2311 results about "Frequency mixing" patented technology

A laser system capable of efficient production of high energy sub-nanosecond pulses in the 2-15 μm spectral region is disclosed. Diode pumped solid state lasers are used as pump sources. The system design is simple, reliable and compact allowing for easy integration. The laser system includes a combination of compact solid-state ˜1 micron laser sources, producing high power picosecond pulses, with optical parametric amplification and a quasi-continuous wave laser for seeding the amplification process that enables the efficient conversion of the high power ˜1 micron laser radiation to tuneable mid-infrared sub-ns pulses. New parametric processes are presented for achieving high gains in bulk nonlinear crystals. Furthermore, a method of exceeding the fundamental conversion efficiency limit of direct three wave mixing is presented. The compact and robust nature of this novel laser system opens up the use of high power and high peak power mid-infrared laser pulses to a wide variety of important medical and dental applications.

Disclosed are a system and method to detect RFID tags in electronic article surveillance systems using frequency mixing. The system includes an RFID module that includes an energy coupler to receive transmitted energy that includes a first signal at a first frequency and a second signal at a second frequency, and a mixing element to mix the first and second signals, to generate a third signal at a third frequency, and the energy coupler to transmit the third signal to an EAS detection system. Other embodiments are described and claimed.

The invention provides a personnel detection and counting system based on a millimeter wave radar, wherein the millimeter wave radar is installed at a set position of a monitoring area, the millimeterwave radar transmits millimeter wave band radio frequency signals to the monitoring area through a multi-transmitting and multi-receiving antenna of the millimeter wave radar and receives echo signals at the same time, the echo signals are subjected to frequency mixing with the transmitted signals and then subjected to down-conversion to obtain beat intermediate frequency signals, and the beat intermediate frequency signals are sampled to obtain an echo sampling sequence. A digital signal processor reads the echo sampling sequence and performs signal processing to obtain a detected point cloud data set. An ARM processor reads the point cloud data set, meanwhile, Kalman filtering tracking is carried out on the point cloud data, continuous observation of states and the number of a pluralityof human body moving targets is achieved, the positions and the number of people in the monitoring area are obtained, and the number of people in the monitoring area is counted. The personnel detection and counting system based on the millimeter wave radar can track at least 20 targets simultaneously, provide the position and speed information of the targets, effectively judge the state of the targets and give early warning in time.

The invention discloses a multi-mode multi-frequency global navigational satellite system receiver radio frequency front end device. The device comprises a low-noise amplifier, a power divider, and multiple radio-frequency signal processing circuits, wherein the low-noise amplifier, the power divider, and the multiple radio-frequency signal processing circuits are connected in sequence. Each radio-frequency signal processing circuit comprises a first radio-frequency switch, a radio-frequency filter bank, a second radio-frequency switch, a radio-frequency amplifying module, a lower frequency mixing module, an intermediate frequency filter module, an intermediate frequency amplifying module, and an automatic gain control unit, wherein the first radio-frequency switch, the radio-frequency filter bank, the second radio-frequency switch, the radio-frequency amplifying module, the lower frequency mixing device, the intermediate frequency filter module, the intermediate frequency amplifying module, and the automatic gain control unit are connected in sequence. The lower frequency mixing module comprises a lower frequency mixing device and a local oscillating generating module which are connected with each other. A control unit is connected with the first radio-frequency switch and the second radio-frequency switch of each radio-frequency signal processing circuit and the local oscillating generating module of the lower frequency mixing module. The device can flexibly select intermediate frequency inputting from various combination frequency ranges of a quad-mode 11 frequency range, and therefore functions of collecting in the same module and processing navigation system intermediate frequency signals of four system satellites are realized, namely a global position system (GPS), Glonass, Galileo, and Big Dipper.

The invention discloses a measuring method for electrical resistivity of electromagnetic waves while drilling, comprising the following steps: generating an electromagnetic wave power signal with specific frequency; emitting the electromagnetic wave power signal into a ground layer through an emitting antenna coil; receiving two electromagnetic wave power signals including measured ground layer information through two receiving antenna coils so as to generate two paths of electromagnetic wave power signals including the measured ground layer information; carrying out band-pass filtering to the two paths of the electromagnetic wave power signals including the measured ground layer information, and carrying out AD sampling to the two paths of the electromagnetic wave power signals including the measured ground information which is subjected to the band-pass filtering so as to generate two paths of electromagnetic sampling digital signals; carrying out frequency mixing transformation and low-pass filtering to the electromagnetic wave sampling digital signals so as to generate amplitude value information and phase information; generating amplitude value ratio and phase difference according to the amplitude value information and the phase information; and generating an electrical resistivity drawing board of the electromagnetic wave power sinals in a chart inversion method according to the amplitude value ratio and the phase difference. An embodiment of the invention also discloses a measuring device for the electrical resistivity of the electromagnetic waves while drilling.

Several methods are disclosed for the generation of coherent short-wavelength electromagnetic radiation through optical nonlinear frequency mixing means. The invention involves several stages of efficient nonlinear frequency conversion to shift the output of high-power infra-red fiber-lasers into the vacuum ultraviolet (VUV). The described laser source architecture is designed around non-critically phase-matched (NCPM) sum-frequency mixing (SFM) interactions in the nonlinear crystal CLBO. The NCPM interaction is an optimum condition for bulk frequency conversion of cw radiation because it allows tight focusing of the input laser radiation without Poynting vector walk-off, thereby increasing the non-linear drive significantly. The sub-200-nm output wave is generated from SFM of a long-wave IR laser field and a short-wave UV laser field. The long-wave laser beam may be derived directly from a rare-earth-doped fiber laser, whereas the short-wavelength UV beam is provided as the fourth frequency harmonic of a second rare-earth-doped fiber laser system.

The embodiment of the invention discloses a radio-frequency module, a transceiver and a method for switching control of the transceiver. The radio-frequency module comprises a first receiving amplification branch, a first receiving frequency mixer, a second receiving frequency mixer, a frequency mixing switching module and a control module, wherein the first receiving amplification branch is connected with the first receiving frequency mixer; the frequency of a local oscillation signal adopted by the first receiving frequency mixer is more than, less than or equal to that of a local oscillation signal adopted by the second receiving frequency mixer; and the control module is used for controlling the frequency mixing switching module to establish a connection between the first receiving amplification branch and the second frequency receiving mixer, or controlling the frequency mixing switching module to switch off the connection between the first receiving amplification branch and the second receiving frequency mixer. In the technical proposal provided by the embodiment of the invention, the radio-frequency module of the transceiver adopts an expandable framework, can expand the framework and switch working modes as required, and can adapt to various application scenes.

A low-interception speed measurement method comprises the steps that 1, frequency modulated continuous waves are generated, echo signals of an object with measured speed are received through an antenna, frequency mixing is carried out on the echo signals and B-path signals, and baseband signals are obtained; 2, the baseband signals are converted into digital signals, sampling and zero filling are carried out, FFT is carried out on the rising part of trace frequency, FFT is carried out on the reduction part of return trace frequency after conjugate taking, and frequency spectrums corresponding to positive/negative frequency modulation slopes are obtained; 3, the frequency spectrums corresponding to the positive/negative frequency modulation slopes are subtracted after module taking, the difference value is changed into an absolute value, and an objective frequency spectrum is obtained; 4, whether an object to be detected exists or not is determined, and if the object to be detected exists, the frequency corresponding to two peak value points within the frequency spectrum normalization range is found out in the objective frequency spectrum, and the speed of the object to be detected is worked out. The invention further discloses a low-interception speed measurement radar. The low-interception speed measurement method and radar have the advantage that the probability that the lower-measurement-speed radar is intercepted by a radar detector can be effectively reduced due to the adoption of the frequency modulated continuous waves with low-interception-probability wave forms.

A method for measuring Brillouin backscattering from an optical fibre (18), comprises frequency mixing a first signal with a frequency f B (t) representative of the Brillouin frequency shift in backscattered light received from a deployed optical fibre with a second signal at a frequency f i (t) that varies in time in the same manner as a Brillouin shift previously measured from the fibre to produce a difference signal with a difference frequency iF(t) that has a nominally constant value corresponding to the situation where the received light has a Brillouin shift that matches the previously measured shift. The difference signal is acquired and processed to determine properties of the Brillouin shift and corresponding physical parameters producing the shift. The frequency mixing can be carried out. optically or electrically. Techniques for acquisition of the difference signal include the use of parallel frequency measurement channels and fast rate digital sampling.

The invention discloses a wireless terminal transceiver of a 60GHz RoF (Radio over Fiber) access system. Secondary subharmonic frequency mixing is adopted, and the frequency of a needed local oscillation signal is reduced in a frequency multiplication frequency mixing way, so that the problem of leakage of the local oscillation signal to an antenna, i.e., a radiofrequency transmitting end in the conventional wireless terminal transceiver scheme is solved, and the circuit modulation performance is improved. Meanwhile, a downlink medium frequency analog signal obtained after secondary subharmonic down-conversion is subjected to downlink medium frequency digital signal processing after ADC (Analog to Digital Conversion) to obtain a needed downlink digital baseband signal; and an uplink digital baseband signal is subjected to uplink medium frequency digital signal processing to obtain an uplink medium frequency digital signal. A series of medium frequency digital signal processing such as odd-even extraction or interpolation, symbol modulation, delay filtering, demodulation or modulation and the like is performed in a digital domain, so that the problem of IQ orthogonal mismatch caused by 90-degree phase change on a local oscillation signal for obtaining two paths of analog signals in an analog frequency domain of the conventional receiver is solved.

The invention discloses a fully-digital direct sequence spread spectrum communication system and a rapid pseudo code capturing method thereof. A digital signal is processed by using an FPGA (Field Programmable Gate Array) which comprises a pseudo code capturing module, a sampling signal of an ADC (Analog To Digital Converter) is subjected to frequency mixing with a signal of a local carrier NCO (Numerically Controlled Oscillator) and filtered to obtain a baseband signal, residual carrier Doppler frequency is eliminated from the baseband signal by adopting a differential multiplying mode, thus the phase deviation of a receiving signal and a local pseudo code is further obtained through an FFT (Fast Fourier Transform) algorithm without scanning on a carrier frequency domain; and when the phase deviation of the pseudo code is obtained, a local pseudo code phase is modified and is subjected to correlation degree of dissociation with the receiving signal, and the carrier Doppler frequency is figured out by using the FFT algorithm, and is compensated to a carrier NCO and a pseudo code NCO, thus carrier frequency capturing and pseudo code capturing are realized.

The invention brings forward a pulse laser coherent wind measuring radar, for the purpose of providing a pulse laser coherent wind measuring radar which has the advantages of high measuring precision, simple structure and convenient installation and debugging. The pulse laser coherent wind measuring radar is realized through the following technical scheme: a fiber pulse laser emission system is taken as an emission source for generating two beams of laser, one beam of high repetition frequency pulse sequence laser for wind field detection is directly coupled through an optical circulator and enters an optical transmit-receive scanning system to perform collimated emission towards a target spatial domain, the optical circulator utilizes a polarization splitting characteristic to carry out isolation splitting on emission light and air aerosol scattering echo wave light, the air aerosol scattering echo wave light is selected to enter a fiber combiner, the other beam of laser, generated by the fiber pulse laser emission system, is taken as local oscillator light for inputting into a balance amplification photoelectric detector together with the echo wave light in a frequency mixing mode for optical amplification of a frequency mixing signal, through acquisition processing of a signal acquisition processor, the radial speed of each range gate in a current laser emission direction is calculated, and the radial speeds are transmitted to a radar operation display interface.

The invention discloses a delay-locked-loop-based remote microwave signal phase-stabilized optical fiber transmission device, which realizes the phase synchronization of a local microwave signal and a remote microwave signal by utilizing a delay-locked loop. The device realizes optoelectronic heterodyne mixing by utilizing the nonlinear effects of an optoelectronic modulator for phase detection, drives and controls a microwave delayer by feeding a phase difference signal back, performs phase change on the microwave signals, compensates microwave signal phase disturbance caused by the delay change of a transmission link, keeps a phase synchronism relationship between the local microwave signal and the remote microwave signal, solves the problem of phase asynchronism between the local microwave signal and the remote microwave signal, fulfills the aim of phase-stabilized transmission of the microwave signals, adopts noncoherent correction, and has the advantages of wide dynamic range, high stability and the like, besides a long phase-stabilized transmission distance.

The invention relates to a compressive-sensing-based sparse signal under-sampling method and an implementation device, which are used for lowering a sampling rate of frequency-domain sparse signals on the premise of guaranteeing the restoration effect of the signals. The method comprises the following steps of: generating a trigger signal and an m sequence by an FPGA (Field Programmable Gate Array), carrying out frequency mixing on the m sequence and the measured sparse signal after the m sequence is modulated, and carrying out filtering by a low pass filter; sampling the filtered signal and storing sampled data by a data sampling module after the data sampling module detects the triggering signal; and calculating a transfer function of a system and the m sequence corresponding to the sampled data when the signal is reconstructed, and then restoring the original signal by an OMP (Orthogonal Matching Pursuit) signal reconstructing algorithm. The compressive-sensing-based sparse signal under-sampling method and the implement device are suitable for the under-sampling of frequency-domain sparse analogue signals.

The invention discloses a Doppler radar-based non-contact type vibration measuring method. The method includes the following steps: S1. directly facing a measured vibration object to emit single-frequency microwaves in the form of continuous waves, and receiving radar echoes after modulation by vibration motion; S2. performing amplifying, filtering and quadrature mixing on echo signals and taking down conversion signals to obtain two paths of baseband signals I(t) and Q(t); S3. performing data collection on the baseband signals to obtain discrete digital signals; and S4. performing phase demodulation processing on the discrete baseband signal I[n] and Q[n], and extracting vibration amplitude and frequency information. The Doppler radar-based non-contact type vibration measuring method provided by the invention uses a microwave radar to perform non-contact type vibration measurement based on a Doppler effect, has good low frequency measurement sensitivity, is high in environmental adaptation, and can perform accurate vibration measurement under the condition of containing a barrier. The microwave radar used by the method is compact in structure and low in cost and has relatively low power consumption, thereby providing a solution to integration of a large-scale vibration measuring system.

A method for producing low-noise laser output at various wavelengths and/or in various operation modes in a monolithic microchip laser comprises schemes of generating two fundamental beams in separate cavities, precise intracavity beam combination based on the walk-off effect in birefringent crystal, and wavelength conversion in nonlinear optical crystals. The fundamental beams are produced from light sources selected upon the desired wavelengths, polarizations, and other features related to the laser output. Low-noise laser devices operated in SLM or with spectra of flat-top or desired bandwidths are constructed according to the method. High-volume fabrication is feasible. Apparatus of compact size and efficient frequency conversion is demonstrated with various configurations including those for generating low-noise 491 nm laser, as a replacement of Argon ion laser.

The invention discloses a film system structure for enhancing Terahertz radiation absorption rate and a preparation method of the film system structure, wherein the film system structure is located at the top layer of a sensitive unit of a Terahertz detector and comprises a dielectric thin film and a Terahertz absorption layer located on the dielectric thin film; the dielectric thin film is a low-stress silicon nitride or silicon oxide thin film prepared by PECVD (Plasma Enhanced Chemical Vapor Deposition) frequency-mixing technology and etched into a micro nanometer-level rough surface by reactive ions; and the Terahertz absorption layer is prepared on the rough-surface dielectric thin film via a magnetic control sputtering method. As surface-to-volume ratio of the Terahertz absorption layer is increased by the rough surface structure of the dielectric thin film, the Terahertz radiation absorption rate is effectively enhanced; and the preparation process is simple and reasonable, and large-area preparation and integration are easy to carry out, so that the film system structure can be widely applied to the field of various Terahertz detecting and imaging technologies and strong support is provided to the development of high-performance Terahertz detectors.

The invention relates to an automobile active anti-collision radar based on pseudorandom code and linear frequency modulated continuous wave, belonging to the field of automobile radar, comprising a pseudorandom code and linear frequency modulated control signal generator, a pseudorandom code and linear frequency modulated continuous wave emitter, a sending antenna, a receiving antenna, a low-noise amplification mixed frequency receiving channel, a linear frequency modulated signal processing and pseudorandom code multi-path parallel correlation processor, a parallel data processor and an executing terminal. The pseudorandom code is used for modulating the phase of radar carrier wave and performing linear frequency modulation to the radar carrier wave so as to form a double-modulation emitting signal. Two systems are combined, so that the inhibition ability of interference echo is improved; the false alarm caused by false targets is removed; different codes of different automobile radars are achieved; the interference caused by the automobile radar is removed; the detection ability of the active anti-collision radar is improved; the false alarm rate is improved; and the inhibitionability under complex road condition is good.

The invention relates to a high/intermediate-frequency front-end circuit of a digital short-wave receiver, which mainly comprises a PIN diode electric control attenuator, digital control electric tuning preselected tracking filter groups, a gain control low-noise amplifier, a direct digital frequency synthesizer, a plurality of frequency mixers, an intermediate-frequency amplifier, an amplitude detection and grain control circuit and a preselected controller, wherein a weak signal sensed by an antenna is subjected to tracking frequency selection by the first digital control electric tuning preselected tracking filter group after passing through the PIN diode electric control attenuator and then is subjected to frequency selection by the second digital control electric tuning preselected tracking filter group after being amplified by the gain control low-noise amplifier, the signal after being subjected to frequency selection is subjected to frequency mixing three times with the plurality of frequency mixers by three local oscillators formed by the frequency synthesizer and is transmitted to a demodulator for demodulation after being subjected to multistep intermediate-frequency amplification and gain control processing. The high/intermediate-frequency front-end circuit of the digital short-wave receiver can meet the requirement of high sensitivity, strong anti-interference performance and wide dynamic range for the short-wave receiver, is suitable for a frequency-hopping receiving machine with rapid frequency change and has the effects of low insertion loss, low in-band ripple and high selectivity.

The invention relates to a turbine rotor blade accelerated life test load design method taking regard of flight damage. The method includes: 1) conducting frequency mixing treatment and rain flow counting on aeroengine flight missions and training subjects to acquire the frequency and time of each rotation speed cycle in actual flight, thus obtaining the load basic data of an engine within certain flight hours; 2) acquiring the temperature field and stress strain distribution of the blade under all states by finite element method, analyzing the blade static strength and endurance, and determining a lifetime testing part of the blade; 3) calculating the fatigue damage and creep damage of the blade testing part under a true flight load to acquire a ratio of creep damage and fatigue damage during rise and fall of a flight; and 4) designing a accelerated life test load spectrum of a full-size blade, and determining a conversion coefficient of the blade test load spectrum relative to out-field flight. The method provided by the invention can be used for acquiring the technical life of the blade and studying the remaining life of the blade, and saves time and economic cost for the fatigue-creep lifetime test of the blade.