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 $\sigma \! $ -axis of the complex plane $s = \sigma + j\Omega $ , are generated, and we obtain a flat group delay. If another port position is used, two transmission zeros are generated on the $j\Omega $ -axis, $\Omega = (\omega /\omega _{0} - \omega _{0}/\omega)$ /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.