US Government As Represented by the Secretary of the Army

Electric Power Research Institute Incorporated

The Magnavox Company

Zeger-abrams Incorporated

Andrew E Zeger

Burton S Abrams

Joseph L Rose

Gurvinder P Singh

Michael J Avioli

Disclosed is a multiple-signal receiver system for direct sequence, code division multiple access (CDMA), spread spectrum (SS) signals. The receiver is structured to overcome inter-signal interference during signal acquisition and data reception even when the ratio of received signal powers exceeds the bandwidth spreading ratio of the signals. The receiver contains one processing channel for each signal in which correlation with the spread spectrum code of its particular signal is used to selectively isolate that signal so that its waveform parameters can be estimated, its data demodulated, and its waveform reconstructed. Each reconstructed CDMA waveform is individually adjusted in amplitude and phase to cancel its particular CDMA signal from the composite input of multiple CDMA signals. This receiver structure allows cancellation at the input of each receiver signal processing channel of all CDMA signals except the particular desired signal for that channel.

Multiple signal receiver for direct sequence, code division multiple

An ultrasonic return signal analyzing instrument and method including analog circuitry for making partial power measurements on two selected frequency bands of the frequency spectrum of an ultrasonic return signal waveform and digital circuitry for measuring selected features of the envelope of the ultrasonic return signal waveform. Digital waveform measurements are converted to analog signals and then combined in an algorithmic combining circuit to produce a test statistic signal. A decision circuit receives the test statistic signal and registers a decision on a characteristic of the structure under examination based on the value of the test statistic signal. The instrument includes a signal normalization circuit to normalize the ultrasonic return signal to a fixed peak value and includes a frequency up-converter in the normalizing circuit and frequency down-converters in the partial power measurement circuits for increasing the accuracy of peak detection in the normalizing circuit and envelope detection for the partial power band signals and the total power signal. The digital waveform feature measurement circuitry includes circuitry for measuring the rise time and duration time of the ultrasonic return signal envelope and logic is provided for handling two distinct return signal waveforms with rise time and duration time measurements being accomplished on the highest distinct pulse within the GATE signal window of the instrument. A GATE signal generated from the delayed GATE input of the pulser receiver of an ultrasonic instrument is utilized to GATE the various measurement functions so that measurements will be made only on the selected segment of the ultrasonic return signal waveform desired to be analyzed. A Fisher linear discriminant function is used as the algorithm in connection with analyzing ultrasonic return signals from stainless steel pipe having possible intergranular stress corrosion cracking conditions therein.

System and method for measuring ultrasonic return signals

Disclosed is an in-band, non-sampling, real time VHF radio relay or signal epeater for use in two-way, multi-hop remote sensor data links. Each signal repeater comprises a transceiver which includes interference cancellation circuits for preventing the high level signal produced by the radio repeater's transmitter section from desensitizing the low noise RF amplifier circuitry incorporated in the front end of the radio repeater's receiver section. Such apparatus is utilized to implement a remote sensor data collection network consisting of a plurality of subject radio repeaters and several sensors normally arranged in groups. The data which flows over the relay network can either originate at the sensors and flow to a read out station or it may originate at the read out station and flow to the sensors. Sensor originated information may be either digital or analog, or both, while read-out station originated information is digital only. The relay operates with either analog or digitally-modulated signals. When used with an omnidirectional antenna, it is not direction-preferential.

VHF Sensor in-band radio relay

A phase alignment system for a self-phasing antenna array is described. A single time-shared processor sequentially phase aligns each array element with a suitable reference signal. This technique is applicable to a self-phasing array in which the random phase of the signal received at each array element is slowly varying (bandlimited). Individual antenna signals are summed and the phase of the signal from a selected one of those antennas is compared to the phase of the sum (reference) and a variable phase shift is introduced into that selected one antenna output to bring that output into closer conformity with the phase of the sum. This process is repeated sequentially for the entire group of antennas and optionally the sequential comparing and adjusting may be interrupted, maintaining the phase-shifts for the several antennas at their most recent value, and the antenna array employed for a transmitter to thereby provide a transmission radiation pattern substantially the same as the reception sensitivity pattern as it existed just prior to the interruption.

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Wyndmoor, PA, United States of America

Andrew E Zeger