Two-dimensional lossless two-port for circularly symmetric digital filtering

The problem of applying two-dimensional (2-D) lossless two-ports to circularly symmetric wave digital filtering is treated. In approximating some useful symmetries, such as diagonal and quadrantal symmetries which are desired for circular symmetry, a kind of two-port possessing such properties is derived by using the subnetwork concept. Following this concept, a two-port suitable for circularly symmetric filtering is derived. Some considerations on filter design and realization are given. The theory is then confirmed by an example