CPAL-based PT symmetric sensor for enhancing NQR signal detection

Abstract

The invention discloses a PT symmetric sensor based on CPAL for enhancing NQR signal detection. The NQR signal detection system of the sensor is used for detecting NQR signals of a detected object for multiple times and accumulating the NQR signals to serve as excitation signals, and the PT symmetric sensor system based on CPAL receives the excitation signals and coherent signals of the excitation signals to obtain detection signals so as to detect the type of the detected object. Due to the fact that the center frequencies of NQR signals of different substances have a certain difference, a PT symmetric sensor system based on CPAL can generate different outputs for excitation input of different frequencies, and the characteristic and the high sensitivity of the CPAL effect are utilized, so that the NQR signals of different substances can be accurately measured. The problem that detection cannot be carried out due to too low electromagnetic signal energy in the NQR signal-based explosive or drug detection process is effectively solved, and the detection sensitivity and accuracy are enhanced.

Description

Technical Field

[0001] The present invention relates to a symmetric sensor, which relates to the field of NQR signal detection enhancement, and particularly relates to a PT symmetric sensor based on CPAL for enhancing NQR signal detection. Background Art

[0002] The physical mechanism of nuclear quadrupole resonance (NQR) is as follows: The atomic nuclei in a substance are in a non-uniform electric field environment generated by the surrounding charge distribution. When there is an electric field gradient in this electric field, the electric quadrupole moment of the atomic nucleus will couple with the electric field gradient. This interaction causes the energy levels of the atomic nucleus to split, forming a quantized energy state structure. At this time, if the energy quantum (hν) of the externally applied electromagnetic field exactly matches the energy difference between the nuclear energy levels, a resonance phenomenon will occur - the atomic nucleus realizes the transition from the low energy state to the high energy state by absorbing electromagnetic waves, and at the same time, the excited-state atomic nucleus will also return to the ground state by emitting electromagnetic radiation of the same frequency. This electromagnetic transition phenomenon between nuclear energy levels that does not depend on an external magnetic field is called nuclear quadrupole resonance NQR, and the electromagnetic signal of the corresponding frequency radiated by the excited-state atomic nucleus is called the quadrupole resonance NQR signal. The spectral characteristics of nuclear quadrupole resonance depend on the microscopic structure of the substance itself. The applied electromagnetic field is only used to excite the resonance, and the resonance frequency is completely determined by the electric quadrupole moment - electric field gradient coupling of the substance itself. Even for the same type of atomic nucleus, in different molecules, different quadrupole resonance NQR spectra will be shown due to the difference in the local electric field gradient. Therefore, by measuring the resonance spectrum, not only can the nuclide type be identified, but also the molecular structure can be inferred to achieve non-destructive identification of substances. This molecular-specific quadrupole resonance NQR response gives it unique advantages in the fields of chemical analysis, explosive detection, and drug identification.

[0003] In a parity-time (PT) symmetric system composed of a coupled gain and loss oscillator, a coherent perfect absorber laser (CPAL) point can be observed. Generally speaking, the coherent perfect absorber (CPA) state represents a dark medium that completely absorbs the incident radiation, while the laser state is a completely different concept, aiming to generate and propagate coherent electromagnetic radiation with a zero linewidth. At the CPAL point of the parity-time (PT) symmetric coherent perfect absorber laser, by adjusting the initial phase difference between two counter-propagating monotonic input waves, the laser and coherent perfect absorber (CPA) states with completely different scattering characteristics can be switched, thus demonstrating the excellent ability of the parity-time (PT) symmetric sensor based on the coherent perfect absorber laser (CPAL) to enhance sensitivity in the radio frequency range.

[0004] The nuclear quadrupole resonance NQR technology has the advantages of high specificity, non-destructive testing, non-contact operation, and no involvement in radioactive or chemical pollution. However, its practical application faces significant challenges: 1. Weak signal: The nuclear quadrupole resonance NQR relies on the weak electromagnetic signals released by the substance to be measured, and its inherent intensity is low, resulting in limited detection sensitivity; 2. Low signal-to-noise ratio SNR (Signal-to-Noise Ratio): Radio frequency interference RFI (Radio Frequency Interference), electromagnetic noise in the environment, and spurious signals of the instrument itself will seriously interfere with the nuclear quadrupole resonance NQR measurement, making it difficult to extract the effective signal; 3. Difficult detection: Since the signal is easily interfered, advanced signal processing techniques and optimized detection methods are required to improve the signal-to-noise ratio and achieve reliable detection. Summary of the Invention

[0005] To solve the problems existing in the background technology, the present invention provides a CPAL-based PT-symmetric sensor for enhancing NQR signal detection. The present invention designs and manufactures a specific antenna for receiving quadrupole resonance NQR signals of a specific frequency, and uses a parity-time PT-symmetric sensor system based on a coherent perfect absorption laser CPAL to enhance the accuracy and sensitivity of quadrupole resonance NQR signal detection.

[0006] The technical solution adopted by the present invention is: The CPAL-based PT-symmetric sensor for enhancing NQR signal detection of the present invention includes: A quadrupole resonance NQR signal detection system for repeatedly detecting the quadrupole resonance NQR signals of the object to be measured and accumulating them as an excitation signal.

[0007] A parity-time PT-symmetric sensor system based on a coherent perfect absorption laser CPAL for receiving the excitation signal and its coherent signal and then obtaining a detection signal to detect the category of the object to be measured.

[0008] The described quadrupole resonance NQR signal detection system includes a computer, a radio frequency signal generator and receiver, a radio frequency power amplifier, a radio frequency switch, a preamplifier, and a radio frequency antenna. The object to be measured is placed at the center of the radio frequency antenna, and both the object to be measured and the radio frequency antenna are located in an electromagnetic shielding environment. The radio frequency signal generator and receiver include a radio frequency signal generator and a radio frequency signal receiver. When the quadrupole resonance NQR signal detection system performs signal stimulation, the computer controls the radio frequency signal generator to generate a stimulation signal, which is then sequentially transmitted through the radio frequency power amplifier and the radio frequency switch to the radio frequency antenna, so that the center frequency of the radio frequency antenna is the preset center frequency. The radio frequency antenna receives the initial signal generated by the object to be measured, and after passing through the preamplifier, the initial quadrupole resonance NQR signal is output. The initial quadrupole resonance NQR signal is then transmitted through the radio frequency signal receiver to the computer for display. After multiple signal stimulations, the individual initial quadrupole resonance NQR signals are accumulated as the excitation signal and transmitted to the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL.

[0009] The center frequency of the described radio frequency antenna is approximately equal to the design frequency of the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL, and is approximately equal to the center frequency of the quadrupole resonance NQR signal of the object to be measured.

[0010] The described radio frequency signal generator uses an arbitrary waveform signal generator with a frequency range of 0 - 20 MHz.

[0011] The described radio frequency antenna is a hollow solenoid coil and is made of enameled wire.

[0012] The parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL includes a first coupler, a first oscilloscope, a transmission line, a second coupler, a second oscilloscope, a loss element, and an amplification element. The first coupler, the loss element, the transmission line, the amplification element, and the second coupler are connected in sequence. The first coupler and the second coupler are respectively connected to the first oscilloscope and the second oscilloscope. After the excitation signal V1 and its coherent signal V2 are simultaneously transmitted to the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL composed of the loss element, the amplification element, and the transmission line for processing, the output first detection signal V3 and second detection signal V4 are respectively transmitted to the first oscilloscope and the second oscilloscope through the first coupler and the second coupler for display.

[0013] The amplitude ratio of the described excitation signal V1 and its coherent signal V2 is 2 1 / 2 / 2, and the phase difference is 90 degrees.

[0014] The described loss element has a positive conductance G, and the amplification element has a negative conductance -G.

[0015] The transmission lines between the described first coupler, first oscilloscope, transmission line, second coupler, second oscilloscope, loss element, and amplification element are all separated by an electrical length x, where x = π / 2 + δx, and δx is the phase offset of the electrical length x.

[0016] The described second detection signal V4 has an extreme value at the design frequency of the parity-time (PT) symmetric sensor system based on a coherent perfect absorption laser (CPAL), and then it is detected that the current object to be measured is the object category corresponding to the design frequency.

[0017] The parity-time (PT) symmetric sensor system based on a coherent perfect absorption laser (CPAL) operates in the radio frequency domain, consists of a two-port equivalent transmission model, adopts a monotonic sensing scheme, and is realized by detecting whether there is an impedance perturbation at a given frequency as a function of the output intensity.

[0018] The beneficial effects of the present invention are as follows: The present invention innovatively combines a quadrupole resonance NQR detection system and a parity-time (PT) symmetric sensor based on a coherent perfect absorption laser (CPAL), uses a special antenna, takes the quadrupole resonance NQR signal obtained by the quadrupole resonance NQR detection system as the input with maximized excitation and inputs it into the parity-time (PT) symmetric sensor based on a coherent perfect absorption laser (CPAL), and determines the substance corresponding to the quadrupole resonance NQR signal by judging the output of the parity-time (PT) symmetric sensor based on a coherent perfect absorption laser (CPAL).

[0019] Quadrupole resonance NQR detection is to judge by collecting the electromagnetic signals released by the object to be detected. However, the energy of the electromagnetic signals that the substance itself can release is relatively low, and it is difficult to collect signals. Moreover, interferences such as radio frequency interference (RFI) and false signal interference will result in a relatively low signal-to-noise ratio, making it difficult to extract useful signals. The parity-time (PT) symmetric sensor based on a coherent perfect absorption laser (CPAL) has excellent ability to enhance sensitivity in the radio frequency range. The combination of the two can effectively improve the sensitivity and accuracy of the quadrupole resonance NQR detection of explosives, and effectively solve the problem that the electromagnetic signal energy is too low to be detected in the explosive detection based on the quadrupole resonance NQR signal.

[0020] Since the central frequencies of the NQR signals of different substances have certain differences, and the PT symmetric sensor system based on CPAL will produce very different outputs for excitation inputs of different frequencies, the present invention utilizes this characteristic and the high sensitivity of the CPAL effect to effectively solve the problem that the electromagnetic signal energy is too low to be detected in the process of explosive or drug detection based on the NQR signal, and enhances the sensitivity and accuracy of detection. Description of the Drawings

[0021] Figure 1 Schematic diagram of the combination of the two-port equivalent transmission line model of the parity-time (PT) symmetric sensor based on the coherent perfect absorption laser (CPAL) of the present invention and the quadrupole resonance NQR signal Figure 2 Schematic diagram of the quadrupole resonance NQR signal detection system of the present invention Figure 3 Schematic diagram of the principle of excitation and generation of the quadrupole resonance NQR signal of the substance to be detected Figure 4 Schematic diagram of the design of the radio frequency antenna of the present invention Figure 5 Spectrum diagram of the processed quadrupole resonance NQR signal of the present invention Figure 6 Schematic diagram of the parity-time (PT) symmetric sensor system based on the coherent perfect absorption laser (CPAL) of the present invention in the radio frequency (RF) domain Figure 7 Schematic diagram of the T-type equivalent circuit adopted by the transmission line of the present invention Figure 8 Schematic diagram of the relationship between the sensor output and the input frequency when using the transmission line model of the present invention Figure 9 Schematic diagram of the relationship between the sensor output and the input frequency when using the T-type equivalent circuit model of the present invention In the figure: 11. First coupler, 12. First oscilloscope, 13. Transmission line, 14. Second coupler, 15. Second oscilloscope, 16. Loss element, 17. Amplifying element, 21. Computer, 22. Radio frequency signal generator and receiver, 23. Radio frequency power amplifier, 24. Radio frequency switch, 25. Preamplifier, 26. Radio frequency antenna, 27. Electromagnetic shielding environment. Detailed implementation manners

[0022] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present application.

[0023] The terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "the" and "said" used in the present application are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0024] It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to a determination".

[0025] Specific embodiments are given below to introduce the technical solutions of this application in detail.

[0026] The PT-symmetric sensor based on CPAL for enhancing NQR signal detection in the present invention includes a quadrupole resonance NQR signal detection system and a parity-time (PT) symmetric sensor system based on a coherent perfect absorption laser (CPAL). The quadrupole resonance NQR signal detection system is used to detect the quadrupole resonance NQR signal of the object to be measured multiple times and accumulate it as an excitation signal; the parity-time (PT) symmetric sensor system based on a coherent perfect absorption laser (CPAL) is used to receive the excitation signal and its coherent signal and then obtain a detection signal to detect the category of the object to be measured.

[0027] The object to be measured in the present invention uses 500 g of sodium nitrite, a nitrogen-containing compound. Through experimental data verification, its quadrupole resonance NQR center frequency is approximately in the range of 4.6 - 4.8 MHz. Among them, due to different 14 N abundances of different sodium nitrites, etc., there will be differences in its center frequency. The sodium nitrite used in the present invention has a center frequency of approximately 4.6 MHz. This range is only given based on rigor, and the safety of this drug is relatively good compared to other nitrogen-containing explosives. The nitrogen-containing compound sodium nitrite is placed in a plastic box for detection.

[0028] As Figure 2 shown, the quadrupole resonance NQR signal detection system includes a computer 21, a radio frequency signal generator and receiver 22, a radio frequency power amplifier 23, a radio frequency switch 24, a preamplifier 25, and a radio frequency antenna 26. The radio frequency antenna 26 is a hollow solenoid coil made of enameled wire. The object to be measured is placed at the center of the radio frequency antenna 26. Both the object to be measured and the radio frequency antenna 26 are located in an electromagnetic shielding environment 27. As Figure 4 shown, the radio frequency antenna 26 of the present invention can be a hollow solenoid coil made of copper pipe and made of enameled wire. The entire coil has a diameter of 11 cm, a length of 17 cm, and a pitch of 10 mm, so as to be able to completely wrap the object to be measured. The radio frequency signal generator and receiver 22 includes a radio frequency signal generator and a radio frequency signal receiver. The radio frequency signal generator uses an arbitrary waveform signal generator with a frequency range of 0 - 20 MHz, which can be controlled by a host computer PC, and the output frequency accuracy can reach 10 -6Order of magnitude.

[0029] The working process of the quadrupole resonance NQR signal detection system is divided into two stages: excitation and reception. Among them, in the excitation process, the computer 1 sets the parameters of the radio frequency pulse and controls the radio frequency signal generator with arbitrary waveform to synthesize the excitation signal. After the excitation signal is amplified by the power amplifier, it is switched to the transmission mode through the radio frequency switch 24. The amplified pulse is radiated through the radio frequency antenna 26 in the electromagnetic shielding environment 27 to excite the object under test to generate the quadrupole resonance NQR signal; in the reception process, the weak quadrupole resonance NQR signal released by the object under test in the same radio frequency antenna 26 is preliminarily enhanced by the preamplifier to reduce the influence of subsequent processing noise. Then the signal is received by the radio frequency signal receiver and finally transmitted to the computer 1 for filtering and other processing; among them, the maximum output power of the power amplifier is 20W, the maximum output amplitude is 28Vpp, the maximum output current is 1A, the voltage gain can be doubled or quadrupled, and the signal input bandwidth is DC~5MHz; the bandwidth of the preamplifier is 20KHz~3000MHz, the gain is 32dB, and the noise figure is 2.5dB. When the quadrupole resonance NQR signal detection system performs signal stimulation, the computer 21 controls the radio frequency signal generator to generate the stimulation signal, which is then transmitted to the radio frequency antenna 26 through the radio frequency power amplifier 23 and the radio frequency switch 24 in sequence, so that the center frequency of the radio frequency antenna 26 is the preset center frequency. The center frequency of the radio frequency antenna 26 is approximately equal to the design frequency of the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL, and is approximately equal to the center frequency of the quadrupole resonance NQR signal of the object under test. Specifically, in implementation, the radio frequency antenna 26 is designed with an inductance of 3μH and an internal resistance of 0.3Ω, so that its center frequency is approximately 4.6MHz, that is, near the design frequency, as Figure 5 shown; the initial signal generated by the object under test received by the radio frequency antenna 26 is output as the initial quadrupole resonance NQR signal after passing through the preamplifier 25. The initial quadrupole resonance NQR signal is then transmitted to the computer 21 through the radio frequency signal receiver for display. After multiple signal stimulations, each initial quadrupole resonance NQR signal is accumulated as the excitation signal and transmitted to the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL.

[0030] As Figure 3 shown, it is the excitation and generation process of the quadrupole resonance NQR signal of the atomic nucleus. For an atom, when an electromagnetic signal under certain conditions acts externally, the product of the frequency of the electromagnetic signal and Planck's constant (hv) satisfies the energy level difference △E of the nuclear transition, and the atomic nucleus can absorb its electromagnetic energy to generate a transition, from the equilibrium state to the excited state. After the electromagnetic wave stops acting, the transition atomic nucleus will release an electromagnetic signal during the process of returning to the equilibrium state due to instability. This signal is the quadrupole resonance NQR signal.

[0031] As Figure 6 shown, the received quadrupole resonance NQR signal is roughly converted into the spectrogram shown through processing such as low-noise pre-amplification, cumulative sampling, filtering, etc., and then through fast Fourier transform FFT (Fast Fourier Transform). To simplify the experimental process and eliminate unnecessary interference, an arbitrary waveform generator AWG (Arbitrary Waveform Generator) can be directly used to generate two coherent signals with a frequency of 4.6 MHz, which are used as the input waves at the two ports of the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL.

[0032] As Figure 1 shown, the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL includes a first coupler 11, a first oscilloscope 12, a transmission line 13, a second coupler 14, a second oscilloscope 15, a loss element 16, and an amplification element 17. The first coupler 11, the loss element 16, the transmission line 13, the amplification element 17, and the second coupler 14 are connected in sequence. The loss element 16 has a positive conductance G, and the loss element 16 can be a resistor or a capacitor. The amplification element 17 has a negative conductance -G, and the amplification element 17 uses a negative impedance converter NIC (Negative Impedance Converter) with a negative conductance -G. The transmission lines between the first coupler 11, the first oscilloscope 12, the transmission line 13, the second coupler 14, the second oscilloscope 15, the loss element 16, and the amplification element 17 are all separated by an electrical length x, and x = π / 2 + δx, where δx is the phase shift of the electrical length x.

[0033] The first coupler 11 and the second coupler 14 are respectively connected to the first oscilloscope 12 and the second oscilloscope 15. After the excitation signal V1 and its coherent signal V2 are simultaneously transmitted to the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL composed of the loss element 16, the amplification element 17, and the transmission line 13 for processing, the output first detection signal V3 and second detection signal V4 are respectively transmitted to the first oscilloscope 12 and the second oscilloscope 15 through the first coupler 11 and the second coupler 14 for display. Among them, the amplitude ratio of the excitation signal V1 and its coherent signal V2 is 2 1 / 2 / 2, with a phase difference of 90 degrees. The second detection signal V4 has an extreme value at the designed frequency of the parity-time (PT) symmetric sensor system based on the coherent perfect absorption laser (CPAL), then it is detected that the current object under test is the object category corresponding to the designed frequency. The parity-time (PT) symmetric sensor system based on the coherent perfect absorption laser (CPAL) operates in the radio frequency domain and consists of a two-port equivalent transmission model, adopts a monotonic sensing scheme, and realizes by detecting whether the impedance perturbation at a given frequency is a function of the output intensity.

[0034] As Figure 7 shown, the T-type equivalent circuit adopted by the transmission line in the parity-time (PT) symmetric sensor system based on the coherent perfect absorption laser (CPAL) of the present invention. The parity-time (PT) symmetric sensor system based on the coherent perfect absorption laser (CPAL) consists of a loss element 16 with a conductance G and an amplification element 17 with an effective negative conductance -G. These gain and loss elements are separated by an electrical length x = π / 2 + δx, and the electrical length can be realized by a transmission line or a compact T-type equivalent circuit. The system operates at the set frequency of 4.6 MHz, and thus can be based on the following formula: C 1 = Y 0 / ( ω 0 sin x) L 1 = L 2 = sin x / ( Y 0 ω 0 (1 – cos x)) Wherein, C 1 is the capacitance, C 1 = 684.84 pF; Y 0 is an intermediate parameter, G / Y0 = 2 1 / 2 ; ω 0 is the intermediate frequency, ω 0 = f / 2π, f is the designed frequency; L 1 and L 2 are the first and second inductances, L 1 = L 2 = 1712.09 nH.

[0035] In addition, the pseudo-tensor R p is used to simulate the impedance change in the sensing or driving element; the designed frequency of the transmission line is 4.6 MHz.

[0036] The coherent perfect absorption laser CPAL point is a self-coupled spectral singularity of a parity-time PT symmetric system. At this point, the laser state and the coherent perfect absorption CPA state (which can be regarded as time-reversed laser) can coexist at a given wavelength (i.e., the so-called coherent perfect absorption laser CPAL point). The voltage peaks of the excitation signal V1 and its coherent signal V2 of the present invention are 2.42 and 1 respectively. The coherent quadrupole resonance NQR signal is input into the sensor system, and circuit simulation is carried out using the Advanced Design System (ADS). In the Advanced Design System ADS, Figure 1 the model shown is subjected to AC simulation to obtain the spectrograms of the first detection signal V3 and the second detection signal V4, as Figure 8 shown, where the X-axis of the spectrogram represents the frequency of the coherent signal input at both ends of the system. Since the values of the first detection signal V3 and the second detection signal V4 are both zero when there is no input signal at both ports, when the input signal frequency is consistent with the set frequency, the signal amplitude reaches an extreme value, which produces a very large contrast compared with the input signal of the non-set frequency, thereby improving the sensitivity of the quadrupole resonance NQR signal detection to a certain extent. The actual implementation of this system in the radio frequency range can be achieved by using an equivalent circuit to replace the transmission line model, as Figure 7 shown. Repeat the above simulation using the equivalent circuit to obtain the spectrograms of the first detection signal V3 and the second detection signal V4, as Figure 9 shown. After analysis, the error is within an acceptable range.

[0037] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A CPAL-based PT symmetric sensor for enhanced NQR signal detection, characterized in that: include: A quadrupole resonance NQR signal detection system, which is used to detect the quadrupole resonance NQR signal of the object being tested multiple times and accumulate it as an excitation signal; A parity-time PT symmetric sensor system based on a coherent perfect absorption laser CPAL is used to receive an excitation signal and its coherent signal and then obtain a detection signal to detect the category of the object being measured.

2. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 1, characterized in that: The quadrupole resonance NQR signal detection system comprises a computer (21), a radio frequency signal generator and receiver (22), a radio frequency power amplifier (23), a radio frequency switch (24), a preamplifier (25) and a radio frequency antenna (26); the object to be measured is placed at the center of the radio frequency antenna (26); the object to be measured and the radio frequency antenna (26) are both located in an electromagnetic shielding environment (27); the radio frequency signal generator and receiver (22) comprise a radio frequency signal generator and a radio frequency signal receiver; when the quadrupole resonance NQR signal detection system performs signal stimulation, the computer (21) controls the radio frequency signal generator to generate a stimulation signal and then generates a signal according to the electromagnetic shielding environment (27). The radio frequency signal is transmitted to the radio frequency antenna (26) through the radio frequency power amplifier (23) and the radio frequency switch (24), so that the center frequency of the radio frequency antenna (26) is the preset center frequency. The radio frequency antenna (26) receives the initial signal generated by the object to be measured and outputs an initial quadrupole resonance NQR signal after passing through the preamplifier (25). The initial quadrupole resonance NQR signal is then transmitted to the computer (21) for display through the radio frequency signal receiver. After multiple signal stimulations, each initial quadrupole resonance NQR signal is accumulated as an excitation signal and transmitted to a parity-time PT symmetric sensor system based on a coherent perfect absorption laser CPAL.

3. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 2, characterized in that: The central frequency of the radio frequency antenna (26) is equal to the design frequency of the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL.

4. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 2, characterized in that: The radio frequency signal generator adopts an arbitrary waveform signal generator with a frequency range of 0-20MHz.

5. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 2, characterized in that: The radio frequency antenna (26) is a hollow solenoid coil and uses enameled wire.

6. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 1, characterized in that: The parity-time PT symmetric sensor system based on a coherent perfect absorption laser (CPAL) comprises a first coupler (11), a first oscilloscope (12), a transmission line (13), a second coupler (14), a second oscilloscope (15), a loss element (16) and an amplifying element (17). The first coupler (11), the loss element (16), the transmission line (13), the amplifying element (17) and the second coupler (14) are connected in sequence. The first coupler (11) and the second coupler (14) are respectively connected to the first oscilloscope (12) and the second oscilloscope (15). The excitation signal V1 and the coherent signal V2 are simultaneously transmitted to the first detection signal V3 and the second detection signal V4 which are processed by the loss element (16), the amplifying element (17) and the transmission line (13). The output signals are respectively transmitted to the first oscilloscope (12) and the second oscilloscope (15) through the first coupler (11) and the second coupler (14) for display.

7. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 6, characterized in that: The amplitude ratio of the excitation signal V1 and its coherent signal V2 is 2 1 / 2 / 2, the phase difference is 90 degrees.

8. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 6, characterized in that: The loss element (16) has a positive conductance G, and the amplification element (17) has a negative conductance -G.

9. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 6, characterized in that: The first coupler (11), the first oscilloscope (12), the transmission line (13), the second coupler (14), the second oscilloscope (15), the loss element (16) and the transmission line between the amplifying element (17) are all separated by an electrical length x, where x=π / 2+δx, and δx is a phase shift of the electrical length x.

10. The CPAL-based PT symmetric sensor for enhancing NQR signal detection according to claim 6, characterized in that: The second detection signal V4 has an extreme value at the design frequency of the parity-time PT symmetric sensor system based on the coherent perfect absorption laser CPAL, and it is detected that the current object being measured is an object category corresponding to the design frequency.

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