96 results about "Phase coherence" patented technology

The invention discloses a high-sensitivity satellite navigation signal capturing method and a system. The system comprises a digital down-conversion module, an average sampling and block accumulation module, an FFT (fast Fourier transform) module, a circumference shifting module, a local PRN (pseudo random noise) code FFT conjugate memory, a complex multiplier module, an IFFT (inverse fast Fourier transform) module, a differential coherence integration module, a peak detection module and a sequential control module. The digital down-conversion module realizes digital down-conversion operation for satellite digital intermediate frequency signals; the average sampling and block accumulation module averagely samples satellite data and completes a block accumulation function; the FFT module searches code phase frequency domains; the circumference shifting module utilizes Doppler circumference shifting search to replace frequency compensation; the local PRN code FFT conjugate memory stores a local PRN code FFT conjugate result; the complex multiplier module realizes signal de-spreading; the IFFT module calculates different code phase coherence results; the differential coherence integration module accumulates differential coherence energy of de-spread satellite signals; the peak detection module realizes signal capturing output; and the sequential control module controls timing sequence of the various modules of the system. Weak signal capturing speed and sensitivity of a satellite navigation receiver are improved, and parameters can be configured flexibly.

Present-day single or multiple fractional phase-locked loop frequency synthesizers are not phase coherent for they use a digital accumulator modulo a number P with a variable increment K, whose state is a function of the history of the change in values that have been imposed on the increment. This lack of phase coherence rules out the use of these synthesizers in certain fields such as that of Doppler radars. A novel type of single or multiple fractional phase-locked loop frequency synthesizer that is coherent in phase is proposed herein. This type of synthesizer comprises one or more counters with an increment of one, having their rate set by the reference oscillator of the synthesizer and being used in phase memories to enable changes in the increment or increments following a change in the fractional division ratio at instants that are synchronous with the reference oscillator.

Techniques for analog processing of high time-bandwidth-product (TBP) signals use a material with an inhomogeneously broadened absorption spectrum including multiple homogeneously broadened absorption lines. A first set of signals on optical carriers interact in the material during a time on the order of a phase coherence time of the homogeneously broadened absorption lines to record an analog interaction absorption spectrum. Within a time on the order of a population recovery time for a population of optical absorbers it the material, the interaction absorption spectrum in the material is read to produce a digital readout signal. The readout signal represents a temporal map of the interaction absorption spectrum, and includes frequency components that relate to a processing result of processing the first set of signals. The techniques allow processing of RADAR signals for improved range resolution to a target, as well as speed of the target, among other uses.

An apparatus and method for performing coarse frequency synchronization in an orthogonal frequency division multiplexing (OFDM) receiver includes cyclically shifting a received signal X(k) by a predetermined shift amount d, determining the length of a summation interval according to a phase coherence bandwidth and a number K of sub-bands into which the summation interval is divided, generating and adjusting a symbol time offset according to the number K of sub-bands, generating a weighted phase reference signal Z(k) which is phase-shifted by the symbol time offset and weighted by a weighting vector determined according to a frequency band, partially correlating the shifted signal X(k+d) and the weighted phase reference symbol Z(k) and calculating a partial correlation value for each of the K sub-bands; and determining the shift amount d_max at a maximum sum of the partial correlation values and outputs the shift amount d_max as an estimated coarse frequency offset.

A method of detecting GPS signal tampering uses two GPS receivers. A first receiver measures carrier phases of two or more satellite signals and of a tampered signal. A second receiver measures carrier phases of the two or more satellite signals and the tampered signal. A baseline vector between the receiver antennas is measured. Direction cosine vectors of the two or more satellite signals are computed and a dot product is computed from the baseline vector to translate measurements made at antennas of the GPS receivers to a virtual zero baseline condition. The carrier phase measurements are double differenced to obtain double difference residuals. A test statistic of the double difference residuals is computed and tested for phase coherency. An inconsistency in measured signals is flagged when there is an inconsistency in phase coherence indicating the tampered signal is present.

A method for combining beams from multiple laser emitters, which may be optical fibers or bulk amplifiers, to form a composite output beam with desirable beam characteristics, as measured, for example, by Strehl ratio. Beams from the multiple emitters are interferometrically combined in the near field, and the phases of the beams are controlled to provide optimal phase coherence, and thereby to minimize losses. Various techniques are disclosed for controlling the phase angles of the emitted beams, using either a separate phase detector for each emitter beam, or a single detector for the composite output beam, or nulling detectors in spurious outputs from the beam combining optics. All of these techniques achieve an improvement in Strehl, largely because the interferometric combination of beams is independent of the array fill factor.

The invention discloses a method for measuring a target azimuth by single-beam mechanical scanning radar, which relates to the technical field of radar and communication and solves the problems of low angle measurement precision and large operation amount of the conventional single-beam mechanical scanning radar. The method comprises the following steps of: acquiring echo signals by using the single-beam mechanical scanning radar, then performing phase coherence accumulation on the acquired echo signals to acquire a higher signal detection signal-to-noise ratio, taking an azimuth interval of any two echo pulses of a main lobe width of a radar antenna as two beams required for measuring an angle by the single-pulse technology after target information is detected, then calculating two-dimensional images, sum signal intensity and difference signal intensity of a target on two azimuths, and further calculating a sum-to-difference ratio k so as to acquire a target error deflection angle delta theta, wherein the target azimuth theta T is equal to theta i + theta k + delta theta. The method is suitable for radar angle measurement.

The invention relates to a dynamic brain function detection method and system based on a near infrared spectrum and blood pressure information. The method comprises the steps that 1, near infrared spectrum detection equipment is used for collecting a brain blood oxygen signal of a testee, and meanwhile blood pressure equipment is used for collecting arterial blood pressure of the testee; 2, a brain blood oxygen signal and the blood pressure signal collected in the step 1 are input into a wavelet coherence analysis module, the wavelet coherence analysis method is used for performing time frequency analysis on the blood pressure signal and the brain blood oxygen signal of each channel, a pair of near infrared transmitter and an absorption sensor form a channel, and different physiological source rates correspond to different feature frequency sections; 3, according to the time frequency analysis in the step 2, a wavelet coherence coefficient of each feature frequency section is obtained, and the wavelet coherence coefficient shows consistency of the blood oxygen signal and the blood pressure inside the feature frequency section. By means of brain blood oxygen and arterial pressure physiological signals, on the basis of wavelet coherence or wavelet phase coherence or effect connection analysis, the noninvasive dynamic brain function is easily evaluated.

A spatially modulated waveguide Bragg grating mirror is suspended over a substrate by plurality of fingers extending laterally away from the waveguide centerline. The positions of the fingers are coordinated with the positions of crests and valleys of amplitude or phase modulation of the Bragg grating, to avoid disturbing the Bragg grating when it is tuned by heating. When the Bragg grating is heated, the heat flows through the fingers creating a quasi-periodic refractive index variation along the Bragg grating due to quasi-periodic temperature variation created by the heat flow from the grating through the supporting fingers. Due to coordination of the positions of supporting fingers with positions of the crests and valleys of modulation, the optical phase coherence is maintained along the Bragg grating, so that the spectral lineshape or filtering property of the Bragg grating is substantially preserved.

The present disclosure relates to a generally-applicable measurement technique based on coherent quantum enhancement effects and provides embodiments with nonlinear optics. The technique utilizes parametric nonlinear processes where the information-carrying electromagnetic quanta in a number of electromagnetic modes are converted phase coherently to signature quanta in a single mode or a few modes. The phase coherence means that while the quanta before conversion may have unequal or uncertain phase values across the modes, the signature quanta converted from those different modes have the (near) uniform phase. This can lead to significant increase in the signal to noise ratio in detecting weak signal buried in strong background noise. Applications can be found in remote sensing, ranging, biological imaging, field imaging, target detection and identification, covert communications, and other fields that can benefit from improved signal to noise ratios by using the phase coherent effect.

The invention discloses a time digitizer based on a delay ring flop-out method. The time digitizer comprises a start pulse generation module, an end pulse generation module, a start time delay ring, an end time delay ring, a first edge detection module, a second edge detection module, a phase coherence detector and a cycle index counter. A time sequence trigger pulse is shaped to two needed rotary pulse signals by the pulse generation module, the two raising time delay rotary pulse signals of the two rotary pulse signals are detected to be respectively and circularly transmitted in two time delay rings by the first and second edge detector modules, and the cycle indexes of the rotary pulse signals are counted by the cycle index counter at the same time; when the time interval between the two rotary pulse signals is detected to be less than the resolution of the time digitizer by the phase coherence detector, the two time delay rings are off, therefore, the measurement for the time intervals can be finished, and the product of a value of the cycle index counter and the resolution of the time digitizer is a time interval to be detected. The time digitizer provided by the invention is high in measurement resolution, large in measurement range and high in linearity.

The invention provides a multichannel scattering parameter testing circuit and method for a complex modulation and phase coherence system. The multichannel scattering parameter testing circuit comprises a master control computer, a PXI cabinet, a shared local oscillator signal generating unit, a shared clock reference generation unit, a multichannel complex modulation and phase coherence excitation signal generating unit, a multichannel complex modulation and phase coherence excitation signal conditioning unit, a multichannel complex modulation and phase coherence excitation signal separating and reflection extraction unit, a multichannel complex modulation and phase coherence response signal separating and transmission extraction unit, a multichannel complex modulation and phase coherence response signal reception and conditioning unit and a multichannel complex modulation and phase coherence response testing and analyzing unit. During an actual test, the irregular influence factors such as long path and mismatching between a testing port and a testing calibration surface can be reduced or eliminated, and the expansion of signal separating and extraction technical characteristics can be realized through variable performance configuration.

The invention relates to an interpolation transformation and beam forming-based far-field coherent signal DOA estimation method. According to the method, firstly, an interpolation matrix is adopted to convert a non-uniform linear array covariance matrix into a covariance matrix of a virtual uniform linear array. Data on the covariance matrix of the virtual array are subjected to noise pre-whitening to obtain img file = 'DDA 00013602494400000000000011.T'wi = '67 'he = '71 '. After that, img file = 'DDA 00013602494400000000000011.T'wi = '43 'he = '70 ' is subjected to spatial smoothing treatment to resolve the phase coherence, so that a coherence-resolved data covariance matrix is obtained. The coherence-resolved data covariance matrix is processed through constructing a cost function, and then the estimated value of the DOA of a far-field coherent signal is obtained. According to the invention, on the premise that the precision is guaranteed, the operations of feature decomposition, frequency spectrum searching and the like which are complicated in operation, can be avoided. The method is low in calculation complexity, simple and effective. Meanwhile, based on the method, the application range is popularized from a uniform linear array to any linear array, and from a non-coherent signal source to a coherent signal source. Therefore, the method is wider in application range.

In a method and apparatus for converting optical wavelength division multiplexed channels to wireless channels, the information carrying optical carriers are first de-multiplexed and each optical carrier is then extracted from the data using an optical channelizing technique. The optical frequency of each of the extracted optical carriers is then shifted by an amount equal to the desired wireless carrier frequencies in the broadband wireless channels. Optical heterodyning of the frequency-shifted extracted lightwave carriers with the original data-containing optical signals, which are mutually in phase coherence, in a photodetector results in a set of wireless carriers each modulated with the data carried by the corresponding optical channel.

An amplitude-phase consistency compensation system for radar equipment, used to maintain consistency in the amplitude and phase of the radar three-way channel in the radar system, including: radar equipment, amplitude-phase correction server and display; wherein the amplitude-phase correction server It includes a signal mixing input device, an amplitude-phase consistency corrector and a signal mixing output device; the radar equipment includes a phased array antenna, a digital receiver, a radar amplitude-phase consistency corrector, a radar amplitude-phase superposition analyzer and a radar signal processor. After the radar equipment receives the air interface radar echo through the phased array antenna, it is handed over to the digital receiver for receiving and processing, and then corrected by the radar’s own amplitude-phase consistency corrector, and then corrected again by the amplitude-phase correction server, and then the amplitude-phase The data corrected by the correction server is superimposed on the data corrected by itself, and finally sent to the radar signal processor for analysis and processing. The twice-corrected signal can display the status information of the target object more accurately.

Mapping coherent/incoherent acoustic sources as determined from a phased microphone array. A linear configuration of equations and unknowns are formed by accounting for a reciprocal influence of one or more cross-beamforming characteristics thereof at varying grid locations among the plurality of grid locations. An equation derived from the linear configuration of equations and unknowns can then be iteratively determined. The equation can be attained by the solution requirement of a constraint equivalent to the physical assumption that the coherent sources have only in phase coherence. The size of the problem may then be reduced using zoning methods. An optimized noise source distribution is then generated over an identified aeroacoustic source region associated with a phased microphone array (microphones arranged in an optimized grid pattern including a plurality of grid locations) in order to compile an output presentation thereof, thereby removing beamforming characteristics from the resulting output presentation.

Techniques for facilitating and performing frequency-offset estimation are disclosed. The disclosed techniques include methods and apparatus for maintaining phase coherence among reference symbols on different transmission-time intervals (TTI) for an accurate estimation of frequency offset. Corresponding techniques utilize channel estimation or measurements of channel-related parameters based on multiple reference symbols belonging to different TTIs. An example method in a radio transceiver for facilitating frequency offset estimation at a remote receiver begins with determining that phase coherence between reference symbol transmissions in a first TTI and a second TTI is required. The radio transceiver selectively maintains phase coherence between reference symbol transmissions in the first and second TTIs, in response to said determining. The radio transceiver then transmits during at least part of a third TTI, following the second TTI, without maintaining phase coherence to the reference symbol transmissions in the first and second TTIs.

A loudspeaker system consisting of a plurality of direct-radiating electro-acoustical drivers arrayed along a curved line. While in one embodiment the curved line array may be a spiral array, in another embodiment it may be any curved line array (such as an arcuate array). The acoustical drivers are directly coupled to an acoustical waveguide without use of adapters or a throat section. The waveguide and the acoustical drivers may thus be oriented along the curved line so as to produce controlled vertical and horizontal angular coverage with improved phase coherence and reduced distortion. A plurality of phase plugs may be interspersed between the plurality of acoustical drivers to assist in equalizing the sound path to achieve uniform phase at the mouth of the waveguide.

The invention provides frequency conversion phase-shifting integrated photonic microwave mixing device which comprises a laser, a polarization multiplexing parallel light modulator (also known as a dual polarization parallel light modulator, a polarization multiplexing I/Q modulator, a dual polarization I/Q modulator), a bipolarized light filter, an optical domain phase shifter, and an optical coherence detector. A parallel structure photonic mixer based on orthogonal polarization multiplexing technology is realized by the polarization multiplexing parallel optical modulator, which makes the RF modulated optical signal and the LO modulated optical signal in the orthogonal polarization state with phase coherence, and keeps the phase of the two parallel optical signals relatively stable allthe time, and realizes arbitrary phase shifting of the obtained intermediate frequency signal through the optical domain phase shifter. Compared with the traditional microwave mixer, the device has larger bandwidth, spurious-free dynamic range and smaller group delay fluctuation, and can realize the functional integration of frequency mixing and phase shifting.