Multiplier-free FIR filters with periodically time-varying ternary coefficients

A multiplier-free realization for FIR (finite impulse response) filters is proposed. The realization uses a periodically time-varying (PTV) system, preceded and followed by an upsampler and a downsampler, respectively, to achieve time-invariant operation. The PTV system uses only ternary coefficients. With an upsampling ratio of 3 to 5, one can achieve coefficient precision of 9 to 25 bits, which is sufficient for most applications. The implementation requires only add/subtract operations with a few shift-and-add operations at the input and output of the PTV system