Weighted order statistics filter for real-time signal processing applications based on pass transistor logic

The authors describe the rationale of the design of complex weighted order statistics filters (WOS filters) suitable for real-time signal processing applications. It is based on a simple stack-like architecture that decomposes the M-valued signals into a reduced number of binary signals which are filtered by identical boolean logic circuits (binary filters). The main distinguishing feature of the proposed procedure is the efficient implementation of both the decomposition stage and the binary filters. The former is achieved on the basis of introducing a new decomposition scheme which can be economically translated to hardware. The latter comes from realising that the binary filters required for WOS filtering are threshold functions and from the development of a systematic methodology for building pass-transistor networks that implement them. Results for a complex example filter show a sample frequency of over 175 MHz in a 0.35 μm MOS technology at 3.3 V.