Nonlinear node detection unit and detection device

Abstract

The embodiment of the invention provides a nonlinear node detection unit and a detection device. The nonlinear node detection unit comprises a signal transmitting module used for transmitting a fundamental wave signal to a to-be-detected object, a first signal receiving module used for receiving a first-order harmonic signal generated by the to-be-detected object according to the fundamental wave signal, and a second signal receiving module used for receiving a second-order harmonic signal generated by the to-be-detected object, the second signal receiving module is used for receiving a second-order harmonic signal generated by the object to be detected according to the fundamental wave signal; and the third signal receiving module is used for receiving a third-order harmonic signal generated by the object to be detected according to the fundamental wave signal. And the signal processing unit is respectively connected with the first signal receiving module, the second signal receiving module and the third signal receiving module, and is used for obtaining the nonlinear characteristics of the object to be detected according to the first-order harmonic signal, the second-order harmonic signal and the third-order harmonic signal. According to the nonlinear node detection unit and the detection device provided by the embodiment of the invention, various types of objects to be detected can be detected, so that the missing report rate is reduced.

Description

Technical Field

[0001] The present invention relates to the field of detection technology, and in particular to a nonlinear node detection unit and a detection device. Background Art

[0002] In recent years, leaks have become a frequent occurrence. Mobile electronic storage devices like USB flash drives and hard drives, electronic eavesdropping devices like microphones and cameras, and electronic communication devices like mobile phones can all be exploited by criminals to steal data. Detecting these illegal devices at entrances and exits is a crucial component of security inspections in confidential locations. Currently, this is typically done through security gates. However, traditional security gates can only detect metal and are less effective at detecting electronic devices, resulting in a high rate of missed detections. Summary of the Invention

[0003] The technical problem to be solved by the embodiments of the present invention is to provide a nonlinear node detection unit and a detection device in response to some of the above technical defects in the related art.

[0004] The technical solution adopted by the embodiment of the present invention to solve the technical problem is:

[0005] A first aspect of an embodiment of the present invention provides a nonlinear node detection unit, the nonlinear node detection unit comprising:

[0006] A signal transmitting module for transmitting a fundamental wave signal to an object to be detected;

[0007] a first signal receiving module for receiving a first-order harmonic signal generated by the object to be detected according to the fundamental wave signal;

[0008] a second signal receiving module for receiving a second-order harmonic signal generated by the object to be detected according to the fundamental wave signal;

[0009] a third signal receiving module for receiving a third-order harmonic signal generated by the object to be detected according to the fundamental wave signal;

[0010] A signal processing unit is respectively connected to the first signal receiving module, the second signal receiving module and the third signal receiving module, and is used to obtain the nonlinear characteristics of the object to be detected based on the first-order harmonic signal, the second-order harmonic signal and the third-order harmonic signal.

[0011] A second aspect of an embodiment of the present invention provides a detection device, including the above-mentioned nonlinear node detection unit.

[0012] The beneficial effects of the present invention are:

[0013] The present invention relates to the field of detection technology and provides a nonlinear node detection unit and a detection device. By providing a first signal receiving module, a second signal receiving module, and a third signal receiving module, a first-order harmonic signal, a second-order harmonic signal, and a third-order harmonic signal are received respectively. Since different-order harmonic signals have different sensitivities to different types of nodes, this embodiment can detect multiple categories of objects to be detected, thereby reducing the missed detection rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0015] Figure 1 A schematic diagram of the principle of a nonlinear node detection unit provided by one embodiment of the present invention;

[0016] Figure 2 A schematic diagram of a module of a nonlinear node detection unit provided in one embodiment of the present invention;

[0017] Figure 3 A circuit diagram of a nonlinear node detection unit provided by one embodiment of the present invention;

[0018] Figure 4 A circuit diagram of a signal generator provided by one embodiment of the present invention;

[0019] Figure 5 A schematic diagram of a module of a detection device provided in one embodiment of the present invention;

[0020] Figure 6 A partial cross-sectional view of a detection device provided in one embodiment of the present invention;

[0021] Figure 7 A partial cross-sectional view of a detection device provided in another embodiment of the present invention;

[0022] Figure 8 A schematic diagram of specific modules of a detection device provided in one embodiment of the present invention;

[0023] Figure 9 A schematic diagram of the working sequence of the nonlinear node detection unit and the eddy current detection unit provided in one embodiment of the present invention;

[0024] Figure 10 A flow chart of a detection method provided by one embodiment of the present invention;

[0025] Figure 11 This is a flowchart of a detection method provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following will provide a clear and complete description of the solutions of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] It will be understood by those skilled in the art that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of this application refers to the presence of features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected", "electrically connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, "connected" or "coupled" as used herein may include wireless connection or wireless coupling. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0029] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0030] It should be understood that the sequence numbers and sizes of the steps in this embodiment do not imply the order of execution. The order of execution of each process is determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of this application.

[0031] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] See also Figure 1 The embodiment of the present invention discloses a nonlinear node detection unit 1, which includes: a signal transmitting module 10 for transmitting a fundamental wave signal to an object 4 to be detected. A first signal receiving module 11 is used to receive a first-order harmonic signal generated by the object 4 to be detected based on the fundamental wave signal. A second signal receiving module 12 is used to receive a second-order harmonic signal generated by the object 4 to be detected based on the fundamental wave signal. A third signal receiving module 13 is used to receive a third-order harmonic signal generated by the object 4 to be detected based on the fundamental wave signal. A signal processing unit 14 is respectively connected to the first signal receiving module 11, the second signal receiving module 12 and the third signal receiving module 13, and is used to obtain the nonlinear characteristics of the object 4 to be detected based on the first-order harmonic signal, the second-order harmonic signal and the third-order harmonic signal.

[0033] The nonlinear node detection unit 1 can obtain the nonlinear characteristics corresponding to the nonlinear nodes in the object to be detected 4. A PN junction is a typical nonlinear node. If the electronic product does not adopt electromagnetic shielding measures or the electromagnetic shielding is poor, the PN junction in the electronic product can generate harmonic signals under the influence of the fundamental signal emitted by the nonlinear node detection unit 1. For example, the signal transmission module 10 can transmit the fundamental signal. Under the influence of the fundamental signal, the nonlinear node in the object to be detected 4 will generate a first harmonic signal (also known as a first-order harmonic signal), a second harmonic signal (also known as a second-order harmonic signal), and a third harmonic signal (also known as a third-order harmonic signal). Each receiving module of the nonlinear node detection unit 1, for example, receives the above-mentioned first-order harmonic signal, second-order harmonic signal, and third-order harmonic signal and sends them to the signal processing unit 14, thereby obtaining the nonlinear characteristics of the object to be detected 4. The nonlinear characteristics can be the above-mentioned first-order harmonic signal, second-order harmonic signal, and third-order harmonic signal, or can also be a signal obtained after relevant processing (such as down-conversion, sampling, etc.) of the above-mentioned harmonic signals.

[0034] It should be noted that, after a large number of experimental processes, the inventors found that different harmonic signals have different sensitivities to different types of objects to be detected 4. For example, the first-order harmonic signal is more sensitive to loose metal nodes, so the first signal receiving module 11 is more likely to detect loose metal nodes (such as two or more metal structures with unstable overlapping states, such as screws, key chains, etc.). The second-order harmonic signal is more sensitive to semiconductor targets, and therefore is more likely to detect semiconductor targets. The third-order harmonic signal is more sensitive to stable metal nodes (metal structures with stable and unchanged states, such as steel bars inside walls, metal glasses), so it is easier to detect stable metal nodes.

[0035] In this embodiment, a first signal receiving module 11, a second signal receiving module 12 and a third signal receiving module 13 are provided to receive first-order harmonic signals, second-order harmonic signals and third-order harmonic signals respectively. Since different-order harmonic signals have different sensitivities to different types of nodes, this embodiment can detect various types of objects to be detected, thereby reducing the missed detection rate.

[0036] In one embodiment, if Figure 2 As shown, the signal processing unit 14 can be an MCU (Microcontroller Unit), which can include a three-channel synchronous sampling module 141, a data buffer 142, and a USB 143. The signal processing unit 14 can control the signal transmission module 10 to generate a fundamental signal, and can also perform data processing on the received harmonic signal (for example, performing frequency domain conversion on the harmonic signal) and obtain the nonlinear characteristics of the object to be detected 4 (the nonlinear characteristics are, for example, the amplitudes of each frequency point). At this time, the signal processing unit 14 can send the nonlinear characteristics to the back-end processor for target recognition, for example, to determine whether the object to be detected 4 is an electronic device.

[0037] In another embodiment, the signal processing unit 14 may also have both a signal processing function and a target recognition function, and after obtaining the nonlinear characteristics of the object to be detected 4, the target recognition of the object to be detected 4 can be performed directly based on the nonlinear characteristics. In this embodiment, the signal processing unit 14 is used to compare the nonlinear characteristics corresponding to the received harmonic signal with the preset nonlinear characteristics, thereby realizing the detection of the object to be detected 4 (for example, if the preset nonlinear characteristic is an amplitude threshold, then it is judged that the amplitude of the received harmonic signal is greater than the corresponding preset amplitude threshold, and the object to be detected 4 is considered to be an electronic device). Exemplarily, the signal processing unit 14 may include a single-chip microcomputer, a control chip, or a chip or device capable of running a preset operation strategy. Alternatively, the signal processing unit 14 may include at least one of a single-chip microcomputer, a control chip, and a device capable of running a preset operation strategy.

[0038] In the nonlinear node detection unit 1 disclosed in this embodiment, the first signal receiving module 11, the second signal receiving module 12, and the third signal receiving module 13 are all connected to the signal processing unit 14. The signal transmitting module 10 is used to transmit a fundamental wave signal, which is transmitted outwardly to the detection area to be detected by the nonlinear node detection unit 1. When the object 4 to be detected enters the detection area, the nonlinear node in the object 4 to be detected generates a first-order harmonic signal, a second-order harmonic signal, and a third-order harmonic signal under the influence of the fundamental wave signal. Among them, the first signal receiving module 11 is used to receive the first-order harmonic signal generated by the object 4 to be detected based on the fundamental wave signal, and transmit the first-order harmonic signal or the signal obtained by processing the first-order harmonic signal to the signal processing unit 14. The second signal receiving module 12 is used to receive the second-order harmonic signal generated by the object 4 to be detected based on the fundamental wave signal, and transmit the second-order harmonic signal or the signal obtained by processing the second-order harmonic signal to the signal processing unit 14. The third signal receiving module 13 is configured to receive a third-order harmonic signal generated by the object to be detected 4 according to the fundamental signal, and send the third-order harmonic signal or a signal obtained by processing the third-order harmonic signal to the signal processing unit 14 .

[0039] Further, see Figure 3 In the nonlinear node detection unit 1 disclosed in some embodiments, the signal transmission module 10 includes a fundamental wave signal source 101 and a transmission processing circuit 100. The transmission processing circuit 100 generates a fundamental wave signal based on the fundamental wave signal source 101. The first signal receiving module 11 is configured to mix a first reference signal with a first-order harmonic signal to obtain and output a first identification signal. The first reference signal is generated based on the fundamental wave signal source 101.

[0040] It should be noted that, in this embodiment, the first signal receiving module 11 may directly input a first-order harmonic signal before performing mixing processing, or may input a signal after processing the first-order harmonic signal (for example, a more accurate first-order harmonic signal). These are all within the scope of protection of this application.

[0041] The first-order harmonic signal is the signal returned after the fundamental signal is radiated to the nonlinear node on the object to be detected 4. Therefore, the first-order harmonic signal contains the non-zero frequency shift caused by the nonlinear feedback of the object to be detected 4. For example, the frequency of this non-zero frequency shift is Δf1. The first identification signal is the signal obtained by down-converting the first-order harmonic signal. After mixing the first-order harmonic signal with the first reference signal, the non-zero frequency shift of the first-order response caused by the nonlinear node of the object to be detected 4 can be obtained, that is, the first identification signal. The signal processing unit 14 can perform target identification based on the first identification signal, or send the first identification signal to the back-end processor for target identification.

[0042] In a specific embodiment, for a specific nonlinear node detection unit 1, the frequency of its fundamental signal is f0, the frequency of the first reference signal is f0, and the frequency of its first-order harmonic signal is f0+Δf1. In order to extract the signal with a frequency of Δf1 carried in the first-order harmonic signal, when down-converting the first-order harmonic signal, it is necessary to provide a first reference signal with a frequency equal to f0, that is, the frequency of the first reference signal needs to be consistent with the frequency of the fundamental signal.

[0043] In the detection device provided in an embodiment of the present invention, the first reference signal is generated based on the fundamental signal source 101, that is, it can be ensured that the generated first reference signal has exactly the same frequency as the fundamental signal, thereby ensuring that the frequency of the first identification signal extracted after mixing will not be offset, thereby ensuring detection accuracy.

[0044] It should be noted that if the fundamental signal and the first reference signal use different clock signals as reference clocks, for example, the fundamental signal and the first reference signal are generated based on different crystal oscillators, and the frequencies of the crystal oscillators will have slight differences even in the same batch, and the difference between the fundamental signal and the first reference signal obtained after the frequency multiplication operation will be amplified exponentially. Therefore, the frequency of the first identification signal obtained after the mixing operation may have a certain offset. For example, the expected value of Δf1 is 1KHz, but it may be 0.8KHz, 1.2KHz, etc. after mixing, which is a deviation from the expected 1KHz signal, which will affect the detection accuracy of the detection device.

[0045] In one embodiment, fundamental wave signal source 101 includes a first signal generator L01 and a power divider F1. The input of power divider F1 is electrically connected to first signal generator L01. A first output of power divider F1 is electrically connected to transmit processing circuit 100, and a second output of power divider F1 is electrically connected to first signal receiving module 11. The signal output by the second output of power divider F1 is a first reference signal.

[0046] Specifically, if Figure 3As shown, the input of the first signal generator L01 is connected to the signal processing unit 14, the output of the first signal generator L01 is connected to the input of the power divider F1, the first output of the power divider F1 is connected to the transmit processing circuit 100, and the second output of the power divider F1 is connected to the first signal receiving module 11. The first signal generator L01 is used to generate a local oscillator signal under the control of the signal processing unit 14. The power divider F1 is used to distribute the power of the local oscillator signal to multiple output ports. For example, the power of the local oscillator signal generated by the signal generator L01 can be equally divided and sent to the transmit processing circuit 100 via the first output port and to the first signal receiving module 11 via the second output port, respectively, to form a fundamental signal and a first reference signal. In this embodiment, the fundamental signal and the first reference signal are of the same origin, that is, both are signals generated based on the first signal generator L01. Therefore, the frequencies of the fundamental signal and the first reference signal can be guaranteed to be completely consistent, allowing the first signal receiving module 11 to accurately extract the desired signal, ensuring detection accuracy.

[0047] Among them, such as Figure 3 As shown, the transmit processing circuit 100 includes a first amplifier A0, a transmit filter Z0, and a transmit antenna TX, all electrically connected in sequence to the first output terminal of the power divider F1. The transmit filter Z0 can filter out harmonic components carried by the fundamental signal. The first amplifier A0 can also increase signal power, ensuring efficient signal transmission.

[0048] In some embodiments, the first signal receiving module 11 includes a first signal receiving unit 110 and a first mixer M1. A first input of the first mixer M1 is electrically connected to the first signal receiving unit 110, a second input of the first mixer M1 is electrically connected to the second output of the power divider F1, and an output of the first mixer M1 is electrically connected to the signal processing unit 14. The first mixer M1 is configured to mix the first-order harmonic signal with the first reference signal to obtain a first identification signal.

[0049] The first signal receiving unit 110 may include a first receiving antenna RX1, a first filter Z1, and a first receiving amplifier A1 electrically connected in sequence. It should be noted that a first filter Z1 is provided at the front end of the first mixer M1 to allow signals in the target frequency band (i.e., first-order harmonic signals) to pass through while blocking interference and noise. A first receiving amplifier A1 is also provided to increase signal strength while introducing as little noise as possible, thereby providing a high-quality input signal to the first mixer M1.

[0050] Furthermore, in the detection devices disclosed in some embodiments, the second signal receiving module 12 is configured to mix the second-order harmonic signal and the second reference signal to obtain a second identification signal, and send the second identification signal to the signal processing unit 14. The third signal receiving module 13 is configured to mix the third-order harmonic signal and the third reference signal to obtain a third identification signal, and send the third identification signal to the signal processing unit 14. The fundamental signal source 101, the signal source of the second reference signal, and the signal source of the third reference signal are all referenced to the same clock signal.

[0051] For a certain nonlinear node detection unit 1, the frequency of its fundamental signal is f0, and the frequency of its second-order harmonic signal is 2f0+Δf2. In order to extract the signal with a frequency of Δf2 carried in the second-order harmonic signal, a second reference signal with a frequency equal to 2f0 is provided when down-converting the second-order harmonic signal. That is, the frequency of the second reference signal is equal to twice the frequency of the fundamental signal. The frequency of the third reference signal is equal to 3f0. The principle is the same as that of the first reference signal and the second reference signal, and will not be elaborated on here.

[0052] In addition, since the fundamental signal source 101, the signal source of the first reference signal, the signal source of the second reference signal, and the signal source of the third reference signal all refer to the same clock signal, it is possible to ensure that the frequency of the second reference signal is twice the frequency of the fundamental signal, and to ensure that the frequency of the third reference signal is three times the frequency of the fundamental signal, thereby ensuring that the signal obtained after down-conversion is a signal of the desired frequency, and the frequency of the obtained signals (such as the first identification signal, the second identification signal, and the third identification signal) will not shift, which can improve the detection accuracy of the detection device. The specific principle is the same as that of the aforementioned embodiment and will not be elaborated on here.

[0053] Furthermore, if Figure 3 As shown, in the nonlinear node detection unit 1 disclosed in some embodiments, the second signal receiving module 12 may include a second signal receiving unit 120, a second mixer M2, and a second signal generator L02 electrically connected in sequence. The second mixer M2 is also electrically connected to the signal processing unit 14, and the second signal generator L02 is a signal source of the second reference signal.

[0054] In some embodiments, the third signal receiving module 13 includes a third signal receiving unit 130, a third mixer M3, and a third signal generator L03 electrically connected in sequence. The third mixer M3 is electrically connected to the signal processing unit 14, and the third signal generator L03 is a signal source of the third reference signal.

[0055] In the nonlinear node detection unit 1 disclosed in this embodiment, as Figure 3As shown, the second signal receiving unit 120 includes a second receiving antenna RX2, a second filter Z2, and a second receiving amplifier A2, which are electrically connected in sequence. The second receiving amplifier A2 is connected to a first input of a second mixer M2, a second input of the second mixer M2 is connected to a second signal generator L02, and an output of the second mixer M2 is connected to the signal processing unit 14. The second mixer M2 is configured to mix a second reference signal from the second signal generator L02 with a signal processed from the second receiving amplifier A2 after processing the second-order harmonic signal, thereby outputting a second identification signal to the signal processing unit 14. The second filter Z2 has the same function as the first filter Z1, and the second receiving amplifier A2 has the same function as the first receiving amplifier A1, and therefore will not be described in detail here.

[0056] In the nonlinear node detection unit 1 disclosed in this embodiment, the third signal receiving unit 130 includes a third receiving antenna RX3, a third filter Z3, and a third receiving amplifier A3, which are electrically connected in sequence. The third receiving amplifier A3 is connected to a first input of a third mixer M3, a second input of the third mixer M3 is connected to a third signal generator L03, and an output of the third mixer M3 is connected to the signal processing unit 14. The third mixer M3 is configured to mix a third reference signal from the third signal generator L03 with a signal processed from the third receiving amplifier A3 on the basis of the third-order harmonic signal, thereby outputting a third identification signal to the signal processing unit 14. The third filter Z3 has the same function as the first filter Z1, and the third receiving amplifier A3 has the same function as the first receiving amplifier A1, and therefore will not be described in detail herein.

[0057] The second-order local oscillator signal generated by the second signal generator L02 serves as the second reference signal input to the second mixer M2. Because the second-order harmonic signal is the return signal after the fundamental signal is sent to the nonlinear node on the object 4 to be detected, it contains a non-zero frequency shift of the second-order response caused by the nonlinear feedback of the object 4 to be detected. The frequency of this non-zero frequency shift is Δf2. The frequency of the second-order harmonic signal is 2f0 + Δf2. Since the signal with the frequency Δf2 needs to be extracted through mixing, the frequency of the signal output by the second signal generator L02 (the second reference signal) is set to 2Δf0. After mixing the second-order harmonic signal with the second reference signal, the non-zero frequency shift of the second-order response caused by the nonlinear node of the object 4 to be detected, i.e., the second identification signal, can be obtained. Furthermore, since the second signal generator L02 and the first signal generator L01 are both referenced to the same clock signal, the frequency of the second reference signal is guaranteed to be equal to 2f0. This ensures that the signal with the frequency Δf2 is obtained after frequency conversion, thereby improving detection accuracy.

[0058] In this specific embodiment, the third-order local oscillator signal generated by the third signal generator L03 serves as the third reference signal input to the third mixer M3. Because the third-order harmonic signal is the signal returned after the fundamental signal is sent to the nonlinear node on the object to be detected 4, the third-order harmonic signal contains the non-zero frequency shift of the third-order response generated by the nonlinear feedback of the object to be detected 4. The frequency of this non-zero frequency shift of the third-order response is Δf3. The frequency of the third-order harmonic signal is 3f0 + Δf3. Since the signal with a frequency of Δf3 needs to be extracted through mixing, the frequency of the signal output by the third signal generator L03 (the third reference signal) is set to 3Δf0. After mixing the third-order harmonic signal and the third reference signal, the non-zero frequency shift of the third-order response generated by the nonlinear node of the object to be detected 4 can be obtained, i.e., the third identification signal. Furthermore, since the third signal generator L03 and the first signal generator L01 both reference the same clock signal, the frequency of the third reference signal can be guaranteed to be equal to 3f0, thereby ensuring that a signal with a frequency of Δf3 can be obtained after frequency conversion, thereby improving detection accuracy.

[0059] Specifically, see Figure 4 In the nonlinear node detection unit 1 disclosed in some embodiments, the first signal generator L01, the second signal generator L02, and the third signal generator L03 can be, for example, phase-locked loops (PLLs), i.e., each comprising a loop formed by a phase detector, a loop filter, a voltage-controlled oscillator, and a frequency divider. Taking the first signal generator L01 as an example, the first signal generator L01 includes a first phase detector PD1, a first loop filter LF1, and a first voltage-controlled oscillator VCO1 connected in sequence, and also includes a first frequency divider FD1 connected between the first phase detector PD1 and the first voltage-controlled oscillator VCO1. The second signal generator L02 includes a second phase detector PD2, a second loop filter LF2, and a second voltage-controlled oscillator VCO2 connected in sequence, and also includes a second frequency divider FD2 connected between the second phase detector PD2 and the second voltage-controlled oscillator VCO2. The third signal generator L03 includes a third phase detector PD3, a third loop filter LF3, and a third voltage-controlled oscillator VCO3 connected in sequence, and also includes a third frequency divider FD3 connected between the third phase detector PD3 and the third voltage-controlled oscillator VCO3. The first signal generator L01, the second signal generator L02, and the third signal generator L03 adjust the frequency division multiple through the first frequency divider FD1, the second frequency divider FD2, and the third frequency divider FD3 respectively. The first phase detector PD1, the second phase detector PD2, and the third phase detector PD3 are connected to the crystal oscillator X1. The crystal oscillator X1 is the clock signal commonly referenced by the three signal generators. According to Figure 4It can be seen that the first signal generator L01, the second signal generator L02 and the third signal generator L03 all refer to the same clock (for example, the same crystal oscillator signal), which can ensure that the fundamental signal, the first reference signal, the second reference signal and the third reference signal have consistent timing, thereby ensuring that the signal frequency obtained after mixing will not shift, thereby improving the detection accuracy.

[0060] In addition, the frequency of the fundamental signal is close to the frequency of the first-order harmonic signal. Therefore, the frequency of the fundamental signal may fall within the bandwidth of the first-order receiving antenna (the first receiving antenna RX1 mentioned above). If the transmitting antenna TX in the signal transmitting module 10 of the detection device and the first receiving antenna RX1 in the first signal receiving module 11 are close to each other, the fundamental signal may be received by the first receiving antenna RX1, thereby generating a false alarm. In order to prevent the antenna of the signal transmitting module 10 of the detection device from interfering with the antenna of the first signal receiving module 11, the distance between the antenna of the signal transmitting module 10 and the antenna of the first signal receiving module 11 can be increased as much as possible.

[0061] Therefore, in the nonlinear node detection unit 1 disclosed in some embodiments, the antenna of the second signal receiving module 12 (i.e., the second receiving antenna RX2) and / or the antenna of the third signal receiving module 13 (i.e., the third receiving antenna RX3) are arranged between the antenna of the signal transmitting module 10 (i.e., the transmitting antenna TX) and the antenna of the first signal receiving module 11 (i.e., the first receiving antenna RX1). Therefore, while all components are rationally arranged within a limited space, the distance between the transmitting antenna TX and the first receiving antenna RX1 is maximized, thereby improving the isolation between the transmitting antenna TX and the first receiving antenna RX1, thereby reducing the false alarm rate.

[0062] The nonlinear node detection unit 1 provided in the embodiment of the present application can be applied to a detection device. In one embodiment, see Figure 6 , provides a detection device, including the above-mentioned nonlinear node detection unit 1, the detection device can be a through-type detection device. For easy observation, the outer shell of the door panel on one side of the detection device is cut open in the figure to expose part of the internal structure. Figure 6The figure shows the overall structure and part of the internal structure of the detection device, which includes the signal transmission module 10, the first signal receiving module 11, the second signal receiving module 12, and the third signal receiving module 13 in the nonlinear node detection unit 1. It can be seen that the antenna of the second signal receiving module 12 (i.e., the second receiving antenna RX2) and the antenna of the third signal receiving module 13 (i.e., the third receiving antenna RX3) are arranged between the antenna of the signal transmission module 10 (i.e., the transmitting antenna TX) and the antenna of the first signal receiving module 11 (i.e., the first receiving antenna RX1). In other words, the distance between the antenna of the signal transmission module 10 and the antenna of the first signal receiving module 11 is relatively far, which can reduce the probability of the fundamental wave signal being received by the first signal receiving module 11, thereby reducing the false alarm rate.

[0063] Figure 7 FIG shows the overall structure and part of the internal structure of a detection device that only includes a nonlinear node detection unit 1. In some application scenarios, the detection device may only include the nonlinear node detection unit 1. In this embodiment, Figure 7 As shown, the antenna of the second signal receiving module 12 (i.e., the second receiving antenna RX2) and the antenna of the third signal receiving module 13 (i.e., the third receiving antenna RX3) are arranged between the antenna of the signal transmitting module 10 (i.e., the transmitting antenna TX) and the antenna of the first signal receiving module 11 (i.e., the first receiving antenna RX1), which can reduce the false alarm rate. The principle is the same as that of the aforementioned embodiment and will not be elaborated here.

[0064] In the detection device disclosed in some embodiments, as Figure 3 As shown, the first signal receiving module 11 further includes a first capacitor C1 and a first analog-to-digital converter ADC11, and the first mixer M1 is connected to the signal processing unit 14 via the first capacitor C1 and the first analog-to-digital converter ADC11. The second signal receiving module 12 further includes a second capacitor C2 and a second analog-to-digital converter ADC12, and the second mixer M2 is connected to the signal processing unit 14 via the second capacitor C2 and the second analog-to-digital converter ADC12. The third signal receiving module 13 further includes a third capacitor C3 and a third analog-to-digital converter ADC13, and the third mixer M3 is connected to the signal processing unit 14 via the third capacitor C3 and the third analog-to-digital converter ADC13. The first signal receiving module 11 further includes a fourth receiving amplifier A4, and the power divider F1 is connected to the first mixer M1 via the fourth receiving amplifier A4.

[0065] It should be noted that, for a mixer, under ideal conditions, it can mix the input signal and convert it to a set frequency band. In other words, under ideal conditions, the frequency of the mixed signal should be within the set frequency band. However, in actual applications, due to the influence of the hardware characteristics of the mixer itself, the signal at the input end of the mixer may be directly coupled to the signal output by the first mixer M1. For example Figure 3 In the embodiment, the first reference signal output by the power divider F1 and the received processed first-order harmonic signal may be directly coupled to the signal output by the first mixer M1 (in this case, these signals are equivalent to interference signals).

[0066] In one embodiment, if Figure 3 As shown, the first signal receiving module 11 may further include a fourth filter Z4, a fifth amplifier A5, and a fifth filter Z5 connected in sequence. The fourth filter Z4 is also connected to the first mixer M1. The fifth filter Z5 is used to filter out interference signals carried in the signal output by the first mixer M1. In addition, the first mixer M1 mixes the first-order harmonic signal, which will reduce the power of the output signal to a certain extent. Therefore, the fifth amplifier A5 is also provided after the fourth filter Z4 to increase the signal power and ensure that the signal can be effectively transmitted to the signal processing unit 14.

[0067] In addition, the fourth filter Z4 may not be able to completely filter out the interference signal carried in the signal. Therefore, in order to avoid the influence of the interference signal, a fifth filter Z5 can be further provided between the fifth amplifier A5 and the signal processing unit 14 to improve the signal quality.

[0068] The connection relationship and functions of the sixth filter Z6, the sixth amplifier A6, and the seventh filter Z7 in the second signal receiving module 12 are the same as those in the aforementioned embodiment and are not described in detail here. The connection relationship and functions of the eighth filter Z8, the seventh amplifier A7, and the ninth filter Z9 in the third signal receiving module 13 are the same as those in the aforementioned embodiment and are not described in detail here.

[0069] See also Figures 5 to 9 The embodiment of the present invention discloses a detection device, including the nonlinear node detection unit 1 disclosed in any of the above embodiments. The detection device can be installed at the entrance or exit of a place, or other places where there is a need, and is used to detect illegal devices.

[0070] Furthermore, in order to expand the coverage of the detection area of ​​the detection device, reduce the scope of the detection blind area, and reduce the missed alarm rate, in the detection device disclosed in some embodiments, there are multiple nonlinear node detection units 1, and the frequency of the fundamental wave signal emitted by the signal transmission module 10 in each nonlinear node detection unit 1 is different.

[0071] It should be noted that, since the speed of relative movement between the person carrying the object 4 to be detected or the object 4 to be detected and the detection device is relatively fast, the time spent in the detection area of ​​the detection device is relatively short. Therefore, the nonlinear node detection unit 1 must complete sampling in a sufficiently short time. In the detection device disclosed in this embodiment, two or more nonlinear node detection units 1 can work simultaneously. Thus, two or more nonlinear node detection units 1 detect more nonlinear node features of the object 4 to be detected in a shorter passing time, that is, the amount of detected data increases exponentially. These data can facilitate the signal processing unit 14 to use algorithms to identify targets, thereby improving detection accuracy.

[0072] For example, in one embodiment, a single nonlinear node detection unit 1 takes 15 ms to detect one frame of data, while the transit time of an object 4 to be detected passing through a detection device (e.g., a pass-through detection device) is 1 second. Therefore, a single nonlinear node detection unit 1 can detect approximately 6 to 7 frames of data within 1 second. When there are multiple nonlinear node detection units 1, for example, 8, all nonlinear node detection units 1 operate simultaneously, thereby obtaining approximately 42 to 49 more frames of data than when only one nonlinear node detection unit 1 is operating. In other words, increasing the number of nonlinear node detection units 1 and arranging them along a predetermined direction not only reduces the detection blind spot but also enables the acquisition of more data.

[0073] It should be noted that when multiple nonlinear node detection units 1 are provided and multiple nonlinear node detection units 1 work simultaneously, there may be the following two problems. For example, for a solution in which multiple nonlinear node detection units 1 with the same operating frequency are provided in a single-sided door panel, if the operating frequencies of the nonlinear node detection units 1 provided therein are the same, it may cause trouble to the processing process of the harmonic signal of the subsequent signal processing end (such as the signal processing unit 14). For example, when the operating frequencies of different nonlinear node detection units 1 (such as the frequency of the transmitted fundamental signal) are the same, the frequencies of the second-order harmonic signal and the third-order harmonic signal corresponding to the fundamental signal are also the same, and the signal processing unit 14 cannot well distinguish which nonlinear node detection unit 1 the harmonic signal specifically corresponds to, and then in the process of processing the harmonic signal, its calculation amount, calculation time, calculation complexity, etc. are affected, which in turn affects the detection efficiency of the entire detection device.

[0074] For example, in a solution where both door panels are equipped with multiple nonlinear node detection units 1 operating at the same frequency, in addition to the aforementioned issues that may exist with a single door panel, false alarms may occur on the opposite door panel. Specifically, if the fundamental wave signals emitted by the nonlinear node detection units 1 on one door panel and the nonlinear node detection units 1 on the other door panel have the same frequency, for example, the frequency of the fundamental wave signal emitted by the nonlinear node detection unit 1 on the left door panel is f0, while the frequency of the second-order harmonic signal it expects to receive is 2f0. In this case, the fundamental wave signals emitted by the two different nonlinear node detection units 1 on the right door panel both have a frequency of f0. The frequency of the signal resulting from the mixing of the fundamental wave signals emitted by these two different nonlinear node detection units 1 on the right door panel is 2f0, which coincides with the frequency of the second-order harmonic signal that the nonlinear node detection unit 1 on the left door panel expects to receive. This can cause false alarms on the detection device, thereby affecting the detection efficiency and accuracy of the entire detection device. The same applies to the opposite door panel. In addition, after frequency mixing, the three fundamental wave signals emitted by the nonlinear node detection unit 1 on one door panel may have the same frequency as the third-order harmonic signal that the nonlinear node detection unit 1 on the opposite door panel expects to receive.

[0075] Furthermore, in order to enable two or more nonlinear node detection units 1 in the detection device to work simultaneously without affecting the signal processing unit 14 and the side door panel. In the detection device disclosed in this embodiment, the frequencies of the fundamental signals emitted by the signal transmitting module 10 in each nonlinear node detection unit 1 on the same side door panel are different, which can avoid causing trouble to the signal processing process of the signal processing unit 14 or the back-end processor (such as the target recognition unit 3 described below), thereby improving the detection efficiency. Moreover, it can also be ensured that even if the fundamental signals emitted by the various nonlinear node detection units 1 are mixed, a signal with the same frequency as the expected second-order harmonic signal or the expected third-order harmonic signal will not be generated, effectively avoiding the situation where false alarms are generated during subsequent identification and signal processing.

[0076] In some embodiments, multiple nonlinear node detection units 1 may be provided in both door panels, and the operating frequencies of the different nonlinear node detection units 1 provided in the door panels may also be different. This solution can further prevent the nonlinear node detection units 1 in the door panels from interfering with each other (i.e., it can prevent the signal obtained by mixing the fundamental waves of the multiple nonlinear node detection units 1 in the opposite door panels from being mistakenly interpreted as a harmonic signal). Therefore, in this embodiment, all the nonlinear node detection units 1 in the door panels on both sides can operate simultaneously.

[0077] In the detection device provided in this embodiment, when the number of nonlinear node detection units 1 is two or more, all nonlinear node detection units 1 on the same side door panel can be arranged in sequence along a set direction. The set direction can be the direction of gravity. For example, when two or more nonlinear node detection units 1 are arranged in sequence along the direction of gravity, the number of nonlinear node detection units 1 is increased, and the detection area corresponding to each nonlinear node detection unit 1 at least partially does not overlap in the direction of gravity, thereby increasing the coverage of the total detection area corresponding to the nonlinear node detection unit 1 (including the detection areas corresponding to all nonlinear node detection units 1) in the direction of gravity, reducing the range of the detection blind area in the direction of gravity, and reducing the missed alarm rate.

[0078] The detection device can be a pass-through detection device, such as a security gate. If the detection device is a pass-through detection device, and includes a detection channel, the set direction can be the direction of gravity. The detection channel is covered by the detection area corresponding to the nonlinear node detection unit 1, and is capable of detecting the object 4 to be detected that passes through the detection channel.

[0079] Furthermore, taking a security door as an example, in some embodiments, multiple nonlinear node detection units 1 may be provided, spaced apart in sequence along the direction of gravity. This arrangement not only reduces blind spots but also allows an algorithm to calculate which nonlinear node detection unit 1 corresponds to the detection area within which the detected object 4 is located. This allows for zoned detection and obtains location information of the object 4, such as its height.

[0080] In some embodiments, the setting direction of the detection device can also be parallel to the direction of travel of the detection channel, that is, the object 4 to be detected passes through each nonlinear node detection unit 1 in sequence when passing through the detection channel. In addition, multiple nonlinear node detection units 1 can be arranged in sequence at intervals. In this embodiment, the number of nonlinear node detection units 1 in the direction of travel is increased, which can effectively reduce the detection blind spot of the detection channel in the direction of travel, and the amount of data obtained by detection is increased, which can obtain more accurate nonlinear characteristics, improve detection accuracy, and reduce the missed detection rate. The specific principle is the same as the embodiment in which multiple nonlinear node detection units 1 are arranged along the direction of gravity, and will not be described in detail here.

[0081] Furthermore, in the detection device disclosed in some embodiments of the present invention, Figure 5As shown, the detection device may further include a target recognition unit 3, wherein the nonlinear node detection unit 1 is connected to the target recognition unit 3 and is configured to send the nonlinear characteristics to the target recognition unit 3. The detection device also includes an eddy current detection unit 2, which is connected to the target recognition unit 3 and is configured to obtain the eddy current characteristics of the object to be detected 4 and send the eddy current characteristics to the target recognition unit 3. The eddy current detection unit 2 and the nonlinear node detection unit 1 operate simultaneously, and the detection frequency of the nonlinear node detection unit 1 is different from the detection frequency of the eddy current detection unit 2. The target recognition unit 3 is configured to perform target recognition on the object to be detected 4 based on the received nonlinear characteristics and eddy current characteristics.

[0082] Among the relevant leaking devices, some electronic products generally have no electromagnetic shielding function (for example, no metal casing) or poor electromagnetic shielding, such as USB flash drives, eavesdropping devices, and cameras. For the above-mentioned electronic products, the nonlinear node detection unit 1 can achieve relatively good detection results when detecting nonlinear nodes. For electronic products that have taken electromagnetic shielding measures and have good electromagnetic shielding, such as mobile phones, tablets, smart watches, etc., as long as they contain metal, the amplitude and phase characteristics of the secondary magnetic field formed by eddy currents can be used to detect these electronic products through the eddy current detection unit 2, and their eddy current characteristics can be obtained. Among them, eddy current characteristics, such as the amplitude and phase characteristics of the secondary magnetic field formed by electronic products containing metal under the detection of the eddy current detection unit 2. The eddy current detection unit 2 can supplement the lack of detection capabilities of the nonlinear node detection unit 1 for electronic products with electromagnetic shielding functions. At the same time, the nonlinear node detection unit 1 can also make up for the defect that the eddy current detection unit 2 cannot detect electronic products.

[0083] The detection frequency of the eddy current detection unit 2 in the detection device is different from the detection frequency of the nonlinear node detection unit 1. Therefore, the eddy current detection unit 2 and the nonlinear node detection unit 1 do not interfere with each other, and are therefore capable of operating simultaneously. The operating frequency of the nonlinear node detection unit 1 refers to the frequency of the fundamental signal emitted by the nonlinear node detection unit 1. The operating frequency of the eddy current detection unit 2 refers to the frequency band of the drive signal for the transmitting coil in the eddy current detection unit 2. Because the operating frequency bands of the transmitting and receiving antennas in the nonlinear node detection unit 1 (for example, the frequency band in which the transmitting fundamental signal is emitted and the frequency band in which the first-order harmonic signal, second-order harmonic signal, and third-order harmonic signal are received) are relatively high, while the operating frequency bands of the various modules in the eddy current detection unit 2 (for example, the frequency band in which the drive signal for the transmitting coil is received) are relatively low, the two operating frequency bands do not overlap, and therefore do not interfere with each other. Moreover, the eddy current detection unit 2 and the nonlinear node detection unit 1 in the detection device work simultaneously, so that when the detection device detects the object to be detected 4, the eddy current characteristics and the nonlinear characteristics can be obtained at the same time, and as much characteristic data as possible can be obtained within the same time period, thereby reducing the missed reporting rate.

[0084] The target recognition unit 3 is configured to identify the object 4 to be detected based on the received nonlinear characteristics and eddy current characteristics. For example, the target recognition unit 3 may be a single-chip microcomputer, a control chip, or a chip or device capable of executing a preset computing strategy. Alternatively, the target recognition unit 3 may include at least one of a single-chip microcomputer, a control chip, and a device capable of executing a preset computing strategy.

[0085] See also Figure 8 Furthermore, in the detection devices disclosed in some embodiments, the eddy current detection unit 2 may include: a control chip 21, and a digital-to-analog converter 26, a transmitting unit 24, and a magnetic field generating module 22 connected in sequence. The digital-to-analog converter 26 is also connected to the control chip 21. The eddy current detection unit 2 also includes one or more receiving channels, each of which includes a sensing module 23, a receiving unit 25, and an analog-to-digital converter ADC 27 connected in sequence. The analog-to-digital converter ADC 27 is connected to the control chip 21.

[0086] The magnetic field generating module 22 is used to actively generate a primary magnetic field, and the range of the primary magnetic field at least covers the detection area. The sensing module 23 is used to sense the magnetic field at the location and generate a corresponding induced electromotive force. The control chip 21 is used to send a command to the magnetic field generating module 22 to generate a primary magnetic field, and is also used to receive the induced electromotive force sent by the sensing module 23. When the object to be detected 4 in the detection area is an object with conductive properties, the object to be detected 4 will generate a secondary magnetic field under the influence of the primary magnetic field. The secondary magnetic field and the primary magnetic field generated by the magnetic field generating module 22 interact with each other, so that the magnetic field at the location of the sensing module 23 changes and generates a changed induced electromotive force. The control chip 21 receives the changed induced electromotive force and compares it with the induced electromotive force in the original state and other data processing, thereby identifying the object to be detected 4.

[0087] Furthermore, the control chip 21 can be a field programmable gate array module, which is used to output a drive signal. The drive signal is converted from digital to analog by a digital-to-analog converter 26, and is driven and amplified by the transmitting unit 24 and sent to the magnetic field generating module 22 to generate an alternating magnetic field. Specifically, the field programmable gate array module can also be used to obtain the eddy current characteristics of the object to be detected 4 (for example, spectrum data) based on the received induced electromotive force, and send the eddy current characteristics to the target identification unit 3. The magnetic field generating module 22 can generate an alternating magnetic field (original magnetic field) when an alternating current is passed through it. At this time, the induction module 23 has no induced electromotive force. When the object to be detected 4 is a component with conductive properties (such as metal), the object to be detected 4 will generate an induced current under the action of the original magnetic field. The magnetic field generated by the induced current will interact with the original magnetic field, causing the original magnetic field to change. At this time, the induction module 23 can output the induced electromotive force. After being processed by the receiving unit 25, the induced electromotive force is transmitted to the control chip 21 via the analog-to-digital conversion module 27. The control chip 21 then performs data processing, such as fast Fourier transform, and transmits it to the target recognition unit 3. The target recognition unit 3 processes and analyzes the induced electromotive force output by the sensing module 23, enabling detection of the target object 4, such as a metal component or an electronic device with a metal housing. The magnetic field generating module 22 can be a transmitting coil, and the sensing module 23 can be a receiving coil.

[0088] Furthermore, the magnetic field generating module 22 can be provided corresponding to the induction module 23, and the induction module 23 can adopt a single coil (not shown in the figure) or a double coil (such as Figure 6 In a specific embodiment, the detection device is a security door, and the number of receiving coils of the eddy current detection unit 2 can be 12 pairs, with 6 pairs of receiving coils evenly arranged on each side door panel along the direction of gravity.

[0089] In some embodiments, the control chip 21 includes a Fourier transform module U29, which is used to perform a Fourier transform on data received from the analog-to-digital converter ADC 27. The control chip 21 is also used to perform mode control (e.g., switching between multiple operating modes, controlling the power supply of different transmitting coils in different operating modes) and determine the transmission sequence (i.e., outputting a drive signal to cause the magnetic field generating module 22 to generate an alternating magnetic field).

[0090] See also Figure 9 The figure shows an operating timing diagram of an eddy current detection unit 2 and a nonlinear node detection unit 1 (taking the first nonlinear node detection unit A and the second nonlinear node detection unit B as examples). According to the above embodiment, since the operating frequencies of the eddy current detection unit 2 and the nonlinear node detection unit 1 are different, they can work simultaneously to reduce the false alarm rate. The operating time of the two can overlap without affecting each other. In addition, it can be seen that Figure 9 The first nonlinear node detection unit A and the second nonlinear node detection unit B shown in FIG. 1 work simultaneously, that is, the amount of detection data obtained can be increased by setting multiple nonlinear node detection units 1 within the same time period.

[0091] The eddy current detection unit 2, the first nonlinear node detection unit A, and the second nonlinear node detection unit B all have an idle time of 10 ms during each operating cycle. The transmitting and receiving coils of the eddy current detection unit 2 both operate for 14 ms during each operating cycle, meaning that every 24 ms constitutes one operating cycle for the eddy current detection unit 2. The receiving coil operates synchronously with the transmitting coil, forming a complete excitation-induction cycle. The first nonlinear node detection unit A and the second nonlinear node detection unit B have identical operating times. Their transmitting and receiving antennas operate for 5 ms during each operating cycle. In this embodiment, the nonlinear node detection unit 1 simultaneously drives three receiving antennas during a single operating cycle. The transmitting antennas TX of the first nonlinear node detection unit A and the second nonlinear node detection unit B are each located within their respective signal transmission modules 10. The receiving antennas of the first nonlinear node detection unit A and the second nonlinear node detection unit B include a first receiving antenna RX1, a second receiving antenna RX2, and a third receiving antenna RX3, respectively. The first receiving antenna RX1 , the second receiving antenna RX2 and the third receiving antenna RX3 are respectively disposed in the corresponding first signal receiving module 11 , the second signal receiving module 12 and the third signal receiving module 13 .

[0092] Therefore, in this embodiment, the eddy current detection unit 2 and all nonlinear node detection units 1 can operate simultaneously. Although the time it takes for the object 4 to pass through the detection device is relatively short, typically 1 second, both the eddy current detection unit 2 and the nonlinear node detection unit 1 can collect sufficient data within this time period, thereby improving detection accuracy.

[0093] See also Figures 10 and 11 The present invention also discloses a detection method, which can be applied to the detection device disclosed in the above embodiment, and can also be applied to other detection devices provided with a nonlinear node detection unit 1 and an eddy current detection unit 2. The detection method includes:

[0094] S10. Acquire the nonlinear characteristics of the object to be detected 4 obtained by the nonlinear node detection unit 1 and the eddy current characteristics obtained by the eddy current detection unit 2, wherein the detection frequency of the eddy current detection unit 2 is different from the detection frequency of the nonlinear node detection unit 1, and the eddy current detection unit 2 and the nonlinear node detection unit 1 operate simultaneously.

[0095] S20 , performing target recognition on the object to be detected 4 according to the nonlinear characteristics and eddy current characteristics.

[0096] In some embodiments, the detection method can be applied to the detection device in any of the aforementioned embodiments and executed by the target recognition unit 3 in the detection device.

[0097] It should be noted that the nonlinear characteristics of the object to be detected 4 obtained by the nonlinear node detection unit 1 may include harmonic signals (for example, first-order harmonic signals, second-order harmonic signals, and third-order harmonic signals). Eddy current characteristics may include parameters such as phase and amplitude. In one embodiment, the target recognition unit 3 may use the amplitude of the harmonic signal to identify the object to be detected 4. For example, the discrimination is performed by judging the amplitude relationship between the second-order harmonic signal and the third-order harmonic signal.

[0098] In one embodiment, when the amplitude of the second-order harmonic signal is greater than the amplitude of the third-order harmonic signal, the object to be detected 4 is determined to have a nonlinear node, and a first recognition result is obtained. The target recognition unit 3 can also use parameters such as phase and amplitude to identify the object to be detected 4. For example, if the amplitude is greater than a set threshold, the object to be detected 4 is determined to be a mobile phone, and a second recognition result is obtained. In this case, the target recognition unit 3 can output the first recognition result and the second recognition result separately, or it can also derive and output a combined recognition result based on the first and second recognition results.

[0099] In another embodiment, the target identification unit 3 can perform a comprehensive judgment based on both the nonlinear characteristics and the eddy current characteristics of the object to be detected 4, i.e., perform target identification. Specifically, in the detection methods disclosed in some embodiments, the step of identifying the object to be detected 4 based on the nonlinear characteristics and the eddy current characteristics includes: if the eddy current characteristics are determined to be consistent with those of a mobile phone, i.e., the phase and amplitude are both within the threshold range corresponding to a mobile phone, and the nonlinear characteristics are relatively weak, then the object to be detected 4 can be considered to be a mobile phone. If the eddy current characteristics are determined to be relatively weak, and the nonlinear characteristics are relatively strong, then the object to be detected 4 is considered to be an electronic product other than a mobile phone.

[0100] In some embodiments, the detection method can also be applied to other detection devices including devices with computing and processing functions (such as processing chips), and executed by the processing chip in the detection device. Alternatively, the detection method can also be executed by humans.

[0101] It should be noted that the eddy current detection unit 2 is affected by two factors during detection. First, metal components may exist in the nonlinear node detection unit 1. Especially when nonlinear node detection units 1 are installed in both door panels, the metal components in the nonlinear node detection unit 1 in the opposite door panel of any eddy current detection unit 2 will also affect the primary magnetic field generated by the magnetic field generating module 22. Second, environmental noise can also affect the detection accuracy of the eddy current detection unit 2.

[0102] Further, see Figure 11 In order to prevent the background noise generated by the metal nodes and / or environmental noise in the nonlinear node detection unit 1 from affecting the detection of the eddy current detection unit 2, in the detection method disclosed in some embodiments, before the step of identifying the target object 4 based on the nonlinear characteristics and eddy current characteristics, the following step S11 is first performed: the eddy current characteristics are calibrated using the background noise data.

[0103] In some embodiments, the background noise data may be background noise data measured in real time by other devices, or may be background noise data pre-stored in the target recognition unit 3 .

[0104] Furthermore, in the detection methods disclosed in some embodiments, the method for obtaining background noise data includes:

[0105] Step A: When the detection range of the detection device does not contain the object 4 to be detected, initial data detected by the eddy current detection unit 2 is received.

[0106] Step B: Obtain background noise data based on the initial data.

[0107] When there is no object 4 to be detected within the detection range of the detection device, the metal nodes and environmental noise of the nonlinear node detection unit 1 within the detection range generate an induced current under the influence of the original magnetic field generated by the magnetic field generating module 22. The induced current generates a secondary magnetic field and then affects the original magnetic field. The receiving coil generates an unbalanced induced electromotive force, and the voltage signal formed by the induced electromotive force is the initial data. The initial data is converted into a digital signal by, for example, an analog-to-digital conversion circuit (such as an analog-to-digital converter ADC27) and sent to the control chip 21 for data processing to obtain background noise data.

[0108] In some embodiments, the digital signal is sent to the field programmable gate array module for Fourier transform processing, and amplitude and phase analysis is performed to obtain background noise data. For example, when there is no object 4 to be detected passing through, the detection device receives the electromagnetic signal A(t) (the above-mentioned initial data) through the sensing module 23, and performs analog-to-digital conversion on the electromagnetic signal A(t) to obtain a discrete time domain signal An(t). The field programmable gate array module performs a discrete Fourier transform on the discrete time domain signal An(t) to obtain background noise = RE1n(f) + jI1mn(f). Among them, is a complete frequency domain signal representing the background noise, RE1n(f) represents the real part of the frequency domain signal of the background noise, and jI1mn(f) represents the imaginary part of the frequency domain signal of the background noise. The background noise is generated by the environmental noise and the nonlinear node detection unit 1.

[0109] Furthermore, in the detection method disclosed in some embodiments, the step of calibrating the eddy current characteristics using background noise data includes: subtracting the eddy current characteristics from the background noise data and obtaining the subtraction result. The subtraction result is the calibrated data. In actual detection, when the object to be detected 4 passes through the detection device, the electromagnetic signal X(t) is received by the sensing module 23, and the electromagnetic signal X(t) is converted into a digital form to obtain a discrete time domain signal Xn(t). The programmable gate array performs a discrete Fourier transform on the discrete time domain signal Xn(t) to obtain a discrete frequency domain signal = REn(f)+jImn(f). Among them, is a discrete frequency domain signal, REn(f) is the real part of the discrete frequency domain signal, and jImn(f) is the imaginary part of the discrete frequency domain signal. Next, the received signal is calibrated using the background noise, that is. Wherein is the calibrated discrete frequency domain signal, and =REn(f)'+jImn(f)', REn(f)' is the real part of the calibrated discrete frequency domain signal, and jImn(f)' is the imaginary part of the calibrated discrete frequency domain signal. Using the inverse tangent operation, the phase of the calibrated discrete frequency domain signal is calculated, that is, Phasen(f) = arctan(Imn(f)' / REn(f)'), where Phasen(f) is the phase, and arctan(Imn(f)' / REn(f)') is the inverse tangent function of the imaginary part of the discrete frequency domain signal. The amplitude Ampn(f) of the calibrated discrete frequency domain signal is then calculated using the square root operation. The phase Phasen(f) and amplitude Ampn(f) are the data after calibration of the eddy current characteristics.

[0110] Furthermore, in the detection method disclosed in some embodiments, target identification is performed on the object 4 to be detected based on the nonlinear characteristics and eddy current characteristics, that is, the above-mentioned step S20 includes: target identification is performed on the object 4 to be detected based on the nonlinear characteristics and the data after calibration of the eddy current characteristics.

[0111] By combining the nonlinear characteristics of the object 4 to be detected with the data from the calibration of the eddy current characteristics, the product category of the object 4 to be detected is analyzed, thereby achieving target identification. In this embodiment, since the eddy current characteristics are calibrated using the background noise data, interference between the nonlinear node detection unit 1 and the eddy current detection unit 2 can be avoided, thereby improving the accuracy of target identification.

[0112] An embodiment of the present invention further discloses a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above-mentioned detection method when executing the computer program.

[0113] An embodiment of the present invention further discloses a computer-readable storage medium storing a computer program, which implements the steps of the above-mentioned detection method when executed by a processor.

[0114] An embodiment of the present invention further discloses a computer program product, including a computer program, which implements the steps of the above detection method when executed by a processor.

[0115] It is understandable that the above embodiments only express the preferred implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above embodiments or technical features can be freely combined, and several deformations and improvements can be made, which all fall within the scope of protection of the present invention, that is, the embodiments described in "some embodiments" can be freely combined with any of the above and below embodiments. Therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A nonlinear node detection unit, characterized in that: The nonlinear node detection unit includes: A signal transmitting module for transmitting a fundamental wave signal to an object to be detected; a first signal receiving module for receiving a first-order harmonic signal generated by the object to be detected according to the fundamental wave signal; a second signal receiving module for receiving a second-order harmonic signal generated by the object to be detected according to the fundamental wave signal; a third signal receiving module for receiving a third-order harmonic signal generated by the object to be detected according to the fundamental wave signal; A signal processing unit is respectively connected to the first signal receiving module, the second signal receiving module and the third signal receiving module, and is used to obtain the nonlinear characteristics of the object to be detected based on the first-order harmonic signal, the second-order harmonic signal and the third-order harmonic signal.

2. The nonlinear node detection unit according to claim 1, characterized in that: The antenna of the second receiving module and / or the antenna of the third receiving module are arranged between the antenna of the signal transmitting module and the antenna of the first receiving module.

3. The nonlinear node detection unit according to claim 1, characterized in that: The signal transmission module includes a fundamental wave signal source and a transmission processing circuit, and the transmission processing circuit generates the fundamental wave signal based on the fundamental wave signal source; The first signal receiving module is further configured to mix the first reference signal and the first-order harmonic signal and output the mixed signals; The first reference signal is generated according to the fundamental wave signal source.

4. The nonlinear node detection unit according to claim 3, characterized in that: The fundamental wave signal source includes a first signal generator and a power divider; The input end of the power divider is electrically connected to the first signal generator; the first output end of the power divider is electrically connected to the transmission processing circuit, and the second output end of the power divider is electrically connected to the first signal receiving module; wherein the signal output by the second output end of the power divider is the first reference signal.

5. The nonlinear node detection unit according to claim 4, characterized in that: The first signal receiving module includes a first signal receiving unit and a first mixer; the first input end of the first mixer is electrically connected to the first signal receiving unit, the second input end of the first mixer is electrically connected to the second output end of the power divider, and the output end of the first mixer is electrically connected to the signal processing unit.

6. The nonlinear node detection unit according to claim 3, characterized in that: The second signal receiving module is further configured to mix the second-order harmonic signal and a second reference signal and output the mixed signals; The third signal receiving module is further configured to mix the third-order harmonic signal and the third reference signal and output the mixed signals; The fundamental wave signal source, the signal source of the second reference signal, and the signal source of the third reference signal all refer to the same clock signal.

7. The nonlinear node detection unit according to claim 6, characterized in that: The second signal receiving module includes a second signal receiving unit, a second mixer, and a second signal generator electrically connected in sequence; the second mixer is also electrically connected to the signal processing unit; the second signal generator is a signal source of the second reference signal; and / or, The third signal receiving module includes a third signal receiving unit, a third mixer, and a third signal generator electrically connected in sequence; the third mixer is also electrically connected to the signal processing unit; and the third signal generator is a signal source of the third reference signal.

8. A detection device, characterized in that: The invention comprises the nonlinear node detection unit according to any one of claims 1 to 7.

9. The detection device according to claim 8, characterized in that There are multiple nonlinear node detection units, and the frequencies of the fundamental wave signals transmitted by the signal transmitting modules in each nonlinear node detection unit are different.

10. The detection device according to claim 8, characterized in that The detection device further includes a target recognition unit, the signal processing unit is connected to the target recognition unit, and is used to send the nonlinear feature to the target recognition unit; The detection device further includes an eddy current detection unit, which is connected to the target identification unit and is used to obtain eddy current characteristics of the object to be detected and send the eddy current characteristics to the target identification unit; the eddy current detection unit and the nonlinear node detection unit operate simultaneously, and the detection frequency of the nonlinear node detection unit is different from the detection frequency of the eddy current detection unit; The target recognition unit is used to perform target recognition on the object to be detected based on the received nonlinear characteristics and the received eddy current characteristics.

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