Signal receiving circuit, phase jitter suppression method, pass-type detection system and security door detection group

Abstract

The embodiment of the invention discloses a signal receiving circuit, a phase jitter suppression method, a pass-type detection system and a security door detection group. The signal receiving circuit comprises a receiving coil, an analog-to-digital conversion circuit connected with the receiving coil, and a controller connected with the analog-to-digital conversion circuit. The receiving coil is used for receiving an induction signal of magnetic field change, the analog-to-digital conversion circuit is used for performing analog-to-digital conversion on the induction signal and a reference signal to obtain a digital induction signal and a digital reference signal, and the controller corrects the phase of the digital induction signal according to the digital reference signal to obtain a calibration signal. According to the embodiment of the invention, the problem of phase jitter can be solved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of communication technology, and in particular to a signal receiving circuit, a phase jitter suppression method, a pass-through detection system, and a security door detection group. Background Art

[0002] For security gates, if the transmission and reception are realized by digital circuits (such as analog-to-digital / digital-to-analog conversion and digital signal processing), the transmission signal can be flexibly set according to different requirements, so as to meet the needs of more scenarios. Generally, the digital transmission circuit outputs a sine wave to the transmitting coil, and the corresponding digital receiving circuit analyzes whether there is a target object passing through according to the signal coupled back by the receiving coil. Summary of the invention

[0003] In view of the above problems, embodiments of the present invention provide a signal receiving circuit for suppressing phase jitter, a phase jitter suppression method, a pass-through detection system and a security gate detection group, which overcome the above problems or at least partially solve the above problems.

[0004] According to one aspect of an embodiment of the present invention, a signal receiving circuit is provided, comprising: a receiving coil, an analog-to-digital conversion circuit connected to the receiving coil, and a controller connected to the analog-to-digital conversion circuit; the receiving coil is used to receive an induction signal of a magnetic field change, the analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the induction signal and a reference signal, respectively, to obtain a digital induction signal and a digital reference signal; the controller corrects the phase of the digital induction signal according to the digital reference signal to obtain a calibration signal.

[0005] Optionally, there are multiple receiving coils, and the analog-to-digital conversion circuit includes multiple acquisition channels and a reference channel, the reference channel is used to receive the reference signal, and each acquisition channel is connected to one of the receiving coils, respectively, for receiving the induction signal transmitted from the receiving coil.

[0006] Optionally, the controller includes a frequency domain conversion unit connected to the analog-to-digital conversion circuit and a main control unit connected to the frequency domain conversion unit, the frequency domain conversion unit performs frequency domain transformation on the digital sensing signal and the digital reference signal respectively to obtain corresponding frequency domain signals; the main control unit derives a corresponding initial phase based on the frequency domain signal of the digital sensing signal, and derives a corresponding reference phase based on the frequency domain signal of the digital reference signal; the main control unit subtracts the reference phase corresponding to the digital reference signal from the initial phase corresponding to the digital sensing signal to obtain the calibration signal.

[0007] Optionally, the reference signal is generated by a signal sending circuit located corresponding to the signal receiving circuit; the signal sending circuit is used to generate a magnetic field.

[0008] Optionally, the signal sending circuit includes a processor, a digital-to-analog conversion circuit and a transmitting coil connected in sequence; the analog-to-digital conversion circuit is also connected to the digital-to-analog conversion circuit; the processor is used to output a drive signal; the digital-to-analog conversion circuit is used to perform digital-to-analog conversion on the drive signal; the signal output by the digital-to-analog conversion circuit is used to drive the transmitting coil, and is also transmitted to the analog-to-digital conversion circuit as the reference signal.

[0009] Based on the same inventive concept, a phase jitter suppression method is also provided, including: receiving a digital reference signal and a digital sensing signal output by an analog-to-digital conversion circuit; the digital reference signal is a signal obtained after the analog-to-digital conversion circuit performs analog-to-digital conversion on the reference signal, and the digital sensing signal is a signal obtained after the analog-to-digital conversion circuit performs analog-to-digital conversion on the sensing signal output by the receiving coil; and correcting the phase of the digital sensing signal according to the digital reference signal to obtain a calibration signal.

[0010] Optionally, the phase of the digital sensing signal is corrected according to the digital reference signal to obtain a calibration signal with phase jitter removed, including: performing frequency domain transformation on the digital sensing signal and the digital reference signal respectively to obtain corresponding frequency domain signals; deriving a corresponding initial phase according to the frequency domain signal of the digital sensing signal, and deriving a corresponding reference phase according to the frequency domain signal of the digital reference signal; and subtracting a reference phase corresponding to the digital reference signal from the initial phase corresponding to the digital sensing signal to obtain the calibration signal.

[0011] Optionally, the reference signal is generated by a signal sending circuit corresponding to the signal receiving circuit; the signal sending circuit is used to generate a magnetic field.

[0012] Based on the same inventive concept, an embodiment of the present invention further proposes a pass-through detection system, including the aforementioned signal receiving circuit.

[0013] Optionally, the pass-through detection system also includes a processor, a digital-to-analog conversion circuit and a transmitting coil connected in sequence, and the analog-to-digital conversion circuit is also connected to the digital-to-analog conversion circuit; the processor is used to output a drive signal; the digital-to-analog conversion circuit is used to perform digital-to-analog conversion on the drive signal; the signal output by the digital-to-analog conversion circuit is used to drive the transmitting coil, and is also transmitted to the analog-to-digital conversion circuit as the reference signal.

[0014] Based on the same inventive concept, an embodiment of the present invention further proposes a security door detection group, including a plurality of the aforementioned pass-through detection systems.

[0015] The signal receiving circuit of the embodiment of the present invention comprises: a receiving coil, an analog-to-digital conversion circuit connected to the receiving coil, and a controller connected to the analog-to-digital conversion circuit. The receiving coil is used to receive an induction signal of a magnetic field change, and the analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the induction signal and the reference signal, respectively, to obtain a digital induction signal and a digital reference signal. The controller corrects the phase of the digital induction signal according to the digital reference signal to obtain a calibration signal, which can overcome phase jitter, so that the calibration signal can be used to identify whether a target object passes.

[0016] The above description is only an overview of the technical solution of the embodiment of the present invention. In order to more clearly understand the technical means of the embodiment of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0018] Figure 1 shows a schematic diagram of a phase accumulator;

[0019] Figure 2 A schematic diagram of a module of a signal receiving circuit provided by an embodiment of the present invention is shown;

[0020] Figure 3 A schematic diagram of a module of a signal receiving circuit and a signal sending circuit provided by another embodiment of the present invention is shown;

[0021] Figure 4 A specific circuit diagram of a signal receiving circuit according to an embodiment of the present invention is shown;

[0022] Figure 5 A schematic diagram of phase subtraction according to an embodiment of the present invention is shown;

[0023] Figure 6 A schematic diagram of a phase jitter suppression method according to an embodiment of the present invention is shown;

[0024] Figure 7 Shows Figure 6 Schematic diagram of the method of step S12 in FIG. DETAILED DESCRIPTION

[0025] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0026] For a pass-through detection system (such as a security gate), if the transmission and reception are implemented using digital circuits, the transmission signal can be flexibly set according to different requirements to meet the needs of more scenarios. Among them, in the signal transmission circuit, the processor can be used to control the DAC (digital analog converter) to output a sine wave to drive the transmitting coil to generate a magnetic field. In the signal receiving circuit, the analog-to-digital converter (ADC) has a sampling rate of, for example, 192kHz. It needs to receive the sine wave coupled to the receiving coil and perform analog-to-digital conversion, and then send the converted signal to the processor (such as FPGA) for fast Fourier transform (FFT). Finally, the signal after FFT transformation can be used to analyze whether a target object has passed.

[0027] like Figure 1 As shown, the sine wave generated by the DAC in the signal transmission circuit is filtered as shown in TX. If the target passes through the through-type detection system, the receiving coil in the signal receiving circuit generates an induction signal RX. The induction signal RX is first sampled by the ADC, and the sampling points are such as A1, A2, and A3. Then the processor will start collecting signals according to the sampling trigger signal Trig for FFT processing. It is assumed that the rising edge of the sampling trigger signal Trig is used as the trigger signal, that is, the rising edge corresponds to the sampling trigger signal point such as P1 (P1'), P2 (P2'), and P3 (P3'). The processor will start sampling at the sampling trigger point P1 (P1'). After the sampling trigger signal Trig of the next cycle arrives, it will start collecting data again from the sampling trigger point P2 (P2'). Among them, the duration between the sampling trigger points P1 (P1') and P2 (P2') is 1 / operating frequency. Then multiple cycles will be repeated. The phases of the sampling trigger points P1 (P1'), P2 (P2'), P3 (P3')... are the phases corresponding to the target object.

[0028] If the working frequency of the through-type detection system is 6kHz, the sampling rates of ADC and DAC are both 192kHz. Since 192kHz can be divided by 6kHz, the sampling trigger points P1, P2, P3, etc. can all correspond to the sampling points of the ADC, so the phases are consistent, that is, the phase will not jitter. However, if the working frequency is other values ​​that cannot be divided by 192kHz, such as 5.9kHz, if Figure 1 As shown, the sampling trigger signal points (such as P1', P2', P3') cannot be aligned with the sampling points, and are usually located between two adjacent sampling points, so that the phase of each sampling trigger point is inconsistent, that is, the phase is jittered, so the target cannot be accurately identified based on the phase.

[0029] Therefore, due to the above reasons, if the sampling rates of DAC and ADC are fixed, the operating frequency of the through-type detection system can only use one frequency (i.e. 6khz). If it is switched to other operating frequencies, it will cause phase jitter. Since the received signal is needed to identify the target object, if the received signal has phase jitter, the target object cannot be accurately identified. In addition, if multiple through-type detection systems are required to work at the same time, the operating frequency of each can only be the same frequency (such as 6khz). If the operating frequencies of the through-type detection systems are the same, when the multiple through-type detection systems work at the same time, mutual interference problems will occur, causing multiple through-type detection systems to have false alarms and cannot be used.

[0030] In order to overcome the above phase jitter problem, this embodiment provides a signal receiving circuit. Figure 2 FIG. 2 shows a schematic diagram of the structure of a signal receiving circuit provided by an embodiment of the present invention. Figure 2 As shown, the signal receiving circuit includes: a receiving coil 1, an analog-to-digital conversion circuit (ADC) 2 connected to the receiving coil 1, and a controller 3 connected to the analog-to-digital conversion circuit 2. The receiving coil 1 is used to receive an induction signal of a magnetic field change, and the analog-to-digital conversion circuit 2 is used to perform analog-to-digital conversion on the induction signal and the reference signal to obtain a digital induction signal and a digital reference signal. The controller 3 corrects the phase of the digital induction signal according to the digital reference signal to obtain a calibration signal.

[0031] When a target passes through the detection channel of the through-type detection system, if the target is metal, eddy current will be generated, thereby affecting the magnetic field distribution of the through-type detection system, and the receiving coil 1 can sense the change. Therefore, the receiving coil 1 can receive the induction signal corresponding to the magnetic field change. The method of obtaining the induction signal can refer to the technical principle of the security door in the prior art, which will not be repeated here.

[0032] In addition to receiving the induction signal sent by the receiving coil 1, the analog-to-digital conversion circuit 2 also receives a reference signal. Moreover, the analog-to-digital conversion circuit 2 performs analog-to-digital conversion on the induction signal and the reference signal respectively, and obtains the corresponding digital induction signal and digital reference signal respectively. The controller 3 can correct the phase of the digital induction signal according to the digital reference signal to obtain a calibration signal. Among them, the role of the reference signal is to correct the phase of the induction signal so that the calibration signal obtained after the final correction can remove the phase jitter. For example, the reference signal can have the same phase jitter as the induction signal, and the controller 3 obtains the initial phase of the digital induction signal and the reference phase of the digital reference signal, and subtracts the reference phase of the digital reference signal from the initial phase of the digital induction signal to obtain the calibration signal. In this way, the calibration signal can remove the phase jitter. Among them, the reference signal can be provided directly by the signal sending circuit, or it can be provided by a signal source that can produce the same phase jitter as the induction signal.

[0033] In this embodiment, the controller 3 corrects the phase of the digital sensing signal according to the digital reference signal to obtain a calibration signal, thereby overcoming the problem of phase jitter. Furthermore, if the calibration signal is used to identify whether a metal target passes, the accuracy of target identification can be improved.

[0034] In one embodiment, see Figure 3 , the controller 3 includes a frequency domain conversion unit 31 connected to the analog-to-digital conversion circuit 2 and a main control unit 32 connected to the frequency domain conversion unit 31, and the frequency domain conversion unit 31 performs frequency domain conversion on the digital sensing signal and the digital reference signal to obtain corresponding frequency domain signals. For example, the frequency domain conversion unit 31 performs fast Fourier transform (FFT) on the digital sensing signal and the digital reference signal to obtain corresponding frequency domain signals. The frequency domain conversion unit 31 is, for example, an FPGA (Field-Programmable Gate Array). The main control unit 32 obtains the corresponding initial phase according to the frequency domain signal of the digital sensing signal, and obtains the corresponding reference phase according to the frequency domain signal of the digital reference signal. The main control unit 32 subtracts the reference phase corresponding to the digital reference signal from the initial phase corresponding to the digital sensing signal to obtain a calibration signal with phase jitter removed. The main control unit 32 is, for example, an MCU (MicroControl Unit) or a SoC (System on Chip).

[0035] In this embodiment, combined with Figure 4Since the phase of the sensing signal has jitter, the main control unit 32 calibrates the phase, that is, the initial phase (Phase_RXn) corresponding to the digital sensing signal is subtracted from the reference phase (Phase_REF) corresponding to the digital reference signal to obtain the phase difference (Phase_RXn-REF) between the digital sensing signal and the digital reference signal. The phase difference (Phase_RXn-REF) is the phase of the calibration signal. Since the phase jitter of the digital sensing signal and the digital reference signal is the same, a stable phase can be obtained by subtracting their phases. In addition, the amplitude data of the calibration signal can still be the amplitude of the digital sensing signal. In this way, the through-type detection system can identify whether a metal target passes through based on the calibration signal.

[0036] The specific scheme of the controller for identifying metal targets using calibration signals is not limited by this scheme, and can be implemented by referring to the scheme of security gates in the prior art (for example, comparing the amplitude and phase of the calibration signal with the characteristic data of various types of targets that have been stored to determine whether it is a metal target). The controller 3 is also not limited to the method of being implemented by the frequency domain conversion unit 31 and the main control unit 32. In other embodiments, the controller 3 can be implemented by only one chip, or by more than two chips working together, all of which are within the protection scope of this application.

[0037] In one embodiment, the reference signal is generated by a signal sending circuit corresponding to the signal receiving circuit. The signal sending circuit is used to generate a magnetic field. When the pass-through detection system starts working, the signal sending circuit can first generate a magnetic field. When no metal target passes through, the magnetic field generated by the signal sending circuit does not change, and the signal receiving circuit cannot receive the induction signal. When a metal target passes through, the magnetic field generated by the signal sending circuit changes, and the signal receiving circuit can receive the induction signal corresponding to the change in the magnetic field. Since the induction signal received by the signal receiving circuit of the pass-through detection system is generated based on the magnetic field generated by the signal sending circuit, the reference signal is provided by the signal sending circuit, which can ensure that the reference signal and the induction signal have the same phase jitter, thereby improving the effect of phase calibration of the induction signal.

[0038] In one embodiment, if Figure 3 As shown, the signal transmission circuit includes a processor 4, a digital-to-analog conversion circuit 5 and a transmitting coil 6 connected in sequence. The analog-to-digital conversion circuit 2 is also connected to the digital-to-analog conversion circuit 5. The processor 4 is used to output a driving signal. The digital-to-analog conversion circuit 5 is used to perform digital-to-analog conversion on the driving signal. The signal output by the digital-to-analog conversion circuit 5 is used to drive the transmitting coil 6, and is also transmitted to the analog-to-digital conversion circuit 2 as a reference signal.

[0039] Wherein, the processor 4 is, for example, an FPGA, which outputs a driving signal. The sampling rate of the digital-to-analog conversion circuit 5 is the same as the sampling rate of the analog-to-digital conversion circuit 2. The digital-to-analog conversion circuit 5 performs digital-to-analog conversion on the driving signal and transmits it to the transmitting coil 6, so that the transmitting coil 6 generates a constant magnetic field. When a metal target passes through the through-type detection system, it will cause the magnetic field to change, and the receiving coil 1 receives the induction signal of the magnetic field change for related detection. In this embodiment, the induction signal and the reference signal are equivalent to the digital-to-analog conversion circuit 5 that both come from the signal sending circuit (the induction signal is essentially a signal coupled to the transmitting coil 6, and the signal coupled to the transmitting coil 6 comes from the digital-to-analog conversion circuit 5; the reference signal is directly output from the digital-to-analog conversion circuit 5 to the analog-to-digital conversion circuit 2), so the reference signal can be used to calibrate the phase of the induction signal to overcome the problem of phase jitter.

[0040] It can be understood that in other embodiments, if a filter is further provided between the digital-to-analog conversion circuit 5 and the transmitting coil 6 in the signal sending circuit, the reference signal can also be sent by the filter to the analog-to-digital conversion circuit 2, that is, the output end of the filter is respectively connected to the transmitting coil 6 and the analog-to-digital conversion circuit 2, so that the reference signal and the induced signal can be guaranteed to have the same source, that is, have the same phase jitter.

[0041] In one embodiment, there are multiple receiving coils 1, and the analog-to-digital conversion circuit 2 includes multiple acquisition channels and a reference channel. The reference channel is used to receive a reference signal, and each acquisition channel is connected to one of the receiving coils 1, for receiving the induction signal transmitted from the receiving coil 1. The acquisition channel and the reference channel are, for example, internal channels of the analog-to-digital conversion circuit 2. For example, if there are 12 receiving coils, a total of 3 analog-to-digital conversion circuits 2 are used, one of which includes a reference channel and 3 acquisition channels, and each of the other two analog-to-digital conversion circuits 2 includes 4 acquisition channels. Each acquisition channel is connected to a receiving coil 1, and the reference channel is connected to the digital-to-analog conversion circuit 2. For the convenience of explanation, the embodiment of the present invention is described by taking two of the analog-to-digital conversion circuits 2 as an example. Figure 4As shown, ADC1 and ADC 2 represent two analog-to-digital conversion circuits 2. RX1~RX7 are 7-channel sensing signals, REF represents the reference signal, and CH1-CH7 are internal channels of the digital-to-analog conversion circuit 2, namely the above-mentioned acquisition channels. Among them, the reference channel CH8 receives the reference signal (REF signal) introduced from the digital-to-analog conversion circuit 5 (DAC), and the reference signal is, for example, a reference sine wave signal. The frequency domain conversion unit 31 (FPGA_FFT) performs frequency domain transformation on the digital sensing signal and the digital reference signal to obtain corresponding frequency domain signals. The main control unit 32 derives the corresponding initial phase according to the frequency domain signal of the digital sensing signal, and derives the corresponding reference phase according to the frequency domain signal of the digital reference signal. The main control unit 32 also subtracts the reference phase corresponding to the digital reference signal from the initial phase corresponding to the digital sensing signal to obtain a calibration signal with phase jitter removed. Among them, the main control unit 32 can be any single-chip microcomputer or processor that can perform corresponding functions, such as Figure 4 The processor model in is RK3568 14.

[0042] The working principle of the traditional receiving circuit is: first, the sensing signal enters the ADC, and then is given to the FPGA_FFT for FFT. At this time, if a frequency other than 6kHz is used, the amplitude of the frequency domain signal after FFT is stable, but the phase is always jumping. Figure 4 , Figure 5 , multiple sensing signals (such as RX1~RX7) are sent to ADC 1 and ADC2 for analog-to-digital conversion through acquisition channels (such as CH1-CH7), and reference channel CH8 receives reference signal REF from digital-to-analog conversion circuit 5 (DAC). ADC 1 and ADC2 perform analog-to-digital conversion on each sensing signal and reference signal, respectively, to obtain signals as shown in S1-S7 and S8. Then, the signals output by ADC 1 and ADC2 are input to FPGA_FFT for Fourier transform, and the frequency domain signals [I1, Q1]...[I7, Q7] corresponding to the 7 sensing signals and the frequency domain signals [I8, Q8] corresponding to the reference signals are obtained, that is, digital sensing signals and digital reference signals are obtained. The main control unit 32 calculates the phase and amplitude according to the frequency domain signals of the digital sensing signals and the digital reference signals. Specifically, the main control unit 32 obtains the corresponding initial phase according to the frequency domain signal of the digital sensing signal, and obtains the corresponding reference phase according to the frequency domain signal of the digital reference signal. The main control unit 32 obtains a phase-stable calibration signal by subtracting the reference phase corresponding to the digital reference signal from the initial phase corresponding to the digital sensing signal. Among them, RXn represents the sensing signal, and n is a natural number, such as Figure 5 The reference phase of the digital reference signal is Among them, REF represents the reference signal, such as Figure 5 If we subtract the two, we get a stable phase, which is Figure 5 The Phase_(RXn-REF) shown remains constant with no jitter, where Phase_(RXn-REF) is the phase of the calibration signal.

[0043] Therefore, please refer to Figure 4 The frequency domain signals [I1, Q1] ... [I8, Q8] are converted into phase and amplitude in the main control unit 32 to obtain the phase n and Amp n If the frequency is not 6Khz, the amplitudes Amp1, ...Amp7 are stable, but the phases Phase1, ...Phase7 are always jumping, where Amp1, ...Amp7 represent the amplitudes of the digital sensing signals of each channel. Phase1, ...Phase7 are the above-mentioned Phase_RX1, ...Phase_RX7. Phase8 is the above-mentioned Phase_REF. At the same time, the amplitude of Amp8 is also stable, and the phase of Phase8 is jumping. In this embodiment, the main control unit 32 also subtracts the phase of the digital sensing signal of each acquisition channel from the phase of the digital reference signal to obtain Phase1-Phase8, ... Phase7-Phase8. Since the jitter size of any one of Phase1, ... Phase7 is consistent with that of Phase8, the phase difference between any one of Phase1, ... Phase7 and Phase8 is constant, so a phase-stable signal can be obtained by subtracting any one of Phase1-Phase7 from Phase8, and the amplitude does not need to be subtracted. After that, the main control unit 32 can use the stable calibration signal to identify whether there is a target object passing through the security gate. Regarding the calibration signal, taking RX1 as an example, the amplitude of the calibration signal corresponding to RX1 is Amp1, and the phase is Phase1-Phase8.

[0044] Therefore, in the embodiment of the present invention, the reference channel CH8 is introduced to receive the reference signal. Although the amplitude of the reference signal is stable and the phase jumps, since the phase jumps of the reference signal and the sensing signal are the same (because the signal sources of the reference signal and the sensing signal are both the digital-to-analog conversion circuit 5), the phase difference between the two is stable. Therefore, the main control unit 32 subtracts the phases of the two to obtain a fixed phase value, thereby achieving the effect of stable phases at frequencies other than 6kHz, that is, the signal reception signal can be applicable to various frequencies.

[0045] Furthermore, since the signal receiving circuit of the embodiment of the present invention introduces a reference channel, no matter what frequency band the transmitting coil 6 and the receiving coil 1 operate in, the final calibration signal will not have a phase jitter effect. Therefore, if applied to a through-type detection system, different through-type detection systems can operate in different frequency bands. This can prevent different through-type detection systems from interfering with each other, and enable multiple through-type detection systems to operate simultaneously.

[0046] For the convenience of description, the above device is described as various modules according to their functions. Of course, when implementing the embodiment of the present invention, the functions of each module can be implemented in the same or multiple software and / or hardware.

[0047] Based on the same inventive concept, an embodiment of the present invention further provides a pass-through detection system, which includes the aforementioned signal receiving circuit.

[0048] Based on the same inventive concept, an embodiment of the present invention further provides a security door detection group, comprising a plurality of the aforementioned pass-through detection systems.

[0049] For traditional through-type detection systems, if the transmission and reception are implemented by digital circuits, there will be defects as mentioned above, that is, the through-type detection system can only work at one frequency without phase jitter, and cannot work at other frequencies. In this way, when there are multiple through-type detection systems, these through-type detection systems have the same operating frequency, which will cause interference between them.

[0050] In this embodiment, different through-type detection systems can obtain calibration signals without phase jitter through the internal signal receiving circuits provided in the above embodiments, so as to use the stable signals to identify whether a metal target has passed through, that is, no matter which frequency band the through-type detection system operates in, it can output calibration signals without phase jitter. In this way, different through-type detection systems can operate in different frequency bands, so that they do not interfere with each other.

[0051] Based on the same concept, an embodiment of the present invention further provides a flow chart of a phase jitter suppression method. The phase jitter suppression method is applied to the signal receiving circuits of the aforementioned embodiments, and can be specifically executed by a controller in the signal receiving circuit. Figure 6 As shown, the phase jitter suppression method includes the following steps.

[0052] Step S11: receiving a digital reference signal and a digital sensing signal output by an analog-to-digital conversion circuit; the digital reference signal is a signal obtained by the analog-to-digital conversion circuit performing analog-to-digital conversion on a reference signal, and the digital sensing signal is a signal obtained by the analog-to-digital conversion circuit performing analog-to-digital conversion on a sensing signal output by a receiving coil.

[0053] In an embodiment of the present invention, when a target object passes through the through-type detection system, the magnetic field where the receiving coil in the signal receiving circuit is located changes, and the receiving coil receives the induction signal of the magnetic field change. The analog-to-digital conversion circuit includes multiple acquisition channels and a reference channel. The reference channel is used to receive the reference signal transmitted from the digital-to-analog conversion circuit in the signal sending circuit, and each acquisition channel is connected to a receiving coil, respectively, for receiving the induction signal transmitted from the receiving coil. The analog-to-digital conversion circuit performs analog-to-digital conversion on the collected induction signal and reference signal to obtain a digital induction signal and a digital reference signal, respectively, and outputs the digital induction signal and the digital reference signal to the controller, respectively.

[0054] Step S12: Correcting the phase of the digital sensing signal according to the digital reference signal to obtain a calibration signal.

[0055] The controller subtracts the phase of the digital sensing signal from the phase of the digital reference signal to perform phase correction, thereby obtaining a calibration signal after removing the phase jitter. Figure 7 As shown, the following steps are included.

[0056] Step 121: Perform frequency domain transformation on the digital sensing signal and the digital reference signal respectively to obtain corresponding frequency domain signals.

[0057] Specifically, the frequency domain conversion unit in the controller can perform frequency domain conversion on the digital sensing signal and the digital reference signal to obtain corresponding frequency domain signals. For example, the digital sensing signal and the digital reference signal can be subjected to fast Fourier transform (FFT) to obtain corresponding frequency domain signals.

[0058] Step 122: derive a corresponding initial phase according to the frequency domain signal of the digital sensing signal, and derive a corresponding reference phase according to the frequency domain signal of the digital reference signal.

[0059] Specifically, the main control unit in the controller can obtain the corresponding initial phase according to the frequency domain signal of the digital sensing signal, and obtain the corresponding reference phase according to the frequency domain signal of the digital reference signal.

[0060] Step 123: Subtract the reference phase corresponding to the digital reference signal from the initial phase corresponding to the digital sensing signal to obtain the calibration signal.

[0061] In the embodiment of the present invention, a reference phase corresponding to the digital reference signal is subtracted from an initial phase corresponding to the digital sensing signal to obtain a calibration signal with a stable phase.

[0062] The specific solution of the phase jitter suppression method provided in this embodiment can refer to the signal receiving circuit in the above embodiment, which will not be described again here.

[0063] The above specific embodiments of the present invention are described. In some cases, the actions or steps recorded in the embodiments of the present invention can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the process depicted in the accompanying drawings does not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0064] The method of the above embodiment is applied to the corresponding device in the above embodiment, and has the beneficial effects of the corresponding device embodiment, which will not be described in detail here.

[0065] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure is limited to these examples. Based on the concept of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0066] This application is intended to cover all such substitutions, modifications and variations that fall within the broad scope of all embodiments. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the scope of protection of this disclosure.

Claims

1. A signal receiving circuit, characterized in that: The signal receiving circuit includes: a receiving coil, an analog-to-digital conversion circuit connected to the receiving coil, and a controller connected to the analog-to-digital conversion circuit; the receiving coil is used to receive an induction signal of a magnetic field change, and the analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the induction signal and a reference signal, respectively, to obtain a digital induction signal and a digital reference signal; the controller corrects the phase of the digital induction signal according to the digital reference signal to obtain a calibration signal.

2. The signal receiving circuit according to claim 1, characterized in that: There are multiple receiving coils, and the analog-to-digital conversion circuit includes multiple acquisition channels and a reference channel, and the reference channel is used to receive the reference signal; each acquisition channel is connected to one of the receiving coils, respectively, to receive the induction signal transmitted from the receiving coil.

3. The signal receiving circuit according to claim 1, characterized in that: The controller comprises a frequency domain conversion unit connected to the analog-to-digital conversion circuit and a main control unit connected to the frequency domain conversion unit, wherein the frequency domain conversion unit performs frequency domain conversion on the digital sensing signal and the digital reference signal to obtain corresponding frequency domain signals; The main control unit obtains a corresponding initial phase according to the frequency domain signal of the digital sensing signal, and obtains a corresponding reference phase according to the frequency domain signal of the digital reference signal; The main control unit subtracts a reference phase corresponding to the digital reference signal from an initial phase corresponding to the digital sensing signal to obtain the calibration signal.

4. The signal receiving circuit according to claim 1, characterized in that: The reference signal is generated by a signal sending circuit corresponding to the signal receiving circuit; the signal sending circuit is used to generate a magnetic field.

5. The signal receiving circuit according to claim 4, characterized in that: The signal transmission circuit includes a processor, a digital-to-analog conversion circuit and a transmitting coil connected in sequence; The analog-to-digital conversion circuit is also connected to the digital-to-analog conversion circuit; the processor is used to output a drive signal; the digital-to-analog conversion circuit is used to perform digital-to-analog conversion on the drive signal; the signal output by the digital-to-analog conversion circuit is used to drive the transmitting coil, and is also transmitted to the analog-to-digital conversion circuit as the reference signal.

6. A phase jitter suppression method, characterized in that: The phase jitter suppression method comprises: Receive a digital reference signal and a digital sensing signal output by an analog-to-digital conversion circuit; the digital reference signal is a signal obtained by the analog-to-digital conversion circuit performing analog-to-digital conversion on the reference signal, and the digital sensing signal is a signal obtained by the analog-to-digital conversion circuit performing analog-to-digital conversion on the sensing signal output by the receiving coil; The phase of the digital sensing signal is corrected according to the digital reference signal to obtain a calibration signal.

7. The method according to claim 6, characterized in that Correcting the phase of the digital sensing signal according to the digital reference signal to obtain a calibration signal includes: Performing frequency domain transformation on the digital sensing signal and the digital reference signal respectively to obtain corresponding frequency domain signals; Determine a corresponding initial phase according to the frequency domain signal of the digital sensing signal, and determine a corresponding reference phase according to the frequency domain signal of the digital reference signal; The calibration signal is obtained by subtracting a reference phase corresponding to the digital reference signal from an initial phase corresponding to the digital sensing signal.

8. The method according to claim 6, characterized in that The reference signal is generated by a signal sending circuit corresponding to the signal receiving circuit; the signal sending circuit is used to generate a magnetic field.

9. A pass-through detection system, characterized in that: The invention comprises the signal receiving circuit as claimed in any one of claims 1 to 5.

10. The pass-through detection system according to claim 9, characterized in that: The pass-through detection system also includes a processor, a digital-to-analog conversion circuit and a transmitting coil connected in sequence, and the analog-to-digital conversion circuit is also connected to the digital-to-analog conversion circuit; the processor is used to output a drive signal; the digital-to-analog conversion circuit is used to perform digital-to-analog conversion on the drive signal; the signal output by the digital-to-analog conversion circuit is used to drive the transmitting coil, and is also transmitted to the analog-to-digital conversion circuit as the reference signal.

11. A security door detection group, characterized in that: The invention comprises a plurality of pass-through detection systems as described in any one of claims 9 to 10.

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