On causal linear phase IIR digital filters

Abstruct-This paper addresses the issue of the existence of causal linear phase IIR digital filters. The conditions for their existence are derived, and a set of examples satisfying these conditions is given. Specifically, the sequences must be integer samples of a continuous-time function, band-limited to ( n, n), which is symmetric and has zero crossings at the negative integers. Also, the point of symmetry can he neither an integer nor a half integer. A number of interesting properties of the related discreteand continuous-time functions are developed.