199results about How to "Improve detection signal-to-noise ratio" patented technology

The invention discloses a high-dynamic weak-signal rapid capture method for a direct sequence spread spectrum system, belonging to the field of radio communication. Because a spread spectrum carrier has a chirp signal characteristic under the condition of high-dynamic motion (high-speed and high-acceleration), the high-dynamic weak-signal rapid capture method comprises the steps of: firstly, carrying out carrier Doppler frequency compensation by using a time frequency focusing characteristic of fractional order Fourier transform; secondly, carrying out incoherent accumulation on a spread frequency signal by using an order resolving capacity of the fractional order Fourier transform; and finally, carrying out capture judgment on the signal in an order Fourier domain by using a constant false alarm rate detection technology. According to the invention, the difficulty of incapability of long-time coherent accumulation under the high-dynamic condition in the traditional Fourier transform based rapid capture method is solved; and under the condition of high dynamicity and low signal to noise ratio, the signal to noise ratio is effectively increased and the signal capture time is shortened. In addition, a rapid algorithm exists in the invention and is easy to realize on the engineering in real time.

The invention provides an LFMCW radar detection moving human body target method based on a human body model. The method comprises the steps that analog-to-digital conversion is carried out on an LFMCW radar echo beat signal; FFT processing is carried out on each PRI echo beat datum to acquire the LFMCW radar echo beat signal frequency domain data when a human body slowly moves, and rearranging is carried out in a slow time-distance domain two-dimensional plane; a Boulic human body walking model is constructed; according to the human body moving gait frequency and an initial phase range, a number of human body trunk moving models with different parameters are constructed on a gait frequency-initial phase two-dimensional plane; an LFMCW radar echo nonlinear phase compensation signal is reconstructed, and phase compensation is carried out on the rearranged data; FFT processing is carried out to acquire a four-dimensional space processing result; whether a target is in a distance unit is judged through constant false-alarm detection processing; and the information of distance, velocity and gait frequency of the target are acquired in the presence of the target. According to the invention, the signal-to-noise ratio of LFMCW radar detection is improved, and the human body target detection performance in strong ground clutter is improved.

The invention relates to a gas sensing technology and particularly provides a single-tube and coaxial photo-acoustic spectrum sound detector and a gas detection device adopting the sound detector, aiming at solving the technical problems that the acoustic coupling efficiency between an acoustic resonant cavity and a large tuning fork is relatively low when the large tuning fork is used as a sound detector in a current quartz enhanced photo-acoustic spectrum. The single-tube and coaxial photo-acoustic spectrum sound detector has the beneficial effects that firstly, a novel quartz enhanced photo-acoustic spectrum sound detector is designed, and a complete single-tube acoustic resonant cavity is inserted into an oscillation arm gap of a tuning fork type quartz crystal oscillator by virtue of the characteristics of the large oscillation arm gap of the novel tuning fork type quartz crystal oscillator; square holes are formed in the two sides of the single-tube acoustic resonant cavity, and acoustic waves push oscillation arms of the tuning fork type quartz crystal oscillator through the square holes so as to generate an electric signal; the acoustic coupling efficiency is greatly improved by single-tube and coaxial configuration, and the detection signal-to-noise ratio is improved; and secondly, a standing wave mode in the single-tube acoustic resonant cavity is relatively close to an acoustic standing wave mode in a one-dimensional acoustic resonant cavity, so that the length of the resonant cavity is greatly shortened, and meanwhile, the size of a sensor is reduced.

The invention relates to an ultraviolet three-frequency high spectrum resolution laser radar system based on three-channel FP etalon and a detection method thereof, wherein the system and the method can be used to simultaneously detect a 0-35km height wind field, a temperature and an aerosol in a high precision mode. The system is characterized in that an emission laser frequency is alternatively changed among v0, v0-2GHz and v0+2GHz; channels L, 1 and 2 of the etalon are designed into one body, a free spectral spacing is 8GHz, spectral widths are 0.2GHz, 1GHz and 1GHz, 1-L and 1-2 peak to peak intervals are 0.1GHz and 4GHz; the v0 is locked at a peak value of the channel 1; and a quarter wave plate and a polarizing beam splitter prism form a cascading light path. The system and the method have advantages that a single radar can simultaneously measure the 0-35km height wind field, the temperature and the aerosol in the high precision mode; and disadvantages that detection precision of a single parameter detection technology is not high, a detection range can not be covered and three parameters mutually influence each other so that an inversion error is large are overcome.

The invention provides a loudspeaker diaphragm tester with a controlled excitation source. The tester comprises a to-be-tested platform, the controlled excitation source, a laser displacement sensor and a control device. To-be-tested diaphragm is fixed on the to-be-tested platform. The laser displacement sensor is fixed on the to-be-tested platform. To-be-tested diaphragm and the laser displacement sensor are coaxially arranged on the to-be-tested platform. The control device inputs a control signal into the controlled excitation source. The controlled excitation source generates an excitation signal according to the control signal. The to-be-tested diaphragm is excited by an excitation signal generated by the controlled excitation source to generate vibration. The laser displacement sensor detects vibration information when the diaphragm vibrates. According to the tester, the to-be-tested diaphragm can be excited by the controlled excitation source to vibrate well; physical parameters of the diaphragm are obtained through various channels such as measuring air pressure and diaphragm displacement; and the tester has relatively high test precision and relatively high stability.

The invention discloses a trace gas measurement device and method with adoption of photo-acoustic spectroscopy. A photo-acoustic cell with a double-resonant-cavity structure is used for measurement, two resonant cavities have different lengths and radiuses but have the same resonance frequency, and the same to-be-measured gas enters the two resonant cavities from buffer gas chambers in two ends of the photo-acoustic cell and flows out from a buffer gas chamber between the two resonant cavities. The concentration of the gas is measured indirectly through differential resonance photo-acoustic signals of the two resonant cavities, the influence of related noise caused by a photo-acoustic effect in solids can be reduced obviously, the detecting signal to noise ratio of the photo-acoustic signals is increased, and the detection limit of the trace gas can be further improved.

The invention provides a light splitting slice and a laser coaxial range finder and application thereof. The laser coaxial range finder comprises a light beam source and comprises a second lens, the light splitting slice, and a first lens which are successively arranged along an optical axis direction. The light splitting slice is provided with a half reflection zone and a reflection zone. Light beams emitted from the light beam source pass the half reflection zone and the first lens to form parallel light beams to irradiate a target object. Light beams reflected by the target object are converged by the first lens and are reflected by the reflection zone and the half reflection zone to a measurement position or observation position. A light-slitting system can be used in a measurement system or observation system. The laser coaxial range finder solves a problem that laser reflected by an object leaks so as to cause a detection blind spot in a pitting method. The laser coaxial range finder improves a detection signal-to-noise ratio, and achieves coaxial measurement of common objects and coaxial measurement of far objects, weak-reflection objects, and mirror objects.

The invention discloses a time division multiplexing based single-detector all-fiber polarization lidar. The lidar adopts all-fiber link, utilizes a delay fiber to realize time division multiplexing, and uses a single detector to realize simultaneous detection of parallel polarization signals and vertical polarization signals in radar echoes. Detection of atmospheric depolarization ratio is realized with the single detector, and the liar has the advantages of low cost, system stability, relative eye safety, all-fiber link, compact structure and the like.

The invention relates to a magnetic resonance multi-channel detection method and apparatus using a pre-polarization field to enhance the amplitude of a signal. The method comprises: a plurality of direct-current transmitting coils and a direct-current /alternating-current transmitting coil are set, direct currents are emitted to form a pre-polarization field, and the magnetization intensity of hydrogen protons in water is enhanced; after emission for a period of time, the direct currents are cut off, the direct-current /alternating-current transmitting coil emits an alternating current with aLarmor frequency to excite the hydrogen protons to generate a magnetic resonance phenomenon; after the alternating current is cut off, the hydrogen protons release freely-sensing attenuation magneticresonance signals, and a plurality of receiving coils and one reference coil are set to measure magnetic resonance signals and noise signals; and the alternating current amplitude is controlled to complete measurement of different pulse torques. Therefore, the signal amplitude is enhanced; the detection signal-to-noise ratio is increased; and detection on a non-layered complex water-containing structure is carried out to realize multi-dimensional magnetic resonance measurement of a uniform pre-polarization field in a high-noise environment like an environment with manual noises or serious power interference or a large tunneling area like a tunnel or mine.

The invention discloses a double-wavelength single receiving channel-based rotation Raman temperature measurement laser radar. The laser radar is based on two working wavelengths and a single receiving channel. The two working wavelengths of the laser radar are respectively composed of odd number pulses and even number pulses. The low-quantum-number rotation Raman signals of one working wavelength and the high-quantum-number rotation Raman signals of the other working wavelength are extracted by the receiving channel of the laser radar. The laser radar is operated alternately at the two working wavelengths in the time division multiplexing manner. The atmospheric temperature is calculated based on the ratio of high-quantum-number rotation Raman signals to low-quantum-number rotation Raman signals. According to the technical scheme of the invention, the rotation Raman temperature measurement is realized only by means of a single filter, a single detector and a single acquisition card. Compared with a single-wavelength double receiving channel-based rotation Raman temperature measurement laser radar, the above laser radar is compact in structure, wherein the difficulty of optical path adjustment and the difficulty of system parameter calibration are lowered. Meanwhile, the double-wavelength single receiving channel-based rotation Raman temperature measurement laser radar is low in cost. The working performance difference between the filter and the detector caused by the inconsistence of working environments can be avoided. Moreover, the detection accuracy, the system stability and the environmental adaptability are improved.

The invention provides a type of fluorescent probes for detecting formaldehyde. The probes have the structures shown as formulas I to IV. Benzene ring correspondingly substituted coumarin is firstly subjected to backflow reaction with Lawson reagents in toluol; an obtained product continuously performs backflow reaction with hydrazine hydrate in ethanol. The fluorescent probes per se provided by the invention do not have fluorescence in the water solution, but can take a specific fast reaction with formaldehyde to produce products with strong fluorescence, so that the specific sensitive detection and quantitative analysis of formaldehyde is realized. The stability is high; the long-time storage use can be realized; the detection signal-to-noise ratio is high; the sensitivity is high; the excellent selectivity is realized; the specific formaldehyde detection in complicated biological samples can be realized; good biomembrane permeability is realized, so that the fluorescent probes can be used for formaldehyde detection in living cells; the detection reaction is fast; the detection result can be given within 1 minutes for formaldehyde in the water solution; during the formaldehyde detection, the formaldehyde concentration in the environment cannot be influenced. The general molecular formulas of the probes provided by the invention are shown as the accompanying drawing.

The invention provides a device of detection time-resolved transient absorbance spectrum. The device includes a pumping unit, a detection unit, and an analysis unit. The pumping unit is used for emitting pulse laser to pump and stimulate the sample to be measured. The detection unit is used for emitting wide spectrum detection beam to irradiate the pumped and stimulated area of the sample to be measured. The analysis unit is used for analyzing the changes of the absorption spectrum and absorbancy of the wide spectrum detection beam of the sample to be measured before and after suffering pumping and stimulating. The detection unit comprises a light intensity or phase modulator, and the analysis unit comprises an optical filter and a lock-in amplifier.

The disclosed device comprises three pieces of parallel placed convex lenses with coincided centerlines, a beam splitting plate, a plane reflector and a Bragg acousto-optic modulator. Received by lens 1 and passing through lens 2, an inquire light becomes a narrow beam. Then, passing through the beam splitting plate, the beam is divided into a transmission light and a reflection light. The transmission light is a receiving signal. Reflected by the plane reflector, the reflection light forms an echo light beam and passing through the Bragg acousto-optic modulator to return in direction parallel to the inquire light. Diaphragm and light filter can be added to the device to filter the inquire light in space and frequency in order to raise detection SNR at response party. Features are: small loss of luminous energy, simple structure, and small size. Moreover, the invention increases communication and identification distances, and possesses better modulation effect.

The invention provides a low light level imaging detector. The detector comprises a casing (7), an input window (1), a photoelectric cathode layer (2), a micro-channel-plate image enhancer (3), an inductive coding anode (4), vacuum electrodes (6) and electrode leads (5), wherein the input window (1) and the metal casing (7) form an enclosed high-vacuum environment, and the photoelectric cathode layer (2), the micro-channel-plate image enhancer (3), the inductive coding anode (4) and the electrode leads (5) are all arranged in the high-vacuum environment. The low light level imaging detector can effectively reduce the aberration of a detection image, reduce the amount of used optical components and improve the imaging quality, and also has the advantages of simple structure, reasonable design, simple preparation process, high preparation efficiency and high quality.

An ultraviolet laser bioparticle counter for measuring the diameter and biological characteristics of the bioparticles suspended in air is composed of ultraviolet laser lighting path using ultraviolet laser device as light source, scattered light receiving path, fluorescence receiving path, and sampling air channel. It is characterized by that the filter in scattered light receiving path can reflect all fluorescence and the filter in fluorescence receiving path can reflect all ultraviolet laser beam. Its advantages are multiple function, and high sensitivity, receiving efficiency and S/N ratio.

The invention provides a GNSS long code signal capturing method and device assisted by a low earth orbit satellite. The GNSS long code signal capturing method assisted by the low earth orbit satellitecomprises the following steps: acquiring GNSS baseband signals; performing frequency mixing operation; performing segment correlation operation; performing long-time coherent integration; carrying out incoherent integral operation; and performing peak detection and threshold judgment. The method and the device have the advantages that GNSS navigation signal auxiliary information, including roughDoppler information and rough code phase information, is acquired under the assistance of a low-orbit satellite, so that on one hand, the rough code phase information is used for generating sub-codesof local ranging codes and participating in related operation; it is guaranteed that the influence of bit hopping on coherent integration time is eliminated after correlation operation, high-sensitivity capturing of long codes is achieved through long-time coherent integration, and the long code signal capturing performance in the low signal-to-noise ratio environment is improved; and on the otherhand, rough Doppler information and rough code phase information of the GNSS navigation signals are utilized, the searching time of the signals in the frequency dimension and the code dimension is shortened, the capturing efficiency is improved, and rapid capturing of GNSS long code signals is achieved.

The invention provides a flow-through fluorescence detection cell. The flow-through fluorescence detection cell comprises an upper clamping member, a lower clamping member and a quartz tube. The upper clamping member has a cylindrical structure, the lower end surface of the upper clamping member is provided with a through rectangular upper groove, and the upper end surface of the upper clamping member is downward vertically provided with a light through hole; the top of the lower clamping member is provided with a through rectangular lower groove; and the quartz tube is clamped between the upper groove and the lower groove as a flow-through cell, and the through directions of the upper groove and the lower groove parallel to the axial direction of the quartz tube. Light from a light source goes through the through hole and irradiates to the quartz tube, and strongly reflected excitation light generated by an air-quartz tube external surface optical interface is blocked by two inner side edges of the upper groove, and cannot be propagated to a fluorescence collection light path, so the high background noise caused by reflected excitation light is effectively weakened, and the detection signal-to-noise ratio is improved. The detection cell has the advantages of simple structure and easy manufacturing, and is suitable for capillary electrophoresis, liquid chromatography and flow analysis fluorescence detectors.