidth of not less than 10MHz and a gain of not less than 25dB.

[0033] In order for the union of the operating frequency bands of such a set of narrowband JPAs to cover 4000MHz~4100MHz, we need at least 10 narrowband JPAs with operating frequency bands of 4000MHz~4010MHz, 4010MHz~4020MHz, ..., 4090MHz~4100MHz respectively.

[0034] (2) Using narrowband JPA groups and a corresponding number of circulators, a high-sensitivity signal amplification link is built in an extremely low temperature environment.

[0035] The main purpose of this step is to cascade narrowband JPA groups and utilize the property of reflective JPAs to amplify signals within the operating frequency band while reflecting signals outside the operating frequency band, so that the narrowband JPA groups can cover the frequency band of the signal to be detected and amplify all signals within the frequency band.

[0036] 1) Pair the narrowband JPA with the circulator one by one.

[0037] A reflective narrowband JPA is a single-port device; the signal is input from the port and reflected back from the port. A circulator is a three-port device (the three ports are denoted as A, B, and C); its signal transmission direction is directional, such as A->B->C->A, and it cannot be transmitted in reverse. Based on the number of narrowband JPA groups in (1), prepare the same number of circulators and connect the ports of the JPAs to the B ports of the circulators one by one.

[0038] In this embodiment, as Figure 1 As shown, a JPA port is connected to port B of a circulator. A signal is input from port A of the circulator, output from port B to the JPA, and then reflected back to port B. The signal is then input from port B and output from port C of the circulator. During this process, if the signal is within the JPA's operating frequency band, its power is amplified by 25 dB; if the signal is outside the JPA's operating frequency band, it is not amplified.

[0039] 2) Connect multiple narrowband JPA-circulators end-to-end to form a link.

[0040] Connect port C of the circulator in the previous set of "narrowband JPA-circulator" combinations to port A of the circulator in the next set of "narrowband JPA-circulator" combinations, and so on. Connect port A of the circulator in the first set of "narrowband JPA-circulator" combinations to the input signal, and connect port C of the circulator in the last set of "narrowband JPA-circulator" combinations to the ambient temperature amplifier.

[0041] In this embodiment, as Figure 2 As shown, the 10 narrowband JPAs are each configured according to... Figure 1 The method shown is to combine and pair the components, and sort them from 1 to 10. Input the signal to be detected into port A of combination 1, connect port C of combination 1 to port A of combination 2, port C of combination 2 to port A of combination 3, and so on. Finally, send port C of combination 10 out to the low-temperature environment for further amplification by the room-temperature amplifier.

[0042] (3) Construct the signal post-amplification and sampling link using an amplifier and an analog-to-digital converter (ADC) at room temperature.

[0043] The purpose of this step is primarily to further amplify the signal after JPA amplification to meet the digital sampling requirements of the ADC; the ADC is then used to digitally sample the signal, converting the analog signal into a digital level for easier subsequent analysis and processing. For example... Figure 3 As shown.

[0044] 1) Use a room temperature amplifier to further amplify the signal to be detected.

[0045] Room temperature amplifiers can typically achieve a large bandwidth, so a room temperature amplifier that covers the frequency range of the signal to be detected can be selected to further amplify the signal after JPA amplification.

[0046] In this embodiment, a room-temperature amplifier with a gain of 35dB and a bandwidth covering 4000MHz~4100MHz is selected to further amplify the signal.

[0047] 2) Use an analog-to-digital converter (ADC) to convert the signal from analog to digital to generate a digital sampling signal.

[0048] The signal, which is further amplified by the ambient temperature amplifier, is digitally sampled using an ADC to obtain sampled level data. This data is then used for further processing and analysis.

[0049] (4) Use computers and other equipment to process the ADC sampling results and complete signal detection.

[0050] The purpose of this step is mainly to read the sampling level data and detect the presence or absence of a signal.

[0051] 1) Use a computer or other equipment to read the data generated by the ADC.

[0052] Based on the format of the ADC data, data processing software such as MATLAB is used to read the data.

[0053] 2) Detect the presence or absence of a signal within the frequency band of the signal to be detected.

[0054] The data is processed, and a segment of data outside the detection signal frequency band is selected to calculate the average value as the noise reference. According to the signal detection accuracy requirements, a threshold for the detection level is set, and data exceeding the threshold is checked within the detection signal frequency band.

[0055] In this embodiment, it is assumed that there is a signal input detection device with a power of -80dBm, a frequency band of 4036MHz~4037MHz, and a bandwidth of 1MHz. When the signal enters a low-temperature environment, it will be amplified by the fourth JPA, reducing the power to -55dBm. Afterward, when the signal enters a normal-temperature environment, it will be amplified by a normal-temperature amplifier, reducing the power to -20dBm. Assuming a loss of 10dB during the entire link transmission process, the final signal power is -30dBm, and the signal spectral power density after digital sampling is -30dBm / 1MHz = -90dBm / Hz. The system noise reference, calculated based on the equivalent noise at the input end T = 1K, with the Boltzmann constant k = 1.38*10-23J / K, means the noise spectral power density after digital sampling is kT + 25dB + 35dB = -138.6dBm / Hz. If the detection threshold is set to exceed the noise by 20dB, since the signal is more than 48dB larger than the noise, the signal can be successfully detected.

[0056] The broadband signal detection method based on reflective narrowband JPA proposed in this invention utilizes the ultra-high sensitivity of JPA to effectively receive and detect extremely weak signals. At the same time, by cascading multiple narrowband JPAs, and taking advantage of the direct reflection of signals outside the frequency band by reflective JPAs, it can respond to signals in a wide frequency range, thus improving the practicality of this type of signal detection equipment.

[0057] Many specific details have been set forth in the foregoing description to provide a thorough understanding of the present invention. However, the above description is merely a preferred embodiment of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed above. Furthermore, any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, using the methods and techniques disclosed above, without departing from the scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A broadband signal detection method based on reflective narrowband JPA, characterized in that: Includes the following steps: S1, determine the frequency band range of the signal to be detected and select a suitable narrowband JPA group; S2 uses a narrowband JPA group and a corresponding number of circulators to build a high-sensitivity signal amplification link in an extremely low temperature environment; S3 uses an amplifier and ADC to build a signal post-amplification and sampling link at room temperature; S4 processes the ADC sampling results to complete signal detection.

2. The broadband signal detection method based on reflective narrowband JPA according to claim 1, characterized in that: In S1, the frequency band range is determined based on the source and characteristics of the signal to be detected. If the radar signal is being received and detected, the operating frequency band range of the radar transmitter is referenced; if the communication signal is being intercepted and detected, the frequency band used by the communication equipment is referenced.

3. The broadband signal detection method based on reflective narrowband JPA according to claim 1, characterized in that: In S1, the union of the operating frequency bands of the selected narrowband JPA group can cover the frequency band range of the signal to be detected, and the gain of the JPA can ensure that the amplified level meets the requirements of the ADC.

4. The broadband signal detection method based on reflective narrowband JPA according to claim 1, characterized in that: S2 includes: S21, Pair the narrowband JPA with the circulator one by one: Based on the number of narrowband JPA groups in S1, prepare the same number of circulators, and connect the ports of the JPAs to the B ports of the circulators one by one to form several combinations of narrowband JPA-circulators. S22, connect multiple narrowband JPA-circulators end to end to form a link: connect the C port of the circulator in the previous narrowband JPA-circulator combination to the A port of the circulator in the next narrowband JPA-circulator combination, and so on. In the first group of narrowband JPA-circulator combinations, port A of the circulator is connected to the input signal, while in the last group of narrowband JPA-circulator combinations, port C of the circulator is connected to a room-temperature amplifier.

5. The broadband signal detection method based on reflective narrowband JPA according to claim 1, characterized in that: In S3, a room-temperature amplifier covering the frequency band of the signal to be detected is selected to further amplify the signal after JPA amplification. An ADC is then used to digitally sample the signal further amplified by the room-temperature amplifier to obtain the sampling level data.

6. The broadband signal detection method based on reflective narrowband JPA according to claim 1, characterized in that: S4 includes: S41, according to the format of the ADC data, use data processing software to read the data; S42 processes the data, selects a segment of data outside the detection signal frequency band, calculates the average value as the noise reference, sets the detection level threshold according to the signal detection accuracy requirements, and checks whether there is data exceeding the threshold within the detection signal frequency band.

Images