Nonlinear node detector for measuring target distance

Abstract

The invention provides a nonlinear node detector for measuring a target distance. The nonlinear node detector comprises a transmitting module, a receiving module and a signal processing module, the transmitting module transmits a detection signal with the frequency of f1, the receiving module receives a reflected signal radiated by a nonlinear node through excitation of the detection signal, the frequency f1 of the detection signal is f0 + delta f, f0 is a fundamental frequency, delta f is a beat signal frequency in direct proportion to time, and the frequency f1 of the detection signal is equal to f0 + delta f; the signal processing module calculates the target distance according to the interval between the transmitting signal and the receiving signal. On the basis of a conventional nonlinear node detector, target distance measurement is realized by adding a frequency modulation scheme and designing a new distance measurement algorithm. The nonlinear node detector provided by the invention can accurately determine the target orientation and distance, can greatly improve the position accuracy of the found target, improves the working efficiency, and is wider in application scene.

Description

Technical Field

[0001] The present invention relates to the field of early warning detection, in particular, to a nonlinear node detector for measuring target distance, and more specifically, to a nonlinear node detector for checking and locating hidden dangerous items such as time bombs, remote-controlled bombs, and eavesdropping devices. Background Art

[0002] Nonlinear node detectors (also known as harmonic radars, electronic target detectors, etc.) are devices that use the special physical properties of electronic components to detect specific targets. Electronic devices with PN nodes (also called nonlinear nodes) will radiate electromagnetic wave signals such as second and third harmonics of higher frequencies or second and third combination waves when irradiated with electromagnetic waves; however, objects that exist in nature do not have PN nodes of electronic components and cannot radiate similar higher frequency electromagnetic wave signals when irradiated with electromagnetic waves. Using the above principles, nonlinear node detectors illuminate the target area by emitting electromagnetic waves with a frequency of f0 and receiving electromagnetic wave signals in space. It determines whether there are targets such as electronic devices in the search area by detecting whether electromagnetic waves such as second harmonics with a frequency of 2f0, third harmonics with a frequency of 3f0, or combination waves are received. Its working principle is as follows: Figure 1 .

[0003] There are many types of nonlinear node detectors, and the working mechanisms they adopt are also different. The common feature of these devices is that they can only determine whether there is a target in the search area, but cannot measure the distance from the target to the detector.

[0004] With the technological advancement of nonlinear node detectors, the detection distance of the device has increased from the usual 2 to 3 meters to more than 30 meters, and the application scenarios of the device have become more extensive. In this case, the detector can only detect whether the target exists and its approximate direction, which has become a limitation. If it is possible to detect the approximate direction of the target while providing the distance information of the target, the positioning accuracy and search efficiency of the detector will be significantly improved.

[0005] Electromagnetic waves travel at the speed of light (c = 3 × 10 8m / s) propagates in space. In theory, the distance between two target objects can be calculated by measuring the time it takes for electromagnetic waves to propagate. Usually, the time it takes for electromagnetic waves to propagate between two target objects is very short, so short that it is difficult to measure directly using existing technology. In order to solve this problem, a frequency modulated continuous wave solution is usually used when measuring distance with electromagnetic waves, that is, a set of beat signals Δf whose frequency is proportional to time is modulated on a transmission signal with a fixed frequency of f0, so that the electromagnetic wave signal changes in a certain proportional function relationship with time. At a certain moment, the signal received by the electromagnetic wave ranging device is the signal propagating forward from the transmission signal and reflected back from the target, and a propagation delay is generated in the process. In the same delay, the transmission signal has a frequency shift of Δf. The propagation delay is calculated by comparing the frequency difference Δf between the transmission signal and the received signal. The time multiplied by the speed of light gives the distance of electromagnetic wave propagation. This principle is used to achieve indirect measurement of the distance between two objects.

[0006] Conventional electromagnetic wave ranging equipment uses very close frequencies for the transmitting signal and receiving signal, which are close to the same frequency. In comparison, the nonlinear node detector transmits the signal f0, and the receiving signal is the second harmonic 2f0, the third harmonic 3f0 or a combination wave. The frequency difference between the transmitting signal and the receiving signal is very large, and the above electromagnetic wave ranging scheme cannot be used to measure the target distance. It is precisely because of the above reasons that a new nonlinear node detector needs to be invented to measure the target distance. Summary of the invention

[0007] In view of the defects in the prior art, an object of the present invention is to provide a nonlinear node detector for measuring the distance of a target.

[0008] A nonlinear node detector for measuring target distance provided by the present invention comprises: a transmitting module, a receiving module and a signal processing module;

[0009] The transmitting module transmits a detection signal with a frequency of f1, and the receiving module receives a reflected signal radiated by the nonlinear node after being excited by the detection signal. The frequency of the detection signal f1=f0+Δf, wherein f0 is the fundamental frequency, and Δf is the beat signal frequency which is proportional to time. The signal processing module calculates the target distance according to the interval between the transmitting signal and the receiving signal.

[0010] Preferably, the target distance calculation method includes:

[0011] The transmitting frequency is a linear frequency modulation continuous wave f1, the linear frequency modulation slope is f1, and at a certain time t, the transmitting frequency is:

[0012] f1=f0+k*t;

[0013] The actual receiving frequency of the receiving module is:

[0014] f2=2f0+2k*(t-△t);

[0015] The frequency deviation caused by the delay is:

[0016] △f=2f1-f2;

[0017] The delay can be calculated by the delay frequency deviation as:

[0018] △t=△f / 2k;

[0019] The target distance calculation formula is:

[0020]

[0021] Preferably, the transmitting module includes a transmitting source, a control circuit, an excitation circuit, a power amplifier circuit, a filter, an isolator and a frequency modulation circuit.

[0022] Preferably, the receiving module comprises a filter, an amplifier, a control circuit, a mixer, and a low noise amplifier; the signal of the receiving channel is mixed with the local oscillator signal to obtain an intermediate frequency signal, which is sent to the signal processing module for processing.

[0023] Preferably, the nonlinear node detector further comprises a display alarm module, and the display alarm module displays the detected signal by sound, photoelectricity or vibration.

[0024] Preferably, the nonlinear node detector further comprises an antenna module, which is respectively connected to the transmitting module and the receiving module and is used for radiating high-power signals and receiving tiny radio signals.

[0025] Preferably, the nonlinear node detector further includes an interface module, which includes a WiFi module, a USB interface, and a network interface for connecting to external devices.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] Based on the conventional nonlinear node detector, the present invention realizes the target distance measurement by adding a frequency modulation scheme and designing a new distance measurement algorithm. The nonlinear node detector of this patent invention can accurately determine the target direction and distance, greatly improve the accuracy of the target location, improve work efficiency, and have a wider range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0029] Figure 1It is a working principle diagram of a nonlinear node detector in the prior art;

[0030] Figure 2 It is a system structure diagram of a nonlinear node detector for measuring target distance disclosed in the present invention;

[0031] Figure 3 It is a frequency-time relationship diagram of the unmodulated transmission signal in the present invention;

[0032] Figure 4 A frequency-time relationship diagram of adding modulation to the transmission signal in the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0034] The present invention discloses a nonlinear node detector for measuring target distance. The system structure of the nonlinear node detector is as follows: Figure 2 As shown, it includes a transmitting module, a receiving module, a signal processing module, a control module, a display module, an antenna module, a power module, an interface module, etc. The specific functions of each module are as follows:

[0035] Transmitter module: used to generate transmission signals, consisting of a transmission source, a control circuit, an excitation circuit, a power amplifier circuit, a filter, an isolator, etc. In order to achieve the requirements of measuring distance, the transmitter module of this device also includes a frequency modulation circuit.

[0036] Receiving module: used to receive high-frequency electromagnetic wave signals, composed of filters, amplifiers, control circuits, mixers, etc. In order to improve the receiving sensitivity, a low-noise amplifier is added to the receiving module. The signal of the receiving channel is mixed with the local oscillator signal to obtain the intermediate frequency signal, which is sent to the signal processing module for processing.

[0037] Control module: mainly controls the system clock and the timing of each module. For devices that work in a pulse system, the control module is also responsible for controlling the transmission power and the sensitivity of the receiving module.

[0038] Signal processing module: The main function is to process the intermediate frequency signal transmitted by the receiver. Usually the nonlinear node detector signal processing module contains filtering algorithm, amplitude detection algorithm, etc. and transmits the calculation results to the display module.

[0039] Display alarm module: mainly displays the detected signal through sound, photoelectricity, vibration, etc., which is convenient for the operator to understand.

[0040] Antenna module: mainly responsible for radiating high-power signals and receiving tiny radio signals.

[0041] Power module: mainly responsible for the power supply of the entire machine, including batteries, chargers, switches, power interfaces, etc.

[0042] Interface module: mainly realizes the information interaction between the system and external devices, including WIFI, USB, network interface, etc.

[0043] The distance measurement principle of the nonlinear node detector disclosed in the present invention includes:

[0044] The detector transmits a signal with a frequency of f0, which will excite the nonlinear node to radiate two signals with frequencies of 2f0 and 3f0. There is a time delay Δt between the transmitted signal and the received signal. If the time delay Δt can be measured, the distance can be accurately calculated and indirect ranging can be achieved.

[0045] Since the time delay Δt between the detector's transmitted signal and received signal is very short, it is very difficult to directly measure Δt if the fixed-frequency working mode is used. In order to indirectly measure the time difference Δt between the nonlinear node detector's transmitted signal and received signal, the new nonlinear node detector modulates a beat signal Δf whose frequency is proportional to time on the transmitted signal f0, then the transmitted signal frequency becomes f0+Δf, and the signal received by the device will be a harmonic signal with a frequency of 2f0+2Δf and 3f0+3Δf radiated by the electronic target. The beat signal, time difference, and distance can all be detected or calculated, and the specific calculation formula is as follows:

[0046] Assume that the transmitting frequency is a linear frequency modulated continuous wave f1, the fundamental frequency is f0, and the linear frequency modulation slope is k; at a certain time t, the transmitting frequency is:

[0047] f1=f0+k*t;

[0048] The actual receiving frequency is:

[0049] f2=2f0+2k*(t-△t);

[0050] The frequency deviation caused by the delay is:

[0051] △f=2f1-f2;

[0052] The delay can be calculated by the delay frequency deviation as:

[0053] △t=△f / 2k;

[0054] The time delay multiplied by the speed of light gives the transmission path distance of the transmitted signal plus the received signal, and the target distance is half of this distance. The specific target distance calculation formula is:

[0055]

[0056] Figure 3 It is the frequency-time relationship diagram of the unmodulated transmitted signal. Figure 4 The frequency-time relationship diagram of the modulated transmission signal is added. Because the second harmonic radiated by the electronic target is greater than the third harmonic, in order to simplify the system solution, the system calculates the distance by receiving the second harmonic. Using the same method, the distance can also be calculated by the third harmonic.

[0057] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A nonlinear node detector for measuring target distance, characterized in that: include: Transmitting module, receiving module and signal processing module; The transmitting module transmits a detection signal with a frequency of f1, and the receiving module receives a reflected signal radiated by the nonlinear node after being excited by the detection signal. The frequency of the detection signal f1=f0+Δf, wherein f0 is the fundamental frequency, and Δf is the beat signal frequency which is proportional to time. The signal processing module calculates the target distance according to the interval between the transmitting signal and the receiving signal.

2. The nonlinear node detector for measuring target distance according to claim 1, characterized in that: The target distance calculation method comprises: The transmitting frequency is a linear frequency modulation continuous wave f1, the linear frequency modulation slope is f1, and at a certain time t, the transmitting frequency is: f1=f0+k*t; The actual receiving frequency of the receiving module is: f2=2f0+2k*(t-△t); The frequency deviation caused by the delay is: △f=2f1-f2; The delay can be calculated by the delay frequency deviation as: △t=△f / 2k; The target distance calculation formula is:

3. The nonlinear node detector for measuring target distance according to claim 1, characterized in that: The transmitting module includes a transmitting source, a control circuit, an excitation circuit, a power amplifier circuit, a filter, an isolator and a frequency modulation circuit.

4. The nonlinear node detector for measuring target distance according to claim 1, characterized in that: The receiving module includes a filter, an amplifier, a control circuit, a mixer, and a low noise amplifier; the signal of the receiving channel is mixed with the local oscillator signal to obtain an intermediate frequency signal, which is sent to the signal processing module for processing.

5. The nonlinear node detector for measuring target distance according to claim 1, characterized in that: The nonlinear node detector also includes a display alarm module, which displays the detected signal through sound, photoelectricity, and vibration.

6. The nonlinear node detector for measuring target distance according to claim 1, characterized in that: The nonlinear node detector also includes an antenna module, which is connected to the transmitting module and the receiving module respectively, and is used to radiate high-power signals and receive tiny radio signals.

7. The nonlinear node detector for measuring target distance according to claim 1, characterized in that: The nonlinear node detector also includes an interface module, which includes a WiFi module, a USB interface, and a network interface for connecting to external devices.

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