Accession Number : ADA327545

Title :   Self Cohering an OTH Radar on Clutter Returns.

Descriptive Note : Final rept. Jun 92-Sep 94,

Corporate Author : GORCA SYSTEMS INC MAPLE SHADE NJ

Personal Author(s) : Attia, Hesham ; Abend, Kenneth ; Fell, Barry

PDF Url : ADA327545

Report Date : APR 1997

Pagination or Media Count : 69

Abstract : This investigation develops over-the-horizon (OTH) signal processing techniques that adaptively mitigate adverse time-varying ionospheric propagation effects. Propagation of HF radar returns through the ionosphere often results in a random spread of energy in time and space. Adaptive signal processing techniques use the statistical properties of radar clutter to measure and correct receive phase errors in an OTH radar without the need for a remote beacon. These approaches make use of complex spatial correlations between neighboring elements, or subarrays, in a phased array receive antenna to estimate and correct the differential phase errors, thereby restoring the correlation distance across the receive array to undo propagation-induced directivity and gain degradations. By compensating for time-varying spatial phase errors, this technique also reduces spread-Doppler clutter. Similarly, making use of complex temporal correlations between successive received range sweeps corrects for pulse-to-pulse errors. The algorithms are applied to 0Th backscatter data collected by Rome Laboratory's VALAR facility. Results show wide variation between data sets, and as a function of range within a data set, with significant improvement in cases of severe propagation anomalies. In one instance, a combination of algorithms reduces the spread-Doppler clutter below the noise and provides 10 dB processing gain. These results imply improved subclutter visibility (SCV) in OTH radar and new methods to combat fading in long-range HF communications.

Descriptors :   *RADAR CLUTTER, *OVER THE HORIZON RADAR, DATA BASES, ALGORITHMS, SIGNAL PROCESSING, ANOMALIES, IONOSPHERE, PROPAGATION, SPATIAL DISTRIBUTION, HIGH FREQUENCY, DEGRADATION, CLUTTER, VARIATIONS, CORRELATION, LONG RANGE(DISTANCE), ERRORS, VISIBILITY, GAIN, COMMUNICATION AND RADIO SYSTEMS, STATISTICAL ANALYSIS, RANGE(DISTANCE), ANTENNA ARRAYS, PHASED ARRAYS.

Subject Categories : Active & Passive Radar Detection & Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE