USA As Represented by Secretary of the Navy

James P Hansen

Bernard L Lewis

Frank F Kretschmer, Jr

George J Linde

Jefferson M Willey

James A Ballas

Jean De Graaf

Thomas Herne Crystal

Vincent Michael Stanford

Todd Stephenson

Carol Chang

Hugh Faust

Justin Nevitt

A method for detecting and recognizing speech is provided that remotely detects body motions from a speaker during vocalization with one or more radar sensors. Specifically, the radar sensors include a transmit aperture that transmits one or more waveforms towards the speaker, and each of the waveforms has a distinct wavelength. A receiver aperture is configured to receive the scattered radio frequency energy from the speaker. Doppler signals correlated with the speaker vocalization are extracted with a receiver. Digital signal processors are configured to develop feature vectors utilizing the vocalization Doppler signals, and words associated with the feature vectors are recognized with a word classifier.

Radar microphone speech recognition

An improved countermeasure detection system and technique for determining e range and azimuth of a noise jammer in a radar environment. A signal limiter is inserted into the output loops of a conventional multi-loop side-lobe canceller system such that the loops only respond to interference signals in the main lobe of a radar antenna as it sweeps through the jamming source. Each of the loops develops a weighting signal that is a measure of the absolute phase of the interference signal at an auxiliary antenna with respect to the phase center of the main radar antenna. By using two or more weighting signals and the known placement of each auxiliary antenna relative to the main radar antenna, the range and azimuth of a jammer can be calculated using available processing equipment to solve simultaneous equations.

Determination of jammer range and azimuth by use of a coherent side lobe

An interference suppression system for cancelling undesired signals recei through the mainlobe of an antenna as well as its sidelobes. The interference suppression system has a main channel input having high gain for receiving desired signals and undesired signals and forming a main channel waveform, and an auxiliary channel input having low gain for receiving desired signals and undesired signals and forming an auxiliary channel waveform. A control circuit senses the relative undesired signal power in the two channels and responds by switching the waveforms in the two channels between two inputs of an interference-reducing circuit according to whether sidelobe or mainlobe interference is present in the main channel. The interference-reducing circuit corrects whichever waveform is fed to its first input in amplitude and phase and combines the corrected waveform with the other waveform at its second input to form an output waveform such that undesired signals in the two input waveforms substantially cancel one another while the desired signal is not cancelled.

Mainlobe canceller system

A new technique for improving the operation of a interference suppression stem, particularly in a side-lobe canceller system, against multiple interference sources. A plurality of auxiliary receiving antennas, providing interference signals to side-lobe canceller loops, are spaced about a main directional receiving antenna and positioned to preferably form a configuration such that no lines of sight through any two auxiliary antennas are collinear or parallel to a line of sight through any other two auxiliary antennas. The configuration is then arranged relative to the main antenna such that no lines through any two auxiliary antennas are substantially parallel with the primary direction of a multiple jammer attack.

Directive optimization of coherent sidelobe canceller systems

An improved signal processing system and technique for preprocessing auxiry data signals by sequential decorrelation, particularly for use in systems employing adaptive cancaller loops. Each of a plurality of signal channels sample the environment of a plurality of signal sources and provide inputs to a configuration of adaptive canceller loops. The loops are connected such that an adaptive loop decorrelates the signal from two signal channels to form a preprocessed signal, and each of the remaining adaptive loops are sequentially connected such that each auxiliary channel signal is decorrelated from the preprocessed signal of the previous adaptive loop until all signal channels have been utilized. In a side-lobe canceller system each of the preprocessed outputs is used to form an auxiliary sample input to a main channel canceller loop to cancel interference in the receiving system. By using the preprocessed signals as the auxiliary input, a receiving system can significantly increase interference cancellation and reduce the number of iterations required.

Sampled data processing

A height-determining radar utilizing both direct and multipath signals coising a radar transmitter and receiver and means for measuring the variation of the pulse widths of the received radar signal, the variation being caused by fluctuating multipath contribution to the received signal, and further comprising means for calculating the target height h from the equation h=cR.tau..sub.B /4e, where c is the speed of light, R is the target range, .tau..sub.B is the pulse width variation and e is the radar height. The multipath variation may be enhanced by varying the linear polarization of the emitted radar signal.

Altitude determining radar using multipath discrimination

A device for aligning the phase and amplitude of a quadrature-detected coent two-channel receiver utilizing a mixer in each channel comprising a circuit for providing a sweep frequency signal to each receiver channel; a circuit for detecting the envelopes of the receiver channels at the outputs of the mixers and determining the voltage difference between the envelopes; and a circuit for controlling the amplitude level in one of the receiver channels in accordance with this voltage difference. Simultaneously, the output signals from the two mixers are added with the resulting sum signal being envelope-detected, and also subtracted from each other with the resulting difference signal being envelope-detected. The sum envelope and the difference envelope are subtracted from each other to generate a control signal for controlling the phase of one of the mixer local oscillator signals to ensure that the mixer local oscillator signals are in phase quadrature.

Coherent receiver phase and amplitude alignment circuit

An improved technique for eliminating interference in serial data samples ving signal components which are desired to be removed before being further processed. A limited-iterative technique is employed to reduce components of the incoming data samples which are correlated among prior data samples.

Adaptive MTI system

A quadrature detector wherein the I and Q quadraturely related signals are roduced and processed in the same channel rather than parallel channels. A local oscillator feeds a 90.degree. phase splitter which produces a pair of quadrature signals. These are alternately fed to a balanced modulator for mixing with an input R.F. signal. The sum and difference frequency signals are fed through a low-pass filter which passes only the I and Q difference-frequency signals. These are then separated to provide two output signals corresponding to quadrature components of the input R.F. signal.

Switching quadrature detector

An improved system and technique for reducing interference in signal receng systems, particularly in sidelobe canceller systems. Adaptive canceller loops receive inputs from an auxiliary channel signal and operate on a main channel signal to reduce interference in the main channel signal. The auxiliary channel signal is supplied through a quadrature hybrid circuit to provide I and Q components to the adaptive loops, which loops are connected in series and cascaded such as to form a plurality of serially connected I and Q loops.

Growing community of inventors

Waldorf, MD, United States of America

James P Hansen