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The Fourier transform (FT) decomposes a function of time (a signal) into its constituent frequencies. This is similar to the way a musical chord can be expressed in terms of the volumes and frequencies of its constituent notes. The term Fourier transform refers to both the frequency domain representation and the mathematical operation that associates the frequency domain representation to a function of time. The Fourier transform of a function of time is itself a complex-valued function of frequency, whose magnitude (modulus) represents the amount of that frequency present in the original function, and whose argument is the phase offset of the basic sinusoid in that frequency. The Fourier transform is not limited to functions of time, but the domain of the original function is commonly referred to as the time domain. There is also an inverse Fourier transform that mathematically synthesizes the original function from its frequency domain representation.

InactiveUS7376453B1Improve approximationDiagnostic recording/measuringSensorsStatistical functionFourier transform

The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Owner:JPMORGAN CHASE BANK NA

InactiveUS20070211786A1Low costImprove system performanceSecret communicationMultiplex code generationUltra-widebandTransmission protocol

Carrier Interferometry (CI) provides wideband transmission protocols with frequency-band selectivity to improve interference rejection, reduce multipath fading, and enable operation across non-continuous frequency bands. Direct-sequence protocols, such as DS-CDMA, are provided with CI to greatly improve performance and reduce transceiver complexity. CI introduces families of orthogonal polyphase codes that can be used for channel coding, spreading, and/or multiple access. Unlike conventional DS-CDMA, CI coding is not necessary for energy spreading because a set of CI carriers has an inherently wide aggregate bandwidth. Instead, CI codes are used for channelization, energy smoothing in the frequency domain, and interference suppression. CI-based ultra-wideband protocols are implemented via frequency-domain processing to reduce synchronization problems, transceiver complexity, and poor multipath performance of conventional ultra-wideband systems. CI allows wideband protocols to be implemented with space-frequency processing and other array-processing techniques to provide either or both diversity combining and sub-space processing. CI also enables spatial processing without antenna arrays. Even the bandwidth efficiency of multicarrier protocols is greatly enhanced with CI. CI-based wavelets avoid time and frequency resolution trade-offs associated with conventional wavelet processing. CI-based Fourier transforms eliminate all multiplications, which greatly simplifies multi-frequency processing. The quantum-wave principles of CI improve all types of baseband and radio processing.

Owner:GENGHISCOMM HLDG

InactiveUS8560034B1Improve approximationUltrasonic/sonic/infrasonic diagnosticsCatheterFourier transform on finite groupsComputer science

The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Owner:JPMORGAN CHASE BANK NA

ActiveUS20050180579A1Reduce transmission bandwidth requirementsGain controlSpeech analysisComputation complexityChannel correlation

A scheme for stereo and multi-channel synthesis of inter-channel correlation (ICC) (normalized cross-correlation) cues for parametric stereo and multi-channel coding. The scheme synthesizes ICC cues such that they approximate those of the original. For that purpose, diffuse audio channels are generated and mixed with the transmitted combined (e.g., sum) signal(s). The diffuse audio channels are preferably generated using relatively long filters with exponentially decaying Gaussian impulse responses. Such impulse responses generate diffuse sound similar to late reverberation. An alternative implementation for reduced computational complexity is proposed, where inter-channel level difference (ICLD), inter-channel time difference (ICTD), and ICC synthesis are all carried out in the domain of a single short-time Fourier transform (STFT), including the filtering for diffuse sound generation.

Owner:AVAGO TECH INT SALES PTE LTD

InactiveUS7034292B1Reduce lossesEliminate and reduce numberIsotope separationSpectrometer combinationsFourier transform on finite groupsMass analyzer

A mass spectrometer is configured with individual multipole ion guides, configured in an assembly in alignment along a common centerline wherein at least a portion of at least one multipole ion guide mounted in the assembly resides in a vacuum region with higher background pressure, and the other portion resides in a vacuum region with lower background pressure. Said multipole ion guides are operated in mass to charge selection and ion fragmentation modes, in either a high or low pressure region, said region being selected according to the optimum pressure or pressure gradient for the function performed. The diameter, lengths and applied frequencies and phases on these contiguous ion guides may be the same or may differ. A variety of MS and MS/MS^{n }analysis functions can be achieved using a series of contiguous multipole ion guides operating in either higher background vacuum pressures, or along pressure gradients in the region where the pressure drops from high to low pressure, or in low pressure regions. Individual sets of RF, +/−DC and resonant frequency waveform voltage supplies provide potentials to the rods of each multipole ion guide allowing the operation of ion transmission, ion trapping, mass to charge selection and ion fragmentation functions independently in each ion guide. The presence of background pressure maintained sufficiently high to cause ion to neutral gas collisions along a portion of each multiple ion guide linear assembly allows the conducting of Collisional Induced Dissociation (CID) fragmentation of ions by axially accelerating ions from one multipole ion guide into an adjacent ion guide. Alternatively ions can be fragmented in one or more multipole ion guides using resonant frequency excitation CID. A multiple multipole ion guide assembly can be configured as the primary mass analyzer in single or triple quadrupole mass analyzers with or without mass selective axial ejection. Alternatively, the multiple multipole ion guide linear assembly can be configured as part of a hybrid Time-Of-Flight, Magnetic Sector, Ion Trap or Fourier Transform mass analyzer.

Owner:PERKINELMER U S LLC

InactiveUS20020128544A1Improve approximationUltrasonic/sonic/infrasonic diagnosticsMaterial analysis by optical meansFourier transform on finite groupsComputer science

The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Owner:DIAB MOHAMED K +5

InactiveUS20040239885A1Television system detailsTelevision system scanning detailsProgram codeFourier transform

A technique, associated system and computer executable program code, for projecting a superimposed image onto a target display surface under observation of one or more cameras. A projective relationship between each projector being used and the target display surface is determined using a suitable calibration technique. A component image for each projector is then estimated using the information from the calibration, and represented in the frequency domain. Each component image is estimated by: Using the projective relationship, determine a set of sub-sampled, regionally shifted images, represented in the frequency domain; each component image is then composed of a respective set of the sub-sampled, regionally shifted images. In an optimization step, the difference between a sum of the component images and a frequency domain representation of a target image is minimized to produce a second, or subsequent, component image for each projector. Here, a second set of frequency domain coefficients for use in producing a frequency domain representation of the second component image for each projector is identified. Taking the inverse Fourier transform of the frequency domain representation of the second component image, converts the information into a spatial signal that is placed into the framebuffer of each component projector and projected therefrom to produce the superimposed image.

Owner:UNIV OF KENTUCKY RES FOUND

InactiveUS20070280098A1Good precisionModulated-carrier systemsTime-division multiplexCell specificCarrier frequency offset

Disclosed is a method, a computer program product and a device that includes a receiver for receiving a downlink signal transmitted into a cell. The receiver is operable to obtain time, carrier frequency and cell-specific preamble synchronization to the received signal and includes a plurality of synchronization units that include a first detector to detect a frame boundary using preamble delay correlation; a second detector to detect the frame boundary with greater precision using a conjugate symmetry property over a region identified by the first detector; a cyclic prefix correlator to resolve symbol boundary repetition; an estimator, using the cyclic prefix, to estimate and correct a fractional carrier frequency offset; an operator to perform a Fast Fourier Transform of an identified preamble symbol and a frequency domain cross-correlator to identify cell-specific preamble sequences and an integer frequency offset in sub-carrier spacing. The transmitted signal may be a downlink signal transmitted into the cell from a base station that is compatible with IEEE 802.16*e *(WiMAX).

Owner:NOKIA TECHNOLOGLES OY

ActiveUS20070258094A1Extended processing timeRadiation pyrometryInterferometric spectrometryComputer scienceDispersion compensation

Methods, systems and computer program products for generating parameters for software dispersion compensation in optical coherence tomography (OCT) systems are provided. Raw spectral interferogram data is acquired for a given lateral position on a sample and a given reference reflection. A trial spectral phase corresponding to each wavenumber sample of the acquired spectral interferogram data is postulated. The acquired raw spectral data and the postulated trial spectral phase data are assembled into trial complex spectrum data. Trial A-scan data is computed by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of a result.

Owner:BIOPTIGEN

ActiveUS20160157828A1Increase speedImprove accuracyProcessing detected response signalCatheterEngineeringWavenumber

Beamforming method that allows a high speed and high accuracy beamforming with no approximate interpolations. This beamforming method includes step (a) that generates reception signals by receiving waves arrival from a measurement object; and step (b) that performs a beamforming with respect to the reception signals generated by step (a); and step (b) including without performing wavenumber matching including approximate interpolation processings with respect to the reception signals, and the reception signals are Fourier's transformed in the axial direction and the calculated Fourier's transform is multiplied to a complex exponential function expressed using a wavenumber of the wave and a carrier frequency to perform wavenumber matching in the lateral direction and further, the product is Fourier's transformed in the lateral direction and the calculated result is multiplied to a complex exponential function, from which an effect of the lateral wavenumber matching is removed, to perform wavenumber matching in the axial direction, by which an image signal is generated.

Owner:CHIKAYOSHI SUMI

InactiveUS7292651B2Robust parameter estimationNoise-reduced channelFrequency-division multiplex detailsSecret communicationCommunications systemFourier transform on finite groups

A method and apparatus for pilot-symbol aided channel estimation in a wireless digital communication system which transmits packets of N OFDM data blocks, each data block comprising a set of K orthogonal carrier frequencies. At the transmitter, pilot symbols are inserted into each data packet at known positions so as to occupy predetermined positions in the time-frequency space. At the receiver, the received signal is subject to a two-dimensional inverse Fourier transform, two-dimensional filtering and a two-dimensional Fourier transform to recover the pilot symbols so as to estimate the channel response.

Owner:AMERICAN TELEPHONE & TELEGRAPH CO

InactiveUS20090079993A1Simple structureHigh imagingInterferometersMaterial analysis by optical meansBiological bodyFourier transform on finite groups

A dental optical coherence tomography apparatus for measuring tissue in a stomatognathic region of a living body or an artificial composition in the stomatognathic region as a measured object includes: a variable wavelength light source (**15**); a light splitting portion (**19**) that splits light-source light emitted from the variable wavelength light source (**15**) into reference light (**29**) and measuring light (**28**); an interference portion (**19**) that causes the measuring light (**28**) and the reference light (**29**) to interfere with each other, thereby generating interference light; a photodetection portion (**41**) that measures the interference light; and an arithmetic portion (**27***b*) that generates an image of a measured object (**22**) by Fourier transforming or inverse Fourier transforming the intensity of the interference light, whose wavelength changes with time, that has been detected by the photodetection portion for each of the wavelengths. Accordingly, an optical coherence tomography apparatus applicable to dental measurement can be provided.

Owner:SHOFU INC

ActiveUS20080005838A1Simple systemCatheterRespiratory organ evaluationFast Fourier transformPhysical therapy

A system and method for determining and monitoring various characteristics of a patient positioned on a patient support apparatus, such as a bed, stretcher, or cot, is disclosed. The system and method involve monitoring the forces exerted by the patient on one or more force sensors, which may be load cells on the support apparatus. These force sensors will detect vibrations that correspond to various conditions of the patient, including the patient's heart rate, breathing rate, and/or the seizure status of a patient. These vibrations may be analyzed, such as by Fast Fourier Transforms, in order to determine the various conditions of the patient.

Owner:STRYKER CORP

InactiveUS6393921B1Fluid pressure measurement using inductance variationFluid pressure measurement using magnet displacementMagneto elasticPressure sense

A pressure sensing apparatus for operative arrangement within an environment, having: a sensor comprising a hermetically-sealed receptacle, at least one side of which has an flexible membrane to which a magnetically hard element is attached. Enclosed within the receptacle is a magnetostrictive element that vibrates in response to a time-varying magnetic field. Also included is a receiver to measure a plurality of successive values for magneto-elastic emission intensity of the sensor taken over an operating range of successive interrogation frequencies to identify a resonant frequency value for the sensor. Additional features include: (a) the magnetically hard element may be adhered to an inner or outer side of, or embedded within, the membrane; (b) the magnetostrictive element can include one or more of a variety of different pre-formed, hardened regions; (c) the magneto-elastic emission may be a primarily acoustic or electromagnetic emission; and (d) in the event the time-varying magnetic field is emitted as a single pulse or series of pulses, the receiver unit can detect a transitory time-response of the emission intensity of each pulse (detected after a threshold amplitude value for the transitory time-response is observed). A Fourier transform of the time-response can yield results in the frequency domain. Also, an associated method of sensing pressure of an environment is included that uses a sensor having a magnetostrictive element to identify a magneto-elastic resonant frequency value therefore. Using the magneto-elastic resonant frequency value identified, a value for the pressure of the environment can be identified.

Owner:UNIV OF KENTUCKY RES FOUND

InactiveUS6934316B2Improve dynamic rangeReduce sensitivityData switching by path configurationSynchronisation signal speed/phase controlFrequency-hopping spread spectrumFast Fourier transform

A wireless spread spectrum communication system for transmitting data includes a plurality of end point transmitters and at least one receiver. The end point transmitters transmit data via a frequency hopped spread spectrum signal where the transmitting signal is sent without the benefit of frequency stabilization. The receiver is responsive to the frequency hopping spread spectrum signals and includes a correlator and a signal processor. The correlator samples at least a first portion of a preamble of the signal and correlates the portion of the preamble with a known preamble pattern to determine a probability of correlation. The signal processor applies a Fast Fourier Transform algorithm to the signal in response to the probability of correlation to track a narrowband frequency of the signal based on at least a second portion of the preamble and to decode data encoded within the signal subsequent to the preamble.

Owner:ITRON

ActiveCN107956708AImprove acceleration performanceClear resolutionPump controlNon-positive displacement fluid enginesVibration accelerationCavitation

The invention discloses a pump potential cavitation fault detecting method based on quick spectrum kurtosis analysis. The pump potential cavitation fault detecting method comprises the steps that 1, vibration acceleration signals are collected to be subject to noise reduction to serve as to-be-processed signals; 2, according to the data size of the signals, the resolving order of signal processingis determined; 3, according to the quick spectrum kurtosis algorithm computation result, the optimal carrier frequency and bandwidth are selected; 4, the selected signals within the carrier frequencyand bandwidth are subject to Fourier transformation, and a frequency spectrum envelope diagram is obtained; and 5, an original signal time domain figure, a signal time domain figure treated through quick spectrum kurtosis filtering processing and the frequency spectrum envelope diagram obtained after selected zone Fourier transformation are compared, and cavitation trouble signal time and frequency characteristics are analyzed. By means of the method, more cavitation instant signals can be detected, information in the aspects of time domain and frequency domain is seen more clearly, and the normal state and the cavitation state of a pump can be distinguished obviously.

Owner:ZHEJIANG UNIV

InactiveUS6856400B1Reflectometers dealing with polarizationMaterial analysis by optical meansOptical frequenciesCurve fitting

In order to characterize the optical characteristics of a device, a source of light having a variable frequency with a polarization state which varies linearly with frequency is provided as an input to the device under test. The input light is also passed through a known reference path and is added to the light output from the device under test in a beam combiner. The combined light for the frequencies of interest is split into two orthogonal polarizations which are then detected in a spectral acquisition apparatus and supplied to a microprocessor. The spectral measurements are digitized and curve-fitted to provide optical power versus optical frequency curves. Fourier transforms of each of the curves are calculated by the microprocessor. From the Fourier transforms, the four arrays of constants are calculated for the Jones matrix characterizing the device under test.

Owner:INTUITIVE SURGICAL OPERATIONS INC

ActiveUS20090041381A1Guaranteed corrective effectTelevision system detailsCharacter and pattern recognitionParallaxPhase correction

Method and apparatus for radiance processing by demultiplexing in the frequency domain. A frequency domain demultiplexing module obtains a radiance image captured with a lens-based radiance camera. The image includes optically mixed spatial and angular frequency components of light from a scene. The module performs frequency domain demultiplexing on the radiance image to generate multiple parallax views of the scene. The method may extract multiple slices at different angular frequencies from a Fourier transform of the radiance image, apply a Fourier transform to each of the multiple slices to generate intermediate images, stack the intermediate images to form a 3- or 4-dimensional image, apply an inverse Fourier transform along angular dimension(s) of the 3- or 4-dimensional image, and unstack the transformed 3- or 4-dimensional image to obtain the multiple parallax views. During the method, phase correction may be performed to determine the centers of the intermediate images.

Owner:ADOBE INC

ActiveUS7139320B1Transmission path divisionSynchronisation signal speed/phase controlPilot systemChannel impulse response

Method and apparatus for OFDM synchronization and channel estimation. In a temporal embodiment, received embedded system pilot symbols are inverse Fourier transformed at expected index locations and correlated with computed complex conjugates of inverse Fourier transforms of pilot symbols for providing a correlation function for the channel impulse response. In a frequency domain embodiment, embedded system pilot symbols are augmented with pilot-spaced inferred guard band symbols, multiplied by scaled complex conjugates of computed pilot systems, and inverse Fourier transformed into the channel impulse response. Time and frequency are synchronized in feedback loops from information in the channel impulse response. The channel impulse response is filtered, interpolated, and then Fourier transformed for determining channel estimates for equalization.

Owner:RADIA COMM

ActiveUS20050278171A1Generate efficientlyEliminates noise pumpingSpeech analysisTime domainComfort noise

A background noise estimate based upon a modified Doblinger noise estimate is used for modulating the output of a pseudo-random phase spectrum generator to produce the comfort noise. The circuit for estimating noise includes a smoothing filter having a slower time constant for updating the noise estimate during noise than during speech. Comfort noise is smoothly inserted by basing the amount of comfort noise on the amount of noise suppression. A discrete inverse Fourier transform converts the comfort noise back to the time domain and overlapping windows eliminate artifacts that may have been produced during processing.

Owner:CIRRUS LOGIC INC

InactiveUS20120026466A1Improve signal-to-noise ratioEliminate speckleOptical measurementsRefractometersWavefront sensorLight beam

Example embodiments of a large dynamic range sequential wavefront sensor for vision correction or assessment procedures are disclosed. An example embodiment optically relays a wavefront from an eye pupil or corneal plane to a wavefront sampling plane in such a manner that somewhere in the relaying process, the wavefront beam from the eye within a large eye diopter range is made to reside within a desired physical dimension over a certain axial distance range in a wavefront image space and/or a Fourier transform space. As a result, a wavefront beam shifting device can be disposed there to fully intercept and hence shift the whole beam to transversely shift the relayed wavefront.

Owner:CLARITY MEDICAL SYST

InactiveUS20060159006A1Degradation in error vector magnitudeModulated-carrier systemsOrthogonal multiplexFast Fourier transformGuard interval

An apparatus and a method for reducing an error vector magnitude in an orthogonal frequency division multiplexing (OFDM) receiver. The method includes the steps of inputting a receiving symbol including a guard interval and an effective symbol interval following the guard interval, in which a front portion of the guard interval and a rear portion of the effective symbol interval have windowing intervals corresponding to windowing of a transmitter, and replacing a signal of the rear windowing interval with a signal of an interval between the front windowing interval and the effective symbol interval, thereby outputting a signal of the effective symbol interval, which substitutes for a signal of the rear windowing interval, to a fast Fourier transform (FFT) section.

Owner:SAMSUNG ELECTRONICS CO LTD

An OFDM receiver includes a converter configured to generate a transform signal by Fourier transform of a received signal. A first interpolator is configured to detect a pilot signal from the transform signal, and to provide time interpolation to the pilot signal. An interference detector is configured to provide arithmetic processing to the time interpolated pilot signal, and to detect interference by comparing a result of the arithmetic processing with a threshold. A second interpolator is configured to provide frequency interference interpolation with respect to the interference detected pilot signal, and to provide frequency interpolation to the pilot signal after the interference interpolation. A demodulator is configured to perform demodulation based on the transform signal and the frequency interpolated pilot signal.

Owner:KK TOSHIBA

InactiveUS20110096658A1Time-division multiplexFrequency-division multiplexPrecodingCommunications system

A radio communication system is provided. An uplink transmission method of a user equipment in a radio communication system includes performing Fourier transform on one or more data sequences to generate one or more first frequency-domain sequences, applying precoding for multi-antenna transmission to the one or more first frequency-domain sequences to generate one or more second frequency-domain sequences; performing inverse Fourier transform on the one or more second frequency-domain sequences to generate one or more transmission symbols, and transmitting the one or more transmission symbols via multiple antennas.

Owner:LG ELECTRONICS INC

InactiveUS6310679B1Photomechanical exposure apparatusMicrolithography exposure apparatusOptical axisFourier transform on finite groups

In projection exposure of isolated pattern such as a contact hole, in order to increase the depth of focus a coherence reducing member is disposed on a Fourier transform plane in an image-forming optical path between a mask and a sensitized base, so that coherence is reduced between image-forming beams respectively passing through a plurality of different, concentric regions around the optical axis of the projection optical system on the Fourier transform plane. The coherence reducing member may be a polarization state control member for making a difference in polarization state, a member for making a difference in optical path length, or space filters with different shapes.

Owner:NIKON CORP

InactiveUS20050270968A1Shorten the lengthSecret communicationMulti-frequency code systemsTime domainFast Fourier transform

An apparatus and a method for peak-to-average power ratio reduction of an OFDM signal are disclosed. The method uses the interleaved characteristics of partial transmit sequences to partition input data x[n] of length N into several disjoint subblocks in time domain, and a complete N-point signal {tilde over (x)}[n] is composed after phase optimization, where N is the length of an OFDM signal and n=0, 1, . . . , N−1. Accordingly, the apparatus comprises an N-point inverse fast Fourier transform (N-IFFT), a de-multiplexer, a combiner, a set of memory and an adder. This invention uses only one N-IFFT, whereby it can achieve significant computation reduction. This invention requires (N/2)log_{2 }N complex multiplications and N memory units. It also preserves the inherent property as well as advantages of an OFDM system.

Owner:IND TECH RES INST

A signal receiving apparatus and method which is high in deduction accuracy of transfer characteristic and less in error rate during signal decoding. For each detection signal of a pilot carrier allotted in an OFDM symbol space, a transfer function thereof is calculated. The transfer function is subjected to two-dimensional Fourier transform as to impulse delay time and symbol frequency thereby generating a two-dimensional data space. A predetermined domain of the two-dimensional data space is extracted by a filter extracting domain. The data included in the extracted domain is subjected to two-dimensional inverse Fourier transform as to carrier frequency and symbol time, thereby generating a deduced transfer function.

Owner:ONKYO KK D B A ONKYO CORP

InactiveUS6952460B1Easy to trackBeacon systems using radio wavesCommunication jammingComputation complexityFourier transform on finite groups

A system for efficiently filtering interfering signals in a front end of a GPS receiver is disclosed. Such interfering signals can emanate from friendly, as well as unfriendly, sources. One embodiment includes a GPS receiver with a space-time adaptive processing (STAP) filter. At least a portion of the interfering signals are removed by applying weights to the inputs. One embodiment adaptively calculates and applies the weights by Fourier Transform convolution and Fourier Transform correlation. The Fourier Transform can be computed via a Fast Fourier Transform (FFT). This approach advantageously reduces computational complexity to practical levels. Another embodiment utilizes redundancy in the covariance matrix to further reduce computational complexity. In another embodiment, an improved FFT and an improved Inverse FFT further reduce computational complexity and improve speed. Advantageously, embodiments can efficiently null a relatively large number of jammers at a relatively low cost and with relatively low operating power.

Owner:L 3 COMM CORP

A method and system for processing radar data obtained from a platform which is subjected to non-uniform movement, the distance the platform travels during the formation of an image comprising an aperture; the system comprising software programming for performing a subroutine for building up an average pulse representing a single point on the aperture; the subroutine comprising the steps of inputting radar data from a radar antenna; passing the radar signal through low noise amplifier to reduce impact of electronic noise from the radar system; down converting the signal with a mixer to obtain a lower frequency; filtering out harmonics from the higher frequency range; sampling the radar data using an analog to digital converter at least at Nyquist down range frequency; based upon the IF of the radar; determining a scene center (center of SAR imagery) for the purpose of motion compensation; performing a two stage averaging scheme of the received signals with a variable window function; determining a window function based upon the velocity and acceleration of the platform and scene center; the window function comprising a first stage window; coherently averaging N pulses together to create an average pulse; performing an inverse Fourier transform; compensating to the scene center by multiplying by a complex exponential based upon both the GPS and inertial navigational system; summing the average pulses using low pass filter; the software programming operating to repeat the step of building up an average pulse a first predetermined number of times for a time period that is less than the Nyquist sample time interval; the software programming operating to repeat the step of building an average pulse for a predetermined number of times to generate a second predetermined number of average pulses; the software programming operating to perform a two dimensional inverse Fourier transform to obtain SAR image; outputting the SAR image on a display screen; and a display for displaying the outputted SAR image.

Owner:US SEC THE ARMY THE

InactiveUS6882618B1Improve efficiencySmall limitationsTransmission control/equlisationSecret communicationCommunications systemEstimation methods

A transmitting apparatus, receiving apparatus, communication system, and a signal processing method for each apply a suitable modulation method and transmission path estimation method in accordance with the characteristics of the transmission information and capable of improving the transmission efficiency. At the transmission side, the method of estimation of the transmission path and the modulation method are selected in accordance with an attribute of the data to be transmitted, for example, the size of a packet to be transmitted, the transmission data is mapped by the selected modulation method, the signal is processed in accordance with the transmission path estimation method, and a transmission signal is created by increase fast Fourier transform processing and transmitted. At the reception side, the received signal is fast Fourier transformed, the transmission path is estimated by the transmission path estimation method selected at the transmission side, the received signal is corrected in accordance with the result, and the received data is reproduced in accordance with the modulation method. Therefore, it is possible to always adopt the optimum transmission method in accordance with the attribute of the transmission data etc. and possible to realize an improvement of a transmission efficiency and an enhancement of the quality of communication.

Owner:REDWOOD TECHNOLOGIES LLC

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