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

Nicholas A Pequignot

James B Y Tsui

David M Lin

John M Emmert

Rudy L Shaw

Stephen L Hary

Keith M Graves

James B Tsui

A moderate cost and complexity digital radio receiver system having enhanced instantaneous dynamic range response to the receipt of simultaneous signals and also providing large single signal dynamic range. Multiple signal instantaneous dynamic range improvement is achieved through use of a suppressed zero signal amplitude representation arrangement having a selected number of signal amplitude representing digital bits rather than the larger entire array of digital output bits of the receiver system's analog to digital converter. Digital apparatus for accomplishing the selection of desired high order bits from the analog to digital converter output is also disclosed in detail. Use of a 'Monobit' and related simplified Fourier transformation radio receivers as disclosed in identified previous patents of the recited inventors and colleagues is preferred for embodying the digital radio receiver circuit included in a present system.

Digital receiver instantaneous dynamic range enhancement

A Fourier transformation arrangement usable in an electronic warfare radio receiver for analyzing spectral content of multiple transmitter-sourced brief duration incoming signals for their signal characteristics. The disclosed Fourier transformation arrangement includes approximated Kernel function values disposed in a significant plurality of locations about a real-imaginary coordinate axis origin according to disclosed locating principles. The points are displaced from the origin by magnitudes having real and imaginary component lengths of powers of two commencing with zero. Multiplication involving a power of two component length during a Kernel function utilization are preferably achieved by way of an expanded binary shift multiplication algorithm in lieu of a full fledged digital multiplication algorithm. A group of guiding principles for selecting desirable approximation Kernel function locations is included.

Kernel function approximation and receiver

The technique allows precise angle-of-arrival (AOA) and radio frequency measurements on non-cooperative radar signals, by exploiting precise phase measurement capabilities of frequency measurement receivers. It is assumed that the intercept receivers with this capability are on board an aircraft and there are at least two antennas available. By utilizing the phase measurements, the incident frequency and incident phase angle are calculated using formulae derived under the disclosed technique. By taking multiple samples and averaging, angle measurement errors can be reduced.

Doppler frequency angle measurement technique

To allow measurement of the angle-of-arrival (AOA) of the radar pulses from an uncooperative ground-based emitter, the method exploits the time doppler shift resulting from the velocity of a high performance aircraft and the high maneuver ability available to such aircraft to form initial angle calculations. These initial angle calculations along with inherent radar stability are then used for subsequent AOA measurements. The aircraft is flown at a constant velocity V.sub.B along successive legs with an angle .phi..sub.K between successive legs, and the velocity V.sub.B and the angles .phi..sub.K are found using a navigation system such as GPS or inertial navigation. The time difference T.sub.n '-T.sub.1 ' is measured between the arrival of the first and last of n pulses for each sample. A general approximation equation of T.sub.n '-T.sub.1 ' is normalized such that for any K samples the following equation applies,

Growing community of inventors

Kettering, OH, United States of America

Nicholas A Pequignot