Pipelined CORDIC-based cascade orthogonal IIR digital filters

CORDIC-based cascade orthogonal infinite-impulse response (IIR) digital fil ters possess desirable properties for VLSI implementations such as local co nnection, regularity, absence of limit cycle and overflow oscillations, and good finite word-length behavior. However, the achievable sample rate of t hese filters is limited, since these structures cannot be pipelined at fine r levels (such as bit or multi-bit level) due to the presence of feedback l oops. In this paper, we present a novel approach to design pipelined CORDIC -based cascade orthogonal IIR digital filters using the transfer function a pproach, We first present a systematic way to synthesize cascade orthogonal IIR digital filters using scalar lossless inverse scattering theory, and r ealize the filter transfer function as a cascade inter-connection of orthog onal sections where each section implements one real zero or a pair of comp lex conjugate zeroes of the transfer function. In this way, the filter achi eves low sensitivity over the entire filter spectrum. Novel pipelining tech niques for both coarse-grain and fine-grain pipelining of these filters are then proposed. In coarse-grain pipelining, we present a novel method based on retiming and orthogonal matrix decomposition techniques which can incre ase the maximum filter sample rate to O(1) level which is independent of th e filter order, In fine-grain pipelining, we present a novel method based o n constraint filter design and polyphase decomposition techniques which cou ld increase the maximum filter sample rate to any desired level, The propos ed architecture for coarse-grain pipelining consists of only Givens rotatio ns, and the one for fine-grain pipelining consists of only Givens rotations and a few additions. Both architectures can be realized using CORDIC arith metic-based processors. Finally, finite nord-length simulations are carried out to compare the performance of different topologies.