111 results about "Double frequency" patented technology

The invention discloses a walk-off compensation device for laser frequency tripling, and relates to the technical field of laser, and the device comprises a fundamental frequency light source which is used for generating fundamental frequency laser; the frequency doubling unit is used for converting the fundamental frequency laser into frequency doubling laser; the frequency tripling unit comprises a frequency tripling nonlinear crystal and is used for converting the frequency-doubled laser and the residual fundamental frequency laser into frequency tripled laser; the walk-off pre-compensation unit is arranged between the frequency doubling unit and the frequency tripling unit, the walk-off pre-compensation unit comprises a spherical lens which is eccentrically arranged, the spherical lens is used for enabling the frequency doubling laser and the residual fundamental frequency laser which is not completely converted to generate a preset included angle, and the preset included angle is matched with a walk-off angle generated in the frequency tripling nonlinear crystal; and the light beam shaping unit is used for outputting ultraviolet laser. According to the invention, a complex pre-compensation optical element does not need to be added in front of the frequency tripling unit, walk-off compensation can be realized only through the eccentrically placed spherical lens, and the structure of the optical system is greatly simplified.

The invention discloses an MMC sub-module fault processing method, device and equipment and a storage medium, and the method comprises the steps: obtaining the capacitor voltage value of a sub-module of an MMC and the bridge arm current value of the sub-module, the MMC comprises six bridge arms of three phases, each bridge arm comprises a plurality of sub-modules, the capacitor of each sub-module is connected with an equivalent series resistor in series, and further, the equivalent series resistor is connected with the capacitor voltage value of the sub-module of the MMC; the resistance value of an equivalent series resistor in the sub-module is monitored through the capacitor voltage value and the bridge arm current value, if the resistance value of the equivalent series resistor is higher than a preset resistance value, it is determined that the capacitor of the sub-module fails, fault-tolerant control is carried out on the sub-module through a voltage-sharing and circulating current suppression algorithm, a three-phase switching signal is output, and the three-phase switching signal acts on the MMC. Therefore, the circulating current fundamental frequency component and the double frequency component caused by fault-tolerant control after the fault can be eliminated through the circulating current suppression strategy, the effect of circulating current suppression is achieved, and the stability of system fault operation is improved.

The invention discloses a cable copper shielding layer damage and damage opening size detection method, system and device based on the combination of a frequency doubling measurement method and a step-by-step evaluation method and a storage medium, and is applied to the technical field of power equipment state detection. Comprising the following steps: respectively acquiring measurement results of a cable to be measured under Chirp signal injection of Gaussian envelopes with single and double center frequencies, and determining the starting time of an injection signal and the arrival time of a reflection signal according to an extreme value in a time-frequency cross correlation curve; extracting an injection signal and a reflection signal by taking the starting time and the arrival time as extraction starting points and the length of the injection signal as an extraction width, and calculating the damage degree according to the spectrum ratio of the reflection signal to the injection signal; and calculating characteristic impedance based on the damage degree, and sequentially determining the size and length of the central angle of the cable copper shielding layer damage port by using a step-by-step evaluation method. According to the invention, effective detection and positioning of copper shield damage and effective estimation of the damage size are realized.

The invention discloses a loop current suppression and modulation method for a network-forming inverter of a heavy truck battery swap station, which comprises the following steps: after harmonic waves are suppressed by adopting a reduced-order resonance controller, converting a negative-sequence double frequency, a positive-sequence quadruple component and a frequency loop current harmonic wave component into third-order loop current harmonic waves, and considering a primary frequency modulation characteristic, carrying out secondary frequency modulation on the third-order loop current harmonic waves, and carrying out secondary frequency modulation on the third-order loop current harmonic waves; and a proportional resonance integral controller is connected in parallel to ensure harmonic suppression during frequency deviation, and meanwhile, suppressed harmonic is introduced into a hysteresis controller to correct a nearest level approximation modulation wave. Through a combined control method of direct inhibition and indirect inhibition of the circulating current, the purpose of inhibiting the circulating current is achieved. According to the invention, harmonic suppression after power frequency and frequency deviation is guaranteed, the influence of capacitor voltage ripples of the sub-modules is improved while modulation waves are corrected, and the control mode is simplified.

The invention relates to the technical field of converter control, and provides a loss optimization control method for a modular multilevel converter and related equipment, and the method comprises the steps: solving an expression of the average conduction loss and an expression of the average switching loss of a target modular multilevel converter; according to the expression, the positive correlation between the loss and the absolute average value of the bridge arm current is obtained through analysis, and the expression of the absolute average value of the bridge arm current is obtained; according to the positive correlation, loss optimization is equivalent to optimization of the absolute average value of the bridge arm current, and the optimal value range of the initial phase angle when the absolute average value of the bridge arm current is minimized is analyzed; according to the optimal value range of the initial phase angle, calculating an optimal initial phase angle and an optimal double frequency circulation component when the absolute average value of the bridge arm current is minimized; and controlling the target modular multi-level converter according to the optimal double-frequency circulation component and the optimal initial phase angle. According to the method, the optimization precision can be improved while loss optimization is realized.

The invention relates to the technical field of satellite navigation and wireless communication, and discloses an indoor positioning method and system based on feeder multiplexing Beidou double-frequency, and the method comprises the steps: receiving outdoor B1I and B2a signals through a high-gain Beidou double-frequency receiving antenna, carrying out the frequency separation and signal conditioning through a double-frequency separation filter, and carrying out the positioning of the B1I and B2a signals; and transmitting the B1I signal to an indoor distributed antenna for broadcasting through the existing communication feeder network, and transmitting the B2a signal to a central directional antenna to establish a time synchronization reference. A mobile terminal receives a dual-frequency signal, capturing and tracking are carried out through digital signal processing, and pseudo-range and carrier phase observation values are extracted. And performing pairing processing on observation data of the same antenna, calculating a dual-frequency pseudo-range difference value, eliminating system errors, and performing position calculation by adopting a weighted least square method and Kalman filtering. The method solves the problem that the traditional GPS signal cannot cover the indoor environment, and has a good application prospect in the scenes of underground commercial complexes, tunnels, parking lots and the like.

The invention relates to a double-ridge waveguide antenna array applied to satellite communication, and relates to the technical field of antennas. The antenna comprises a horn radiation layer, a waveguide transmission layer, a low-frequency feed layer and a high-frequency feed layer which are sequentially arranged in the stacking direction. The low-frequency feed layer and the high-frequency feed layer are connected with the horn radiation layer through the waveguide transmission layer and the stepped impedance conversion waveguide; the horn radiation layer comprises dual-band horn common-caliber radiation units, metal blocks and metal strips, the metal blocks and the metal strips are used for constructing ridge waveguide structures, the adjacent dual-band horn common-caliber radiation units are separated by the metal strips, and the ridge waveguide structures constructed by the metal blocks are used for loading and expanding bandwidth; according to the invention, the design complexity of double frequency bands with a large frequency ratio is effectively simplified, and the design compactness of the antenna array is improved.

Many modern Global navigational satellite systems (GNSS) utilize signaling that includes a primary pseudorandom number (PRN) code and a secondary low rate PRN code, the latter of which is modulo-2 added to the first. In some GNSS acquisition receivers in which precise a priori synchronization information is unavailable, the acquisition process performs a set of correlation operations that begin at a time that is not aligned with the epoch of the secondary PRN code. This epoch misalignment results in loss of system performance. This disclosure provides new methods for dealing with such epoch misalignments and minimizes system performance loss. In one embodiment, a method combines a first and a second correlation operation, each using a different correlation epoch, to reduce the effect of epoch misalignments. This disclosure also provides methods for advantageously processing a characteristic double frequency peak that may appear in the acquisition process as a result of the correlation misalignment with the epoch of the secondary code.

The utility model belongs to the technical field of fiber lasers, and particularly relates to a high-efficiency frequency doubling system for a laser. The high-efficiency frequency doubling system for the laser comprises a first lens, a first frequency doubling crystal, a 4f system and a second frequency doubling crystal which are arranged in sequence. According to the high-efficiency frequency doubling system for the laser, the two frequency doubling crystals are used, phase matching is adopted, S polarization light and P polarization light of fundamental frequency light are subjected to frequency doubling in sequence to form P polarization frequency doubling light and S polarization frequency doubling light, two times of frequency doubling of the non-polarization-maintaining fiber laser are achieved through two times of frequency doubling, and high-power green light in the mixed polarization direction is obtained. And under the condition that the infrared fundamental frequency power is kept unchanged, the proportion of S polarization component light to P polarization component light is changed due to the change of the polarization state, but two generated green light beams are complementary, so that the power output is more stable than that of one crystal.

The invention relates to an antenna assembly and a vehicle. The antenna assembly comprises a dielectric body, a first antenna structure, a second antenna structure and a metal frame body. The projections of the plurality of second antenna structures on the dielectric body along the thickness direction of the dielectric body are arranged around the circumferential direction of the first antenna structure, the plurality of second antenna structures are rotationally symmetrical about the center of the first antenna structure, and each second antenna structure is coupled with the first antenna structure. The metal frame body is arranged around the periphery of the first antenna structure, and the metal frame body is connected with the dielectric body. The low-profile antenna structure is realized, the influence caused by the surface wave effect of the dielectric body is improved, the mutual coupling interference between double frequencies is reduced, and the antenna gain and the antenna bandwidth are improved. Besides, the metal frame body can restrain back lobe level energy, capacitance coupling is formed between the first antenna structure and the metal frame body, capacitance coupling is formed between the second antenna structure and the metal frame body, the antenna miniaturization design is further achieved, the overall size is reduced, and the installation space can be prevented from being limited.

The invention discloses a microscopic imaging system and a microscope for simultaneously exciting / collecting two-photon and three-photon signals, and belongs to the technical field of optical microscopic imaging. The microimaging system comprises a laser, a microimaging device and a signal acquisition / separation device, and a single erbium-doped fiber laser is used for simultaneously exciting two-photon signals and three-photon signals of unmarked biological tissues. The system respectively excites a third harmonic signal, a two-photon excitation fluorescence signal and a second harmonic signal through 1550nm fundamental frequency light and 775nm double frequency light. The signal acquisition / separation device can acquire the three signals at the same time to realize real-time imaging and detection. The whole microscopic imaging device part is integrated into a handheld small system and is connected with a laser and a signal acquisition / separation device through optical fibers to form a plug-and-play microscopic imaging system, and the plug-and-play microscopic imaging system is suitable for simultaneous observation of two-photon and three-photon signals of unmarked biological tissues.

The application discloses a high-energy and few-cycle blue light laser generation method and device, and belongs to the technical field of ultrafast laser, wherein the method comprises the following steps: adopting a nonlinear crystal to double frequency of a base frequency pulse after compression, and performing at least twice pulse width compression on the obtained double frequency pulse to obtain high-energy and few-cycle blue light laser; wherein, the double frequency process and the pulse width compression process are both performed in a cavity filled with helium; the pulse width compression process is performed through spectral broadening of a solid sheet; since the helium has extremely low linear dispersion and nonlinear coefficient and extremely high ionization energy, not only the solid sheet damage can be avoided, and a part of spectral broadening is contributed, but also an environment close to vacuum can be provided in terms of dispersion and laser-induced ionization, so that the dispersion compensation of the double frequency pulse is easier, and the energy loss caused by gas ionization and the input energy limitation are avoided, and higher output energy is allowed; the problem that the high-energy and ultra-short pulse width blue light pulse is difficult to be realized simultaneously at present is effectively solved.

1. The name of the design product: full transparent vertical double frequency anti-theft access control. 2. The use of the design product: the design product is used for attendance management, identity recognition and access control management. 3. The design points of the design product: in shape. 4. The picture or photo that best indicates the design points: perspective view 1.

The application discloses a kind of based on decoupling surface and isolation plate's dual polarization and double frequency base station antenna and array, the base station antenna includes low frequency antenna array, high frequency antenna array, antenna floor and multiple first isolation plate being arranged in antenna floor, multiple second isolation plate being arranged in the middle of adjacent two first isolation plate;High frequency antenna array includes multiple columns of high frequency antenna unit column being installed in the middle of adjacent first isolation plate and second isolation plate;Low frequency antenna array includes multiple columns of low frequency antenna unit column being installed in the middle of adjacent two first isolation plate;Each column of low frequency antenna unit column includes multiple low frequency antenna units printed with decoupling surface, decoupling surface includes 8 several Chinese character shape metal strip, 180 square metal patch and 40 rectangular metal patch.Not only solve the problem of low frequency antenna to high frequency antenna's shelter, repair high frequency antenna pattern, but also can effectively improve low frequency antenna and high frequency antenna's same frequency isolation, improve decoupling effect.

The present invention discloses an optical ranging method of a coherent phase-pushing system, which uses a single-frequency microwave signal to perform double-sideband modulation on an optical carrier signal. After the generated modulated optical signal passes through the optical link to be measured, it is polarized and split into two beams of detection optical signals in the horizontal and vertical polarization directions, and the local oscillator optical signal is polarized and split into two beams of local oscillator optical signals in the horizontal and vertical polarization directions; the local oscillator optical signal in the horizontal polarization direction and the detection optical signal, and the local oscillator optical signal in the vertical polarization direction and the detection optical signal are respectively combined, photoelectrically detected, and envelope detected, and then the two obtained electrical signals are combined to generate the electrical signal to be measured; the phase difference between the doubled frequency signal of the single-frequency microwave signal and the corresponding frequency component in the electrical signal to be measured is detected, and the distance of the optical link to be measured is calculated based on the phase difference. The present invention also discloses an optical ranging device of a coherent phase-pushing system. The present invention can effectively improve the optical ranging accuracy of the coherent phase-pushing system.

The application discloses a polarization converter using terminated filter circuit to control frequency characteristics, comprising: a dual-polarized antenna array and a filter circuit arranged on the back of the antenna array floor, the dual-polarized antenna array is used for transmitting the received electromagnetic wave signal to the filter circuit arranged on the back of the antenna array floor, and transmitting the signal output through the filter circuit to the free space; the filter circuit is used for realizing the control on the frequency characteristics of the polarization converter. By arranging different filter circuits on the back of the antenna array floor, the polarization converter with different frequency characteristics can be obtained. The application designs a reflection type polarization converter with super wideband and double frequency band. When linear x-polarized or y-polarized electromagnetic wave irradiates to the surface of the polarization converter, the reflected wave is the orthogonal polarization thereof. The application can be used for antenna design, radar cross section (RCS) reduction and wireless communication technology.

The application discloses a kind of triaxial SERF atom magnetometer quadrature double frequency modulation system and method, the system utilizes signal generation module to generate frequency f m The sine quadrature modulation signal of cosine is respectively driven SERF atom magnetometer X and Y axis magnetic field generating coil, and 2nf m Frequency sine signal of driving Z axis coil, through the integral filter of 3 groups of integral period integration, the open-loop magnetic field signal of X axis, Y axis and Z axis magnetic field component is obtained, and through control module, the driving current of three-axis magnetic field coil is controlled to generate compensation magnetic field, so that the open-loop magnetic field signal of X axis, Y axis and Z axis magnetic field component is zero, at this time, the magnetic field intensity of atom chamber is zero, and the compensation current output by control module is the X, Y and Z axis magnetic field intensity signal measured by triaxial SERF atom magnetometer.The system can directly extract triaxial magnetic field calculation signal from a laser signal, and eliminate the cross-coupling effect when triaxial magnetic field is calculated, improve the measurement range and quadrature of SERF atom magnetometer, with very high engineering application value.

The application provides a time-frequency offset estimation method and device of an LTE system, and relates to the technical field of communication. The method comprises the following steps: a plurality of decimal multiple frequency offsets are used to compensate the initial received signal to obtain a first target signal; after PSS detection and screening of the first target signal, the first m first correlation peak values in descending order, N-ID-2 corresponding to the first correlation peak values, the first timing position and the first frequency offset value are obtained; a plurality of integer multiple frequency offsets are preset and the second correlation peak values corresponding to each first correlation peak value are calculated; the time domain position of each second correlation peak value is located and frequency offset compensation is performed to obtain a second target signal; after SSS detection and screening of the second target signal, the first n second correlation peak values in descending order, N-ID-1 corresponding to the second correlation peak values, the second timing position and the second frequency offset value are obtained, and the cell ID is obtained by combining N-ID-1 and N-ID-2. The application separates the decimal multiple frequency estimation and the integer multiple frequency offset estimation, and the double frequency offset estimation improves the accuracy.

The invention provides a software phase-locked loop algorithm with a notch filter, and belongs to the field of power converters. The method comprises the following implementation steps: step 1, adopting a multiplication phase discriminator as a PD link, and carrying out operation on an input signal and a feedback signal; step 2, adding a notch filter to filter out a double frequency component; 3, controlling the phase difference to be zero through a PI control link; 4, converting the voltage signal passing through the PI (LPF) link into a frequency signal through a voltage-controlled oscillator (VCO); and step 5, after the frequency signal is obtained, inputting the frequency signal back to the phase discriminator through a feedback link as a feedback signal for operation with the input signal.

The present invention discloses a crystal oscillator circuit, comprising a crystal oscillation amplifier circuit, a duty cycle correction circuit and a frequency doubling circuit, wherein the duty cycle correction circuit comprises a first inverter, a single-ended to differential circuit, a comparator, a feedback circuit and a frequency doubling circuit, wherein the crystal oscillation amplifier circuit outputs a clock signal; the first inverter performs reverse processing on the clock signal; the single-ended to differential circuit generates a differential clock signal according to the clock signal output by the first inverter, and the differential clock signal comprises a positive clock signal and a reverse clock signal; the comparator receives the positive clock signal and the reverse clock signal, and outputs a current feedback signal after performing comparison processing; the feedback circuit outputs a voltage feedback signal to the input end of the first inverter according to the current feedback signal, so as to adjust the bias voltage of the first inverter, thereby adjusting the duty cycle of the clock signal output by the first inverter; the output end of the frequency doubling circuit outputs the doubled frequency clock signal to the clock system, so as to serve as a reference clock source.

The invention specifically relates to a microwave photon ultra-wideband tunable linear frequency modulation signal generator, and belongs to the technical field of microwave photonics. The device is composed of a first laser, a polarization controller, a double-parallel Mach-Zehnder modulator, an optical filter, an optical coupler, a photoelectric detector, a radio frequency amplifier, a second laser, a baseband signal source, a direct-current voltage source and a 90-degree coupler. By adjusting the bias voltage of the dual-parallel Mach-Zehnder modulator, double frequency multiplication and triple frequency multiplication of a linear frequency modulation signal are realized, so that a single microwave photon frequency multiplication system can simultaneously realize double frequency multiplication and triple frequency multiplication functions. Frequency multiplication and frequency conversion of baseband signals are completed in one-time electro-optical-photoelectric conversion through a method of reserving a single high-order sideband and beat frequency of a tunable laser, and multiple times of photoelectric conversion are not needed. And meanwhile, the use of a tunable optical filter is avoided, and the complexity and the cost of the system are reduced.

The application relates to the technical field of signal processing, and provides a signal processing method and system of a rubidium atomic frequency standard, a main frequency standard adopts a double-threshold amplitude comparison circuit, a standby frequency standard adopts a single-threshold amplitude comparison circuit, and the existence of a signal, the validity of an amplitude and a locking state are synchronously monitored; double-threshold detection of the main frequency standard ensures reliability, single-threshold detection of the standby frequency standard ensures readiness for quick switching, and the reliability and switching efficiency are balanced; through preset logic rule fusion analysis, the validity is comprehensively judged in combination with a frequency standard locking signal. A control signal is generated based on a priority rule, the main frequency standard is kept when the main frequency standard is valid, a high-level pulse synchronized with a 10MHz signal zero-crossing point is generated when the main frequency standard is invalid and the standby is ready, an abnormal alarm is triggered when the double frequency standards fail, and the control signal is transmitted to a frequency standard switching circuit through a level conversion subunit, so that the trigger timing requirement of a high-speed switching module is met, quick response switching is ensured, the stability in the switching process is ensured, and the whole is reliable and stable.

The invention discloses a three-phase current source inverter fault diagnosis and positioning method based on phase angle signal characteristics, and belongs to the technical field of new energy converter fault diagnosis and positioning. Firstly, a three-phase load current signal of a system is measured, and a three-phase current fitting degree is calculated according to the three-phase load current signal for fault judgment; secondly, converting three-phase load current in an abc coordinate system into an alpha-beta coordinate system according to Clark coordinate conversion, dynamically calculating a module value of a space current vector in real time, performing normalization processing on current signals in a two-phase static coordinate system, and calculating the processed signals through a frequency doubling phase angle feature classification method; next, a fault phase angle is judged through a three-phase current fitting degree and frequency doubling phase angle feature classification method, sampling is carried out, and coding is carried out according to a sampling result to carry out fault positioning. A real-time processing and judging process is adopted in the fault judging and positioning process, and the dynamic performance and the anti-jamming capability of the system are improved.

The invention discloses an LPWG-based on-chip carrier envelope offset frequency detector and a self-beat frequency detection method. The detector comprises an ultra-short pulse port, a super-continuum spectrum SCG generation area, a long-period waveguide grating LPWG, a single-mode straight waveguide, an output straight waveguide, a coupling straight waveguide and a tuning electrode. The device is highly integrated, frequency beating can be completed only through one integrated waveguide chip, the problems that an existing detection method is high in cost, a system is complex, and a frequency beating system is difficult to operate are solved, a single chip is benefited to generate a cross-octave super-continuum spectrum and frequency doubling light at the same time, an extra frequency doubling crystal is not needed any more, and the device is simple in structure and convenient to operate. And due to the fact that the working bandwidth of the LPWG can limit the filtering effect, an external filtering element is not needed any more, and the successful research and development of the LPWG has wide application backgrounds in the aspects of high-precision frequency measurement, optical atomic clocks, stable and reliable on-chip optical frequency comb research and development and the like, and has important scientific significance and profound practical significance.

The present invention provides a broadband passive doubler, comprising: a double-sided microwave circuit board, a first input suspension microstrip line, a second input suspension microstrip line, an input short-circuit line, a diode bridge stack, a first output suspension microstrip line, a second output suspension microstrip line, a first output short-circuit line and a second output short-circuit line; the first input suspension microstrip line and the first output suspension microstrip line are arranged on the front side of the double-sided microwave circuit board and connected to the diode bridge stack; the second input suspension microstrip line and the second output suspension microstrip line are arranged on the reverse side of the double-sided microwave circuit board and connected to the diode bridge stack; the diode bridge stack runs through the double-sided microwave circuit board; the input short-circuit line, the first output short-circuit line and the second output short-circuit line are all connected to the diode bridge stack, so as to better match the input and output suspension strip lines with the diode bridge stack. The broadband passive doubler provided by the present invention has a small size, low frequency multiplication loss and a wide operating frequency bandwidth.

This invention discloses an adaptive dual-mode direction backtracking system based on double frequency conversion, comprising a radio frequency (RF) circuit, a control circuit, a local oscillator (LOO), and an antenna array. The RF circuit amplifies, filters, and mixes the RF signals received by the antenna array to form signal transmission links in mixed-mode and Van Atta array modes. The control circuit provides unified control over the RF switches and the transmit / receive delays of each channel, and outputs control signals according to the operating mode switching requirements. The LEO generates and distributes a fixed LEO signal and an adaptive LEO signal to achieve frequency matching under different incoming wave frequencies. The antenna array receives external incoming wave signals and transmits direction backtracking signals, employing an adjacent transceiver unit interconnection method in mixed-mode and a centrally symmetrical array element interconnection method in Van Atta array mode. This invention enables stable direction backtracking under different incoming wave frequencies and different application scenarios.

The invention relates to an energy storage converter harmonic wave and double frequency suppression method. By sampling the inductive current output by the DC / AC converter, dead time compensation is carried out, low-order harmonics in the output voltage can be reduced, and the quality of output electric energy is improved. Band elimination filtering is performed on voltage sampling feedback of the DC / DC converter, so that the output DC capacitor of the DC / DC converter bears frequency doubling power, the power fluctuation of an energy storage element is reduced, the service life of the energy storage element can be prolonged, the loss of the energy storage converter is reduced, and the performance and the power density of the energy storage converter are improved.

The present application relates to a kind of large specification 86CrMoV7 steel kind embossing roller processing technology, roller body processing method: roller body quenching and tempering piece-frame position-rough boring inner hole-half precision turning-outer circle grinding-magnetic exploration-double frequency quenching+tempering-precision turning frame position-precision boring inner hole-precision turning and shaft head hot mounting;Shaft head processing method: shaft head quenching and tempering piece-precision turning and roller body hot mounting.Processing method is adopted after roller body hollow double frequency quenching and then hot mounting, selects reasonable process parameter, solves the precision control problem of fit length and total length, avoids the quality problems such as quenching crack, deformation, uneven hardness easily appeared in hollow double frequency quenching process, effectively guarantees product quality, satisfies user demand.

The application relates to a group velocity mismatch-based closed defect reference-free positioning method and system, which comprises the following steps: acquiring attribute information of a sample to be tested, determining ultrasonic excitation parameters based on the attribute information; generating an ultrasonic signal based on the ultrasonic excitation parameters, and propagating into one end of the sample to be tested; receiving a receiving signal generated at the other end of the sample to be tested; performing time-frequency analysis on the receiving signal to determine whether a fundamental frequency signal and a double frequency signal exist simultaneously, if yes, extracting peak times of the fundamental frequency signal and the double frequency signal, and if no, determining that there is no closed defect; and determining the position of the closed defect in the sample to be tested based on the peak times and a group velocity curve of the sample to be tested. Compared with the prior art, the application can reference-free identify and position the closed defect by using the contact acoustic nonlinear effect of the closed defect without damaging the sample to be tested, and has the advantages of fast detection, high defect positioning accuracy and the like.

The microstrip line filter comprises a PCB substrate, a reference ground plane and a filter body, the reference ground plane is located on the bottom layer of the PCB substrate, and the filter body is located on the top layer of the PCB substrate. The filter body comprises an input matching unit, a first filtering unit, a second filtering unit, a third filtering unit, a fourth filtering unit, a fifth filtering unit and an output matching unit; the input matching unit and the output matching unit are impedance microstrip lines with the same shape, and the input matching unit and the output matching unit are symmetrically distributed on the PCB substrate with the third filtering unit as the center. The microstrip line filter designed by the utility model is small in size, high in precision, easy to process, low in cost, large in power capacity and easy to integrate into a circuit; the microstrip line filter is small in insertion loss, small in reflection coefficient and excellent in performance; the microstrip line filter provided by the utility model is high in out-of-band rejection, especially high in out-of-band rejection at a frequency doubling position.