AMPS interference rejection by exploiting the SAT information

Cyclostationarity is a common characteristic for many digital and analog communication signals. AMPS signals exhibit this characteristic because of the supervisory audio tone (SAT). The effect of the SAT is to replicate the modulated voice spectrum at multiples of the SAT frequency, and thus, the signal exhibits spectral correlation. A time-dependent adaptive filter can be designed to exploit the cyclostationary characteristic of the AMPS signal and suppress the co-channel interference. The adaptive algorithm used to optimize the filter does not need any reference signal to train the filter and it works in realistic channels. Using digitized signals, a two-stage time-dependent filter improves the CIR from 11 dB (typical at the boundary for a three-cell reuse pattern) to 18 dB (typical at the boundary for a standard seven-cell reuse pattern), even in the presence of strong multipath and Rayleigh fading