Rejection of low frequency interference using lattice IIR notch filter

The comparison made with three kinds of structures and sensitivity of lattice IIR notch filters shows that the approach based on all-pass filter has the least sensitivity at low frequency. The new method proposed uses 2M-order all-pass filter to construct the multiple notch filter with M frequencies. Due to the mirror-image symmetry relation between the numerator and denominator polynomials of all-pass filter, the notch filter can be implemented by an efficient pure lattice (PL) structure with very low sensitivity. A design example indicates that notch frequency shift of PL structure after coefficient quantization is much less than that of cascade lattice (CL) structure. Moreover, an actual application in power line communication is presented to demonstrate the performance of this notch filter.