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

James N Hedge

James B Tsui

James B Y Tsui

Rudy L Shaw

Keith M Graves

Vasu Chakravarthy

David C Tsui

An electronic warfare radio receiver of the monobit type wherein the signal processing circuitry, including a bandpass filter array, analog to digital converter circuit and Fourier transformation circuit, are located in a plurality of parallel-disposed but isolated receiver channels. The parallel disposed receiver channels limit interference between received signals and enable the customary processing of two simultaneous input signals of differing signal strength in each receiver channel; this increases the number of simultaneous input signals processable by a factor equaling the number of receiver channels used. Single chip embodiment of the receiver is disclosed thereby tending to compensate for the added complexity of the channelized processing. Signals falling in digital filter overlap regions are addressed by the invention.

Channelized monobit electronic warfare radio receiver

The technique to measure the frequency very accurately for electronic warfare (EW) applications, and is simple in hardware, and which can accomplish this goal with a signal with real data (in contrast to complex data). It uses trigonometric identities to compute the location of the zero, which is very precise, but requires the use of an inverse trigonometric function. From these crossings, one can find the frequency very accurately using only one channel of data. The input signal is down converted and digitized with one A/D converter. The digitized data is used to find the zero crossing. The resolution of the zero crossing is limited by the clock cycle. Three uniformly digitized points around a zero crossing are used to find the time for the crossing. The device according to the invention will calculate the frequency very accurately using only one channel of data. This method can be used to measure the angle of arrival in a two antenna configuration with very precise results where the distance between the two antennas does not exceed half the wavelength of the incoming signal.

Highly accurate zero crossings for frequency determination

An IFM (Instantaneous Frequency Measurement) receiver is disclosed that can process two simultaneous signals for electronic warfare application. Three IFM receivers are employed (cooperating in the 2 to 4 GHZ range) and have three filters in front of them. Filter 1 is a 2-4 GHz band pass receiver in front of the first receiver. In front of the second receiver is a low pass filter with a band edge at 2 GHz. In front of the third receiver is a high pass filter with the band edge at 4 GHz. In filters 2 and 3, the skirts of the filters are used rather than their pass bands. Details on the signal conditions, calculations for the frequencies, and the equations are disclosed.

Instantaneous frequency measurement (IFM) receiver with two signal

The apparatus detects the presence of long or short pulse phase shift keyed (PSK) modulated signals and determines the underlying clock frequency and modulation code associated with such signal, in real time, using an instantaneous frequency measurement (IFM) receiver as its signal source, without affecting the band-width or sensitivity of this receiver. It monitors the output of the IFM correlators for transients which occur in the correlator's outputs when a PSK signal is present. Logic circuits are used to declare the PSK signal is present, determine its clock rate, a record the modulation or total number of pulses.

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Medway, OH, United States of America

James N Hedge