CN111929738A

CN111929738A - Nonlinear node detector

Info

Publication number: CN111929738A
Application number: CN202010896332.8A
Authority: CN
Inventors: 刘虎; 沈昊宸; 姚帅; 胡世超
Original assignee: Chengdu Kechuang Space Time Technology Co ltd
Current assignee: Chengdu Kechuang Space Time Technology Co ltd
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2020-11-13

Abstract

The invention relates to a nonlinear node detector, belonging to the technical field of electronic equipment detection. In order to solve the problem that the detection instrument limits the improvement of detection sensitivity due to the interference of self harmonic, the invention 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 primary frequency conversion receiver 1 and a primary frequency conversion receiver 2; the signal processing module is provided with an FPGA and an MCU. After the intermodulation product generated by the two-tone signal through the nonlinear network is processed by the receiver, the amplitude information of the second-order intermodulation product and the third-order intermodulation product is extracted through fast Fourier transform for comparison, so that the sensitivity of the receiver is improved, the measurement time is shortened, and the detection distance is increased.

Description

Nonlinear node detector

Technical Field

The invention relates to the technical field of electronic equipment detection, in particular to a nonlinear node detector.

Background

The nonlinear node detector, also known as a semiconductor detector, transmits radio waves to a region to be detected, receives signals generated after objects in the region to be detected are excited by the radio waves, and distinguishes whether semiconductor equipment, particularly technical prevention equipment for sensitive targets such as eavesdropping, steal, remote control bombs and the like exist in the region to be detected.

When excited by radio waves, nonlinear nodes generate second, third and higher harmonics, which are usually significant for measurements. In order to receive the second harmonic and the third harmonic, the radio transmitter is required to have extremely high harmonic suppression, and cannot generate the harmonic by itself, so that a high-power amplifier needs to be backed to a linear region for use, and the improvement of the transmission power is limited; and meanwhile, strict filtering is required, so that the volume of the equipment is increased. Since the transmitting and receiving usually use one set of antenna or two sets of closely spaced antennas, the transmitted signal will also be received by the receiving antenna, so the transmitted signal must be strictly filtered at the receiving end, otherwise, because the receiver itself is composed of semiconductor devices, it will generate harmonic waves by itself. These factors lead to extremely harsh design criteria and high cost of semiconductor detectors, and even with harsh designs, the interference of self harmonics still exists, limiting the improvement of detection sensitivity. Meanwhile, in order to improve the sensitivity of the receiver, a lower analysis bandwidth is required, which results in prolonged measurement time, larger response delay and influence on the use effect.

Disclosure of Invention

The invention aims to provide a nonlinear node detector which can reduce the requirement on the linearity of a transmitter, allow the linearity to have harmonic indexes slightly lower than those of the traditional scheme, simplify the design of an active circuit of the transmitter, adopt higher transmitting power and improve the measuring speed on the premise of not reducing the sensitivity of a receiver, thereby integrally improving the detection sensitivity and improving the use effect.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

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 primary frequency conversion receiver 1 and a primary 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 one input end of the combiner, the single-tone signal 2 generated by the second single-tone signal channel is connected to the other input end of the combiner, the double-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 double-tone signal and then connects the double-tone signal to one input end of the multiplexer, the output signal of the multiplexer is connected with the antenna interface, the double-tone signal transmits an excitation signal through the antenna interface, and the excitation signal transmits to a target object to generate an echo signal;

the antenna interface receives an echo signal and accesses the input end of the multiplexer, the echo signal is divided into a secondary signal wave and a tertiary signal wave through the multiplexer and is respectively connected with the input ends of the primary variable frequency receiver 1 and the primary variable frequency receiver 2, an intermediate frequency signal obtained after the processing of the primary variable frequency receiver 1 and the primary variable frequency receiver 2 is accessed into the FPGA sampling port through the output port, the FPGA is used for collecting the intermediate frequency signal to carry out fast Fourier transform, and amplitude information of second-order intermodulation and third-order intermodulation products is extracted and transmitted to the MCU for analysis and comparison.

Further, the first single-tone signal channel comprises 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 comprises a phase-locked loop 2, a low-pass filter 2, a driving amplifier 2 and a power amplifier 2; the primary frequency conversion receiver 1 comprises 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 primary frequency conversion receiver 2 comprises 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;

the phase-locked loop 1 is used for generating a single-tone signal 1 and transmitting the single-tone signal 1 to the low-pass filter 1; the low-pass filter 1 is used for filtering high-frequency signal interference in the single-tone signal 1 and transmitting the single-tone signal 1 with the high-frequency signal interference being filtered to the driving amplifier 1; the driving amplifier 1 is used for amplifying the single-tone signal 1 and then transmitting the amplified signal to the power amplifier 1; the power amplifier 1 is used for carrying out power amplification on the scanning signal 1 again and transmitting the single-tone signal 1 after power amplification to the combiner;

the phase-locked loop 2 is used for generating a single-tone signal 2 and transmitting the single-tone signal 2 to the low-pass filter 2; the low-pass filter 2 is used for filtering high-frequency signal interference in the single-tone signal 2 and transmitting the single-tone signal 2 with the high-frequency signal interference being filtered to the driving amplifier 2; the driving amplifier 2 is used for amplifying the monophonic signal 2 and then transmitting the monophonic signal to the power amplifier 2; the power amplifier 2 is used for carrying out power amplification on the scanning signal 2 again and transmitting the single-tone signal 2 after power amplification to the combiner;

the band-pass filter 1 is used for receiving secondary signal waves in the multiplexer separation echo signals, filtering fundamental wave interference in the secondary signal waves, and transmitting the secondary signal waves with the fundamental wave interference being filtered to the preamplifier 1; the preamplifier 1 is used for amplifying the secondary signal wave and transmitting the amplified secondary signal wave to the harmonic mixer 1; the harmonic mixer 1 is used for receiving the secondary signal wave amplified by the preamplifier 1 and the local oscillation frequency generated by the phase-locked loop 2, mixing the secondary signal wave and the local oscillation frequency, and transmitting the generated mixed signal to the intermediate frequency filter 1; the intermediate frequency filter 1 is used for filtering high and low signals in the mixing signals, and transmitting the intermediate frequency signal 1 obtained after filtering to the intermediate frequency amplifier 1; the intermediate frequency amplifier 1 is used for amplifying the intermediate frequency signal 1 and transmitting the amplified intermediate frequency signal 1 to the analog-to-digital converter 1;

the band-pass filter 2 is used for receiving the tertiary signal waves in the echo signals separated by the multiplexer, filtering fundamental wave interference in the tertiary signal waves, and transmitting the tertiary signal waves with the fundamental wave interference being filtered to the preamplifier 2; the preamplifier 2 is used for amplifying the third signal wave and transmitting the amplified third signal wave to the harmonic mixer 2; the harmonic mixer 2 is used for receiving the third signal wave amplified by the preamplifier 2 and the local oscillation frequency generated by the phase-locked loop 3, mixing the third signal wave and the local oscillation frequency, and transmitting the generated mixed signal to the intermediate frequency filter 2; the intermediate frequency filter 2 is used for filtering high and low signals in the mixing signals, and transmitting the intermediate frequency signals 2 obtained after filtering to the intermediate frequency amplifier 2; the intermediate frequency amplifier 2 is configured to amplify the intermediate frequency signal 2, and transmit the amplified intermediate frequency signal 2 to the analog-to-digital converter 2.

Further, the phase-locked loop 2 is a signal source of the second single-tone signal channel and is a local oscillator of the primary frequency conversion receiver 1.

Further, the phase locked loops 1 and 2 are provided with pulse modulated switches that control the transmitter to be switched off during data processing.

Further, the low-pass filter 1 and the low-pass filter 2 both adopt TLCC devices.

Further, the antenna interface is a transmitter signal outlet and simultaneously a receiver signal interface.

Compared with the prior art, the invention has the following advantages:

according to the invention, after the harmonic wave is measured instead of the intermodulation product, the backspacing requirement of the power amplifier is reduced by 10dB, which means that the power can be increased by 10 times on the premise of keeping the cost of a single power amplifier unchanged. The filtering index originally born by the low-pass filter 3 independently is decomposed into the filtering indexes born by the low-pass filters 1, 2 and 3 together, and the requirement on harmonic waves is integrally reduced, so that the suppression index of the low-pass filter 3 at the harmonic frequency is greatly reduced by 20 dB. The indexes of the low-pass filters 1 and 2 are very low, and a common TLCC device is adopted. By adopting the harmonic mixer 1 and analyzing intermodulation products, one phase-locked loop is saved, so that the whole machine adopts two transmitting frequencies, but the number of the phase-locked loops is not increased compared with the prior art. The requirement for harmonic distortion of the preamplifiers 1 and 2 is reduced by 3dB, which is equivalent to improving the usable sensitivity of the receiver, so that less points can be used for fast Fourier transform, and the measurement time is greatly shortened. The transmitter is turned off during data processing through the work of the pulse modulation switch, so that the power consumption is saved, a battery is not required to be added while the transmitting power is increased, and the reduction of the volume of the equipment is facilitated. In general, compared with the existing scheme, the detection distance of the invention is increased to 2 times of the existing scheme, the circuit design difficulty is reduced, and the equipment volume is reduced.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Detailed Description

The invention will be further described with reference to the following specific embodiments and the accompanying drawings, which are given only as the main structural modules of the design and do not represent the number of elements actually used, but should not limit the scope of the invention.

As shown in fig. 1, the technical solution provided by the present invention is a nonlinear node detector, which 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.

The single-tone signal 1 generated by the first single-tone signal channel is connected to one input end of the combiner, the single-tone signal 2 generated by the second single-tone signal channel is connected to the other input end of the combiner, the double-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 double-tone signal and then connects the double-tone signal to one input end of the multiplexer, the output signal of the multiplexer is connected with the antenna interface, the double-tone signal transmits an excitation signal through the antenna interface, and the excitation signal transmits to a target object to generate an echo signal.

In the above module, the first single-tone signal channel may include a phase-locked loop 1, a low-pass filter 1, a driver amplifier 1 and a power amplifier 1; the second single-tone signal path may include a phase locked loop 2, a low pass filter 2, a driver amplifier 2, and a power amplifier 2; the primary frequency conversion receiver 1 comprises 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 primary frequency conversion receiver 2 comprises 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.

The phase-locked loop 1 is used for generating a single-tone signal 1 and transmitting the single-tone signal 1 to the low-pass filter 1; the low-pass filter 1 is used for filtering high-frequency signal interference in the single-tone signal 1 and transmitting the single-tone signal 1 with the high-frequency signal interference being filtered to the driving amplifier 1; the driving amplifier 1 is used for amplifying the monophonic signal 1 and then transmitting the amplified monophonic signal to the power amplifier 1; the power amplifier 1 is configured to perform power amplification on the scanning signal 1 again, and transmit the power-amplified single-tone signal 1 to the combiner.

The phase-locked loop 2 is used for generating a single-tone signal 2 and transmitting the single-tone signal 2 to the low-pass filter 2; the low-pass filter 2 is used for filtering high-frequency signal interference in the single-tone signal 2 and transmitting the single-tone signal 2 with the high-frequency signal interference being filtered to the driving amplifier 2; the driving amplifier 2 is used for amplifying the monophonic signal 2 and then transmitting the amplified monophonic signal to the power amplifier 2; the power amplifier 2 is configured to perform power amplification on the scanning signal 2 again, and transmit the power-amplified single-tone signal 2 to the combiner.

The band-pass filter 1 is used for receiving secondary signal waves in the multiplexer separation echo signals, filtering fundamental wave interference in the secondary signal waves, and transmitting the secondary signal waves with the fundamental wave interference being filtered to the preamplifier 1; the preamplifier 1 is used for amplifying the secondary signal wave and transmitting the amplified secondary signal wave to the harmonic mixer 1; the harmonic mixer 1 is used for receiving the secondary signal wave amplified by the preamplifier 1 and the local oscillation frequency generated by the phase-locked loop 2, mixing the secondary signal wave and the local oscillation frequency, and transmitting the generated mixed signal to the intermediate frequency filter 1; the intermediate frequency filter 1 is used for filtering high and low signals in the mixing signals, and transmitting the intermediate frequency signal 1 obtained after filtering to the intermediate frequency amplifier 1; the intermediate frequency amplifier 1 is configured to amplify the intermediate frequency signal 1 and transmit the amplified intermediate frequency signal 1 to the analog-to-digital converter 1.

The band-pass filter 2 is used for receiving the tertiary signal waves in the echo signals separated by the multiplexer, filtering fundamental wave interference in the tertiary signal waves, and transmitting the tertiary signal waves with the fundamental wave interference being filtered to the preamplifier 2; the preamplifier 2 is used for amplifying the third signal wave and transmitting the amplified third signal wave to the harmonic mixer 2; the harmonic mixer 2 is used for receiving the third signal wave amplified by the preamplifier 2 and the local oscillation frequency generated by the phase-locked loop 3, mixing the third signal wave and the local oscillation frequency, and transmitting the generated mixed signal to the intermediate frequency filter 2; the intermediate frequency filter 2 is used for filtering high and low signals in the mixing signals, and transmitting the intermediate frequency signals 2 obtained after filtering to the intermediate frequency amplifier 2; the intermediate frequency amplifier 2 is configured to amplify the intermediate frequency signal 2 and transmit the amplified intermediate frequency signal 2 to the analog-to-digital converter 2.

Preferably, the phase-locked loop 2 is a signal source of the single-tone signal channel 2 and is a local oscillator of the primary frequency conversion receiver 1, so that one phase-locked loop can be saved, the whole receiver adopts two transmitting frequencies, but the number of the phase-locked loops is not increased compared with the prior art, and the structure is simple.

Preferably, the phase-locked loop 1 and the phase-locked loop 2 are provided with pulse modulation switches, the pulse modulation switches control the transmitter to be turned off during data processing, power consumption is saved, a battery does not need to be added while the transmitting power is increased, and the size and the weight of equipment are reduced.

Preferably, both the low-pass filter 1 and the low-pass filter 2 adopt TLCC devices, and because the back-off requirement on the power amplifier is reduced after the harmonic wave measurement is changed into the intermodulation product measurement, the filtering index originally borne by one low-pass filter is decomposed into three low-pass filters which bear the harmonic wave jointly, so that the index requirements of the low-pass filter 1 and the low-pass filter 2 are low.

Preferably, the antenna interface is a transmitter signal outlet and a receiver signal interface, and the antenna interface is a transmitting port and a receiving port, so that the antenna interface can tolerate the transmitting power, can ensure good gain, efficiency and return loss at transmitting and receiving frequencies, reduces the self harmonic influence, reduces the cost and simplifies the whole equipment.

The working principle of the invention is as follows: the method comprises the steps of adopting double-tone transmission, respectively generating two single-tone signals through a phase-locked loop 1 and a phase-locked loop 2, processing and synthesizing the double-tone signals by a combiner after filtering and amplifying, filtering harmonic waves and intermodulation products by a low-pass filter C, processing the double-tone signals by a multiplexer, transmitting the double-tone signals through an antenna interface, generating echo signals by a target object, wherein the echo signals contain the intermodulation signals, receiving the echo signals through the antenna interface, separating the echo signals into a second term and a third term through the multiplexer, respectively entering two primary frequency conversion receivers for filtering, amplifying and mixing to obtain intermediate frequency signals, converting the intermediate frequency signals into digital signals by an analog-to-digital converter, digitally down-converting the sampled intermediate frequency signals through an FPGA (field programmable gate array), extracting amplitude information of second-order intermodulation and third-order intermodulation products through fast Fourier transform, providing the amplitude information for MCU (microprogrammed control, if the quadratic term and the term are generated to be higher than the cubic term, the target is a nonlinear node, otherwise, the target is not. The pulse modulation switch turns off the transmitter during data processing and turns on the signal channel during operation of the transmitter.

Claims

1. The utility model provides a non-linear node detection appearance, includes transmitter, receiver, antenna interface and signal processing module, its 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 primary frequency conversion receiver 1 and a primary frequency conversion receiver 2; the signal processing module is provided with an FPGA and an MCU;

2. The nonlinear node probe according to claim 1, wherein: the first single-tone signal channel comprises 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 comprises a phase-locked loop 2, a low-pass filter 2, a driving amplifier 2 and a power amplifier 2; the primary frequency conversion receiver 1 comprises 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 primary frequency conversion receiver 2 comprises 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;

3. The nonlinear node probe according to claim 2, wherein: the phase-locked loop 2 is a signal source of a second single-tone signal channel and is a local oscillator of the primary frequency conversion receiver 1 at the same time.

4. The nonlinear node probe according to claim 2, wherein: the phase locked loops 1 and 2 are provided with pulse modulated switches which control the transmitter to be switched off during data processing.

5. The nonlinear node probe according to claim 2, wherein: the low-pass filter 1 and the low-pass filter 2 both adopt TLCC devices.

6. The nonlinear node probe according to claim 1, wherein: the antenna interface is a transmitter signal outlet and is simultaneously a receiver signal interface.