39results about How to "SNR" patented technology

The invention discloses a high-resolution X-ray energy spectrometer based on an Si-PIN detector array. Detectors of the energy spectrometer employ an m row*n column Si-PIN detector array, each row of the detectors share one charge sensitive amplifier, there are n columns all together, X rays detected by the detectors are respectively sent to a time discrimination unit and a signal filtering weighting unit through amplification of the amplifiers, and n time signals and single-path energy signals are formed. Inside a digital multichannel pulse-amplitude analyzer, accurate pulse amplitude is extracted after the time signals and the energy signals are processed by an offline correction module and a trapezoid shaping module, and an energy spectrum of the X rays is finally output. The high-resolution X-ray energy spectrometer has the following advantages: the detection efficiency of the detectors in detecting the X rays especially high-energy X rays is improved, the problem of introduction of quite large noise during application of the detector array under common conditions is solved, the signal-to-noise ratio is improved, and the energy resolution of the X-ray energy spectrometer is effectively improved.

Disclosed is a remote transmitting meter number wheel radial transmission photoelectric direct-reading device, which fundamentally solves the problems of large number of elements, low noise ratio and high error code probability of the existing photoelectric direct-reading device; the photoelectric direct-reading device of the invention comprises a meter bracket, as well as a character wheel shaft, a code reader and a multi-bit encoding number wheel fixed on the meter bracket. The invention is mainly technically characterized in that the character wheel shaft adopts a split cylindrical light-shading shaft with a light transmission window; light-emitting diodes are arranged on a built-in circuit board of the shaft; the encoding number wheel is composed of a light transmission wheel body and a light-shading wheel body through assembly; the code reader is composed of a closed cover, as well as a photoconductive framework with a photoconductive slot, a receiving circuit board with a triode, and an encoder which are sealed inside the closed cover; the center of each light-emitting diode is superposed with the centerline of the light transmission wheel web of the light transmission wheel body, and the centerline of the photoconductive slot. The device of the invention has rational structural design, high transmission light path signal-to-noise ratio, small light loss, less elements and low manufacturing costs, which is suitable for mass production and can avoid <number hopping and error code> to significantly improve the reading accuracy.

The invention discloses an ultrasonic testing special probe for butt girth welding of an austenitic stainless steel pipe. The probe adopts a send-receive double crystal focusing structure, so that geometrical scattering of the inner wall of a steel pipe is reduced, and random and interfering echo caused by a wedge block is reduced; an inward concave curved surface is arranged at the bottom of a delay tapered wedge, so that the top of the inward concave curved surface is in contact with the steel pipe to be tested; a horizontal polarized shear wave is generated in the austenitic stainless steel pipe by the special probe and cannot be converted into other types of waves when compared with other wave forms and reflected from the surface parallel to the polarization direction; random echo is less; the horizontal polarized shear wave is almost entirely transmitted into the weld metal, and the acoustic beam directional deflection is minimum when compared with other wave forms. The ultrasonic testing special probe can solve the technical problems that deficiencies are found in the sensibility, the signal to noise ratio and the resolution of ultrasonic testing for butt girth welding of small caliber austenitic stainless steel pipes with phi 34 mm to phi 168 mm external diameter and 3.5 mm to 20 mm wall thickness.

The invention discloses a weak target detection method based on automobile millimeter wave radar, a tracking method and a system. The weak target detection method based on automobile millimeter wave radar comprises the following steps of estimating the corresponding target angle of an echo signal in each period according to a corrected linear frequency modulation continuous wave signal in each period and the corresponding echo signal in each period; comparing whether the target angles of the echo signal in a plurality of coherent processing periods are consistent or not; if the target angles of the echo signal in the plurality of coherent processing periods are consistent, judging that a target to be resolved corresponding to the echo signal is a real target; and if the target angles of the echo signal in the plurality of coherent processing periods are not consistent, judging that the target to be resolved corresponding to the echo signal is a false target. Compared with the prior art, the weak target detection method based on automobile millimeter wave radar belongs to a low-signal-to-noise ratio target detection technology with the advantages that the goal of detecting a weak target in a long distance can be achieved; meanwhile, the number of false targets is greatly reduced; and the low-false-alarm-probability constraint is finally realized.

The present invention discloses a complex and weak object detection and tracking method suitable for passive towed line array sonar. The objective of the invention is to overcome the technical problem that a traditional algorithm is bad in low signal-to-noise-ratio complex object detection and tracking effect. Conventional beamforming is employed to process received signals to obtain the spatial spectral measurement of each resolution element, the method of fitting measurement data statistics characteristics is employed to design a likelihood function model to calculate weights of particles to realize object tracking through adoption of the particle filter algorithm; and multi-time snapshot particle weights are accumulated to determine the generation and disappearance of the object. According to the embodiment, the complex and weak object detection and tracking method suitable for the passive towed line array sonar effectively solve the problems that the traditional algorithm equalization measurement data loses information and the tracking mode of the traditional algorithm cannot be suitable for tracking of a low signal-to-noise-ratio object scene and the fixing of the number of the objects so as to realize the effective tracking of the sonar complex and weak objects.

The invention provides a robustness combined signal processing method of a source end and a relay end of a relay system. The method includes the following steps: transmitting a training sequence to a relay by the source end, carrying out channel estimation and obtaining an estimated channel from the source end to the relay by the relay, transmitting the training sequence to a user side by the relay, carrying out channel estimation and obtaining an estimated channel from the relay to a legal user by the legal user, carrying out channel estimation and obtaining an estimated channel from the relay to an eavesdropping user and a channel error variance by the eavesdropping user, feeding the channel information back to a relay node by a user side, transmitting the channel information to a central processing unit by the relay node, performing an iterative algorithm on a pre-code of the source end and a pre-code of the relay by the central processing unit, transmitting the computed pre-codes to the relay node by the central processing unit, feeding the pre-code of the source end back to the source end by the relay, modulating transmitted signals and transmitting the signals to the relay by the source end, pre-processing the signals and then broadcasting the signals to the users by the relay, and detecting the received signals by the legal user. The method promotes safety performance of the system.

The invention discloses an FPM-based micro imaging system. The system comprises a digital micro mirror, a micro lens array, a laser used for emitting light to the digital micro mirror for enabling thedigital micro mirror to reflect the light to the lens array, and an illumination objective lens used for converting spherical waves into plane waves after the micro lens array converts the plane waves into the spherical waves and transmits the light to the illumination objective lens, and irradiating the light to an imaging object placed on an object carrying hole to perform imaging. According tothe system, a to-be-tested sample can be illuminated at different angles by cooperation of the digital micro mirror and the micro lens array; an imaging instrument obtains a low-resolution image; andthen an FPM algorithm is used for iterative reconstruction, so that the image resolution is improved and is equivalent to the resolution of the high-power objective lens, the wider field of view is achieved, the energy of the system is improved, the signal-to-noise ratio is reduced, and the imaging speed is improved.

The invention discloses an outer radiation source intelligent satellite selection method, a system and a radar platform based on a navigation satellite; the method comprises the following steps: usingthe visibility between the radar platform and the navigation satellite as constraint conditions so as to determine the available navigation satellite at a random moment, and building a visible satellite set; using the radar platform detection range scope and the geometric position visibility between the radar platform and the target as constraint conditions so as to constrain the target position,and building a target space position matrix; using the visibility between the target and the navigation satellite as constraint conditions, traversing each available navigation satellite in the visible satellite set, and determining the target visible position matrix corresponding to each available navigation satellite; determining the actual selected satellite by using scattering enhanced area conditions as constraints according to the target visible position matrix corresponding to each available navigation satellite. The method and system can solve the problems that an existing method cannot select the satellite if the target position is not determined.

The invention provides an absolute type grating scale absolute position information correction and read circuit and belongs to the field of precision machining and measurement. The absolute type grating scale absolute position information correction and read circuit comprises a photoelectric detector array, a signal amplification circuit array, a sampling holding circuit array, a signal reference correction circuit, a signal gain correction circuit and a correction data storer; the photoelectric detector array sends a position optical signal to the signal amplification circuit array, and the signal amplification circuit array amplifies the signal, and sends the signal to the sampling holding circuit array; the signal reference correction circuit reads reference correction data in the correction data storer and generates a bias voltage; the signal gain correction circuit reads gain correction data and sets a gain range; the signal reference correction circuit and the signal gain correction circuit perform reference, gain and amplification on the signal output by the sampling holding circuit array, so as to provide the signal for A / D use. The circuit solves problems about common-mode noise, non-uniform distribution of a light source, mismatching of a photoelectric detector and the like, and has the characteristics that the structure is simple, the circuit parameters can be configured, and on-chip integration is realized.

The related mobile communication broadband direct-transmission TD-SCDMA station comprises: a host, including a filter, a low-noise amplifier, a power amplifier, a duplexer, and a monitor plate; a donor antenna, and a re-transmission antenna, wherein the up and down RF signal has working frequency as 2010-2050MHz. This invention applies advanced technology, increases capacity -price ratio, reduces cost and maintenance, decreases system noise, and convenient to evolution.

The invention discloses a defect detection device and a defect detection method. The defect detection device comprises an illumination module and an imaging detection module; the illumination module is used for generating a detection light beam and enabling the detection light beam to be incident on a detection surface of a product to be detected; the imaging detection module is used for detectingwhether the detection light beam is scattered by the detection surface of the product to be detected to generate a scattered imaging light beam or not, and determining defect information of the product to be detected according to the scattered imaging light beam; the illuminance of the detection light beam satisfies that (U1*R) / (U2*L) is greater than or equal to S1; and the half width W of the detection light beam satisfies that d*[tan alpha+ tan beta] is greater than FOV / 2+W. According to the embodiments, the detection light beam generated by the illumination module is determined by determining the relative illuminance between the half-wide edge of the detection light beam and the center of the detection light beam and the half-width of the detection light beam, so that crosstalk generated in the defect detection process is suppressed, and the defect detection precision is improved.

The invention discloses a method and device for detecting a signal under a multipath channel, wherein the method comprises the following steps of utilizing a received signal of a channel estimation value and a baseband frequency domain, and obtaining a likelihood distance of the received signal according to a maximum A posteriori criterion; taking the quotient of the square root result of modular squaring of the likelihood distance and the channel estimation as soft information; and taking one modulation encoding block as a unit, intercepting high n bit after performing uniform shift scaling for the soft information, and inputting the intercepted high n bit in a given and fixed point bite decoder, wherein n is the bit number of the input parameters including sign bits of the bit decoder. With the adoption of the method and the device provided by the invention, error code rate of the soft information output by the fixed point soft demodulator can be reduced.

The invention provides an adaptive radio frequency interference elimination method for radio astronomical signals. The method comprises the following steps of acquiring the reference data and observation data, and performing channel division on the reference data and the observation data; initializing a gain function and the output of an adaptive filter; calculating the average power of each datablock of the reference data and each data block of the observation data; calculating the standardized parameters; calculating a cross-correlation function of the output of the adaptive filter and thereference data; obtaining a cross-correlation average value; calculating the gain function of the adaptive filter; using the gain function to modify the amplitude and phase of the reference data, andobtaining the output of the adaptive filter. According to the method, ta cross-correlator is designed according to the correlation characteristics between the reference data and the observation data,the automatic adjustment of the gain function of the adaptive filter is flexibly realized according to the reference data, the radio frequency interference in the astronomical signals is effectively eliminated, the operation efficiency is high, the lossless recovery of the astronomical signals is realized, the problem of more complex radio frequency interference is solved, and the anti-interference performance is very high.

The invention proposes an all-fiber acousto-optic frequency shifter and an all-fiber heterodyne measurement system applying the all-fiber acousto-optic frequency shifter, wherein the all-fiber acousto-optic frequency shifter includes a Bragg grating fiber, an aluminum cone and piezoelectric ceramics, the piezoelectric ceramics is fixedly adhered on the bottom plane of the aluminum cone, there is an angle in a range of 1.11 degrees to 1.15 degrees between the top plane and the bottom plane of the aluminum cone, and the top plane of the aluminum cone is vertically adhered on an end face of the Bragg grating fiber. A reflectance spectrum of the all-fiber acousto-optic frequency shifter changes with respect to a reflectance spectrum of an all-fiber acousto-optic frequency shifter under the action of an existing typical acoustic wave of a transverse flexural wave or an acoustic wave of a longitudinal wave, so that the all-fiber acousto-optic frequency shifter has higher reflectivity with the same driving power. The manufacturing cost of the all-fiber acousto-optic frequency shifter is reduced, while the power consumption is reduced, so that problems of a complicated structure, low coupling efficiency and a small modulation range and other problems of an existing all-fiber acousto-optic frequency shifter are solved.

Disclosed is a pulse laser signal-to-noise ratio detection device, which includes a first fiber optic splitter, a delay fiber, an adjustable delayer, a polarization controller, a pulse bias generator,a dual-stage electrooptic intensity modulator, a second fiber optic splitter, a trigger unit, an attenuation device, a delay device, a signal gain device, a multi-optical path multiplexing device, aphotoelectric detection device, an electric signal processing device and the like. The pulse laser signal-to-noise ratio detection device in the invention detects the background noise intensity of thelaser output pulse by using the first fiber optic splitter, the delay fiber, the adjustable delayer, the polarization controller, the pulse bias generator, the dual-stage intensity modulator, the second fiber optic splitter, the trigger unit and the signal gain device, detects the signal intensity of the main peak of the pulse at the same time by using the first fiber optic splitter, the second fiber optic splitter, the attenuation device and the delay device, and obtains the signal-to-noise ratio. The detection range of the signal-to-noise ratio of the device can reach 50dB with an accuracyof 1dB. The device has the characteristics of easy operation, high test accuracy, good reliability and the like.

The invention discloses a pressure wave propagation model cable space charge test system. A protection resistor (16), a model cable (18) and a capacitor (19) are disposed inside a metal shielding case (20). A DC generator (11), a high-voltage lead (12) and the protection resistor (16) are sequentially connected. The high-voltage lead (12) penetrates the wall of the metal shielding case (20). The protection resistor (16) is connected to a conductor of the model cable (18). The model cable (18) comprises a first connecting end close to the protection resistor (16) and a second connecting end far from the protection resistor (16), wherein the first connecting end of the model cable (18) is connected to the capacitor (19), and the second connecting end is grounded. The wall of the metal shielding box (20) is provided with a light hole, and the light emitted by a pulse laser (21) can shine on the model cable (18) through the light hole. According to the invention, the system can carry out pressure wave propagation (PWP) model cable space charge tests, strong signals can be obtained, the reliability of the signals can be tested, and the tests can be carried out without temperature limitation.

The invention relates to an all-fiber current transformer with an integrated optical path and a manufacturing technology. The all-fiber current transformer comprises a photoelectric optical path integrated module and a modulation optical path integrated module which are connected with each other. When the photoelectric optical path integrated module and the modulation optical path integrated module are on different substrates, the photoelectric optical path integrated module and the modulation optical path integrated module are two modules packaged respectively, the output tail fiber of the photoelectric optical path integrated module and the input tail fiber of the modulation optical path integrated module are in zero-degree welding connection. When the photoelectric optical path integrated module and the modulation optical path integrated module are on the same substrate, the output tail fiber of the photoelectric optical path integrated module is employed an input tail fiber of the modulation optical path integrated module, and the photoelectric optical path integrated module and the modulation optical path integrated module are packaged in an integrated manner. The all-fiber current transformer has advantages of high signal to noise ratio, small size, simple installation and low production cost.

The invention discloses a grating enhanced distributed vibration demodulation system based on three-pulse dislocation interference. The system comprises a laser device, a pulsed light modulator, a three-pulse generation polarization-maintaining structure, a first erbium-doped optical fiber amplifier, a first optical circulator, a fiber grating array, a second erbium-doped optical fiber amplifier, a second optical circulator, a three-in-three optical coupler, a first Faraday rotator mirror, a second Faraday rotator mirror and a four-channel data acquisition card. Based on the distributed fiber grating vibration sensing system, the three-pulse dislocation interference and three-in-three optical coupler digital phase demodulation technology is adopted, XX and XY pulses are utilized to complement interference visibility, and demodulation is performed by selecting a better one, so that polarization fading resistance and interference signal high visibility in the distributed fiber grating vibration sensing system are realized.

The invention provides a reversible 3D polygonal grid data hiding algorithm based on segment displacement. The algorithm mainly includes an information hiding part and an information extracting part, wherein the core part is information processing conducted through a 3D grid, normal control coordinates and normal label information are acquired and segmented, information hiding and information extraction are conducted, and finally a processed 3D grid model is acquired through model reconstitution. According to the hiding algorithm, a segmenting hiding strategy is adopted in the model, so that a hiding error is controlled within a small and controllable range, a user is capable of hiding infinite information on the 3D grid model, the high signal to noise ratio is guaranteed, and the problem that the information hiding amount and the signal to noise ratio are contradictory directly is really solved. As a new 3D model information hiding mode, the reversible 3D polygonal grid data hiding algorithm has high application value in the fields such as grid communication, digital families and information security.

The invention discloses an additive manufacturing online detection device and method based on transmission-type laser ultrasound. In the technical scheme, a pulse transmitter is connected with a piezoelectric sensor and located at the bottom of a substrate to excite an ultrasonic signal, and a laser vibration meter is used for being connected with an optical head to transmit detection laser with a certain wavelength; the detection laser vertically enters the surface of the printed piece through the scanning galvanometer to scan and collect an ultrasonic signal; the ultrasonic signal is carried by reflected light of the receiving laser on the surface of the printed piece and returns to the laser vibration meter through the scanning galvanometer. And setting an imaging area according to the ultrasonic coverage range of a single ultrasonic sensor, carrying out sonic path distance calculation on each point in the imaging area according to the propagation law of diffraction transverse waves, extracting the amplitude of each scanning point when an A scanning signal corresponds to sound, carrying out delay superposition, and carrying out three-dimensional imaging on the defect. The problems that an existing laser ultrasonic online monitoring device is low in ultrasonic energy, unstable in signal and insufficient in buried defect detection capacity can be solved, and three-dimensional visualization of buried defects is achieved.

The invention relates to the technical field of medical health, in particular to a heart rate calculation method based on heart sound. The method comprises the following steps of: acquiring real-timeheart sound signal and processing the waveform of the heart sound signal to form a calculable characteristic waveform; detecting the time interval T between adjacent two peaks and calculating an instantaneous heart rate value; calculating arithmetic mean values of the instantaneous heart rate values in turn according to each successive five beats; utilizing a system estimation method to process the arithmetic average values to obtain corresponding estimation values; carrying out anti-misjudgment processing on the calculated values and the estimated values. According to the calculation method,under the premise of accurate detecting the heart rates, the calculation amount is small, the complexity is low and the real-time property is good, and the calculation method is suitable for calculation on the basis of an embedded chip, so that the development cost of a enterprise product can be reduced; Kalman estimation equation is used in the data processing, so that the final result cannot beinfluenced by the signal-to-noise ratio and the human and environmental interference, and meanwhile, stable and reliable heart rate results can be obtained.

The invention discloses a method for multiplying integral time based on satellite dynamic time-varying whisk broom scanning, which relates to the field of space optical satellite dynamic imaging. Themethod comprises the following steps: pointing the pitch of a satellite to a certain angle; establishing an image plane moving speed vector model corresponding to multiple integral time; and calculating the dynamic maneuvering angular velocity of the satellite with multiple integral time under a certain pitch angle, so as to realize the dynamic and maneuverable reduction of the push broom scanningspeed of the satellite and the multiplier increase of the imaging integration time. The method greatly improves the imaging integration time in the conventional push broom scanning without changing the inherent optical parameters of a high-resolution camera. By establishing a functional relationship between the dynamic real-time shifting maneuver and the image shifting speed of push broom scanning of the satellite at different pitch angles, the real-time maneuvering speed reduction of the satellite attitude is achieved, and the push broom scanning speed of the image plane is reduced, the goalof increasing the imaging integration time of the camera and keeping it unchanged is achieved, the image quality of the camera is significantly improved.

The invention relates to a biosensor, and in particular relates to a high-sensitivity environmental compensation type capacitive surface stress biosensor. The problem that the conventional surface stress biosensor has low signal to noise ratio and low sensitivity is solved. The high-sensitivity environmental compensation type capacitive surface stress biosensor comprises a substrate, wherein an active supporting film and a reference supporting film are respectively fixed on the upper surface of the substrate; a first bottom electrode is arranged in the inner cavity of the active supporting film; the first bottom electrode is fixedly attached to the upper surface of the substrate; a first top electrode is fixedly attached to the outer top surface of the active supporting film; the first bottom electrode is dead against the first top electrode; a second bottom electrode is arranged in the inner cavity of the reference supporting film; the second bottom electrode is fixedly attached to the upper surface of the substrate; a second top electrode is fixedly attached to the outer top surface of the reference supporting film; and the second bottom electrode is dead against the second top electrode. The high-sensitivity environmental compensation type capacitive surface stress biosensor is suitable for detection and monitoring of living matters and chemical substances.

The invention relates to an all-fiber current transformer with an integrated light path and a manufacturing process thereof. The all-fiber current transformer comprises a photoelectric light path integrated module and a modulation light path integrated module which are connected with each other. When the photoelectric light path integrated module and the modulation light path integrated module are on different substrates, the photoelectric light path integrated module and the modulation light path integrated module are two modules encapsulated separately, and the output tail fiber of the photoelectric light path integrated module and the input tail fiber of the modulation light path integrated module are fusion-welded at 0 degree. When the photoelectric light path integrated module and the modulation light path integrated module are on the same substrate, a modulation light path integrated module assembly without an encapsulation shell is arranged in the direction of the output optical axis of a third collimator adhered to the end face of a splitting prism to form a spatial light path, and the photoelectric light path integrated module and the modulation light path integrated module are integrally encapsulated. The all-fiber current transformer of the invention has the advantages of high signal-to-noise ratio, small size, easy installation, and low production cost.

The invention discloses a non-contact heart rate detection method based on head movement. the invention realizes the amplification of the head movement signal used in the cardiography technology, themovement state of the head is characterized by the light spot signal amplified by the movement amplitude, The signal-to-noise ratio (SNR) of the motion trajectory signal can be effectively improved incomplex background, and the accurate non-contact heart rate detection can be realized by processing the light spot motion signal, which can solve the problem that the amplitude of the original signalis small and the SNR is low.

The invention belongs to the technical field of satellite navigation, and discloses an inter-symbol difference and code parallel GPS weak signal capturing method and system. Comprising a digital down-conversion module, a code merging module, a data storage module, a Doppler stripping module, a data folding module, a step-by-step matching coherence module, an inter-symbol difference module, a Doppler compensation module, a step-by-step coherence module, a step-by-step incoherence module, a peak value judgment module, a Purler search completion judgment module, a Doppler regulation and control module and a result output module. According to the high-orbit GPS signal capturing method based on inter-symbol difference and code parallelism, a rapid and efficient capturing algorithm is provided for a navigation receiver; an inter-symbol difference algorithm is adopted to avoid the influence of navigation data jump on the coherent integration duration, and the capture sensitivity of the GPS signal is improved by improving the coherent integration duration. According to the invention, a step-by-step coherent algorithm and a step-by-step incoherent algorithm are adopted, so that rapid acquisition of signals with different intensities is realized, and the first positioning time of a navigation receiver is shortened.

The invention belongs to the technical field of semiconductor lighting, and particularly relates to a synthesized isoenergetic white light standard light source adopting a halogen tungsten lamp and amulti-primary-color LED light source. The synthesized isoenergetic white light standard light source comprises an integrating sphere, the multi-primary-color LED light source, the halogen tungsten lamp, a baffle and a light outlet lens, the multi-primary-color LED light source and the halogen tungsten lamp serve as light sources and are installed on the sphere wall of the integrating sphere, and light emitted by the light source is mixed through the integrating sphere and then emitted through the light outlet lens. The baffle is arranged in front of the light outlet. The multi-primary-color LED light source is composed of LED chips with various primary color spectrums and fluorescent powder. The relative spectral radiation intensities of the standard light source spectrum in the target effective waveband range are the same, and the influence caused by the difference of the signal-to-noise ratios of different wavelengths of the light source in the metering test can be avoided.

The invention discloses a method and device for eliminating the code pattern effect through the red shift chirp characteristic and relates to the technical field of photoelectronics. The nonlinear cross modulation effect in a semiconductor optical amplifier is mainly utilized for the method, and data information carried by pump light is modulated to probe light; pump light is filtered out through a square wave filter, the red shift chirp component is extracted, meanwhile, a normal-phase probe light output signal is acquired, and at the moment, the output probe light is accompanied by a certain code pattern effect; according to the characteristic that large red shift probe light has a high output light intensity, a Gaussian filter is made to work on a sloping transmission curve at low output light intensity corresponding to large wavelength, and the probe light signal is shaped to eliminate the code pattern effect. The chirp characteristic of the semiconductor optical amplifier and the advantages generated by combination of the filters are fully utilized, and thus the full-optical signal processing speed is increased. Through the red shift chirp characteristic, the normal-phase output signal can be directly obtained; through combination of the filters, the defect that the output signal has the code pattern effect is overcome.

Disclosed is a pulse laser signal-to-noise ratio detection device, which includes a first fiber optic splitter, a delay fiber, an adjustable delayer, a polarization controller, a pulse bias generator,a dual-stage electrooptic intensity modulator, a second fiber optic splitter, a trigger unit, an attenuation device, a delay device, a signal gain device, a multi-optical path multiplexing device, aphotoelectric detection device, an electric signal processing device and the like. The pulse laser signal-to-noise ratio detection device in the invention detects the background noise intensity of thelaser output pulse by using the first fiber optic splitter, the delay fiber, the adjustable delayer, the polarization controller, the pulse bias generator, the dual-stage intensity modulator, the second fiber optic splitter, the trigger unit and the signal gain device, detects the signal intensity of the main peak of the pulse at the same time by using the first fiber optic splitter, the second fiber optic splitter, the attenuation device and the delay device, and obtains the signal-to-noise ratio. The detection range of the signal-to-noise ratio of the device can reach 50dB with an accuracyof 1dB. The device has the characteristics of easy operation, high test accuracy, good reliability and the like.

The invention discloses an MEMS (micro-electro-mechanical system) microphone. The MEMS microphone comprises a circuit board, a package structure enclosed by a housing, and a sound hole, wherein an EMS DIE sensor and an integrated circuit ASIC (application specific integrated circuit) chip which are fixed on the circuit board are arranged inside the package structure; the sound hole is formed in the housing; the open end of an inner cavity of the EMS DIE sensor faces towards one side of the sound hole; a sealed passage is formed between the sound hole and the open end of the inner cavity of the sensor. The sound hole of the MEMS microphone is formed in the housing so as to ensure that in a reflow soldering process, impurities cannot enter the cavity of the EMS DIE sensor; the MEMS DIE is inverted to enlarge a back cavity of a forward-sound MEMS MIC, so that the defects that the sensitivity and signal-noise ratio of a forward-sound MEMS MIC product are low due to too small back cavity are overcome and the sensitivity and the signal-noise ratio of the forward-sound product are effectively improved.