Interdigital Microstrip Circuit Parameters Using Empirical Formulas and Simplified Model

Empirical formulas are given for single- and multiple-coupled microstrips, directly giving propagation mode admittances and phase velocities to be used in simplified expressions for the admittance parameters for the 2N-port network in the form of N-coupled strips, thus forming the basis for both analysis and synthesis of interdigital microstrip circuits. Calculated and measured results are presented for two interdigital band-pass filters synthesized as Chebyshev filters.