An audio frequency negative feedback Doppler microwave sensor and its manufacturing process

Abstract

The present invention discloses an audio negative feedback Doppler microwave sensor and its manufacturing process. The bottom layer of the sensor is a PCB substrate, on the surface of which a microstrip antenna, a power ground port GND, a signal port and a power interface are soldered. The middle layer is an organic resin insulating layer, and the top layer is a piezoelectric ceramic layer. The organic resin insulating layer and the PCB substrate are correspondingly provided with a power ground port GND. Inner electrodes are embedded in the piezoelectric ceramic, and the inner electrodes are energized with the PCB substrate through the power ground port GND provided on the insulating layer and the PCB substrate. By applying the microstrip antenna and the piezoelectric ceramic to the traditional microwave sensor, the present invention makes a multifunctional microwave sensor that can directly filter out audio signals without additional devices, which has a compact structure, is convenient for disassembly and assembly, and has strong anti-interference ability. It can be applied to measurement systems such as heart rate and respiration that require high precision and miniaturization of the instrument volume.

Description

Technical Field

[0001] The present invention relates to the technical field of Doppler microwave sensors, and in particular to an audio-frequency negative feedback Doppler microwave sensor and its manufacturing process. Background Art

[0002] A microwave sensor, also known as a microwave radar, is an instrument made using the Doppler principle of electromagnetic waves, including information such as the presence, moving speed, distance, and angle of an object. It has currently become a common component in target detection devices and is widely used in industries, transportation, and civilian devices, such as vehicle speed measurement, liquid level determination, automatic doors, production line material detection, and reverse radars. Its working principle is based on the Doppler effect (the change in the frequency of electromagnetic waves or sound waves caused by the relative motion of the feed source itself or with the target object). During the detection process of a microwave sensor, it is often interfered by various audio-frequency signals of longitudinal waves, and multiple additional filters need to be used in combination, which is not conducive to application in miniaturized devices.

[0003] The present invention designs a new type of Doppler microwave sensor, applying a piezoelectric ceramic sensor to a traditional microwave sensor to make a multifunctional microwave sensor that can directly filter out audio-frequency signals without additional devices. The device can be applied to measurement systems such as heart rate and respiration that require high precision and have requirements for miniaturization of the instrument volume. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the prior art and provide an audio-frequency negative feedback Doppler microwave sensor and its manufacturing process. By applying a piezoelectric ceramic sensor to a traditional microwave sensor, a multifunctional microwave sensor that can directly filter out audio-frequency signals without additional devices is made, enabling it to be applicable to measurement systems such as heart rate and respiration that require high precision and have requirements for miniaturization of the instrument volume.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] An audio-frequency negative feedback Doppler microwave sensor includes a piezoelectric ceramic layer and a PCB substrate; a microstrip antenna, a power ground port GND, a signal port, and a power interface are etched on the PCB substrate, and the signal port includes a signal transmitting antenna and a signal receiving signal; an organic resin insulating layer is coated between the PCB substrate and the piezoelectric ceramic layer, and power ground port GNDs are correspondingly arranged on the organic resin insulating layer and the PCB substrate; inner electrodes are embedded in the piezoelectric ceramic, and the inner electrodes are energized with the PCB substrate through the insulating layer and the power ground port GND arranged on the PCB substrate.

[0007] A manufacturing process for an audio-frequency negative feedback Doppler microwave sensor includes the following steps:

[0008] S1. Prepare a glue layer on the PCB substrate, and then use photolithography technology to expose the unit pattern of the microstrip antenna, the power ground port GND, the signal transmitting antenna, the signal receiving antenna and the power interface;

[0009] S2. After etching the microstrip antenna, signal transmitting antenna, signal receiving antenna and power interface on the exposed adhesive layer of the PCB substrate, a layer of organic resin insulating layer is applied;

[0010] S3. A sintered piezoelectric ceramic layer is covered on the organic resin insulating layer to obtain an audio negative feedback Doppler microwave sensor.

[0011] In step S2, a power ground port GND is reserved on the organic resin insulating layer, which corresponds to the power ground port GND etched on the PCB substrate.

[0012] In step S3, a layer of piezoelectric ceramic is sintered on the organic resin insulating layer, and the sintered piezoelectric ceramic has an inner electrode embedded therein.

[0013] In step S3, a piezoelectric ceramic is sintered on the organic resin insulating layer. The sintering of the piezoelectric ceramic includes the following steps:

[0014] S31 Ingredients: Pre-treat the raw materials, remove impurities and moisture, and then weigh the raw materials according to the formula ratio;

[0015] S32 mixed calcination: After the above raw materials are mixed, the resulting mixture is calcined;

[0016] S33 grinding and mixing: grinding the calcined mixture into powder, adding a binder and mixing evenly;

[0017] S34 molding and sintering: the mixture is molded by adding a binder, and sintered at high temperature to obtain a piezoelectric ceramic semi-finished product;

[0018] S35. High-voltage polarization: polarize the obtained piezoelectric ceramic semi-finished product at a high voltage of 3000 V / mm to obtain a piezoelectric ceramic with piezoelectric properties.

[0019] The adhesive used in step S33 is a polyvinyl acetate adhesive, which solidifies the ground mixture and participates in the solid phase reaction of the subsequent sintering process.

[0020] The grinding method in step S33 is dry grinding or wet grinding.

[0021] The temperature of the high temperature sintering in step S33 is controlled between 1000-1500°C.

[0022] The beneficial effects of the present invention are:

[0023] 1) The present invention applies a microstrip antenna and a piezoelectric ceramic to a traditional microwave sensor to make a multifunctional microwave sensor that can directly filter out audio signals without additional devices, reducing the production cost of the sensor.

[0024] 2) It has a compact structure and is convenient for disassembly and assembly.

[0025] 3) It has multiple filter circuits and strong anti-interference ability.

[0026] 4) It can be used in measurement systems such as heart rate and respiration that require high precision and miniaturization of the instrument volume. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of an audio negative feedback Doppler microwave sensor of the present invention;

[0028] Figure 2 It is a process flow chart for manufacturing an audio negative feedback Doppler microwave sensor of the present invention;

[0029] Figure 3 It is a process flow chart for manufacturing a piezoelectric ceramic of the present invention;

[0030] Figure 4 It is a logic circuit diagram of an audio negative feedback Doppler microwave sensor of the present invention;

[0031] In the figure: 1. Piezoelectric ceramic layer; 2. Organic resin insulating layer; 3. PCB substrate; 4. Electrode; 5. Power ground port GND; 6. Mixer; 7. Signal receiving antenna; 8. Microstrip antenna; 9. Signal transmitting antenna; 10. Power supply; 11. Filter. Detailed Embodiments

[0032] The present invention will be further described below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described below are only used to explain the present invention and are not used to limit the present invention; unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0033] As Figure 1 shown, an audio negative feedback Doppler microwave sensor includes a piezoelectric ceramic layer and a PCB substrate; a microstrip antenna, a power ground port GND, a signal port, and a power interface are etched on the PCB substrate, and the signal port includes a signal transmitting antenna and a signal receiving signal; an organic resin insulating layer is coated between the PCB substrate and the piezoelectric ceramic layer, and a power ground port GND is correspondingly arranged on the organic resin insulating layer and the PCB substrate; inner electrodes are embedded on the piezoelectric ceramic, and the inner electrodes are energized with the PCB substrate through the power ground port GND arranged on the insulating layer and the PCB substrate.

[0034] like Figure 2 As shown, a manufacturing process of an audio frequency negative feedback Doppler microwave sensor comprises the following steps:

[0035] S1. Prepare a glue layer on the PCB substrate, and then use photolithography technology to expose the unit pattern of the microstrip antenna, the power ground port GND, the signal transmitting antenna, the signal receiving antenna and the power interface;

[0036] S2. After etching the microstrip antenna, signal transmitting antenna, signal receiving antenna and power interface on the exposed adhesive layer of the PCB substrate, a layer of organic resin insulating layer is applied;

[0037] S3. A sintered piezoelectric ceramic layer is covered on the organic resin insulating layer to obtain an audio negative feedback Doppler microwave sensor.

[0038] In step S2, a power ground port GND is reserved on the organic resin insulating layer, which corresponds to the power ground port GND etched on the PCB substrate.

[0039] In step S3, a layer of piezoelectric ceramic is sintered on the organic resin insulating layer, and the sintered piezoelectric ceramic has an inner electrode embedded therein.

[0040] In step S3, a sintered piezoelectric ceramic layer is formed on the organic resin insulating layer. Figure 3 As shown, the sintering of piezoelectric ceramics includes the following steps:

[0041] S31 Ingredients: Pre-treat the raw materials, remove impurities and moisture, and then weigh the raw materials according to the formula ratio;

[0042] S32 mixed calcination: After the above raw materials are mixed, the resulting mixture is calcined;

[0043] S33 grinding and mixing: grinding the calcined mixture into powder, adding a binder and mixing evenly;

[0044] S34 molding and sintering: the mixture is molded by adding a binder, and sintered at high temperature to obtain a piezoelectric ceramic semi-finished product;

[0045] S35. High-voltage polarization: polarize the obtained piezoelectric ceramic semi-finished product at a high voltage of 3000 V / mm to obtain a piezoelectric ceramic with piezoelectric properties.

[0046] The adhesive used in step S33 is a polyvinyl acetate adhesive, which solidifies the ground mixture and participates in the solid phase reaction of the subsequent sintering process.

[0047] The grinding method in step S33 is dry grinding or wet grinding.

[0048] The temperature control for sintering at high temperature described in step S33 is between 1000 - 1500 °C.

[0049] The working principle of an audio frequency negative feedback Doppler microwave sensor of the present invention is as follows:

[0050] To measure the speed and distance of an object, the radar actively emits electromagnetic waves to the target object and receives the returned reflected wave. If microwaves are emitted to an object moving at a relative speed v at a position r from the transmitting antenna, due to the Doppler effect, the reflected frequency f r shifts: f r = f0 + f D where f D is the Doppler frequency and can be expressed as f D = 2f0v / c, where c is the speed of light. Therefore, according to the measured beat signal frequency, the relative speed can be determined. If the phase difference between two Doppler output components is ΔΦ, the formula for calculating the distance r is: r = cΔΦ / 4π(f2 - f1).

[0051] The working process of an audio frequency negative feedback Doppler microwave sensor of the present invention is as follows:

[0052] As Figure 4 shown, the sensor consists of circuits such as a microwave oscillator, a power divider, a transmitting antenna, a receiving antenna, a mixer, and a detector. The transmitting antenna emits microwaves outward in a specific direction. When the microwaves encounter an object, they are reflected. The reflected wave is received by the receiving antenna, mixed with the oscillator wave after audio frequency filtering, and based on the low-frequency signal after mixing and detection, the moving speed and distance of the object after filtering out the audio frequency signal can be obtained according to the above relative speed and distance formulas.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of the present invention or make equivalent replacements. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. An audio negative feedback Doppler microwave sensor, characterized in that It comprises a piezoelectric ceramic layer and a PCB substrate; a microstrip antenna, a power ground port GND, a signal port and a power interface are etched on the PCB substrate, and the signal port comprises a signal transmitting antenna and a signal receiving signal; an organic resin insulating layer is coated between the PCB substrate and the piezoelectric ceramic layer, and a power ground port GND is correspondingly arranged on the organic resin insulating layer and the PCB substrate; an inner electrode is embedded in the piezoelectric ceramic, and the inner electrode is energized with the PCB substrate through the insulating layer and the power ground port GND arranged on the PCB substrate; The manufacturing process of the audio frequency negative feedback Doppler microwave sensor comprises the following steps: S1. Prepare a glue layer on the PCB substrate, and then use photolithography technology to expose the unit pattern of the microstrip antenna, the power ground port GND, the signal transmitting antenna, the signal receiving antenna and the power interface; S2. After etching the microstrip antenna, signal transmitting antenna, signal receiving antenna and power interface on the exposed adhesive layer of the PCB substrate, a layer of organic resin insulating layer is applied; A power ground port GND is reserved on the organic resin insulating layer, corresponding to the power ground port GND etched on the PCB substrate; S3. A layer of sintered piezoelectric ceramic is covered on the organic resin insulating layer to obtain an audio negative feedback Doppler microwave sensor; the sintered piezoelectric ceramic has an inner electrode embedded therein, and the inner electrode is powered by the PCB substrate through the insulating layer and a power ground port GND provided on the PCB substrate.

2. The audio frequency negative feedback Doppler microwave sensor according to claim 1, characterized in that, In step S3, a piezoelectric ceramic is sintered on the organic resin insulating layer. The sintering of the piezoelectric ceramic includes the following steps: S31 Ingredients: Pre-treat the raw materials, remove impurities and moisture, and then weigh the raw materials according to the formula ratio; S32 mixed calcination: After the above raw materials are mixed, the resulting mixture is calcined; S33 grinding and mixing: grinding the calcined mixture into powder, adding a binder and mixing evenly; S34 molding and sintering: the mixture is molded by adding a binder, and sintered at high temperature to obtain a piezoelectric ceramic semi-finished product; S35. High-voltage polarization: polarize the obtained piezoelectric ceramic semi-finished product at a high voltage of 3000 V / mm to obtain a piezoelectric ceramic with piezoelectric properties.

3. The audio negative feedback Doppler microwave sensor according to claim 2, characterized in that, The adhesive used in step S33 is a polyvinyl acetate adhesive, which solidifies the ground mixture and participates in the solid phase reaction of the subsequent sintering process.

4. A audio negative feedback Doppler microwave sensor according to claim 2, characterized in that, The grinding method in step S33 is dry grinding or wet grinding.

5. The audio negative feedback Doppler microwave sensor according to claim 2, characterized in that The temperature of the high temperature sintering in step S33 is controlled between 1000-1500°C.

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