196 results about "Self excited oscillation" patented technology

The embodiment of the invention discloses a light amplification device and a related system and method. The light amplification device comprises an optical fiber isolator, a pump light source, a beam combiner and an EYDF. A large amount of pump light in the EYDF cannot be completely absorbed by ytterbium ions, and ytterbium-band ASE light generated by the ytterbium ions can be further amplified by the pump light, so that effective amplification of signal light by the pump light is limited by the ytterbium-band ASE light. According to the embodiment of the invention, the optical fiber isolator in the light amplification device is modified, the optical fiber isolator can reflect the ytterbium-band ASE light as an auxiliary signal back to the EYDF, the excited amplification of the auxiliary signal and the absorption of the auxiliary signal by the EYDF can effectively inhibit the EYDF from generating the ytterbium-band ASE light, the self-oscillation and self-pulsation of the ytterbium-band ASE light are avoided, and the reliability of the light amplification device is improved. Therefore, the pumping conversion efficiency and the stability of the output power are improved. Meanwhile, the optical amplification device provided by the embodiment of the invention can effectively inhibit the EYDF from generating the ytterbium-band ASE light without adding an additional device, and is beneficial to reducing the cost and the power consumption.

The invention discloses a joint heat dissipation structure and a robot in the technical field of robots. The joint heat dissipation structure comprises a joint, the joint is provided with a shell, a containing cavity is formed in the inner side of the shell, a motor is fixedly arranged in the containing cavity, the joint heat dissipation structure is further provided with a heat dissipation assembly used for reducing the temperature in the containing cavity, the heat dissipation assembly is a pulsating heat pipe, and the pulsating heat pipe comprises an evaporation section and a condensation section. The evaporation section is attached to the outer wall of the motor, and the condensation section is attached to the inner wall of the shell. The pulsating heat pipe is used for heat dissipation, based on the phase change heat transfer principle, no extra fan or pump is needed, self-oscillation flowing is achieved completely through thermal driving, and the overall energy consumption of the robot is remarkably reduced. The pulsating heat pipe is small in occupied space, light in weight, simple in structure, low in maintenance cost and suitable for long-term operation, and joint movement flexibility and load capacity are effectively improved; the condensation section is attached to the inner wall of the shell, the joint shell can be heated while heat dissipation is conducted, and the warm touch feeling can be provided without extra energy consumption.

The invention provides a multi-feedback-channel fluid oscillator, and belongs to the technical field of fluid jetting devices. Comprising an oscillation cavity, an inlet, a nozzle and at least three feedback channels, the inlet is formed in one end of the oscillation cavity, the nozzle is formed in the other end of the oscillation cavity, the nozzle and the inlet are oppositely arranged along the central axis of the oscillation cavity, and the feedback channels are circumferentially distributed around the central axis of the oscillation cavity. And each feedback channel is provided with a feedback channel inlet and a feedback channel outlet. Through the configuration design of the multiple feedback channels, the fluid can form feedback control flow through the feedback channels, and the fluid entering the oscillation cavity through the inlet flows along the wall of the oscillation cavity in multiple directions and is switched through the coupling effect of the fluid coanda effect and multi-channel backflow feedback. And finally, multi-direction sweeping self-oscillation jet flow is formed at the nozzle, so that the space coverage range and the atomization efficiency of the jet flow are greatly improved.

The invention discloses a single-magnet-ring dual-processing-circuit switching wide-range leakage current sensor and method. A magnetic core works in a deep magnetic saturation state based on a magnetic modulation principle and is used for sensing a leakage current signal; the square wave self-oscillation circuit is used for sending a square wave signal to the coil by utilizing the inductance effect of the coil; each of the two signal processing circuits comprises a filter, a proportional amplifier and a lock-in amplifier, and only amplification factors of the proportional amplifiers are different, and the proportional amplifiers are used for processing induced leakage current signals; and the microprocessor is used for analyzing and processing the signal output by the signal processing circuit. The system can monitor the insulation state of the energy storage system in real time, effectively improves the safety and reliability of the system, and is suitable for photovoltaic power generation, wind power generation and other application scenes related to the energy storage system.

The invention discloses an aeration generation system containing a self-excited oscillation turbulent shearing device and an application method of the aeration generation system. The aeration generation system comprises the self-excited oscillation turbulent shearing device, a water inlet unit, an air inlet unit and an aeration tank, wherein the water inlet unit and the air inlet unit are connected to the upstream of the self-excited oscillation turbulent shearing device, and the aeration tank is connected to the downstream of the self-excited oscillation turbulent shearing device. According to the method, through cooperative regulation and control of micro-channel geometric parameters and fluid dynamics, accurate control over the size and distribution of the bubbles is achieved, the particle size is concentrated, and particle size dispersion caused by random breaking or insufficient turbulent shearing in a traditional method is avoided. Only a low-pressure pump is needed to drive fluid, a high-pressure container and a high-power ultrasonic or electrode assembly are not needed, energy consumption is greatly reduced, the risk of electrode passivation or membrane pollution is avoided, and the device is suitable for fluid containing particulate matter or high-turbidity fluid. The provided self-oscillation turbulent shearing device is not provided with a micro-channel, is different from an existing nano bubble generator which must be provided with a releaser, and is not easy to block.

The invention provides a self-excited cesium optical pump atomic magnetometer and a magnetic field measurement method. The magnetometer comprises a physical probe part and a circuit part. The physical probe part comprises a cesium spectrum lamp, an optical element, a cesium atom absorption gas chamber, a radio frequency coil and a photoelectric detector; the circuit part comprises a photoelectric conversion circuit, a phase-locked amplification circuit and a radio frequency excitation circuit modulated by square waves. A macroscopic magnetic moment is generated by pumping cesium atoms through left-handed circularly polarized light, a radio frequency magnetic field induces Larmor precession, light intensity changes are detected and fed back to a radio frequency coil to form self-oscillation, and the external magnetic field intensity is calculated according to the linear relation between oscillation frequency and the magnetic field. Square wave modulation is adopted to broaden the measurement bandwidth, a magnetic field direction adjusting system is additionally arranged to automatically keep an angle of 45 degrees between an optical axis and a magnetic field so as to eliminate a blind area, the hemisphere automatic switching function is achieved, and the advantages of being high in sensitivity, fast in response, high in adaptability, small in size and low in power consumption are achieved.

The invention provides a quartz crystal microbalance resonant frequency detection system, a control method and a terminal, a direct digital frequency synthesis excitation unit is adopted to generate a frequency sweep excitation signal with a preset frequency range and stepping, and the frequency sweep excitation signal is conditioned by a signal injection and conditioning unit and then injected into a QCM sensor. And then the pure amplitude response detection unit measures and quantifies voltage response amplitudes of the QCM sensor under different excitation frequencies, and the resonant frequency intelligent determination unit determines the resonant frequency of the QCM sensor according to the voltage response amplitudes. According to the invention, a QCM self-oscillation circuit does not need to be designed and debugged, a precise phase detection assembly does not need to be configured, the circuit board layout is simpler, and components are greatly reduced. The QCM resonant frequency can be accurately measured only through efficient amplitude detection, a complex algorithm is avoided, the operational capability requirement and the software development difficulty are reduced, the QCM resonant frequency measuring device has the advantages of being simple in structure, low in cost, easy to integrate and the like, miniaturization and low-power-consumption design can be easily achieved, and the QCM resonant frequency measuring device is suitable for portable and wearable application.

The invention provides a handheld shock wave generating system which comprises a shock wave balloon and a driving circuit, and the driving circuit comprises a primary power supply circuit, a high-voltage booster circuit, a voltage doubling circuit and a control circuit. After a voltage signal VCCS2 output by the primary power supply circuit is subjected to self-oscillation and boosting of the high-voltage boosting circuit and multiple rounds of voltage multiplication of the voltage doubling circuit, the voltage signal VCCS2 can be increased by hundreds or even thousands of times, a storage battery and a mains supply do not need to be used, miniaturization can be achieved, and carrying is convenient.

The invention relates to a zero-flux closed-loop circuit which comprises a self-oscillation fluxgate current sensor, a magnetic integrator and a feedback circuit. Wherein the self-oscillation fluxgate current sensor can generate a magnetic field signal under the action of excitation current, the magnetic integrator can generate a corresponding voltage signal according to the magnetic field signal, the feedback circuit can generate a feedback signal according to the magnetic field intensity corresponding to the voltage signal, and the feedback signal acts on the self-oscillation fluxgate current sensor. Therefore, the self-oscillation fluxgate current sensor adjusts the excitation current, thereby ensuring that the magnetic flux of a fluxgate of the self-oscillation fluxgate current sensor is kept near a zero magnetic flux point. Therefore, through the zero-magnetic-flux closed-loop circuit, the electrified current of the electrified wire can be detected in a zero-magnetic-flux environment, the influence of noise can be effectively reduced, the distortion degree of signals is reduced, and the precision of current detection is improved.

The invention provides an ultra wide band millimeter wave transition structure based on gold wire bonding, and relates to the technical field of millimeter wave chip packaging, and the transition structure comprises a substrate, a rectangular cavity, a chip, a parallel gold wire connection structure, a stepped grounding coplanar waveguide GCPW matching structure, and a plurality of blind holes. The substrate comprises a top dielectric layer, a middle metal layer and a bottom metal layer, the rectangular cavity is arranged on the top dielectric layer; the chip is fixed in the rectangular cavity; the parallel gold wire connecting structure is used for connecting the chip and the stepped grounding coplanar waveguide GCPW matching structure; and the plurality of blind holes vertically penetrate through the substrate, are positioned in an area right below the edge of the rectangular cavity and gold wire bonding, are connected with the middle metal layer and the bottom metal layer, and are used for suppressing self-excited oscillation. According to the method provided by the invention, the transition from the chip to the substrate with the average loss lower than 0.28 dB is realized within the frequency band of 30-100GHz.

The invention provides a reconfigurable network-fused high-efficiency power amplifier and a design method thereof, and a circuit structure comprises an input fundamental wave broadband matching network, an input reconfigurable network, a stabilizing circuit, a biasing circuit, an output harmonic control network, an output fundamental wave broadband matching network and an output reconfigurable network, wherein the input fundamental wave broadband matching adopts conjugate matching and is mainly responsible for optimizing small signal parameters of the circuit; the stabilizing circuit is a lossy network, so that self-oscillation caused by overlarge gain of the circuit is prevented; the biasing circuit provides direct-current voltage for the transistor; and an output fundamental wave broadband matching network in the output matching network adopts power matching and is mainly responsible for optimizing the output power and efficiency of the circuit under a large signal. According to the power amplifier, the reconfigurable network connected with the switching devices is adopted, and switching of the working frequency bands of the power amplifier is controlled. Finally, the harmonic control type reconfigurable high-efficiency power amplifier which can be applied to Bluetooth, Wi-Fi, radar and base station communication is realized.

The invention relates to an audio decoding output stage circuit and audio equipment, the audio decoding output stage circuit comprises an I / V conversion module and a low-pass filtering module, and the I / V conversion module comprises a conversion circuit, a crossed diamond amplification circuit, an overcurrent protection circuit and a Roche network circuit; the conversion circuit comprises a JFET (Junction Field Effect Transistor) audio operational amplifier chip and an I / V (Input / Output) conversion resistor and is used for converting an input current into an analog voltage signal; the crossed diamond amplifying circuit can reduce the input offset voltage; the over-current protection circuit can carry out over-current protection; the rowbell network circuit can prevent high-frequency self-oscillation of the power output stage; and the low-pass filtering module comprises a filtering circuit and an ultrahigh frequency filtering circuit arranged at the output end of the audio decoding output stage circuit. The scheme can bring high-performance sound performance, and has the advantages of lower distortion, higher conversion rate, low output impedance and large pushing current.

The invention provides a radio frequency power generator, and relates to the technical field of radio frequency. The radio frequency power generator is characterized in that a first input end of an inverter module is connected with a second output end of an oscillation module; the first output end of the inverter module is connected with the second input end of the oscillation module; the power output end of the voltage stabilizing circuit is connected with the power supply voltage input end of the phase inverter module; the power supply input end of the voltage stabilizing circuit inputs external direct-current voltage; the voltage stabilizing circuit generates a target direct-current voltage according to the external direct-current voltage and the sine wave reference amplitude, and inputs the target direct-current voltage into the power supply voltage input end; the oscillation module performs self-oscillation and generates an initial sine wave signal; and the inverter module amplifies the initial sine wave signal according to the target DC voltage, and inputs the amplified initial sine wave signal to the oscillation module, so that the signal output end of the oscillation module outputs a target sine wave signal. According to the invention, the convenience of amplitude adjustment of the radio frequency signal is improved.

The present application belongs to the field of fans and relates to a fan fault detection method, device, computer equipment and storage medium. The method includes the following steps: configuring the fan type and speed fault threshold; calculating the fan fault signal frequency and processing the fan feedback signal flip flag based on the configuration of the fan type and speed fault threshold; adaptively adjusting the cycle time of a single fan based on the fan fault signal frequency and the fan feedback signal flip flag; determining the current fan order based on the actual cycle time of the single fan by counting through a DSP time base counter; determining the fan type of the currently determined fan based on the fan order and the fan type configured during initialization, and determining the fan fault. By using a multiplexing switch and one isolation device to detect fan faults, the detection circuit is simple and can detect multiple sets of fan fault feedback signals simultaneously, reducing costs; generating a control signal through self-excited oscillation, it is convenient for fans with different fault feedback signals to be compatible.

The application provides a salt-preventing ocean high-pressure water pump port ring structure based on coupled oscillation, and belongs to the technical field of ocean water pump equipment, and comprises a pump body port ring and an impeller port ring, and an annular gap is formed between the two; a nozzle-shaped first groove is arranged on the inner circumferential surface of the pump body port ring, and a second groove with an inclined wall surface and a backflow channel is arranged on the outer circumferential surface of the impeller port ring; the first groove and the second groove are connected to form a fluid oscillation channel. Through the matching design of the circumferential interval of the groove and the rotating speed of the impeller, the groove connection-separation frequency reaches the ultrasonic frequency band, and double coupling of fluid self-excitation oscillation and ultrasonic vibration is realized. The application effectively prevents salt deposition under the premise of not changing the existing lubrication mode, and significantly improves the water film lubrication performance and the service life of the equipment.

This invention relates to a ball-operated plugging device for downhole pulsating hydraulic fracturing, comprising a main body assembly. A conical valve seat is disposed in the middle of the main body assembly, and an umbrella-shaped valve is slidably connected within the conical valve seat. The umbrella-shaped valve includes a valve head boss and a valve stem. A self-excited oscillation chamber is also provided at the bottom of the conical valve seat. A spring support seat is disposed below the self-excited oscillation chamber, with a central circular hole at the geometric center of the spring support seat. A spring is placed on the spring support seat, and the top of the spring contacts the valve head boss of the umbrella-shaped valve. A through-hole flow channel is provided in the middle of the umbrella-shaped valve, with its upper and lower ends communicating with cavity A and cavity B, respectively. The valve stem of the umbrella-shaped valve passes through the spring, and its bottom is inserted into the central circular hole of the spring support seat. A spherical groove is provided at the top of the umbrella-shaped valve for placing a soluble plugging ball. This invention can adjust the pressure variation of the pulsating fluid at the bottom of the well during construction.

The application discloses a kind of digital frequency tracking and synchronous sampling control system for resonant gyro, including self-excitation oscillation and automatic gain control device, preamplifier circuit and digital signal processor, digital signal processor includes first A / D conversion unit, second A / D conversion unit, frequency error detection unit FD, phase error detection unit PD, digital control oscillator NCO, sampling frequency generator and quadrature demodulation unit, the vibration signal of drive channel is handled after device output to first A / D conversion unit, conversion obtains the vibration signal after conversion, FD obtains frequency difference by frequency error detection, PD obtains phase difference by phase error detection, NCO is adjusted the frequency and phase of sampling frequency generator according to frequency difference and phase difference in real time, until the resonant frequency and phase of drive channel are tracked;The vibration signal of detection channel is handled after circuit output to second A / D conversion unit, obtains the vibration signal after conversion, and quadrature demodulation unit carries out quadrature demodulation and obtains speed signal.

The invention discloses a self-excited oscillation filtration coal powder system used in the coalbed methane mining process, the system comprises: an outer cylinder seat, an end cover, a spring assembly, a filter assembly, an oscillation sheet, a water inlet pipe, a water outlet pipe and a sand pump; the outer cylinder seat is a cylindrical body with a chamber provided therein, and a hole is opened at the center of the bottom; the upper pipe opening of the water inlet pipe extends upward from the hole at the bottom of the outer cylinder seat into the inner cavity of the outer cylinder seat; the lower pipe opening of the water inlet pipe is downwardly connected to the coalbed methane mining well; the end cover sealing cover is closed at the upper end of the outer cylinder seat; the center of the end cover is provided with an air outlet connected to an external coalbed methane gas production pipeline; the end cover, the spring assembly, the filter assembly and the oscillation sheet are connected in sequence from top to bottom; the filter assembly surrounds the air outlet; the oscillation sheet is suspended directly above the pipe opening of the water inlet pipe; a water outlet is provided at the bottom of the outer cylinder seat; and the sand pump is connected to the water outlet through the water outlet pipe. The invention effectively separates coalbed methane from coal powder, and the coalbed methane and coal powder are collected separately, thereby improving the extraction efficiency.

This invention relates to the field of flow battery technology and discloses a method and system for regulating self-excited oscillation in flow batteries. By integrating a flow oscillation generator into the electrolyte circulation loop of the flow battery, the periodic vortex ring oscillation and acoustic-fluid positive feedback phenomenon generated by the flow within the resonant cavity of this device are utilized to achieve pulsating regulation of electrolyte flow rate and pressure. This fundamentally improves the convective mass transfer efficiency at the electrode / electrolyte / diaphragm interface within the flow battery stack, thereby alleviating concentration polarization at the battery reaction interface caused by factors such as uneven flow rate, thickened diffusion boundary layer, and restricted ion migration. Furthermore, this device eliminates the need for long-term, additional electrical drive and complex control components, exhibiting a simple structure and stable operation.

The present invention discloses a method and structure for suppressing high-order mode oscillations in a multi-beam klystron. The present invention belongs to the technical field of vacuum electronic devices. The method proposed in the present invention adds a mode filter structure to the inner wall of the coaxial resonator of the multi-beam klystron. Its length is equal to half of the wavelength of the operating mode and is close to three-quarters of the wavelength of the high-order mode. Based on the principle of half-wavelength repeatability, this structure has the characteristic of having little influence on the frequency of the operating mode. Based on the principle of quarter-wavelength impedance transformation, this structure has the characteristic of having a greater influence on the high-order mode. By optimizing the design of the dimensions of the mode filter structure, it is possible to suppress spurious modes and eliminate the influence of high-order mode self-excited oscillations without affecting the frequency, field magnitude, and symmetry of the operating mode of the multi-beam klystron, providing technical support for the simulation design and engineering tube manufacturing of the multi-beam klystron.

The application relates to a zero-flux closed-loop circuit, which comprises a self-oscillating fluxgate current sensor, a magnetic integrator and a feedback circuit; wherein the self-oscillating fluxgate current sensor can generate a magnetic field signal under the action of an excitation current, the magnetic integrator can generate a corresponding voltage signal according to the magnetic field signal, the feedback circuit can generate a feedback signal according to the corresponding magnetic field intensity of the voltage signal, and the feedback signal acts on the self-oscillating fluxgate current sensor, so that the self-oscillating fluxgate current sensor adjusts the excitation current, thereby ensuring that the magnetic flux of a fluxgate through the self-oscillating fluxgate current sensor is kept near a zero-flux point. Therefore, the zero-flux closed-loop circuit can effectively reduce the influence of noise and the distortion degree of a signal when detecting the current of a current-carrying wire in a zero-flux environment, thereby improving the precision of current detection.

The utility model discloses a device for restraining self-excited oscillation of a grating-cavity flow field. The device for restraining the self-excited oscillation of the grating-cavity flow field comprises a box body (3), a grating (2) arranged at the top end of the box body and a restraining structure (1) arranged on the box body (3). According to the device for inhibiting the self-excited oscillation of the grid-cavity flow field, the self-excited oscillation phenomenon of the flow field is inhibited by utilizing the flow characteristic that fluid skims over the grid-cavity flow field inhibiting structure. The streamline appearance is adopted, so that the negative effects of flow resistance increase and the like caused by the existing oscillation suppression device can be reduced as much as possible. Meanwhile, the device is simple in structure and easy to machine and install, and the effects of prolonging the service life of related equipment with low cost can be achieved.

The present invention discloses an aeration generation system containing a self-excited oscillation turbulent shear device and an application method thereof. The aeration generation system includes a self-excited oscillation turbulent shear device, a water inlet unit and an air inlet unit connected upstream of the self-excited oscillation turbulent shear device, and an aeration tank connected downstream of the self-excited oscillation turbulent shear device. Through the coordinated regulation of the microchannel geometric parameters and fluid dynamics, the present invention realizes the precise control of the bubble size and distribution, and the particle size is relatively concentrated, avoiding the particle size dispersion caused by random fragmentation or insufficient turbulent shear in the traditional method. Only a low-pressure pump is required to drive the fluid, without high-pressure vessels, high-power ultrasound or electrode components, greatly reducing the energy consumption, and there is no risk of electrode passivation or membrane pollution, and it is suitable for fluids containing particulate matter or high turbidity. The proposed self-excited oscillation turbulent shear device has no microchannels and is also different from the existing nanobubble generators that must be equipped with release devices, and is not easy to block.

The utility model relates to a kind of load impedance measurement circuit, system and equipment, including waveform control circuit, load impedance acquisition circuit, signal amplification circuit, analog signal conversion PWM circuit, filter circuit and MCU connected in turn;Waveform control circuit includes self-oscillation circuit and rectangular wave output circuit, rectangular wave output circuit receives the rectangular wave that self-oscillation circuit exports and reference voltage comparison generates complementary rectangular wave output to load impedance acquisition circuit, load impedance acquisition circuit gathers load impedance and exports direct current signal to signal amplification circuit, analog signal conversion PWM circuit gathers amplified signal conversion as digital signal to filter circuit and carries out filter processing, and MCU receives the signal after filter processing of filter circuit.The utility model uses self-oscillation and complementary rectangular wave output circuit to form sampling circuit combination, the signal gathered is more accurate, and it is easy to be read and further processed by lower circuit, and finally the impedance measurement value of equipment is more accurate.

The invention discloses a thermal resistance-compression resonant accelerometer in an axial expansion mode, and belongs to the field of micro electro mechanical systems. Comprising an inertia force sensitive module and two sets of frequency modulation modules symmetrically connected to the two ends of the inertia force sensitive module, the inertia force sensitive module senses acceleration and converts the acceleration into inertia force applied to the two sets of frequency modulation modules, and the loading direction of the inertia force is perpendicular to the vibration direction of the two sets of frequency modulation modules; the frequency modulation module forms alternating thermal expansion force through a closed loop in the frequency modulation module, and self-oscillation of the frequency modulation module is completed under the action of the alternating thermal expansion force. The problems that an existing accelerometer is complex in control circuit, high in power consumption and the like are solved.

The application provides a power amplifier packaging structure. The power amplifier packaging structure comprises a power amplifier chip, a substrate, a wall, a transmission ceramic, a transmission lead and a cover plate; the power amplifier chip is arranged on the upper surface of the substrate; the wall is arranged around the power amplifier chip and is connected with the upper surface of the substrate; a plurality of through holes are arranged on the side surface of the wall and at the connection position of the upper surface of the substrate; one end of the transmission ceramic is arranged on the inner side of the side surface of the wall through the through holes and is connected with the corresponding pin on the power amplifier chip respectively, and the other end is arranged on the outer side of the side surface of the wall and is connected with the transmission lead respectively; the cover plate is arranged on the upper surface of the wall; and the cover plate is made of ceramic. The application can effectively eliminate the low-temperature self-excitation oscillation phenomenon of the power amplifier.

The application provides a vertical state carrier rocket self-excitation oscillation suppression network design method, mainly including a vertical state carrier rocket dynamics model construction and a vertical state carrier rocket self-excitation oscillation suppression method. Aiming at the self-excitation oscillation phenomenon in the target test of the carrier rocket in the vertical state, a carrier rocket self-excitation oscillation suppression method is provided. Firstly, a vertical state carrier rocket dynamics model is established; then frequency domain analysis is carried out based on the dynamics model; finally, a dithering elimination network is designed and time domain simulation verification is carried out. The method can effectively solve the self-excitation oscillation phenomenon in the target test of the carrier rocket in the vertical state, eliminate the influence of the periodic dithering of the carrier rocket on the loaded rocket product, and effectively ensure the safety of the rocket ground test and take-off.

The invention discloses a self-driven high-frequency induction heating circuit structure suitable for in-situ pyrolysis in an oil-rich coal well, and relates to the technical field of pyrolysis. The circuit structure comprises an uncontrolled rectifying circuit, a self-driven high-frequency inverter circuit and an induction heating coil, the uncontrolled rectifying circuit converts an alternating current power supply into direct current and is connected to a power supply node VCC2; the self-driven high-frequency inverter circuit is composed of a main circuit, a self-driven protection circuit and an output circuit, the main circuit comprises an upper bridge arm structure and a lower bridge arm structure, the self-driven protection circuit achieves automatic driving of a switching device through a pull-down unit, a pull-up unit and a turn-off guide unit, and the output circuit comprises a resonant capacitor set and two inductors. The induction heating coil is connected between the VCC1 and the VCC. According to the scheme, self-oscillation is achieved by means of inconsistency of device parameters, direct current is converted into high-frequency alternating current, a control chip and a detection circuit are omitted, the system structure is simplified, and the operation reliability in the underground high-temperature and high-humidity environment is improved.

A self-excitation microwave sensor suitable for non-destructive testing of metal mesh film, belonging to microwave sensor technology, comprising a resonant sensing structure, a microwave amplifier, a phase shift element, a band-pass filter, a radio frequency detector, a digital-to-analog converter and a microprocessor; wherein the resonant sensing structure, the microwave amplifier, the phase shift element and the band-pass filter form a self-excitation oscillation loop, the resonant sensing structure has a band-pass characteristic, is located in the feedback branch of the loop, the resonant frequency thereof is consistent with the center frequency of the band-pass filter, and the loop gain and the phase shift satisfy the self-excitation oscillation condition at the frequency; by reasonably setting the gain of the microwave amplifier and collecting the self-excitation oscillation signal power in real time, the sensor can realize detection of sub-millimeter width crack damage and identification of high square resistance samples, has high detection sensitivity, compact structure, small volume and low cost, does not need other external microwave analysis instruments, and can be applied to on-site non-destructive testing of metal mesh film.