Trisection Bandpass Filter With Mixed Cross-Coupling and Different Paths for Signal Propagation

In this letter, new patterns of symmetric trisection bandpass filter (BPF) with reflection-type half-wave resonators, mixed cross-coupling, and different paths for signal propagation are discussed. The various coordinates of the conductive connection of loads to the end half-wave resonators are used in the filter. This leads to different signal paths from input to output of the filter. Due to the various connections of loads and mixed cross-coupling, satisfying condition K 13 = 0, the same filter has different frequency responses. When we use one port position, two transmission zeros, located on the σ-axis of the complex plane s = σ + jΩ, are generated, and we obtain a flat group delay. If another port position is used, two transmission zeros are generated on the jΩ-axis, Ω = (ω/ω 0 - ω 0 /ω)/fractional bandwidth (FBW), and a quasi-elliptic response is presented. In both cases, two transmission zeroes are equidistant relative to s = 0 and they are controlled by a mixed coupling coefficient. The results of the measurements and simulation are presented.