Self Cohering an OTH Radar on Clutter Returns.
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1997
- Accession Number
- ADA327545
Entities
People
- Barry Fell
- Hesham Attia
- Kenneth Abend