Design of an elliptic filter in a microstrip configuration

The design of dual mode elliptic function filters using microstrip patches is discussed. The design, illustrated for a four pole filter, proceeds from an electromagnetic analysis of the structure which produces set curves relating the physical parameters of the system to its resonant frequencies. These frequencies are then related to the required couplings between modes through a lumped element representation of the filter. The problem is formulated using the electric field integral equation in the spectral domain, and solved with the method of moments. Basis functions are used which reflect the physical nature of the currents; the edge condition is included.<>