Non-linear junction detection unit and detection apparatus

Abstract

The embodiment of the present application provides a kind of nonlinear node detection unit and detection device, nonlinear node detection unit includes: for emitting fundamental wave signal to the signal emitting module of object to be detected, for receiving the first signal receiving module of the first-order harmonic signal generated by object to be detected according to fundamental wave signal, for receiving the second signal receiving module of the second-order harmonic signal generated by object to be detected according to fundamental wave signal, for receiving the third signal receiving module of the third-order harmonic signal generated by object to be detected according to fundamental wave signal.Signal processing unit is connected with first signal receiving module, second signal receiving module and third signal receiving module respectively, for obtaining the nonlinear feature of object to be detected according to first-order harmonic signal, second-order harmonic signal and third-order harmonic signal.The nonlinear node detection unit and detection device provided by the embodiment of the present application can detect various categories of objects to be detected, thereby reducing the false negative rate.

Description

Technical Field

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

[0002] In recent years, data breaches have occurred frequently. Electronic storage devices such as USB drives and hard drives, electronic eavesdropping and surveillance devices such as microphones and cameras, and electronic communication devices such as mobile phones can all be exploited by criminals to steal data. For secure locations, detecting these illegal devices at entrances and exits is a crucial part of security checks. Currently, this is generally done using security gates. However, traditional security gates can only detect metal and are less effective at detecting electronic devices, resulting in a high false negative rate. 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 detection device, which addresses the above-mentioned technical defects in related technologies.

[0004] The technical solution adopted by the embodiments of the present invention to solve its technical problem is as follows:

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

[0006] A signal transmission module for transmitting fundamental wave signals to the object to be detected;

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

[0008] A second signal receiving module for receiving the second harmonic signal generated by the object to be detected based on the fundamental wave signal;

[0009] A third signal receiving module for receiving the third harmonic signal generated by the object to be detected based on the fundamental wave signal;

[0010] The signal processing unit is connected to the first signal receiving module, the second signal receiving module, and the third signal receiving module, respectively, 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 the present invention provides a detection device, including the nonlinear node detection unit described above.

[0012] The beneficial effects of this invention are:

[0013] This invention relates to the field of detection technology and provides a nonlinear node detection unit and detection device. By setting a first signal receiving module, a second signal receiving module, and a third signal receiving module, the unit receives first-order harmonic signals, second-order harmonic signals, and third-order harmonic signals, respectively. Since different harmonic signals have different sensitivities to different types of nodes, this embodiment can detect multiple types of objects to be detected, thereby reducing the false alarm rate. Attached Figure Description

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

[0015] Figure 1 This is a schematic diagram of the principle of a nonlinear node detection unit provided in an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of a nonlinear node detection unit provided in an embodiment of the present invention;

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

[0018] Figure 4 This is a circuit diagram of a signal generator provided in an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of a detection device provided in an embodiment of the present invention;

[0020] Figure 6 This is a partial cross-sectional view of a detection device provided in an 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 This is a schematic diagram of the specific modules of a detection device provided in an embodiment of the present invention;

[0023] Figure 9 This is a schematic diagram illustrating the operating timing of a nonlinear node detection unit and an eddy current detection unit provided in an embodiment of the present invention.

[0024] Figure 10 A flowchart of a detection method provided in an embodiment of the present invention;

[0025] Figure 11 A flowchart of a detection method provided in another embodiment of the present invention. Detailed Implementation

[0026] The present invention will now be clearly and completely described in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] Those skilled in the art will understand that, unless explicitly stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in the specification of this application means 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 say an element is “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 present. Furthermore, “connected” or “coupled” as used herein may include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any units 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 used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

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

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] See Figure 1 This 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 for receiving the first harmonic signal generated by the object 4 based on the fundamental wave signal; a second signal receiving module 12 for receiving the second harmonic signal generated by the object 4 based on the fundamental wave signal; a third signal receiving module 13 for receiving the third harmonic signal generated by the object 4 based on the fundamental wave signal; and a signal processing unit 14, connected to the first signal receiving module 11, the second signal receiving module 12, and the third signal receiving module 13, for obtaining the nonlinear characteristics of the object 4 based on the first, second, and third harmonic signals.

[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 take electromagnetic shielding measures or has poor electromagnetic shielding, the PN junction inside the electronic product can generate harmonic signals under the influence of the fundamental wave signal emitted by the nonlinear node detection unit 1. For example, the signal transmitting module 10 can transmit a fundamental wave signal, and the nonlinear nodes in the object to be detected 4 will generate first harmonic signals (also called first-order harmonic signals), second harmonic signals (also called second-order harmonic signals), and third harmonic signals (also called third-order harmonic signals) under the influence of the fundamental wave signal. Each receiving module of the nonlinear node detection unit 1 receives, for example, the aforementioned first-order harmonic signals, second-order harmonic signals, and third-order harmonic signals, 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 aforementioned first-order harmonic signals, second-order harmonic signals, and third-order harmonic signals, or they can be signals obtained after performing relevant processing on the aforementioned harmonic signals (e.g., down-conversion, sampling, etc.).

[0034] It should be noted that, after extensive experimentation, the inventors discovered that different harmonic signals exhibit varying degrees of sensitivity to different types of objects to be detected. For example, first-order harmonic signals are more sensitive to loosely connected metal nodes, making it easier for the first signal receiving module 11 to detect them (e.g., two or more unstable metal structures with overlapping joints, such as screws or keychains). Second-order harmonic signals are more sensitive to semiconductor targets, thus making them easier to detect. Third-order harmonic signals are more sensitive to stable metal nodes (metal structures with stable and unchanging states, such as steel bars inside a wall or metal eyeglasses), making them easier to detect.

[0035] In this embodiment, by setting a first signal receiving module 11, a second signal receiving module 12, and a third signal receiving module 13, first-order harmonic signals, second-order harmonic signals, and third-order harmonic signals are received respectively. Since different harmonic signals have different sensitivities to different types of nodes, this embodiment can detect multiple types of objects to be detected, thereby reducing the false alarm rate.

[0036] In one embodiment, such as Figure 2 As shown, the signal processing unit 14 can be an MCU (Microcontroller Unit), which may 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 transmitting module 10 to generate a fundamental signal, and can also perform data processing on the received harmonic signals (e.g., frequency domain conversion of the harmonic signals) to obtain the nonlinear characteristics of the object to be detected 4 (the nonlinear characteristics are, for example, the amplitude at each frequency point). At this time, the signal processing unit 14 can send the nonlinear characteristics to the back-end processor for target recognition, such as determining whether the object to be detected 4 is an electronic device.

[0037] In another embodiment, the signal processing unit 14 may also simultaneously possess signal processing and target recognition functions. After obtaining the nonlinear characteristics of the object to be detected 4, it can directly perform target recognition based on these nonlinear characteristics. In this embodiment, the signal processing unit 14 is used to compare the nonlinear characteristics corresponding to the received harmonic signal with preset nonlinear characteristics, thereby achieving the detection of the object to be detected 4 (for example, if the preset nonlinear characteristic is an amplitude threshold, then if the amplitude of the received harmonic signal is greater than the corresponding preset amplitude threshold, the object to be detected 4 is considered to be an electronic device). Exemplarily, the signal processing unit 14 may include a microcontroller, a control chip, or a chip or device capable of running a preset calculation strategy. Alternatively, the signal processing unit 14 may include at least one of a microcontroller, a control chip, and a device capable of running a preset calculation 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 the fundamental wave signal, which is transmitted outward to the detection area to be detected by the nonlinear node detection unit 1. When the object to be detected 4 enters the detection area, the nonlinear nodes in the object to be detected 4 generate first-order harmonic signals, second-order harmonic signals, and third-order harmonic signals under the influence of the fundamental wave signal. Specifically, the first signal receiving module 11 is used to receive the first-order harmonic signal generated by the object to be detected 4 according to the fundamental wave signal, and transmit the first-order harmonic signal or the signal obtained after 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 to be detected 4 according to the fundamental wave signal, and transmit the second-order harmonic signal or the signal obtained after processing the second-order harmonic signal to the signal processing unit 14. The third signal receiving module 13 is used to receive the third harmonic signal generated by the object to be detected 4 based on the fundamental wave signal, and send the third harmonic signal or the signal obtained after processing the third harmonic signal to the signal processing unit 14.

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

[0040] It should be noted that, in this embodiment, the input to the first signal receiving module 11 before mixing can be a first-order harmonic signal, or it can be a signal processed from the first-order harmonic signal (e.g., a more precise first-order harmonic signal). These are all within the scope of protection of this application.

[0041] The first 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 harmonic signal contains a 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 harmonic signal. After mixing the first harmonic signal and the first reference signal, the non-zero frequency shift of the first-order response of the object to be detected 4 caused by the nonlinear node can be obtained, which 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 particular nonlinear node detection unit 1, the frequency of its fundamental signal is f0, the frequency of its first reference signal is f0, and the frequency of its first harmonic signal is f0+Δf1. Specifically, in order to extract the signal with frequency Δf1 carried in the first harmonic signal, when down-converting the first harmonic signal, a first reference signal with a frequency equal to f0 is required; that is, the frequency of the first reference signal must be consistent with the frequency of the fundamental signal.

[0043] The detection device provided in this embodiment of the invention uses a first reference signal generated based on a fundamental wave signal source 101. This ensures that the generated first reference signal has the same frequency as the fundamental wave signal, thereby ensuring that the frequency of the first identification signal extracted after mixing will not shift and 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, if the fundamental signal and the first reference signal are generated based on different crystal oscillators, and the frequencies of crystal oscillators, even within the same batch, will have slight differences—the difference between the fundamental signal and the first reference signal obtained after frequency multiplication will be amplified exponentially. Therefore, the frequency of the first identification signal obtained after the mixing operation may have a certain offset. For example, if the expected value of Δf1 is 1kHz, it may become 0.8kHz, 1.2kHz, etc., after mixing, which deviates from the expected 1kHz signal and thus affects the detection accuracy of the detection device.

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

[0046] Specifically, such as Figure 3As shown, the input terminal of the first signal generator L01 is connected to the signal processing unit 14, and the output terminal of the first signal generator L01 is connected to the input terminal of the power divider F1. The first output terminal of the power divider F1 is connected to the transmission processing circuit 100, and the second output terminal 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 transmission processing circuit 100 through the first output terminal and to the first signal receiving module 11 through the second output terminal, respectively, to form the fundamental wave signal and the first reference signal. In this embodiment, the fundamental wave signal and the first reference signal are from the same source, that is, both are signals generated based on the first signal generator L01. Therefore, the frequencies of the fundamental wave signal and the first reference signal can be guaranteed to be completely consistent, which allows the first signal receiving module 11 to accurately extract the required signal and ensure detection accuracy.

[0047] Among them, such as Figure 3 As shown, the transmission processing circuit 100 includes a first amplifier A0, a transmission filter Z0, and a transmission antenna TX, which are sequentially electrically connected to the first output terminal of the power divider F1. The transmission filter Z0 filters out harmonic components carried in the fundamental signal. The first amplifier A0 increases the signal power, ensuring effective signal transmission.

[0048] In some embodiments, the first signal receiving module 11 includes a first signal receiving unit 110 and a first mixer M1. The first input terminal of the first mixer M1 is electrically connected to the first signal receiving unit 110, the second input terminal of the first mixer M1 is electrically connected to the second output terminal of the power divider F1, and the output terminal of the first mixer M1 is electrically connected to the signal processing unit 14. The first mixer M1 is used to mix a first harmonic signal and a 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, which are electrically connected in sequence. It should be noted that the first filter Z1 is provided at the front end of the first mixer M1, allowing signals in the target frequency band (i.e., first harmonic signals) to pass through while blocking interference and noise. The first receiving amplifier A1 is also provided, which can improve signal strength with minimal noise introduction, providing a high-quality input signal to the first mixer M1.

[0050] Furthermore, in some embodiments of the detection device, the second signal receiving module 12 is used to mix the second harmonic signal and the second reference signal to obtain a second identification signal, and then send the second identification signal to the signal processing unit 14. The third signal receiving module 13 is used to mix the third harmonic signal and the third reference signal to obtain a third identification signal, and then 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 all reference 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 harmonic signal is 2f0 + Δf2. To extract the signal with frequency Δf2 carried in the second harmonic signal, a second reference signal with a frequency equal to 2f0 is provided during the down-conversion of the second harmonic signal; that is, the frequency of the second reference signal is twice the frequency of the fundamental signal. The frequency of the third reference signal is equal to 3f0, and its principle is the same as that of the first and second reference signals, so it will not be elaborated further here.

[0052] Furthermore, 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 reference the same clock signal, it can be guaranteed that the frequency of the second reference signal is always twice the frequency of the fundamental signal, and that the frequency of the third reference signal is always three times the frequency of the fundamental signal. This ensures that the signal obtained after down-conversion is the desired frequency, and that the frequencies of the obtained signals (e.g., the first identification signal, the second identification signal, and the third identification signal) will not deviate, thereby improving the detection accuracy of the detection device. The specific principle is the same as in the aforementioned embodiments and will not be elaborated further here.

[0053] Furthermore, such as Figure 3 As shown, in some embodiments of the nonlinear node detection unit 1, the second signal receiving module 12 may include a second signal receiving unit 120, a second mixer M2, and a second signal generator L02, which are 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 the 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, which are electrically connected in sequence. The third mixer M3 is electrically connected to the signal processing unit 14, and the third signal generator L03 is the signal source of the third reference signal.

[0055] In the nonlinear node detection unit 1 disclosed in this embodiment, as follows: 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 the first input terminal of the second mixer M2, the second input terminal of the second mixer M2 is connected to the second signal generator L02, and the output terminal of the second mixer M2 is connected to the signal processing unit 14. The second mixer M2 is used to mix the second reference signal from the second signal generator L02 and the signal processed by the second receiving amplifier A2 to output 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, which 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 the first input terminal of the third mixer M3, the second input terminal of the third mixer M3 is connected to the third signal generator L03, and the output terminal of the third mixer M3 is connected to the signal processing unit 14. The third mixer M3 is used to mix the third reference signal from the third signal generator L03 and the signal processed by the third harmonic signal from the third receiving amplifier A3 to output 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, which will not be described in detail here.

[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. Since the second-order harmonic signal is the signal returned after the fundamental signal is sent to the nonlinear node on the object to be detected 4, it contains a non-zero frequency shift in the second-order response generated by the nonlinear feedback of the object to be detected 4. The frequency of this non-zero frequency shift is Δf2. The frequency of the second-order harmonic signal is 2f0 + Δf2. Because mixing is required to extract the signal with frequency Δf2, the frequency of the signal output from the second signal generator L02 (the second reference signal) is set to 2Δf0. After mixing the second-order harmonic signal and the second reference signal, the non-zero frequency shift of the second-order response generated by the nonlinear node on the object to be detected 4 can be obtained, which is the second identification signal. Furthermore, since the second signal generator L02 and the first signal generator L01 both reference the same clock signal, the frequency of the second reference signal can be guaranteed to be equal to 2f0, thus ensuring that a signal with frequency Δf2 can be obtained after frequency conversion, improving detection accuracy.

[0058] In this specific embodiment, the third-order local oscillator signal generated by the third signal generator L03 is the third reference signal input to the third mixer M3. Since 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, it contains a 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 is Δf3. The frequency of the third-order harmonic signal is 3f0 + Δf3. Since mixing is required to extract the signal with frequency Δf3, 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 on the object to be detected 4 can be obtained, which is the third identification signal. Furthermore, since the third signal generator L03 and the first signal generator L01 both reference the same clock signal, it is guaranteed that the frequency of the third reference signal is equal to 3f0, thereby ensuring that a signal with a frequency of Δf3 can be obtained after frequency conversion, thus improving the detection accuracy.

[0059] Specifically, see Figure 4 In some embodiments of the nonlinear node detection unit 1, the first signal generator L01, the second signal generator L02, and the third signal generator L03 can be, for example, phase-locked loops, i.e., each is a loop formed by a phase detector, a loop filter, a voltage-controlled oscillator (VCO), 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 VCO1 connected in sequence, and also includes a first frequency divider FD1 connected between the first phase detector PD1 and the first VCO1. The second signal generator L02 includes a second phase detector PD2, a second loop filter LF2, and a second VCO2 connected in sequence, and also includes a second frequency divider FD2 connected between the second phase detector PD2 and the second 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 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 their division ratios via 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 all connected to a crystal oscillator X1. The crystal oscillator X1 serves as the common reference clock signal for the three signal generators. Figure 4It can be seen that the first signal generator L01, the second signal generator L02, and the third signal generator L03 all reference the same clock (e.g., the same crystal oscillator signal), which ensures that the fundamental signal, the first reference signal, the second reference signal, and the third reference signal are in the same timing sequence, thereby ensuring that the frequency of the signal obtained after mixing will not be shifted, thus improving the detection accuracy.

[0060] Furthermore, the frequency of the fundamental wave signal is similar to the frequency of the first harmonic signal. Therefore, the frequency of the fundamental wave signal may fall within the bandwidth of the first receiving antenna (the aforementioned first receiving antenna RX1). 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 too close, the fundamental wave signal may be received by the first receiving antenna RX1, resulting in a false alarm. To prevent interference between the antennas of the signal transmitting module 10 and the first receiving module 11, the distance between them 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 disposed 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). Thus, while rationally arranging all components 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 and reducing the false alarm rate.

[0062] The nonlinear node detection unit 1 provided in this application embodiment can be applied to a detection device. In one embodiment, see [link to embodiment]. Figure 6 A detection device is provided, including the aforementioned nonlinear node detection unit 1, which can be a through-type detection device. For ease of observation, the outer shell of one side panel of the detection device is cut open in the figure to expose part of the internal structure. Figure 6The diagram shows the overall structure and some internal structures of the detection device. These internal structures include a signal transmitting module 10, a first signal receiving module 11, a second signal receiving module 12, and a third signal receiving module 13 in the nonlinear node detection unit 1. It can be seen that the antennas of the second signal receiving module 12 (i.e., the second receiving antenna RX2) and the third signal receiving module 13 (i.e., the third receiving antenna RX3) are positioned 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). That is, the greater distance between the antenna of the signal transmitting module 10 and the antenna of the first signal receiving module 11 reduces the probability that the fundamental wave signal will be received by the first signal receiving module 11, thereby reducing the false alarm rate.

[0063] Figure 7 The image shows the overall structure and part of the internal structure of a detection device that includes only the nonlinear node detection unit 1. In some application scenarios, the detection device may only include the nonlinear node detection unit 1. In this embodiment, as shown... Figure 7 As shown, the antennas of the second signal receiving module 12 (i.e., the second receiving antenna RX2) and the third signal receiving module 13 (i.e., the third receiving antenna RX3) are positioned 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 in the previous embodiment, and will not be described in detail here.

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

[0065] It should be noted that, ideally, a mixer can mix the input signal and convert it to a set frequency band. That is, ideally, the frequency of the mixed signal should be within the set frequency band. However, in practical applications, due to the inherent hardware characteristics of the mixer, the signal at the mixer's input may be directly coupled to the signal output by the first mixer M1. For example... Figure 3 In the process, the first reference signal output by the power divider F1 and the received processed first harmonic signal may be directly coupled to the signal output by the first mixer M1 (at this time, these signals are equivalent to interference signals).

[0066] In one embodiment, such as 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. Furthermore, the first mixer M1 mixes the first harmonic signal, which reduces the power of the output signal to some extent. Therefore, the fifth amplifier A5 is 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] Furthermore, the fourth filter Z4 may not be able to completely filter out interference signals carried in the signal. Therefore, in order to avoid the influence of interference signals, a fifth filter Z5 can also be set between the fifth amplifier A5 and the signal processing unit 14 to improve signal quality.

[0068] The connection relationships 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 previous embodiments, and will not be described in detail here. The connection relationships 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 previous embodiments, and will not be described in detail here.

[0069] See Figures 5 to 9 This invention discloses a detection device, including the nonlinear node detection unit 1 disclosed in any of the above embodiments. This detection device can be installed at entrances / exits of a location, or other locations where such detection is needed, and is used to detect unauthorized equipment.

[0070] Furthermore, in order to expand the coverage area of ​​the detection area of ​​the detection device, reduce the range of the detection blind zone, and lower the false alarm rate, in some embodiments of the detection device, 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, because the relative movement speed between the person carrying the object 4 to be detected or the object 4 itself and the detection device is relatively fast, the time spent in the detection area of ​​the detection device is short. Therefore, the nonlinear node detection unit 1 must complete sampling within a sufficiently short time. In the detection device disclosed in this embodiment, two or more nonlinear node detection units 1 can operate simultaneously. Thus, two or more nonlinear node detection units 1 can detect more nonlinear node features of the object 4 to be detected within a short time, meaning the amount of detected data increases exponentially. This data facilitates target recognition by the signal processing unit 14 using algorithms, thereby improving detection accuracy.

[0072] For example, in one embodiment, the time required for a single nonlinear node detection unit 1 to detect one frame of data is 15ms, while the passage time of the object 4 to be detected passing through the detection device (e.g., a through-type detection device) is 1s. Therefore, a single nonlinear node detection unit 1 can detect approximately 6 to 7 frames of data within 1s. When the number of nonlinear node detection units 1 is multiple, for example, 8 units, since all nonlinear node detection units 1 operate simultaneously, approximately 42 to 49 more frames of data can be obtained compared to when only one nonlinear node detection unit 1 is operating. That is, increasing the number of nonlinear node detection units 1 and arranging them along a predetermined direction not only reduces the detection blind zone but also allows for the acquisition of more data.

[0073] It should be noted that having multiple nonlinear node detection units 1 operating simultaneously may present the following two problems. For example, in a scheme where multiple nonlinear node detection units 1 with the same operating frequency are set within a single door panel, if the operating frequencies of these nonlinear node detection units 1 are identical, it may cause problems for the processing of harmonic signals in the subsequent signal processing unit (e.g., signal processing unit 14). For instance, when different nonlinear node detection units 1 have the same operating frequency (e.g., the frequency of the transmitted fundamental signal), the frequencies of the second-order and third-order harmonic signals corresponding to the fundamental signal are also the same. The signal processing unit 14 cannot effectively distinguish which nonlinear node detection unit 1 corresponds to the harmonic signal, thus affecting the computational load, computation time, and computational complexity during the harmonic signal processing, and consequently affecting the detection efficiency of the entire detection device.

[0074] For example, in a scheme where multiple nonlinear node detection units 1 with the same operating frequency are installed in both door panels, in addition to the problems that may occur in a single-side door panel, false alarms may also occur in the opposite door panel. Specifically, when the fundamental frequency of the nonlinear node detection unit 1 on one side of the door panel and the nonlinear node detection unit 1 on the other side of the door panel is the same, taking the left door panel as an example, the frequency of the fundamental frequency of the nonlinear node detection unit 1 on the left side of the door panel is f0, while the frequency of the second harmonic signal it expects to receive is 2f0. At this time, the fundamental frequency of the two different nonlinear node detection units 1 on the right side of the door panel is both f0. Therefore, the frequency of the signal after the fundamental frequency of the two different nonlinear node detection units 1 on the right side of the door panel is mixed together is 2f0, which happens to be the same as the frequency of the second harmonic signal that the nonlinear node detection unit 1 on the left side of the door panel expects to receive. As a result, the detection device may false alarm, thereby affecting the detection efficiency and accuracy of the entire detection device. Similarly, the same applies to the other side of the door panel. In addition, after mixing, the three fundamental signals emitted by the nonlinear node detection unit 1 on one side of the door panel may have the same frequency as the third harmonic signal that the nonlinear node detection unit 1 on the opposite side of the door panel expects to receive.

[0075] Furthermore, to enable two or more nonlinear node detection units 1 within the detection device to operate simultaneously without affecting the signal processing unit 14 or the side door panel, the detection device disclosed in this embodiment emits fundamental signals at different frequencies from the signal transmission modules 10 in each nonlinear node detection unit 1 on the same side door panel. This avoids interfering with the signal processing process of the signal processing unit 14 or the back-end processor (e.g., the target identification unit 3 described below), thereby improving detection efficiency. Moreover, it ensures that even if the fundamental signals emitted by each nonlinear node detection unit 1 mix, no signal with the same frequency as the desired second-order harmonic signal or the desired third-order harmonic signal will be generated, effectively preventing false alarms during subsequent signal identification and processing.

[0076] In some embodiments, multiple nonlinear node detection units 1 can be provided in both side door panels, and the operating frequencies of the different nonlinear node detection units 1 in the side door panels are also different. This scheme can further avoid mutual interference between the nonlinear node detection units 1 in the side door panels (that is, to avoid the situation where the signal obtained after fundamental frequency mixing of multiple nonlinear node detection units 1 in the opposite side door panel is mistakenly identified as a harmonic signal). Therefore, in this embodiment, all nonlinear node detection units 1 in the side door panels can work 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 panel can be arranged sequentially along a set direction. This set direction can be the gravity direction. For example, when two or more nonlinear node detection units 1 are arranged sequentially along the gravity direction, the number of nonlinear node detection units 1 is increased, and the detection area corresponding to each nonlinear node detection unit 1 does not overlap in the gravity direction at least partially. This increases the coverage of the total detection area (including the detection areas corresponding to all nonlinear node detection units 1) in the gravity direction, reduces the detection blind zone in the gravity direction, and lowers the false alarm rate.

[0078] The detection device can be a walk-through detection device, such as a security gate. When the detection device is a walk-through detection device, it has a detection channel, and 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, which can detect the object 4 to be detected passing through the detection channel.

[0079] Furthermore, taking a security gate as an example, in some embodiments, multiple nonlinear node detection units 1 can be set up, and these multiple nonlinear node detection units 1 are arranged sequentially at intervals along the direction of gravity. This arrangement can not only reduce the blind zone area, but also, in conjunction with algorithms, calculate which nonlinear node detection unit 1 corresponds to which the detected object 4 is located, thus enabling zoned detection and obtaining the position 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 travel direction of the detection channel, that is, the object 4 to be detected passes through each nonlinear node detection unit 1 sequentially when passing through the detection channel. Furthermore, multiple nonlinear node detection units 1 can be arranged sequentially at intervals. In this embodiment, increasing the number of nonlinear node detection units 1 in the travel direction can effectively reduce the detection blind zone of the detection channel in the travel direction, and increase the amount of data obtained, resulting in more accurate nonlinear characteristics, improved detection accuracy, and reduced false alarm rate. The specific principle is the same as in the embodiment where multiple nonlinear node detection units 1 are arranged along the direction of gravity, and will not be elaborated further here.

[0081] Furthermore, in the detection device disclosed in some embodiments of the present invention, such as Figure 5As shown, the detection device may further include a target recognition unit 3. The nonlinear node detection unit 1 is connected to the target recognition unit 3 and is used to send nonlinear features 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 used to acquire the eddy current features of the object 4 to be detected, and send the eddy current features 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 that of the eddy current detection unit 2. The target recognition unit 3 is used to perform target recognition of the object 4 to be detected based on the received nonlinear features and eddy current features.

[0082] Among the related information leakage devices, some electronic products generally lack electromagnetic shielding (e.g., they lack a metal casing) or have poor electromagnetic shielding, such as USB flash drives, eavesdropping devices, and cameras. For these electronic products, the nonlinear node detection unit 1 can achieve good detection results when detecting nonlinear nodes. For electronic products with electromagnetic shielding measures or good electromagnetic shielding, such as mobile phones, tablets, and smartwatches, as long as they contain metal, the amplitude and phase characteristics of the secondary magnetic field formed by eddy currents can be utilized. Eddy current detection unit 2 can then detect these electronic products and obtain their eddy current characteristics. These eddy current characteristics include, for example, the amplitude and phase characteristics of the secondary magnetic field formed by electronic products with metal components under the detection of eddy current detection unit 2. Eddy current detection unit 2 can supplement the insufficient detection capability of nonlinear node detection unit 1 for electronic products with electromagnetic shielding. Simultaneously, nonlinear node detection unit 1 can also compensate for the inability of eddy current detection unit 2 to detect electronic products.

[0083] The detection frequency of eddy current detection unit 2 in the detection device is different from that of nonlinear node detection unit 1. Therefore, eddy current detection unit 2 and nonlinear node detection unit 1 will not interfere with each other, thus enabling simultaneous operation. The operating frequency of nonlinear node detection unit 1 refers to the frequency of the fundamental wave signal emitted by nonlinear node detection unit 1. The operating frequency of eddy current detection unit 2 refers to the frequency band of the driving signal of the transmitting coil in eddy current detection unit 2. Since the operating frequency bands of the transmitting and receiving antennas in nonlinear node detection unit 1 (e.g., the frequency band of its transmitted fundamental wave signal and the frequency bands of its received first, second, and third harmonic signals) are relatively high, while the operating frequency bands of the modules in eddy current detection unit 2 (e.g., the frequency band of its transmitting coil driving signal) are relatively low, their operating frequency bands do not overlap, therefore they will not interfere with each other. Furthermore, 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, it can simultaneously obtain eddy current characteristics and nonlinear characteristics, and obtain as much feature data as possible in the same time period, thereby reducing the false alarm rate.

[0084] The target recognition unit 3 is used to identify the object 4 to be detected based on the received nonlinear and eddy current characteristics. For example, the target recognition unit 3 can be a microcontroller, a control chip, or a chip or device capable of running a preset calculation strategy. Alternatively, the target recognition unit 3 can include at least one of a microcontroller, a control chip, and a device capable of running a preset calculation strategy.

[0085] See Figure 8 Furthermore, in some embodiments of the detection device disclosed, 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 receiving channel including 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 actively generates a primary magnetic field, the range of which at least covers the detection area. The sensing module 23 senses the magnetic field at its location and generates a corresponding induced electromotive force (EMF). The control chip 21 sends a command to the magnetic field generating module 22 to generate a primary magnetic field and also receives the induced EMF sent by the sensing module 23. When the object to be detected 4 in the detection area is a conductive object, the object to be detected 4 will generate a secondary magnetic field under the influence of the primary magnetic field. This secondary magnetic field interacts with the primary magnetic field generated by the magnetic field generating module 22, causing a change in the magnetic field at the location of the sensing module 23 and generating a changed induced EMF. The control chip 21 receives this changed induced EMF and performs data processing such as comparing it with the induced EMF in the original state, thereby identifying the object to be detected 4.

[0087] Furthermore, the control chip 21 can be a field-programmable gate array (FPGA) module. The FPGA module outputs a drive signal, which is converted from digital to analog by a digital-to-analog converter (DAC) 26 and amplified by the transmitting unit 24 before being sent to the magnetic field generation module 22 to generate an alternating magnetic field. Specifically, the FPGA module can also be used to obtain the eddy current characteristics (e.g., spectral data) of the object to be detected 4 based on the received induced electromotive force (EMF), and send the eddy current characteristics to the target identification unit 3. The magnetic field generation module 22 generates an alternating magnetic field (original magnetic field) when an alternating current is applied; at this time, the sensing module 23 has no induced EMF. When the object to be detected 4 is a conductive component (e.g., metal), the object to be detected 4 will generate an induced current under the influence of the original magnetic field. The magnetic field generated by the induced current will interact with the original magnetic field, causing a change in the original magnetic field. At this time, the sensing module 23 can output an induced EMF. The induced electromotive force (EMF) is processed by the receiving unit 25 and then transmitted to the control chip 21 via the analog-to-digital converter 27. The control chip 21 further processes the data, such as performing a fast Fourier transform, and then transmits it to the target recognition unit 3. The target recognition unit 3 processes and analyzes the induced EMF output by the sensing module 23, enabling the detection of the target object 4, including metallic components or electronic devices with metal casings. 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 correspondingly configured with the sensing module 23, and the sensing module 23 can be a single coil (not shown in the figure) or a double coil (e.g., Figure 6 (As shown). In a specific embodiment, the detection device is a security gate, 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 along the direction of gravity on each side of the gate panel.

[0089] In some embodiments, the control chip 21 includes a Fourier calculation module U29, which is used to perform Fourier transform on the data received from the analog-to-digital converter ADC 27. The control chip 21 is also used for mode control (e.g., switching between multiple operating modes, controlling different transmitting coils to be energized in different operating modes) and determining 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 Figure 9 The figure shows the timing diagram of an eddy current detection unit 2 and a nonlinear node detection unit 1 (using the first nonlinear node detection unit A and the second nonlinear node detection unit B as examples). As can be seen from the foregoing embodiments, since the eddy current detection unit 2 and the nonlinear node detection unit 1 operate at different frequencies, they can operate simultaneously to reduce the false negative rate. Their operating times can overlap without affecting each other. Furthermore, it can be seen that... Figure 9 The first nonlinear node detection unit A and the second nonlinear node detection unit B shown in the figure 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] In this embodiment, the idle time of eddy current detection unit 2, the first nonlinear node detection unit A, and the second nonlinear node detection unit B is 10ms in each working cycle. The working time of the transmitting coil and the receiving coil of eddy current detection unit 2 is 14ms in each working cycle, that is, each working cycle of eddy current detection unit 2 is 24ms. When the transmitting coil is working, the receiving coil works synchronously, forming a complete excitation-induction cycle. The working time of the first nonlinear node detection unit A and the second nonlinear node detection unit B is the same. The working time of their transmitting antenna and receiving antenna is 5ms in each working cycle, and in this embodiment, the nonlinear node detection unit 1 drives three receiving antennas to work simultaneously in a single working time. The transmitting antenna TX of the first nonlinear node detection unit A and the second nonlinear node detection unit B are respectively set in their signal transmitting module 10. The receiving antennas of the first nonlinear node detection unit A and the second nonlinear node detection unit B include their respective first receiving antenna RX1, second receiving antenna RX2, and third receiving antenna RX3. The first receiving antenna RX1, the second receiving antenna RX2, and the third receiving antenna RX3 are respectively disposed in their corresponding first signal receiving module 11, second signal receiving module 12, and third signal receiving module 13.

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

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

[0094] S10. Obtain the nonlinear characteristics of the object 4 to be detected 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 that of the nonlinear node detection unit 1, and the eddy current detection unit 2 and the nonlinear node detection unit 1 work simultaneously.

[0095] S20. Target identification is performed on the object to be detected 4 based on nonlinear and eddy current characteristics.

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

[0097] It should be noted that the nonlinear characteristics of the object 4 to be detected obtained by the nonlinear node detection unit 1 may include harmonic signals (e.g., first-order, second-order, and third-order harmonic signals). Eddy current characteristics may include parameters such as phase and amplitude. In one embodiment, the target recognition unit 3 can use the amplitude of the harmonic signals to perform target recognition of the object 4 to be detected. For example, the judgment can be made by determining the amplitude relationship between the second-order and third-order harmonic signals.

[0098] In one embodiment, when the amplitude of the second harmonic signal is greater than the amplitude of the third 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 perform target recognition on the object to be detected 4. For example, if the amplitude is determined to be 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. At this time, the target recognition unit 3 can output the first recognition result and the second recognition result separately, or it can obtain a comprehensive recognition result based on the first and second recognition results and output it.

[0099] In another embodiment, the target recognition unit 3 can simultaneously make a comprehensive judgment based on the nonlinear characteristics and eddy current characteristics of the object to be detected 4, i.e., perform target recognition. Specifically, in some embodiments of the detection method, the step of recognizing the object to be detected 4 based on the nonlinear characteristics and eddy current characteristics includes: if the eddy current characteristics are determined to match the characteristics of a mobile phone, i.e., the phase and amplitude are within the threshold range corresponding to a mobile phone, and the nonlinear characteristics are 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 weak, and the nonlinear characteristics are 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 that include computing processing functions (e.g., a processing chip), and executed by the processing chip in the detection device. Alternatively, the detection method can also be performed by a human.

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

[0102] Further, see Figure 11 To avoid the background noise generated by the metal nodes and / or environmental noise in the nonlinear node detection unit 1 affecting the detection of the eddy current detection unit 2, in some embodiments of the detection method, before the step of target identification of the object 4 to be detected based on the nonlinear characteristics and eddy current characteristics, the following step S11 is performed: calibrating the eddy current characteristics using background noise data.

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

[0104] Furthermore, in some of the detection methods disclosed in the embodiments, the method for acquiring the noise floor data includes:

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

[0106] Step B: Obtain the noise floor 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 of the nonlinear node detection unit 1 within the detection range and the ambient noise generate induced currents under the influence of the original magnetic field generated by the magnetic field generation module 22. The induced currents generate secondary magnetic fields, which in turn affect the original magnetic field. The receiving coil generates an unbalanced induced electromotive force, and the voltage signal formed by this induced electromotive force is the initial data. This initial data is converted into a digital signal, for example, via an analog-to-digital conversion circuit (such as an analog-to-digital converter ADC 27), and sent to the control chip 21 for data processing to obtain the noise floor data.

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

[0109] Furthermore, in some embodiments of the detection method, the step of calibrating the eddy current feature using noise floor data includes: subtracting the eddy current feature from the noise floor 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 sensing module 23 receives the electromagnetic signal X(t) and performs analog-to-digital conversion on the electromagnetic signal X(t) 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). Here, is the 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 noise floor, i.e. Here, is the calibrated discrete frequency domain signal, and = REn(f)' + jImn(f)', where 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 arctangent operation, the phase of the calibrated discrete frequency domain signal is calculated, i.e., 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. Then, using the square root operation, the amplitude Ampn(f) of the calibrated discrete frequency domain signal is calculated. The phase Phasen(f) and amplitude Ampn(f) are the data after calibrating the eddy current characteristics.

[0110] Furthermore, in some embodiments of the detection method, target identification is performed on the object to be detected 4 based on nonlinear features and eddy current features, i.e., the above-mentioned step S20, which includes: target identification on the object to be detected 4 based on nonlinear features and data calibrated for eddy current features.

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

[0112] Embodiments of the present invention also disclose a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described detection method.

[0113] This invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the above-described detection method.

[0114] Embodiments of the present invention also disclose a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described detection method.

[0115] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above embodiments or technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. That is, the embodiments described "in some embodiments" can be freely combined with any of the preceding and following embodiments. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A nonlinear node detection unit, characterized in that, The nonlinear node detection unit includes: A signal transmission module for transmitting fundamental wave signals to the object to be detected; A first signal receiving module for receiving the first harmonic signal generated by the object to be detected according to the fundamental wave signal; A second signal receiving module for receiving the second harmonic signal generated by the object to be detected based on the fundamental wave signal; A third signal receiving module for receiving the third harmonic signal generated by the object to be detected based on the fundamental wave signal; The signal processing unit is connected to the first signal receiving module, the second signal receiving module, and the third signal receiving module, respectively, and is used to obtain the nonlinear characteristics of the object to be detected based on the first harmonic signal, the second harmonic signal, and the third 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 disposed 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, wherein 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 harmonic signal and output them; The first reference signal is generated based on the fundamental signal source.

4. The nonlinear node detection unit according to claim 3, characterized in that, The fundamental signal source includes a first signal generator and a power divider; The input terminal of the power divider is electrically connected to the first signal generator; the first output terminal of the power divider is electrically connected to the transmission processing circuit, and the second output terminal of the power divider is electrically connected to the first signal receiving module; wherein, the signal output by the second output terminal 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 terminal of the first mixer is electrically connected to the first signal receiving unit, the second input terminal of the first mixer is electrically connected to the second output terminal of the power divider, and the output terminal 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 also used to mix the second harmonic signal and the second reference signal and then output the result. The third signal receiving module is also used to mix the third harmonic signal and the third reference signal and output them; The fundamental signal source, the signal source of the second reference signal, and the signal source of the third reference signal all reference 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, which are electrically connected in sequence; the second mixer is also electrically connected to the signal processing unit; the second signal generator is the 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 connected in sequence; the third mixer is also electrically connected to the signal processing unit; and the third signal generator is the signal source of the third reference signal.

8. A detection device, characterized in that, Includes the nonlinear node detection unit as described in any one of claims 1-7.

9. The detection device according to claim 8, characterized in that, The number of nonlinear node detection units is multiple, and the frequency of the fundamental wave signal emitted by the signal transmission module in each nonlinear node detection unit is different.

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

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