Abstract: The invention is embodied in improvements in calculating discrete Fourier transform (DFT) using recursive digital filtering in a method for determining the velocity of a target located in a medium for vibratory energy. In the method a transmitter electrical signal of prescribed frequency is generated. Coherent vibratory energy, the frequency of which is in fixed relationship with said prescribed frequency, is transmitted into the medium and is directed toward the target. The transmitting is done in recurring pulses of prescribed duration. During range gate intervals each of prescribed duration, the transmitted coherent vibratory energy is received from the medium after its interaction with the target. The vibratory energy which is received during the range gate intervals is converted to a receiver electrical signal. The transmitter and receiver electrical signals are mixed together to obtain a demodulated electrical signal through heterodyning or homodyning.

Abstract: Apparatus for producing a magnetic field gradient for magnetic resonant imaging of the head of a subject employs two fingerprint coils disposed apart from each other, creating a generally cylindrical cavity in which subject's head is placed. A power supply provides current through the two fingerprint coils. The fingerprint coils are comprised of concentric current-carrying paths with each path being elongated along the length of the cylindrical cavity on only one end. The shape and geometry of the fingerprint coils create a magnetic field gradient that has high linearity inside the cavity, and monotonically decreases outside the cavity, thereby minimizing artifacts introduced by the body of the subject.

Abstract: Frame/slot synchronization is applied to a received Time Division Multiple Access (TDMA) signal and a temporal position of a reference feature is acquired, such as a synchronizing bit stream or preamble, associated with a desired time slot. The desired time slot is but one of a plurality of time slots that comprise a frame. Verification that the acquired temporal position corresponds to the desired time slot is performed by repetitively estimating a temporal position of the reference feature in a subsequent frame and sampling the subsequent frame at the estimated temporal position to determine if the reference feature is present. The temporal position of the reference feature of the desired time slot relative to the frame is maintained over a plurality of received frames.

Abstract: Parallel architectures preprocesses large matrices from sampled coherent time apertures receiving signals from distant sources to produce lower order matrices, derived from pseudo coherent time apertures, which are computationally less burdensome. The large matrices are processed by frequency shifting, low pass filtering with an FIR filter, and executing front-end decimation to create the pseudo coherent time apertures, each corresponding to different subbands of the temporal frequency spectrum. The signals representing the pseudo coherent time apertures are processed using matrix based superresolution spectral estimation algorithms such as the Tufts-Kumaresan (T-K) reduced rank modified covariance algorithm and the Linear Minimum Free Energy algorithms to produce an image of the sources.

Abstract: A digital radio receiver for synchronization of radiowave transmissions for digital and analog FM signals in TDMA systems such as cellular telephones uses a Sine/Cosine detector that minimizes the bit error rate. The detector employs an A/D converter, a sorter circuit that produces a predetermined number of samples to be used in the decoding based upon a sample timing adjustment, and a sample and phase adjustment circuit that selects samples based on a sample timing adjustment and adds a carrier phase adjustment to the samples. A cosine detector and a sine detector each decode samples into signals that are measured by a cosine level check circuit and a sine level check circit respectively. A decision logic circuit produces a pair of bits from the levels detected by the cosine level check circuit and the sine level check circuit as the decoded transmitted information.

Abstract: A method of imaging and quantitatively measuring blood velocity distribution within a selected vessel employs Nuclear Magnetic Resonance cylindrical excitation of the sample to be imaged, followed by Fourier velocity encoding excitation along a second axis for selectively encoding molecules based upon their flow velocities, then sensing the re-radiated signal data acquired in the presence of a readout gradient to provide resolution along the cylindrical axis, and reconstructing a velocity profile. Spatial localization is accomplished with an excitation pulse having a cylindrical rather than slab geometry. This method can be combined with cardiac synchronization to measure flow dynamics or it can be applied without synchronization to measure steady flow. The geometry of the measurement is flexible in that the directions of flow sensitivity and geometric resolution are independent.

Abstract: Parallel architectures preprocesses large matrices from sampled coherent time apertures receiving signals from distant sources to produce lower order matrices, derived from pseudo coherent time apertures, which are computationally less burdensome. The large matrices are processed by frequency shifting, low pass filtering with an FIR filter, and executing front-end decimation to create the pseudo coherent time apertures, each corresponding to different subbands of the temporal frequency spectrum. The signals representing the pseudo coherent time apertures are processed using matrix based superresolution spectral estimation algorithms such as the Tufts-Kumaresan (T-K) reduced rank modified covariance algorithm and the Linear Minimum Free Energy algorithms to produce an image of the sources.

Abstract: Parallel architectures preprocesses large matrices from digital phased array systems, receiving signals from distant sources, to produce lower order matrices, called pseudo coherent apertures, which are computationally less burdensome. The large matrices are processed by frequency shifting, low pass filtering with an FIR filter, and executing front-end decimation to create the pseudo coherent apertures, each corresponding to different sectors of the spatial frequency spectrum. The pseudo coherent apertures are processed using matrix based superresolution spectral estimation algorithms such as the Tufts-Kumaresan (T-K) reduced rank modified covariance algorithm and the Linear Minimum Free Energy algorithms produce an image of the sources.

Abstract: A gradient current speed-up circuit, for use in a higher-speed NMR imaging system having an associated gradient coil, has a gradient power amplifier receiving an input analog signal controlling the current in an amplifier output circuit connected in series between first and second portions of a single gradient coil. Semiconductor switching elements selectively connect the coil portion-amplifier-coil portion between first and second potential sources, and are turned on and off in selected patterns to cause a current to be suddenly applied to, and removed from, flow through the associated gradient coil and the amplifier output circuit.

Abstract: A technique that reconciles the differences between the estimator and the filter of a multi-pulse linear predictive voice encoder achieves a higher quality in the output speech. The technique simultaneously solves for the pulse amplitudes and pitch tap gain to minimize the estimator bias in the multi-pulse excitation and thereby improves, performance of the system. The increased signal-to-noise ratio is accomplished by first modifying the pitch predictor such that the pitch synthesis filter accurately reflects the estimation procedure used to find the pitch tap gain and, second, improving the excitation analysis technique such that the pitch predictor tap gain and pulse amplitudes are solved for simultaneously, rather than sequentially. Neither of these modifications results in an increased transmission rate and they do not significantly increase the complexity of the multi-pulse coding algorithm.

Abstract: Protection of a digital multi-pulse speech coder from fading pattern bit errors common in a digital mobile radio channel is accomplished with error detection techniques which are simple to implement and require no error correcting codes. A synthetic regeneration algorithm is employed which uses only the perceptually significant bits in the transmitted frame. Separate parity checksums for line spectrum pair frequency data, pitch lag data and pulse amplitude data are added to each frame of speech coder bits in the transmitter. The bits are then transmitted through a mobile environment susceptible to fading that induces bursty error patterns in the stream. At the receiving station, the parity checksum bits and speech coder bits are used to determine if an error has occurred in a particular section of the bit stream. Detected errors are flagged and supplied to the speech decoder. The speech decoder uses the error flags to modify its output signal so as to minimize perceptual artifacts in the output speech.

Abstract: A low-overhead method of protecting multi-pulse speech coders from the effects of severe random or fading pattern bit errors combines a standard error correcting code (convolutional rate 1/2 coding and Viterbi trellis decoding) for protection in random errors with cyclic redundancy code (CRC) error detection for fading errors. Compensation for detected fading errors takes place within the speech coder. Protection is applied only to the perceptually significant bits in the transmitted frame.

Abstract: Improved unvoiced speech performance in low-rate multi-pulse coders is achieved by employing a multi-pulse architecture that is simple in implementation but with an output quality comparable to code excited linear predictive (CELP) coding. A hybrid architecture is provided in which a stochastic excitation model that is used during unvoiced speech is also capable of modeling voiced speech by use of random codebook excitation. A modified method for calculating the gain during stochastic excitation is also provided.

Abstract: A scanning spectral-analysis micro-probe subsystem, for a surface imaging system, utilizes a micro-probe to detect the precise position of a point on a sample object surface having surface dimensions changing responsive to surface absorption of incident radiation from a modulated radiation source. The modulated incident radiation causes the sample region dimensions, in the vicinity of the micro-probe, to be modulated, so that the micro-probe detects this dimensional modulation, with a detected modulation strength directly proportional to the incident radiation absorption.

Abstract: A method for the reduction of synchronous fading effects in a time-diversity multiple-access communications system, in which the data to/from a particular user is to appear in a particular assigned slot, varies the position of the time slot assigned to that particular user, so that the slot has a different position in each successive frame in which that assigned slot appears. The position may be set relative to a frame feature, such as its start time and the like. Selected-schedule patterns may be used, with the pattern either being preset at the various stations or being sent to the stations prior to use, as part of a preamble, in-band supervisory signaling and the like.