United States of America As Represented by the Secretary of the Air Force

Joseph Caschera

James B Tsui

Rudy L Shaw

The circuit may be used to encode the channel outputs of a Bragg cell receiver, or other type of channelized receiver. Bragg cell receivers use acousto-optic delay lines to analyze signals such as radar pulses present in the Electronic Warfare (EW) environment. These receivers require high probability of intercept with low false alarm rates. The present design in determining frequency from a Bragg receiver is by comparing the amplitude from adjacent outputs. If the output of a certain channel is higher than its neighboring ones and the signal crosses threshold, the frequency of the input signal is determined by that channel. There is one major deficiency from this approach, that is, the design generates false alarms. A frequency encoding circuit is proposed which uses five adjacent channels to make a decision on whether a given output is a true signal, or a false alarm. With this approach, two guard channels will be needed at both ends of the channels.

Frequency encoding circuit in Bragg cell receiver

A memory system for histogramming the pulse descriptor word output of a radar warning receiver for initial processing of the received data for quickly determining the numbers and types of emitters in the system's environment. The disclosed apparatus histograms the number of pulses received in a given time interval versus scaled values of frequency and time differences of arrival plus it assigns available memory locations only when confirmed data is received. A typical histogram size of 1,024 (radio frequency) by 8,192 (time difference of arrival), or 8,388,608 pixels is disclosed along with comparisons and contrasts with less efficient conventional histogramming arrangements.

Radar warning receiver compressed memory histogrammer

An apparatus for use in conjunction with an instantaneous frequency measurement (IFM) receiver, for detecting the presence of two or more RF signals, differing in frequency, between the onset of the first RF signal pulse and the completion of the frequency encoding strobe. High frequency sample and hold circuits detect the level of the video upon stabilization of the leading edge of the first received pulse. Thereafter, comparators monitor both the video and sampled levels to detect defined differences therebetween. Monitoring ceases at the termination of the frequency encode strobe. Ambiguities in the encode frequency are detected by comparator unbalances, which actuate the inputs to a logic OR gate. The output of the OR gate is connected to a logic AND gate, whose other input changes in level upon the termination of the encode strobe. The output of the AND gate latches an alarm, signalling the IFM receiver that the frequency measurement is ambiguous.

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Fairborn, OH, United States of America

Joseph Caschera