A nonlinear node detector

Abstract

The present invention relates to a nonlinear node detector, and belongs to the technical field of electronic device detection. In order to solve the problem that the detection sensitivity of the detector is limited by the interference of its own harmonics, the present invention includes a transmitter, a receiver, an antenna interface and a signal processing module, wherein the transmitter is provided with a single-tone signal channel 1 and a single-tone signal channel 2; the receiver is provided with a primary frequency conversion receiver 1 and a primary frequency conversion receiver 2; the signal processing module is provided with an FPGA and an MCU. A dual-tone signal is used to generate intermodulation products through a nonlinear network, and after being processed by a receiver, the amplitude information of the second-order intermodulation and third-order intermodulation products is extracted by fast Fourier transform for comparison, thereby improving the receiver sensitivity, shortening the measurement time, and increasing the detection distance.

Description

Technical Field

[0001] The invention relates to the technical field of electronic equipment detection, in particular to a nonlinear node detector. Background Art

[0002] Nonlinear node detector, also known as semiconductor detector, transmits radio waves to the area to be tested and receives signals generated by objects in the area to be tested after being excited by radio waves to identify whether there are semiconductor devices in the area to be tested, especially technical defense equipment for sensitive targets such as eavesdropping, stealing photos, and remote-controlled bombs.

[0003] When nonlinear nodes are excited by radio waves, they will generate second, third and higher harmonics. Usually, the second and third harmonics are meaningful for measurement. In order to receive the second and third harmonics, the radio transmitter is required to have extremely high harmonic suppression and cannot generate harmonics by itself. This requires the high-power amplifier to be used in the linear region, which limits the increase in transmission power; at the same time, strict filtering is required, which increases the size of the equipment. Since the transmission and reception usually use one set of antennas or two sets of antennas very close to each other, the transmission signal will also be received by the receiving antenna. Therefore, the transmission signal must be strictly filtered at the receiving end. Otherwise, since the receiver itself is composed of semiconductor devices, it is bound to generate harmonics by itself. These factors lead to extremely demanding design indicators and high costs for semiconductor detectors. Even if a demanding design is adopted, there is still interference from its own harmonics, which limits the improvement of detection sensitivity. At the same time, in order to improve the sensitivity of the receiver, a lower analysis bandwidth is required, which leads to longer measurement time and larger response lag, affecting the use effect. Summary of the invention

[0004] The purpose of the present invention is to propose a nonlinear node detector that can reduce the requirements for transmitter linearity, allow it to have a harmonic index slightly lower than that of traditional solutions, simplify the design of the transmitter active circuit, adopt a larger transmission power, and at the same time, without reducing the sensitivity of the receiver, increase the measurement speed, thereby improving the overall detection sensitivity and improving the use effect.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A nonlinear node detector comprises a transmitter, a receiver, an antenna interface and a signal processing module, wherein the transmitter is provided with a single-tone signal channel 1 and a single-tone signal channel 2; the receiver is provided with a single-frequency conversion receiver 1 and a single-frequency conversion receiver 2; the signal processing module is provided with an FPGA and an MCU;

[0007] The single-tone signal 1 generated by the first single-tone signal channel is connected to an input end of a combiner, the single-tone signal 2 generated by the second single-tone signal channel is connected to another input end of the combiner, the dual-tone signal output by the combiner is connected to an input end of a low-pass filter 3, the low-pass filter 3 filters the dual-tone signal and then connects it to an input end of a multiplexer, the output signal of the multiplexer is connected to an antenna interface, the dual-tone signal transmits an excitation signal through the antenna interface, and the excitation signal generates an echo signal after being transmitted to a target object;

[0008] The antenna interface receives the echo signal and connects it to the input end of the multiplexer. The echo signal is divided into a secondary signal wave and a tertiary signal wave by the multiplexer and connected to the input ends of the primary frequency conversion receiver 1 and the primary frequency conversion receiver 2 respectively. The intermediate frequency signal obtained after being processed by the primary frequency conversion receiver 1 and the primary frequency conversion receiver 2 is connected to the FPGA sampling port through the output port. The FPGA is used to collect the intermediate frequency signal for fast Fourier transform, extract the amplitude information of the second-order intermodulation and third-order intermodulation products, and transmit it to the MCU for analysis and comparison.

[0009] Further, the first single-tone signal channel includes a phase-locked loop 1, a low-pass filter 1, a driving amplifier 1 and a power amplifier 1; the second single-tone signal channel includes a phase-locked loop 2, a low-pass filter 2, a driving amplifier 2 and a power amplifier 2; the single-conversion receiver 1 includes a band-pass filter 1, a preamplifier 1, a harmonic mixer 1, a phase-locked loop 2, an intermediate frequency filter 1, an intermediate frequency amplifier 1 and an analog-to-digital converter 1; the single-conversion receiver 2 includes a band-pass filter 2, a preamplifier 2, a harmonic mixer 2, a phase-locked loop 3, an intermediate frequency filter 2, an intermediate frequency amplifier 2 and an analog-to-digital converter 2;

[0010] The phase-locked loop 1 is used to generate a single-tone signal 1, and transmit the single-tone signal 1 to a low-pass filter 1; the low-pass filter 1 is used to filter out high-frequency signal interference in the single-tone signal 1, and transmit the single-tone signal 1 from which the high-frequency signal interference has been filtered out to a driving amplifier 1; the driving amplifier 1 is used to amplify the single-tone signal 1 and transmit it to a power amplifier 1; the power amplifier 1 is used to power-amplify the scanning signal 1 again, and transmit the power-amplified single-tone signal 1 to a combiner;

[0011] The phase-locked loop 2 is used to generate a single-tone signal 2 and transmit the single-tone signal 2 to a low-pass filter 2; the low-pass filter 2 is used to filter out high-frequency signal interference in the single-tone signal 2, and transmit the single-tone signal 2 from which the high-frequency signal interference has been filtered out to a driving amplifier 2; the driving amplifier 2 is used to amplify the single-tone signal 2 and transmit it to a power amplifier 2; the power amplifier 2 is used to power-amplify the scanning signal 2 again, and transmit the power-amplified single-tone signal 2 to a combiner;

[0012] The bandpass filter 1 is used to receive the secondary signal wave in the echo signal separated by the multiplexer, filter out the fundamental wave interference in the secondary signal wave, and transmit the secondary signal wave with the fundamental wave interference filtered out to the preamplifier 1; the preamplifier 1 is used to amplify the secondary signal wave, and transmit the amplified secondary signal wave to the harmonic mixer 1; the harmonic mixer 1 is used to receive the secondary signal wave amplified by the preamplifier 1 and the local oscillator frequency generated by the phase-locked loop 2, mix the secondary signal wave with the local oscillator frequency, and transmit the generated mixed signal to the intermediate frequency filter 1; the intermediate frequency filter 1 is used to filter out the high and low signals in the mixed signal, and transmit the intermediate frequency signal 1 obtained after filtering to the intermediate frequency amplifier 1; the intermediate frequency amplifier 1 is used to amplify the intermediate frequency signal 1, and transmit the amplified intermediate frequency signal 1 to the analog-to-digital converter 1;

[0013] The bandpass filter 2 is used to receive the third-order signal wave in the echo signal separated by the multiplexer, filter out the fundamental interference in the third-order signal wave, and transmit the third-order signal wave with the fundamental interference filtered out to the preamplifier 2; the preamplifier 2 is used to amplify the third-order signal wave, and transmit the amplified third-order signal wave to the harmonic mixer 2; the harmonic mixer 2 is used to receive the third-order signal wave amplified by the preamplifier 2 and the local oscillator frequency generated by the phase-locked loop 3, mix the third-order signal wave and the local oscillator frequency, and transmit the generated mixed signal to the intermediate frequency filter 2; the intermediate frequency filter 2 is used to filter out the high and low signals in the mixed signal, and transmit the intermediate frequency signal 2 obtained after filtering to the intermediate frequency amplifier 2; the intermediate frequency amplifier 2 is used to amplify the intermediate frequency signal 2, and transmit the amplified intermediate frequency signal 2 to the analog-to-digital converter 2.

[0014] Furthermore, the phase-locked loop 2 is the signal source of the second single-tone signal channel and is also the local oscillator of the single-conversion receiver 1 .

[0015] Furthermore, the phase-locked loop 1 and the phase-locked loop 2 are provided with a pulse modulation switch, and the pulse modulation switch controls the transmitter to be turned off during data processing.

[0016] Furthermore, both the low-pass filter 1 and the low-pass filter 2 use TLCC devices.

[0017] Furthermore, the antenna interface is a transmitter signal outlet and a receiver signal interface at the same time.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] After the present invention changes from measuring harmonics to measuring intermodulation products, the back-off requirement for the power amplifier is reduced by 10dB, which means that the power can be increased by 10 times under the premise of the cost of a single power amplifier remaining unchanged. The filtering index originally undertaken independently by the low-pass filter 3 is decomposed into low-pass filters 1, 2, and 3 to be jointly undertaken, and the overall requirement for harmonics is reduced, so that the suppression index of the low-pass filter 3 at the harmonic frequency is greatly reduced by 20dB. The indexes of low-pass filters 1 and 2 are very low, and common TLCC devices can be used. By adopting a harmonic mixer 1 and analyzing intermodulation products, a phase-locked loop is saved, so that although the whole machine uses two transmission frequencies, the number of phase-locked loops is not increased compared with the prior art. The requirements for harmonic distortion of preamplifiers 1 and 2 are reduced by 3dB, which is equivalent to improving the available sensitivity of the receiver, so that the fast Fourier transform can use fewer points, greatly shortening the measurement time. By working through pulse modulation switching, the transmitter is turned off during data processing, which saves power consumption, and does not need to increase batteries while increasing the transmission power, which is conducive to reducing the size of the device. In general, compared with the existing solutions, the detection distance of the present invention is increased to twice that of the existing solutions, and the difficulty of circuit design is reduced and the size of the equipment is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific embodiments and drawings. The drawings provided in the present invention only show the main structural modules of the design and do not represent the number of components actually used, but this should not limit the protection scope of the present invention.

[0022] like Figure 1 As shown, the technical solution provided by the present invention is a nonlinear node detector, including a transmitter, a receiver, an antenna interface and a signal processing module, the transmitter is provided with a single-tone signal channel 1 and a single-tone signal channel 2; the receiver is provided with a single-frequency conversion receiver 1 and a single-frequency conversion receiver 2; the signal processing module is provided with an FPGA and an MCU.

[0023] The single-tone signal 1 generated by the first single-tone signal channel is connected to one input end of the combiner, and the single-tone signal 2 generated by the second single-tone signal channel is connected to the other input end of the combiner. The dual-tone signal output by the combiner is connected to the input end of the low-pass filter 3. The low-pass filter 3 filters the dual-tone signal and then connects it to one input end of the multiplexer. The output signal of the multiplexer is connected to the antenna interface, and the dual-tone signal transmits an excitation signal through the antenna interface. After the excitation signal is transmitted to the target object, an echo signal is generated.

[0024] The antenna interface receives the echo signal and connects it to the input end of the multiplexer. The echo signal is divided into a secondary signal wave and a tertiary signal wave by the multiplexer and connected to the input ends of the primary frequency conversion receiver 1 and the primary frequency conversion receiver 2 respectively. The intermediate frequency signal obtained after being processed by the primary frequency conversion receiver 1 and the primary frequency conversion receiver 2 is connected to the FPGA sampling port through the output port. The FPGA is used to collect the intermediate frequency signal for fast Fourier transform, extract the amplitude information of the second-order intermodulation and third-order intermodulation products, and transmit it to the MCU for analysis and comparison.

[0025] In the above modules, the first single-tone signal channel may include a phase-locked loop 1, a low-pass filter 1, a driving amplifier 1 and a power amplifier 1; the second single-tone signal channel may include a phase-locked loop 2, a low-pass filter 2, a driving amplifier 2 and a power amplifier 2; the single-conversion receiver 1 includes a bandpass filter 1, a preamplifier 1, a harmonic mixer 1, a phase-locked loop 2, an intermediate frequency filter 1, an intermediate frequency amplifier 1 and an analog-to-digital converter 1; the single-conversion receiver 2 includes a bandpass filter 2, a preamplifier 2, a harmonic mixer 2, a phase-locked loop 3, an intermediate frequency filter 2, an intermediate frequency amplifier 2 and an analog-to-digital converter 2.

[0026] The phase-locked loop 1 is used to generate a single-tone signal 1 and transmit the single-tone signal 1 to a low-pass filter 1; the low-pass filter 1 is used to filter out high-frequency signal interference in the single-tone signal 1, and transmit the single-tone signal 1 from which the high-frequency signal interference has been filtered out to a driving amplifier 1; the driving amplifier 1 is used to amplify the single-tone signal 1 and transmit it to a power amplifier 1; the power amplifier 1 is used to power-amplify the scanning signal 1 again, and transmit the power-amplified single-tone signal 1 to a combiner.

[0027] The phase-locked loop 2 is used to generate a single-tone signal 2 and transmit the single-tone signal 2 to the low-pass filter 2; the low-pass filter 2 is used to filter out high-frequency signal interference in the single-tone signal 2, and transmit the single-tone signal 2 from which the high-frequency signal interference has been filtered out to the driving amplifier 2; the driving amplifier 2 is used to amplify the single-tone signal 2 and transmit it to the power amplifier 2; the power amplifier 2 is used to power-amplify the scanning signal 2 again, and transmit the power-amplified single-tone signal 2 to the combiner.

[0028] The bandpass filter 1 is used to receive the secondary signal wave in the echo signal separated by the multiplexer, filter out the fundamental wave interference in the secondary signal wave, and transmit the secondary signal wave with the fundamental wave interference filtered out to the preamplifier 1; the preamplifier 1 is used to amplify the secondary signal wave, and transmit the amplified secondary signal wave to the harmonic mixer 1; the harmonic mixer 1 is used to receive the secondary signal wave amplified by the preamplifier 1 and the local oscillator frequency generated by the phase-locked loop 2, mix the secondary signal wave with the local oscillator frequency, and transmit the generated mixed signal to the intermediate frequency filter 1; the intermediate frequency filter 1 is used to filter out the high and low signals in the mixed signal, and transmit the intermediate frequency signal 1 obtained after filtering to the intermediate frequency amplifier 1; the intermediate frequency amplifier 1 is used to amplify the intermediate frequency signal 1, and transmit the amplified intermediate frequency signal 1 to the analog-to-digital converter 1.

[0029] The bandpass filter 2 is used to receive the third-order signal wave in the echo signal separated by the multiplexer, filter out the fundamental interference in the third-order signal wave, and transmit the third-order signal wave with the fundamental interference filtered out to the preamplifier 2; the preamplifier 2 is used to amplify the third-order signal wave, and transmit the amplified third-order signal wave to the harmonic mixer 2; the harmonic mixer 2 is used to receive the third-order signal wave amplified by the preamplifier 2 and the local oscillator frequency generated by the phase-locked loop 3, mix the third-order signal wave with the local oscillator frequency, and transmit the generated mixed signal to the intermediate frequency filter 2; the intermediate frequency filter 2 is used to filter out the high and low signals in the mixed signal, and transmit the intermediate frequency signal 2 obtained after filtering to the intermediate frequency amplifier 2; the intermediate frequency amplifier 2 is used to amplify the intermediate frequency signal 2, and transmit the amplified intermediate frequency signal 2 to the analog-to-digital converter 2.

[0030] Preferably, the phase-locked loop 2 is the signal source of the single-tone signal channel 2 and is also the local oscillator of the single-frequency conversion receiver 1, which can save a phase-locked loop. Although the whole machine adopts two transmission frequencies, the number of phase-locked loops is not increased compared with the prior art, and the structure is simple.

[0031] Preferably, the phase-locked loop 1 and the phase-locked loop 2 are provided with a pulse modulation switch, which controls the transmitter to be turned off during data processing, thereby saving power consumption and increasing the transmission power without adding batteries, which is conducive to reducing the size and weight of the device.

[0032] Preferably, both low-pass filter 1 and low-pass filter 2 use TLCC devices. Since the back-off requirement for the power amplifier is reduced by measuring the intermodulation products instead of the harmonics, the filtering index originally borne by one low-pass filter is decomposed into three low-pass filters to be shared, so that the index requirements for low-pass filter 1 and low-pass filter 2 are low.

[0033] Preferably, the antenna interface is the transmitter signal outlet and the receiver signal interface at the same time. The antenna interface serves as both the transmitting port and the receiving port, can withstand the transmitting power, and can ensure good gain, efficiency and return loss at the transmitting and receiving frequencies, thereby reducing the impact of its own harmonics, reducing costs, and simplifying the entire device.

[0034] The working principle of the present invention is as follows: adopting dual-tone emission, two single-tone signals are generated respectively by phase-locked loop 1 and phase-locked loop 2, after filtering and amplifying, the synthesized dual-tone signal is processed by a combiner, after filtering harmonics and intermodulation products by a low-pass filter C, the dual-tone signal is processed by a multiplexer and transmitted through an antenna interface, an echo signal is generated by a target object, the echo signal contains an intermodulation signal, the echo signal is received by an antenna interface, and is separated into a quadratic term and a cubic term by a multiplexer, and enters two primary frequency conversion receivers for filtering, amplification and mixing to become an intermediate frequency signal, which is converted into a digital signal by an analog-to-digital converter, and the sampled intermediate frequency signal is digitally down-converted by FPGA, and the amplitude information of the second-order intermodulation and third-order intermodulation products is extracted by fast Fourier transform, and provided to MCU for analysis, and nonlinear node judgment can be performed by comparing the size of the quadratic term and the cubic term, if the generated quadratic term and term are higher than the cubic term, the target is a nonlinear node, otherwise the target is not. When data processing is performed, the pulse modulation switch closes the transmitter, and the signal channel is connected when the transmitter is working.

Claims

1. A nonlinear node detector, comprising a transmitter, a receiver, an antenna interface and a signal processing module, characterized in that: The transmitter is provided with a first single-tone signal channel and a second single-tone signal channel; the receiver is provided with a single-frequency conversion receiver 1 and a single-frequency conversion receiver 2; the signal processing module is provided with an FPGA and an MCU; the single-tone signal 1 generated by the first single-tone signal channel is connected to an input end of a combiner, the single-tone signal 2 generated by the second single-tone signal channel is connected to another input end of the combiner, the dual-tone signal output by the combiner is connected to an input end of a low-pass filter 3, the low-pass filter 3 filters the dual-tone signal and then connects to an input end of a multiplexer, the output signal of the multiplexer is connected to an antenna interface, the dual-tone signal transmits an excitation signal through the antenna interface, and an echo signal is generated after the excitation signal is transmitted to the target object; The antenna interface receives the echo signal and connects it to the input end of the multiplexer. The echo signal is divided into a secondary signal wave and a tertiary signal wave by the multiplexer and connected to the input ends of the primary frequency conversion receiver 1 and the primary frequency conversion receiver 2 respectively. The intermediate frequency signal obtained after being processed by the primary frequency conversion receiver 1 and the primary frequency conversion receiver 2 is connected to the FPGA sampling port through the output port. The FPGA is used to collect the intermediate frequency signal for fast Fourier transform, extract the amplitude information of the second-order intermodulation and third-order intermodulation products, and transmit it to the MCU for analysis and comparison. The nonlinear node is judged by comparing the size of the quadratic term and the cubic term. If the generated quadratic term and term are higher than the cubic term, the target object is a nonlinear node, otherwise the target object is not.

2. A nonlinear node detector according to claim 1, characterized in that: The first single-tone signal channel includes a phase-locked loop 1, a low-pass filter 1, a driver amplifier 1 and a power amplifier 1; the second single-tone signal channel includes a phase-locked loop 2, a low-pass filter 2, a driver amplifier 2 and a power amplifier 2; The single-conversion receiver 1 includes a bandpass filter 1, a preamplifier 1, a harmonic mixer 1, a phase-locked loop 2, an intermediate frequency filter 1, an intermediate frequency amplifier 1 and an analog-to-digital converter 1; the single-conversion receiver 2 includes a bandpass filter 2, a preamplifier 2, a harmonic mixer 2, a phase-locked loop 3, an intermediate frequency filter 2, an intermediate frequency amplifier 2 and an analog-to-digital converter 2; The phase-locked loop 1 is used to generate a single-tone signal 1, and transmit the single-tone signal 1 to a low-pass filter 1; the low-pass filter 1 is used to filter out high-frequency signal interference in the single-tone signal 1, and transmit the single-tone signal 1 from which the high-frequency signal interference has been filtered out to a driving amplifier 1; the driving amplifier 1 is used to amplify the single-tone signal 1 and transmit it to a power amplifier 1; the power amplifier 1 is used to power-amplify the scanning signal 1 again, and transmit the power-amplified single-tone signal 1 to a combiner; The phase-locked loop 2 is used to generate a single-tone signal 2 and transmit the single-tone signal 2 to a low-pass filter 2; the low-pass filter 2 is used to filter out high-frequency signal interference in the single-tone signal 2, and transmit the single-tone signal 2 from which the high-frequency signal interference has been filtered out to a driving amplifier 2; the driving amplifier 2 is used to amplify the single-tone signal 2 and transmit it to a power amplifier 2; the power amplifier 2 is used to power-amplify the scanning signal 2 again, and transmit the power-amplified single-tone signal 2 to a combiner; The bandpass filter 1 is used to receive the secondary signal wave in the echo signal separated by the multiplexer, filter out the fundamental wave interference in the secondary signal wave, and transmit the secondary signal wave with the fundamental wave interference filtered out to the preamplifier 1; the preamplifier 1 is used to amplify the secondary signal wave, and transmit the amplified secondary signal wave to the harmonic mixer 1; the harmonic mixer 1 is used to receive the secondary signal wave amplified by the preamplifier 1 and the local oscillator frequency generated by the phase-locked loop 2, mix the secondary signal wave with the local oscillator frequency, and transmit the generated mixed signal to the intermediate frequency filter 1; the intermediate frequency filter 1 is used to filter out the high and low signals in the mixed signal, and transmit the intermediate frequency signal 1 obtained after filtering to the intermediate frequency amplifier 1; the intermediate frequency amplifier 1 is used to amplify the intermediate frequency signal 1, and transmit the amplified intermediate frequency signal 1 to the analog-to-digital converter 1; The bandpass filter 2 is used to receive the third-order signal wave in the echo signal separated by the multiplexer, filter out the fundamental interference in the third-order signal wave, and transmit the third-order signal wave with the fundamental interference filtered out to the preamplifier 2; the preamplifier 2 is used to amplify the third-order signal wave, and transmit the amplified third-order signal wave to the harmonic mixer 2; the harmonic mixer 2 is used to receive the third-order signal wave amplified by the preamplifier 2 and the local oscillator frequency generated by the phase-locked loop 3, mix the third-order signal wave and the local oscillator frequency, and transmit the generated mixed signal to the intermediate frequency filter 2; the intermediate frequency filter 2 is used to filter out the high and low signals in the mixed signal, and transmit the intermediate frequency signal 2 obtained after filtering to the intermediate frequency amplifier 2; the intermediate frequency amplifier 2 is used to amplify the intermediate frequency signal 2, and transmit the amplified intermediate frequency signal 2 to the analog-to-digital converter 2.

3. A nonlinear node detector according to claim 2, characterized in that: The phase-locked loop 2 is the signal source of the second single-tone signal channel and is also the local oscillator of the single-conversion receiver 1 .

4. A nonlinear node detector according to claim 2, characterized in that: The phase-locked loop 1 and the phase-locked loop 2 are provided with a pulse modulation switch, and the pulse modulation switch controls the transmitter to be turned off during data processing.

5. A nonlinear node detector according to claim 2, characterized in that: The low-pass filter 1 and the low-pass filter 2 both use TLCC devices.

6. A nonlinear node detector according to claim 1, characterized in that: The antenna interface is a transmitter signal outlet and also a receiver signal interface.

Images