TWOS COMPLEMENT QUANTIZATION IN ORTHOGONAL BIQUAD DIGITAL-FILTERS

A special class of complex biquad digital filters called orthogonal fi lters are investigated for stability under two's complement quantizati on. A sufficient condition is derived for the asymptotic stability of the nonlinear filter. Bounds on the possible limit cycles am also obta ined. Using these bounds, any given filter can be tested for stability . The stability triangle is then scanned using a dense grid, and each point on the grid is tested for stability/limit cycles. By this method , the stability region given by the sufficient condition is extended. Regions within the linear stability triangle where various types of li mit cycles are possible are also identified.