Spectrum-aware jammer suppression using evanescent-mode cavity filters

This work presents the first spectrum-aware closed-loop tunable jammer suppression system, utilizing evanescent-mode cavity filters. The presented system automatically sweeps a bandstop filter (BSF) across its tuning range and detects the location of the jammer in the spectrum by reading the output power of the filter. Once the frequency of the jammer is detected, the BSF is automatically tuned to suppress it. The system operates in real-time as it does not require a special hardware to directly sense the filter´s resonators. The system is implemented and tested under different frequency conditions. The tuning range is 1.8-2.16 GHz, and it can suppress jammers 20 MHz away from the signal by 41-45 dB using a three-pole BSF. This suppression is sufficient to bring the symbol recovery rate up to at least 99.9%, from less than 17% when no jammer suppression is employed. Error vector magnitudes are also experimentally studied for the 16 QAM modulation scheme that is used in the measurements.