On-board AJ enhancement using adaptive nonlinear processing: practical aspects of Smart AGC implementation

The authors have verified the capability of a new antijamming (AJ) approach that could be used for military satellite communication transponders. They have assessed performance in controlled jamming scenarios, and surveyed the capability of current technology to support near-term implementation. Smart AGC uses time-dependent, RF center stripping, the size of which is determined by a fast measurement of the jammer´s amplitude. Results with constant envelope (CE) and slowly varying jamming confirm that the output jammer-plus-intermodulation-to-noise ratio, (J+IM)/S, can be reduced to several decibels above the combination of background noise level and wanted signal level. With Smart AGC, a pure unmodulated carrier jammer at the center of the band would no longer be the optimum jammer for direct-sequence spread-spectrum modulation, nor could a CE signal produce 6-dB small signal suppression or capture the transponder´s effective isotropically radiated power (EIRP)