USA as Represented by Secretary of the Navy

Other

James W Bond

Thomas W Schlosser

William Y Velez

Stefen Hui

Harper J Whitehouse

Paul A Singer

James R Zeidler

David W Stein

Carey E Priebe

David J Marchette

Jeffrey M Speiser

James M Alsup

Isaac Lagnado

Gary A Dressel

Thomas W Schlosset

Williams Velez

Henry J Schmidt

A masked signal transceiver of the present invention comprises a transmitter for transmitting a combined signal of a primary communications signal and an attenuated secondary communications signal occupying substantially the same frequency band concurrently. A receiver receives the combined signal and demodulates the primary communications signal to extract the primary communications signal information. An adaptive locally optimum processor separates the secondary communications signal from the combined signal. The secondary communications signal is then demodulated to extract the secondary communications signal information.

Masked signal transceiver

Processors which process baseband received signal sample amplitudes and ones which process baseband received sample phases are combined in a single general processor which cancels a greater variety of interference than any of the individual processors incorporated into it. This processor combines a wide-range of processors, for example, processors which filter baseband in-phase/quadrature sample amplitudes and phases. This general processor performs against any interferer as well as, or better than, the best of the processors it includes. The general processor assesses individual processor outputs and weights these so that those processors with the best interference suppressed outputs are utilized to form an interference suppressed output.

Adaptive processor integrator for interference suppression

A simplified interference suppressor extends the applicability of adaptive ocally optimum techniques to high speed communication systems. Traditional adaptive locally optimum processing amplitude quantity techniques compel baseband sample amplitudes calculation requiring square root operations that could limit the use of these techniques. The simplified interference suppressor utilizes amplitude squared values of baseband samples while maintaining the performance of those processing algorithms requiring the complexities of baseband sample amplitude calculation.

Simplified interference suppressor

The Beamformer with Adaptive Processors is a practical joint spatial-templ processor suitable for combining multiple antenna signals for a communications receiver. The invention identifies a beam or beams, amongst a discreet set of fixed beams, for which adaptive locally optimum processing will most likely reveal the presence of a weak signal. The invention chooses a suitable form of adaptive locally optimum processing according to the nature of the beam or beams identified. The beam or beams are selected for adaptive locally optimum processing depending on several simple characteristics of a Fast Fourier Transform (FFT) of each beam's output. These are .SIGMA..sigma..sup.2, D, and B (the sum of the squares of the Fourier coefficients, the number of distinct peaks amongst these coefficients, and the total number of coefficients defining the peaks, respectively). A simple logic table is used to define the beam or beams to be used for adaptive processing and to define the nature of the adaptive processing to be used on the beams identified to most likely reveal the presence of a weak signal. The result of the combination of selecting the most promising beam or beams and appropriately adaptively processing the beam or beams is a near optimal implementation of a joint temporal-spatial processor.

Beamformer with adaptive processors

The frequency domain kernel processor of the present invention comprises a cheduler for selecting samples from blocks of Fourier transform coefficients in a predetermined sequence and for outputting the selected samples as serial terms s and as parallel terms u. A transform processor is coupled to the scheduler to receive the terms s and u. The transform processor comprises transform calculators for calculating output values p and f as functions of terms s and u to model the interference and to reveal the desired signal, a first sum calculator for calculating a sum of p values, a second summing calculator for calculating a sum of f values, and a divider for calculating, the quotient of the sum of p values divided by the sum of f values. An output buffer stores the outputs of the divider for formatting as a spectral display.

Frequency domain kernel processor

A frequency domain kernel phase processor comprises an input buffer to st Fourier coefficients input from a Fourier transform of a communications signal. A communications signal suitable for processing by the present invention typically comprises a desired signal masked by a stronger interference signal having varying power that spans a range of frequency bins encompassing the desired signal. A scheduler inputs Fourier transform coefficients from the input buffer and generates a series of magnitude squares and symmetric phase differences for each frequency bin. The magnitude squares and the symmetric phase differences are output to phase transform processors which transform the symmetric phase differences to reveal the desired signal. The transformed outputs from the phase transform processors are output to an output buffer to be formatted and displayed.

Frequency domain kernel phase processor

The narrowband signal revealer comprises a sensor, a baseband generator, an daptive locally optimum processor (ALOP), and a complex signal spectral analyzer. The sensor generates an input signal representative of a tonal signal masked by wideband interference. The baseband generator transforms the input signal into a complex baseband signal. The ALOP processes the complex baseband signal to suppress the interference and generates a complex output signal representative of the tonal signal. The spectral analyzer then analyzes the complex output signal and displays tonal signal power.

Narrowband signal revealer

The adaptive parameter kernel processor of the present invention uses an adaptive locally optimum detection (ALOD) signal processing algorithm to suppress interfering signals in a communications signal. The adaptive parameter kernel processor generates a signal magnitude value for each signal sample, partitions the signal magnitude values into sets, and concurrently executes multiple copies of the ALOD signal processing algorithm. Each copy of the signal processing algorithm applies a probability density function to the sets of signal magnitude values, generating a gain factor for each set. The probability density function includes a parameter that has a different value in each copy of the signal processing algorithm. Each copy of the signal processing algorithm generates an average gain factor associated with the corresponding parameter value. The parameter values are updated respectively in the multiple copies of the signal processing algorithm by a parameter comparator to cause the parameter value associated with the minimum average gain factor to approach the midpoint of the parameter values. An output signal is formed from the signal samples and an arithmetic function of the average gain factor associated with the midpoint of the parameter values.

Adaptive parameter kernel processor

An interference suppression system utilizes a non-adaptive filter to suppress interference from bandspread communication signals. The filter is effective in the cancellation of interference from a bandspread communication signal when the interference dominates the communication signal and Gaussian noise. This invention requires a processor without highly specialized hardware components. The components are cheaper and easier to produce because the required processor needs to perform fewer calculations by several orders of magnitude than previously existing processors providing roughly equivalent interference suppression. By forming phase-differences, the filter is used to estimate whether the signed magnitude of a component of a communication signal phase difference is either 90.degree. or 270.degree. out-of-phase with interference. By estimating this component, high quality reception of spread spectrum radio communication signals in an interference environment is possible.

Non-adaptive phase-difference interference filter

An interference suppression system utilizes an adaptive locally optimum detection algorithm derived from kernel estimation. By utilizing this algorithm in the processor of the invention, fewer receive samples are required to obtain useful estimates of required probability density functions. The new adaptive locally optimum detection algorithm is useable in applications involving very high sampling rates and is thus suitable for rapidly and radically changing interference environments encompassing a wide range of frequencies.

Kernel adaptive interference suppression system

An interference suppression system utilizes a non-adaptive filter to supps interference from bandspread communication signals. The filter is effective in the cancellation of interference from a bandspread communication signal whenever interference has a mean component several times greater than its variable component. By forming amplitude-differences, the filter is used to estimate whether the signed magnitude of a communication signal component is in-phase or 180.degree. out-of-phase with present interference. By estimating this component, high quality reception of spread spectrum radio communication signals in an interference environment is possible.

Non-adaptive amplitude-difference interference filter

A two-dimensional interference suppression system utilizes adaptive locally optimum detection algorithms derived from kernel estimation. By using these algorithms in the process of the invention, fewer receive samples are required to obtain useful estimates of probability density functions. The new adaptive locally optimum detection algorithms lend themselves to use with simple processors permitting applications involving very high sampling rates.

Two-dimensional kernel adaptive interference suppression system

A method and apparatus are provided for suppressing interference from a sence of bandspread communication signals received by a radio receiver. Each sample is defined as a vector having signal and interference vector components. The interference vector component is such that: 1) the interference dominates the signal vector component, and 2) the phase of the interference vector components in the sequence changes slowly with time. Interference is suppressed while a portion of the signal vector component that is normal to the interference vector component is estimated as an indication of the bandspread communication signal. To do this, a phase angle is determined for each sample based upon each sample's defined vector. The phase angle for each sample is transformed into a corresponding phase vector based on a symmetric sampling of phase angles from previous and subsequent received signal samples. All terms of each corresponding phase vector are summed and averaged to generate a corresponding average phase gain for each sample. Each corresponding average phase gain is multiplied by a vector normal to the corresponding sample's defined vector to estimate the signal vector that is normal to the interference vector for each sample. The method and apparatus are effective whenever the phase of the interference vector components is characterized as having a frequency of change that is less than 1/2T, where T is the time required to receive the symmetric sampling.

Method and apparatus for suppressing interference from bandspread

A method and apparatus are provided for suppressing linear amplitude interence (e.g., on-off interference) from a sequence of bandspread communication signals generated by a radio receiver. Each sample is defined as a vector having signal and interference vector components. The interference vector component is such that the amplitude of the interference: 1) is essentially linear, and 2) dominates the signal component. To suppress the linear amplitude interference, a pseudo second derivative is obtained for each sample based upon the current, previous and subsequent sample amplitudes. The pseudo second derivative for each current sample is transformed into a corresponding pseudo second derivative vector based on a symmetric sampling of pseudo second derivatives from previous and subsequent received signal samples. All terms of each corresponding pseudo second derivative vector are summed and averaged to generate a corresponding average enhanced signal gain for each sample. Each corresponding average enhanced signal gain is multiplied by a normalized vector approximately parallel to the corresponding sample's interference vector component. This estimates the signal vector component that is parallel to the interference vector component for each sample as an indication of the desired communication signal. The method and apparatus are effective whenever the amplitude of the interference vector components is approximately linear over the time that the interference is present.

Method and apparatus for suppressing linear amplitude interference from

An adaptive processor for a spread spectrum receiver utilizes an adaptive Wiener filter and an adaptive limiter-canceller in tandem and in conjunction with bypass controls. The adaptive processor derives its cancelling signals from the primary signal. The adaptive processor makes use of bypass switches connected to the adaptive Wiener filter and adaptive limiter-canceller and activated by internally generated control signals to switch the adaptive Wiener filter and adaptive limiter-canceller in or out of the signal processing path.

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San Diego, CA, United States of America

James W Bond