A design technique for separable denominator circularly symmetric 2-D filters

A simple design technique for a separable denominator circularly symmetric lowpass filter is described. In this technique an FIR filter function that has a sharp cutoff characteristic and is amenable to efficient implementation is used to meet the transition band requirement of the filter and to provide approximately circularly symmetric passband. However, the FIR filter has high transmission in stopband. To suppress this unwanted transmission in the stopband, an IIR separable guard filter with rectangular passband response is used