Two-Dimensional Digital Filters Possessing Variable Magnitude Characteristics Starting from A 1-D Monotonic Response

The generation of two-dimensional variable magnitude and contour characteristics by utilizing two 1-D filters in cascade is considered. The starting point for each 1-D filter is a monotonic response obtained by the integration of a second-order Butterworth polynomial. The variable characteristic in each domain is obtained by changing a multiplier in its feedback path. By utilizing a generalized bilinear transformation, a large number of possibilities exist and these are examined in some detail. Some illustrative examples are given