Downsampling Techniques Using Notch Filter for Interference Cancellation in Narrowband Wireless Systems

This paper presents novel downsampling techniques using multiple second-order FIR notch filters for interference cancellation in the frequency division multiplexing (FDM) narrowband wireless systems. The purpose of the presented technique is to reduce the computational complexity of signal prosessor in a low-IF receiver. The presented downsampling technique employs some downsamplers and second-order FIR notch filters where its center notch frequency equals to the half of the sampling frequency. Since its filter are composed of a few adder and register instead of ones of a low pass filter (LPF) with the steep characteristic, the reduction of the computational complexity can be expected. In the presented technique, signal components to be overlapped to desired signal when downsampling is carried out are eliminated by the second-order FIR-NF. The presented technique concentrates in-band channel interferences into a narrow frequency range, and these interferences are cancelled by a harf band filter. Numerical example are shown to valid the effectiveness the presented technique.