Metal detector using asynchronous demodulation
By adopting asynchronous demodulation and Σ-Δ analog-to-digital converters in metal detectors, the limitations of synchronous demodulation and synchronous Delta-Sigma analog-to-digital converters in the prior art are solved, and more efficient metal object detection is achieved and more accurate signal processing.
Patent Information
- Application Number
- CN202280095624.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-12-23
- Publication Date
- 2024-12-13
AI Technical Summary
Existing metal detectors require a synchronous demodulation process to detect metal objects, and rely on a synchronous Delta-Sigma analog-to-digital converter, limiting detection efficiency and flexibility.
A metal detector is designed, using asynchronous demodulation process and Σ-Δ analog-to-digital converter, which converts the received signal and transmitter current into numbers through the AD converter, and uses signal processing, demodulation and The correction unit processes signals, eliminating the need for synchronous demodulation, providing higher performance and flexibility.
The ability to detect metal objects without synchronous demodulation process is realized, which improves detection efficiency and performance, allows the use of different types of analog-to-digital converters, and obtains more accurate amplitude and phase values through asynchronous demodulation, reducing phase differences error.
Smart Images
Figure CN119137509A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to metal detectors. Background Art
[0002] The metal detector comprises a search head. A scanning signal in the form of a magnetic field emitted by a transmitter coil arranged in the search head changes when interacting with a metal object. This changed magnetic field is received by a receiving antenna and converted into a signal. The received signal is synchronously demodulated. Thanks to the demodulated signal, the changes imposed on the magnetic field by the metal object can be detected and information about the metal object can be obtained. This demodulation requires a synchronous analog-to-digital converter.
[0003] Due to the above-mentioned problems, innovation in the related technical field becomes necessary. Summary of the invention
[0004] The present invention relates to a metal detector, aiming to eliminate the above disadvantages and bring new advantages to the relevant technical field.
[0005] The object of the present invention is to provide a metal detector capable of detecting metal without a synchronous demodulation process.
[0006] Another object of the present invention is to provide a metal detector that uses different types of analog-to-digital converters to detect metal.
[0007] Another object of the present invention is to eliminate the need for synchronous delta-sigma analog-to-digital converters.
[0008] In order to achieve all the purposes described above and in the following detailed description, the present invention is a metal detector suitable for detecting underground metal targets, comprising: a transmitter switching circuit for switching the voltage of a transmitter signal composed of a series of multi-cycle rectangular waves; a transmitter coil for transmitting the transmitter signal received from the transmitter switching circuit; a receiver coil, induced by receiving a magnetic field, for generating a receiving signal of the received magnetic field; and a receiver amplifier circuit for amplifying the receiving signal received from the receiver coil. Therefore, the metal detector further includes: an AD converter for converting the received signal and the transmitter current from analog to digital, the AD converter is connected to the receiver amplifier circuit for receiving the amplified received signal, and the AD converter is connected to the transmitter voltage regulation circuit for receiving the transmitter current that generates the transmitter signal, and the AD converter is connected to receive the transmitter signal current; a control unit connected to the AD converter for receiving the received signal and the transmitter current converted to digital, the control unit having a demodulation unit, a correction unit and a signal processing unit, the demodulation unit for obtaining amplitude and phase values by processing the transmitter current and the received signal using an asynchronous demodulation process, the correction unit for correcting the phase difference in the transmitter current and the receiver voltage caused by the asynchronous demodulation, and the signal processing unit for operating the user interface based on the phase-corrected received signal. In this way, the need for synchronous demodulation is eliminated, and different types of analog-to-digital converters can be used.
[0009] A possible embodiment of the invention is characterized in that the AD converter is of the sigma-delta type. It is thus possible to use such a converter and achieve a higher performance by eliminating the need for synchronization.
[0010] Another possible embodiment of the invention is characterized in that the signal processing unit, the demodulation unit and the correction unit are processors.
[0011] Another possible embodiment of the invention is characterized in that the signal processing unit, the demodulation unit and the correction unit are provided as a single processor.
[0012] Another possible embodiment of the invention is characterized in that the user interface comprises an audio warning element.
[0013] Another possible embodiment of the invention is characterized in that the user interface comprises a display.
[0014] Another possible embodiment of the invention is characterized in that the metal detector comprises a transmitter voltage regulating circuit for increasing the voltage to a determined voltage level before transmitting it to the transmitter switching circuit. Thus, recovery of reactive power is also provided. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 A representative view of the metal detector electronics is shown. DETAILED DESCRIPTION
[0016] In this detailed description, the metal detector of the present invention is described only by way of non-limiting examples for a better understanding of the subject matter.
[0017] The metal detector (100) may basically include a search head (not shown), a transport shaft (not shown) to which the search head is connected so that a user can carry it, and a user interface (150) disposed at the other end of the search head.
[0018] Reference Figure 1 The metal detector (100) of the present invention further comprises a control unit (140). The control unit (140) generates a transmitter signal for detection. The transmitter signal comprises a series of multi-cycle rectangular waves. The metal detector (100) comprises a transmitter switching circuit (113) which switches the voltage of the transmitter signal. The metal detector (100) comprises a transmitter coil (112) which transmits a voltage switching transmitter signal. Therefore, the transmitter signal for detecting metal objects is transmitted in the form of a magnetic field.
[0019] The metal detector (100) further includes a receiver coil (122). The receiver coil (122) is induced by the magnetic field to which it is exposed, thereby generating a received signal. The metal detector (100) includes a receiver amplifier circuit (121) that amplifies the received signal from the receiver coil (122). As an innovative aspect of the present invention, the metal detector (100) includes a transmitter current that forms a switching transmitter signal and an AD converter (130) for converting the received signal from analog to digital. The AD converter (130) can be a ∑-Δ (sigma-delta) type. The AD converter (130) receives asynchronous sampling of the received signal and the transmitter current. The control unit (140) receives the converted received signal and the transmitter current from the AD converter (130) as input. The demodulation unit (142) of the control unit (140) performs asynchronous demodulation of the transmitter current and the received signal. More specifically, the demodulation unit (142) processes the voltage of the received signal. The amplitude and phase values are the result of the asynchronous demodulation. The control unit (140) further includes a correction unit (143). The correction unit (143) corrects the phase difference between the transmitter current and the receiver voltage caused by asynchronous demodulation. The signal processing unit (141) provides target detection based on the phase difference corrected received signal and operates the user interface (150) based on the signal.
[0020] The signal processing unit (141), the demodulation unit (142) and the correction unit (143) may be a processor. The signal processing unit (141), the demodulation unit (142) and the correction unit (143) may be arranged in a single processor, that is, the control unit (140) may be a processor.
[0021] In a possible embodiment of the present invention, a transmitter control unit (140) generates a transmitter signal. In this embodiment, a transmitter voltage regulating circuit (111) is provided between the control unit (140) and the transmitter switching circuit (113). The transmitter voltage regulating circuit (111) allows the transmitter signal to be increased to a voltage under predetermined conditions. The transmitter voltage regulating circuit (111) is capable of transmitting the transmitter signal increased to an appropriate voltage level to the transmitter switching circuit (113). In this way, some reactive power is also recovered.
[0022] In a possible embodiment of the present invention, the user interface (150) comprises an audio warning unit (151). In a possible embodiment of the present invention, the user interface (150) comprises a display (152).
[0023] The present invention is also a method. It is carried out using the above-mentioned components of the metal detector (100), and thus comprises the following steps:
[0024] - Generate a transmitter signal consisting of a series of multi-period rectangular waves. In this step, the control unit (140) generates a transmitter signal for metal detection.
[0025] - Switching the voltage of the transmitter signal. In this step it is ensured that the signal is suitable for transmission from the transmitter coil via a transmitter switching circuit (113) comprising switching circuit elements known in the art.
[0026] - In a preferred embodiment, a step of increasing the generated transmitter signal to a predetermined voltage level is provided. In this step, the transmitter signal is increased to a suitable voltage level suitable for switching.
[0027] - The transmitter coil (112) transmits the switched transmitter signal in the form of a magnetic field.
[0028] - A receiving signal related to the magnetic field is generated by the receiver coil. In this step, the transmitter coil transmits the transmitter signal as a magnetic field.
[0029] - amplifying the reception signal received from the receiver coil (122). The transmitter signal propagated in the form of a magnetic field is received by the receiver coil (122) by interacting with the target. The reception signal is generated by induction caused by the magnetic field effect.
[0030] - The received signal is preferably amplified by a receiver amplifier circuit (121).
[0031] -Convert the received signal from analog to digital. In this step, the voltage of the received signal is converted from analog to digital by asynchronous sampling.
[0032] -Converting the transmitter current forming the transmitter signal into digital form. In this step, the transmitter current forming the transmitter signal is asynchronously sampled and converted into digital form.
[0033] - Obtaining the amplitude and phase values by processing the converted transmitter current and received signal using asynchronous demodulation. Through this step, the amplitude and phase values of the transmitter signal current and the received signal voltage are obtained by asynchronous demodulation without synchronous demodulation. The phase of the transmitter signal current and the received signal voltage are received asynchronously. The phase error due to the synchronization difference is very close for both. When the difference between the respective phases of the received signal voltage and the transmitter signal current is calculated, the error is reduced to a negligible level.
[0034] -Corrects the phase difference between the transmitter current and the receiver voltage due to asynchronous modulation based on the angle difference.
[0035] - presenting a signal related to metal detection to a user in a user interface (141) based on the phase corrected received signal. In this step, a signal output for target finding is given by the phase corrected received signal. When the transmitter signal interacts with metal, it adds information to the signal, the transmitter signal acting as a carrier, thereby modifying the received signal. Due to the asynchronous demodulation described above, this information can be extracted and presented to the user through the user interface.
[0036] The protection scope of the present invention is defined in the appended claims and cannot be limited to those explained for sampling purposes in this detailed description.Obviously, those skilled in the art can present similar embodiments based on the above facts without departing from the main concept of the present invention.
[0037] Reference numerals
[0038] 100 Metal Detector
[0039] 111 transmitter voltage regulation circuit
[0040] 112 Transmitter Coil
[0041] 113 Transmitter Switch Circuit
[0042] 121 Receiver Amplifier Circuit
[0043] 122 Receiver Coil
[0044] 130AD Converter
[0045] 140 control unit
[0046] 141 Signal Processing Unit
[0047] 142 Demodulation Unit
[0048] 143 Correction Unit
[0049] 150 User Interface
[0050] 151 Audio warning element
[0051] 152 Display
Claims
1. A metal detector (100) suitable for detecting underground metal targets, include: A transmitter switching circuit (113) for switching the voltage of a transmitter signal composed of a series of multi-cycle rectangular waves; a transmitter coil (112) for transmitting the transmitter signal received from the transmitter switch circuit (113); A receiver coil (122), induced by receiving a magnetic field, for generating a receiving signal of the received magnetic field; as well as a receiver amplifier circuit (121) for amplifying the reception signal received from the receiver coil (122); Characterized in that the metal detector (100) further comprises: an AD converter (130) for converting the received signal and the transmitter current from analog to digital, the AD converter (130) being connected to the receiver amplifier circuit (121) for receiving the amplified received signal, and the AD converter (130) being connected to a transmitter voltage regulating circuit for receiving the transmitter current for generating the transmitter signal, and the AD converter (130) being connected to receive the transmitter signal current; A control unit (140) is connected to the AD converter (130) and is used to receive a received signal and a transmitter current converted into digital form. The control unit (140) has a demodulation unit (142), a correction unit (143) and a signal processing unit (141). The demodulation unit (142) is used to obtain amplitude and phase values by processing the transmitter current and the received signal using an asynchronous demodulation process. The correction unit (143) is used to correct the phase difference in the transmitter current and the receiver voltage caused by the asynchronous demodulation. The signal processing unit (141) is used to operate a user interface (150) based on the phase-corrected received signal.
2. The metal detector (100) according to claim 1, It is characterized in that The AD converter (130) is of sigma-delta type.
3. The metal detector (100) according to claim 1, It is characterized in that The signal processing unit (141), the demodulation unit (142) and the correction unit (143) are processors.
4. The metal detector (100) according to claim 1, It is characterized in that The signal processing unit (141), the demodulation unit (142) and the correction unit (143) are provided as a single processor.
5. The metal detector (100) according to claim 1, It is characterized in that The user interface (150) includes an audio warning element (151).
6. The metal detector (100) according to claim 1, It is characterized in that The user interface (150) includes a display.
7. The metal detector (100) according to claim 1, It is characterized in that A transmitter voltage regulating circuit (111) is included for increasing the voltage to a determined level before transmitting the voltage to the transmitter switching circuit.
8. A method implemented by a metal detector, The following steps are involved: - Generates a transmitter signal consisting of a series of multi-cycle rectangular waves, - switching the voltage of the transmitter signal, - transmitting the switched transmitter signal in the form of a magnetic field via a transmitter coil (112), - generating a receiving signal related to the magnetic field by means of a receiver coil, - amplifying a reception signal received from the receiver coil (122), It is characterized in that it also includes the following steps: - converting said received signal from analog to digital, - converting the transmitter current forming said transmitter signal into digital form, - Obtain amplitude and phase values by processing the converted transmitter current and received signal using asynchronous demodulation, - correcting the phase difference in the transmitter current and the receiver voltage that occurs due to asynchronous modulation based on the angle difference, - presenting a signal related to metal detection to a user in a user interface (141) based on the phase-corrected received signal.
9. The method according to claim 8, in, The step of increasing the generated transmitter signal to a predetermined voltage level is included.