Non-stationary interference mitigation in continuous phase modulated signals using estimation subtraction

Mitigating non-stationary narrowband interference from a continuous phase modulation (CPM) signal is a challenge due to the correlation present in CPM signal samples. For such a scenario, use of a time-varying linear prediction error filter (TVLPEF) based on a decorrelating time-varying autoregressive (DTVAR) model was proposed earlier. TVLPEF based mitigation of the interference from a CPM signal resulted in symbol error rate (SER) performance that degraded for signal-to-interference ratios (SIRs) of -20 dB to 10 dB. The deterioration is attributed to increased interference prediction error. An estimation subtraction approach to mitigate non-stationary interference from a CPM signal is investigated. First, the interference parameters-such as instantaneous frequency, rate of change, phase, and amplitude-are estimated using a DTVAR model; then the estimates are refined using nonlinear optimization. The proposed estimation subtraction approach realizes notable SER performance improvements for SIR of -20 dB to -5 dB.