Angle quantization approach for lattice IIR filter implementation and its trellis de-allocation algorithm

In a multiplier-less digital filter implementation, the sign-power-of-two (SPT) scheme can significantly reduce the hardware complexity but this may seriously degrade the filter performance due to the limited number of SPT terms. Since the CORDIC algorithm is similar to the SPT scheme in that they are both constructed by several shift-and-add operations, the performance would also be significantly affected by the number of these operations. In this paper, we propose the modified angle rotator (MAR) scheme; it provides a systematic solution to enhance the precision of quantized angle without additional hardware overhead. Furthermore, we also apply an appropriate optimization procedure, the trellis de-allocation algorithm, in the angle domain to further reduce the unnecessary operations. Our simulation results show that we can save 40% of the number of adders compared with the direct coefficient quantization approach in normalized lattice filter implementation.