1388 results about "Pulse compression" patented technology

An apparatus generates femtosecond pulses from laser amplifiers by nonlinear frequency conversion. The implementation of nonlinear frequency-conversion allows the design of highly nonlinear amplifiers at a signal wavelength (SW), while still preserving a high-quality pulse at an approximately frequency-doubled wavelength (FDW). Nonlinear frequency-conversion also allows for limited wavelength tuning of the FDW. As an example, the output from a nonlinear fiber amplifier is frequency-converted. By controlling the polarization state in the nonlinear fiber amplifier and by operating in the soliton-supporting dispersion regime of the host glass, an efficient nonlinear pulse compression for the SW is obtained. The generated pulse width is optimized by utilizing soliton compression in the presence of the Raman-self-frequency shift in the nonlinear fiber amplifier at the SW. High-power pulses are obtained by employing fiber amplifiers with large core-diameters. The efficiency of the nonlinear fiber amplifier is optimized by using a double clad fiber (i.e., a fiber with a double-step refractive index profile) and by pumping light directly into the inner core of this fiber. Periodically poled LiNbO3 (PPLN) is used for efficient conversion of the SW to a FDW. The quality of the pulses at the FDW can further be improved by nonlinear frequency conversion of the compressed and Raman-shifted signal pulses at the SW. The use of Raman-shifting further increases the tuning range at the FDW. For applications in confocal microscopy, a special linear fiber amplifier is used.

A laser utilizes a cavity design which allows the stable generation of high peak power pulses from mode-locked multi-mode fiber lasers, greatly extending the peak power limits of conventional mode-locked single-mode fiber lasers. Mode-locking may be induced by insertion of a saturable absorber into the cavity and by inserting one or more mode-filters to ensure the oscillation of the fundamental mode in the multi-mode fiber. The probability of damage of the absorber may be minimized by the insertion of an additional semiconductor optical power limiter into the cavity. To amplify and compress optical pulses in a multi-mode (MM) optical fiber, a single-mode is launched into the MM fiber by matching the modal profile of the fundamental mode of the MM fiber with a diffraction-limited optical mode at the launch end, The fundamental mode is preserved in the MM fiber by minimizing mode-coupling by using relatively short lengths of step-index MM fibers with a few hundred modes and by minimizing fiber perturbations. Doping is confined to the center of the fiber core to preferentially amplify the fundamental mode, to reduce amplified spontaneous emission and to allow gain-guiding of the fundamental mode. Gain-guiding allows for the design of systems with length-dependent and power-dependent diameters of the fundamental mode. To allow pumping with high-power laser diodes, a double-clad amplifier structure is employed. For applications in nonlinear pulse-compression, self phase modulation and dispersion in the optical fibers can be exploited. High-power optical pulses may be linearly compressed using bulk optics dispersive delay lines or by chirped fiber Bragg gratings written directly into the SM or MM optical fiber. High-power cw lasers operating in a single near-diffraction-limited mode may be constructed from MM fibers by incorporating effective mode-filters into the laser cavity. Regenerative fiber amplifiers may be constructed from MM fibers by careful control of the recirculating mode. Higher-power Q-switched fiber lasers may be constructed by exploiting the large energy stored in MM fiber amplifiers.

The present invention relates to an ultrasound imaging system in which the scan head includes a beamformer circuit that performs far field subarray beamforming or includes a sparse array selecting circuit that actuates selected elements. When using a hierarchical two-stage or three-stage beamforming system, three dimensional ultrasound images can be generated in real-time. The invention further relates to flexible printed circuit boards in the probe head. The invention furthermore relates to the use of coded or spread spectrum signalling in ultrasound imaging systems. Matched filters based on pulse compression using Golay code pairs improve the signal-to-noise ratio thus enabling third harmonic imaging with suppressed sidelobes. The system is suitable for 3D full volume cardiac imaging.

An ultrasound imaging method for forming an image of an object using received signals reflected from the object, received after transmitting an ultrasound pulse to the object. The inventive method comprises the steps of (a) transmitting a first set of the ultrasound pulses to the object by applying voltages according to a first code of a pair of modified Golay codes to one or more transducers; (b) performing pulse compression on a first set of reflected signals of the first set of the ultrasound pulses reflected from the object; (c) transmitting a second set of the ultrasound pulses to the object by applying the voltages according to a second code of the pair of the modified Golay codes to said one or more transducers; (d) performing pulse compression on a second set of reflected signals of the second set of the ultrasound pulses reflected from the object; (e) adding the pulse compressed signals of the first and the second sets of the reflected signals; (f) producing a receive-focused signal by using the added signal; and (g) displaying the image according to the receive-focused signal after signal processing.

Systems and method for manipulating optical pulses to implement an optical switch and for pulse shaping (e.g., pulse compression and/or compression) are disclosed. In one embodiment, the system comprises an optical switch apparatus that includes a plurality of resonators optically coupled to a waveguide, two output waveguides, an input light source, a control light source. The system selects some of the input signals emitted from the input light course using control signals emitted from the control light source to route to one of the output waveguides. In another embodiment, the system includes a waveguide optically coupled to a plurality of resonators, input light source, optional resonator modules that can change the refractive index of the resonators, and an optional amplifier. This system can change the shape of the pulses by changing a number of parameters, such as the incoming pulse amplitude and/or the refractive index of the resonators.

The present invention discloses an ultrasound imaging system and method based on simultaneous multiple transmit-focusing using the weighted orthogonal chirp signals so that resolution of an ultrasound image is enhanced without sacrifice in the frame rate. The ultrasound imaging system according to the present invention includes: a storing means for storing weighted orthogonal signals including N number of orthogonal codes wherein the orthogonal codes are orthogonal to each other; a transmitter for transmitting simultaneously the weighted orthogonal signals as ultrasound transmission signals to corresponding N number of focal points within the target object; a receiver for receiving signals reflected from the N number of focal points corresponding to the transmitted ultrasound signals; a pulse-compressor for pulse-compressing with respect to each orthogonal code by extracting the stored N number of orthogonal codes from the reflected signals; a producer for producing receive-focused signals from the pulse-compressed signals; and a display for displaying the receive-focused signals by processing them. As a result, transmission signals are simultaneously transmitted to the plurality of focal points and received signals are separated on reception, thereby improving resolution without sacrifice in the frame rate.

The invention relates to a high precision speed and distance measuring laser radar system and a speed and distance measuring method. The basic principle of the invention is as follows: linear chirp modulation and pseudo-random code modulation of lasers are performed; most lasers after modulation are taken as outgoing lasers and transmitted by a telescope; a small part of the lasers is taken as local oscillator beams and used for coherent detection; laser echo signals are divided into two parts; distance information is obtained after related operation of one part of the laser echo signals and original pseudo-random codes; the frequency difference of the local oscillator beams and echo signal beams is obtained after coherent detection of the other part of the laser echo signals and the local oscillator beams and pulse compression, and simultaneously comprises the distance information and Doppler shift; the Doppler shift is obtained through mathematical manipulation, thereby speed information is obtained. The high precision speed and distance measuring laser radar system and a speed and distance measuring method of the invention is characterized in that the speed information and the distance information of a target can be obtained with high precision.

An indoor ultrasonic location tracking system that can utilize standard audio speakers to provide indoor ranging information to modern mobile devices like smartphones and tablets. The method uses a communication scheme based on linearly increasing frequency modulated chirps in the audio bandwidth just above the human hearing frequency range where mobile devices are still sensitive. The method uses gradual frequency and amplitude changes that minimize human perceivable (psychoacoustic) artifacts derived from the non-ideal impulse response of audio speakers. Chirps also benefit from Pulse Compression, which improves ranging resolution and resilience to both Doppler shifts and multi-path propagation that plague indoor environments. The method supports the decoding of multiple unique identifier packets simultaneously. A Time-Difference-of-Arrival pseudo-ranging technique allows for localization without explicit synchronization with the broadcasting infrastructure. An alternate received signal strength indicator based localization technique allows less accurate localization at the benefit of sparser transmission infrastructure.

This invention provides methods of treatment for work products of materials such as steel, bronze, plastic, etc. and particularly welded steel bodies by pulse impact energy, preferably ultrasonic, to relax fatigue and aging and extend expectant life. The treatment may occur (a) at original production, (b) during the active life period for maintenance or (c) after failure in a repair stage. The ultrasonic treatment improves the work product strength. In welded products residual stress patterns near the weld sites are relaxed and micro-stress defects such as voids and unusual grain boundaries are reduced. The basic method steps are non-destructive in nature, inducing interior pulse compression waves with ultrasonic transducers and accessory tools impacting an external product surface with enough impulse energy to heat and temporarily plasticize the metal interior and relax stresses. The nature of the work product interior structure being treated is determined by sensing the mechanical movement at the impact surface of the work body to produce feedback frequency and phase signals responsive to input impact signals. These signals automatically conform driving pulse energy frequency and phase to the input transducers to match the mechanical resonance frequency of the working transducers and increase efficiency of energy transfer. Such feedback signals also are available for automated procedures which can improve product quality and consistency.

A saturable absorber (SA) is constructed using a fiber taper embedded in a carbon nanotube/polymer composite. A fiber taper is made by heating and pulling a small part of standard optical fiber. At the taper's waist light is guided by the glass-air interface, with an evanescent field protruding out of the taper. Carbon nanotubes mixed with an appropriate polymer host material are then wrapped around the fiber taper to interact with the evanescent field. Saturable absorption is possible due to the unique optical properties of the carbon nanotubes. The device can be used in mode-locked lasers where it initiates and stabilizes the pulses circulating around the laser cavity. The SA can be used in various laser cavities, and can enable different pulse evolutions such as solitons, self-similar pulses and dissipative solitons. Other applications include but are not limited to optical switching, pulse cleanup and pulse compression.

The invention discloses a target detection method based on Keystone and matched filtering and belongs to the radar weak signal detection technology field. The method comprises steps that firstly, a radar is utilized to emit a chirp signal, pulse compression for a received target echo signal is carried out, and first-order range migration caused by no fuzzy speed of a target is corrected through utilizing Keystone transformation; secondly, a fuzzy speed multiple and acceleration of the target are estimated through utilizing combined two-dimensional matched filtering processing of a distance frequency domain, and first-order range migration caused by the fuzzy speed of the target and second-order range bending and Doppler migration caused by acceleration are corrected and compensated; and lastly, phase-coherent accumulation of target energy is realized through fast Fourier transform, and a peak value of phase-coherent accumulation is utilized to carry out target detection. The method is advantaged in that amplitude and the phase information of target echoes are utilized to carry out long time phase-coherent accumulation, so a radar echo signal-to-noise ratio can be effectively improved, and target detection performance of the radar can be improved.

The invention belongs to the technical field of the power supply, in particular to an all solid state high voltage nanosecond pulse power supply. The power supply is divided into the following two parts: a series voltage booster circuit and a pulse compression circuit, wherein the series voltage booster circuit consists of a series of voltage units which are connected in series to realize the function of voltage boost; each voltage unit is provided with a capacitor connected with a switch which can be connected and disconnected, and capacitors of the series of the voltage units form a capacitor unit; one part in the switch is a charge switch to charge the capacitors in parallel, while the other part is a discharge switch to discharge the capacitors in series; the pulse compression circuit is connected with a magnetic switch in a series connection mode by an energy storage capacitor or a sharpening capacitor. The power supply reduces system volume to connect more voltage units in series, and uses a direct current charge power supply with lower voltage to charge a pulse generator; the adopted switch device generator has longer service life and higher frequency; and the used magnetic switch reduces rise time of voltage pulse output by a Marx circuit, and is free of maintenance and has low failure rate.

The invention provides a method for acquiring and imaging data of compressive sensing synthetic aperture radar. The method comprises the following steps of: 1, selecting an observation scene; 2, emitting a Chirp signal by a radar antenna; 3, receiving a distance direction signal of the synthetic aperture radar; 4, constructing a compressive sensing restoring matrix; 5, correcting distance compression and distance migration; 6, constructing an orientation direction filter matrix; and 7, compressing towards the orientation direction. By the method for acquiring and imaging the data, aiming at realizing great reduction of radar stored and transmitted data quantity in the special observation scene and synchronously realizing restoring of a distance direction pulse compression signal and correction of the distance migration, the problem that interpolation calculation cannot be performed on a compressive sensing restoring signal is solved.

The invention concerns a method of synthesizing a replica used in the compression filter of pulse compression radar. The replica is calculated from the spectrum of a required impulse response. The required impulse response is preferably obtained from an analytical function, such as a sinc function or a weighted sinc function, and a template. It is preferable to use calibration signals of the instrument to calculate the replica. The invention also applies to synthetic aperture radar.

The invention discloses an apparatus of generating microwave phase coding signals in an optical manner, and relates to the microwave technology field and the optical communication technology field. The apparatus is mainly applied to generating pulse compression signals in pulse compression radar. By means of the frequency shift characteristics of two parallel Mach-Zehnder modulators, the optical wavelength modulated by coding signals and the optical wavelength after a frequency shift are coupled to each other and then are detected through a photoelectric detector, in this way, phase coding microwave signals can be generated. The apparatus can produce binary, quaternary or multi-nary phase coding microwave signals. The generated phase coding microwave signals are wide in frequency adjustable scope, and have a great time-bandwidth product. A conventional phase coding microwave signal generation mode in the electric field is restricted by the bottleneck of the rate and the bandwidth of an electronic device, and the cost of generation of high frequency signals is extremely high or high frequency signals cannot be produced, the time-bandwidth product is limited, the reconstructiblity and the frequency adjustability of a system are poor, etc. The apparatus of the invention helps to overcome the above problems.

The invention discloses a method for controlling microwave vehicle detecting radar, comprising the following steps: microwave detecting radar work parameter is evaluated; pulse compression in the range direction is carried out; sub-echo of each target vehicle is respectively extracted, and whether advancing vehicle exists is judged, speed search is carried out on data of each sub-echo of advancing vehicle, one matched filtering function is obtained after each search, pulse compression in the azimuth direction is carried out, and then the kurtosis value is calculated; if the largest kurtosis value is obtained, the search speed corresponding to the largest kurtosis value is the traveling speed of the vehicle, frequency modulation slope in the azimuth direction is calculated according to the speed and pulse compression in the azimuth direction is carried out, and then signals of each range gates are added and are compared with the set threshold to obtain vehicle length; if the largest kurtosis value is not obtained, then search is kept on by returning to the previous step. The invention has numerous monitoring lanes, wide detection range and more precise detecting speed, can detect vehicle with low speed or even standing vehicle precisely, and can estimate vehicle length, thereby facilitating traffic control.

The invention discloses a radar foresight super-resolution imaging method which specifically includes: distance toward pulse compression, distance walking corrosion, distance toward inverse fast fourier transform (IFFT), determination of iterations and azimuth deconvolution. The radar foresight super-resolution imaging method performs azimuth modeling on echo scanned by a radar antenna in foresight mode to enable the echo to be in convolution, and estimates front ground feature distribution information in a deconvolution method; and additionally, based on noise statistical property, optimum iterations can be determined according to iteration deconvolution, so that radar can obtain better foresight super-resolution imaging performance. Compared with the background technology, the radar foresight super-resolution imaging method overcomes the restrains on scene of a single-pulse imaging technology and limitation on platform dimension of an array imaging method, further solves the problems of complex synchronization, motion compensation and the like of double-foundation synthetic aperture radar (SAR) and can effectively obtain ground feature distribution information of the area dead ahead the platform.

The invention relates to a sea surface micro-motion target Radon-linear contact transformation (RLCT) long-time phase-coherent accumulation detecting method which belongs to the technical field of radar signal processing and detection. The method comprises the following steps: (1) performing demodulation and pulse compression on radar echo, and completing calculation in pulse; (2) pre-judging sea conditions and detection target types and determining long-time phase-coherent accumulation parameters; (3) adopting RLCT compensation distance and Doppler migration and calculating micro-motion target signal energy; (4) viewing and searching parameters and establishing a distance-RLCT area detection unit graph, and carrying out constant false-alarm detection on the distance-RLCT area detection unit graph; and (5) evaluating micro-motion feature parameters, and outputting motion trace points. The sea surface micro-motion target Radon-linear contact transformation long-time phase-coherent accumulation detecting method applies sea surface target micro-motion features to target detection, meanwhile utilizes range and phase information of the echo to perform long-time phase-coherent accumulation to carry out long-time phase-coherent accumulation, effectively compensates distance and the Doppler migration, improves accumulation gain, has the capacity to detect a micro-motion target in strong clutter, can obtain the motion trace points of the target, and has popularization application value.

The invention discloses a radar detection method based on generalized keystone transformation and non-coherent accumulation, wherein the method mainly solves the detection problem of a high speed and highly accelerated target in a strong Gaussian white noise background. The method is implemented by the following steps: (1) generating radar target multiple-pulse echoes with Gaussian white noise added, and performing frequency domain pulse compression; (2) correcting range curvature of the pulse-compressed echoes by using the generalized keystone transformation; (3) performing fuzzy compensation on the curvature-corrected echoes by using a fuzzy factor; (4) performing non-coherent accumulation on the fuzzy-compensated echoes, and performing velocity compensation and slow time dimensional quadratic term compensation on the echoes by using a target velocity obtained in the non-coherent accumulation; (5) performing coherent accumulation on the slow time dimensional quadratic term compensated echoes to obtain the target to be detected. The method provided in the invention can eliminate effects of the range curvature and migration of the echoes on energy accumulation, can reduce computation of velocity search, and can be used in the detection of the target in the strong Gaussian white noise background.

A gas discharge laser crystallization apparatus and method for performing a transformation of a crystal makeup or orientation in the substrate of a workpiece is disclosed which may comprise, a multichamber laser system comprising, a first laser unit comprising, a first and second gas discharge chamber; each with a pair of elongated spaced apart opposing electrodes contained within the chamber, forming an elongated gas discharge region; a laser gas contained within the chamber comprising a halogen and a noble gas selected to produce laser light at a center wavelength optimized to the crystallization process to be earned out on the workpiece; a power supply module comprising, a DC power source; a first and a second pulse compression and voltage step up circuit connected to the DC power source and connected to the respective electrodes, comprising a multistage fractional step up transformer having a plurality of primary windings connected in series and a single secondary winding passing through each of the plurality of primary windings, and a solid state trigger switch; and a laser timing and control module operative to time the closing of the respective solid state switch based upon operating parameters of the respective first and second pulse compression and voltage step up circuit to effect operation of the first and second laser units as either a POPA configured laser system or a POPO configured laser system to produce a single output laser light pulse beam. As a POPA laser system relay optics may be operative to direct a first output laser light pulse beam from the first laser unit into the second gas discharge chamber; and, the timing and control module operates to create a gas discharge between the second pair of electrodes while the first output laser light pulse beam is transiting the second discharge region, within plus or minus 3 ns and as a POPO, combining optics combine the output beams, and timing creates pulse separation in the combined output a preselected time plus or minus 3 ns.

Laser amplification methods and apparatuses. With the invention, one can increase laser intensity on a target by computing a distance to the target, based upon the distance determining an ultra short laser pulse that will in traveling through a medium compress to approximately a minimum width, and emitting the pulse at the target, whereby an intensity of the pulse is approximately maximized upon contact with the target. One can also amplify and detect a laser return signal by receiving the laser return signal, amplifying the received return signal by optical parametric amplification and detecting the amplified signal. One can further perform spectroscopy by determining an ultra short laser pulse such that the pulse compresses and then expands in traveling through a medium, emitting the pulse at a target, and performing spectroscopic analysis of the pulse after propagation.

A pulsed compression noise correlation radar uses noise modulation and pulse compression technology to scramble recognizable transmit signal characteristics and reduce transmit energy. The pulsed noise correlation radar advantageously uses pulse compression technology, a pulsed linear frequency modulated noise correlation mixer, and a new and innovative noise fused waveform to automatically correlate the pulsed linear frequency modulated (LFM) noise waveform with the received signal. The pulsed noise correlation radar apparatus and system now make it possible to effectively reduce transmitting power, preserve high band widths through oversampling in the receiver, and achieve multi-channel array frequency diversity. A secure pulsed compression noise correlation radar system and methods for undetected target detection with pulsed noise correlation radar and a pulsed LFM fused noise waveform are also provided.

The invention relates to a radar moving target detection method based on short-time sparse fractional Fourier transform (ST-SFRFT), and belongs to the technical field of radar signal processing and detection. The method comprises the steps of: performing radar echo demodulation and pulse compression to realize high range resolution, and selecting a range unit to be detected; performing spare time-frequency analysis parameter initialization, comprising selection of a short-time window function and a window length and design of a sparse decomposition dictionary; performing ST-SFRFT operation for spare optimization solution, thus completing high-resolution spare time-frequency representation of moving target echo; traversing all range search units, performing moving target signal spare domain detection and estimating a target moving parameter. By adopting a high-resolution spare representation method, high-resolution and low-complexity time-frequency representation of time-varying signals is realized at the time frequency-spare domain; and the method is suitable for analyzing the time varying non-stability of signals, suppresses background clutter while improving energy concentration of moving target signals, and significantly improves the radar moving target detection and parameter estimation capability.