Interference Suppression for Spread Spectrum Signals Using Adaptive Beamforming and Adaptive Temporal Filter
Abstract
Interference and jamming signals are a serious concern in an operational military communication environment. This thesis examines the utility and performance of combining adaptive temporal filtering with adaptive spatial filtering (i.e. adaptive beamforming) to improve the signal-to-jammer ratio (SJR) in the presence of narrowband and wideband interference. Adaptive temporal filters are used for narrowband interference suppression while adaptive beamforming is used to suppress wideband interference signals. A procedure is presented for the design and implementation of a linear constraints minimum variance generalized sidelobe canceler (LCMV-GSC) beamformer. The adaptive beamformer processes the desired signal with unity gain while simultaneously and adaptively minimizing the output due to any undesired signal. Using the LCMV-GSC beamformer with a least mean squares (LMS) adaptive algorithm, it was shown that the tapped delay line (TDL) adaptive antenna array is more effective for the suppression of wideband jammer suppression than the linear array sensors (LAS) adaptive antenna array. Also a new technique for adaptive beamforming is presented which improves wideband interference suppression in a frequency-hopped environment. The output SJR improvement for the new technique compared to the conventional technique is as much as 15dB. Sometimes, multipath signals and jammers generated by a smart enemy are correlated with the desired signal which destroys the traditional beamformer's performance. After performing a spatial smoothing technique, adaptive beamforming can also be effective in suppressing the jamming signals that are highly correlated with the desired signal.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1996
- Accession Number
- ADA321365
Entities
People
- Wonjin Park
Organizations
- Air Force Institute of Technology