An interference suppressor for CW and narrow-band signals using filter bank on CDMA communications

Abstract

A novel digital interference suppression method based on Fourier transform has been proposed. Since the frequency power spectrum of CW and narrow band interference signals are larger than that of the spread-spectrum signal, these interference signals can be reduced by limiting the signal level in the frequency domain. The proposed method is composed of FDM/TDM transform using a filter bank and an amplitude limiter adjusted to the spectrum of the spread-spectrum signal. The received signals are divided into separate narrow frequency bands in real time using a frequency function and the amplitude of these signals is limited. This signal processing reduces the interference signals. This paper describes the principle design of the transform circuit and explains the optimum limiting technique. In particular, the proposed digital processing model is compared with the analog processing model which has already been reported. In addition, the adjustment level of the amplitude limiter for the DS and FH spread-spectrum signal is shown. Finally, the improvement in interference suppression using FFT and the optimum limiting limiter is demonstrated with measured the eye pattern of the correlated signal. The performance of this suppressor is shown by measuring the bit error rate in the presence of CW interference signals and Gaussian noise.<>