In-line pseudoelliptic band-reject filters with nonresonating nodes and/or phase shifts

In-line pseudoelliptic band-reject filters with nonresonating nodes (NRNs) and/or phase shifts are introduced. It is shown that general band-reject filters with arbitrarily placed reflection zeros (RZs) can be designed by both classes. A more general low-pass network, which contains both NRNs and phase shifts, is introduced. Prior to implementation, the network, which includes phase shifts, is optimized to take into account dispersion effects and better fit the specifications. Example filters in microstrip and waveguide technologies are presented. Experimental validation of the method is demonstrated by a novel third-order waveguide band-reject filter at K alpha-band with asymmetric response. It provides a transfer characteristic with all three RZs below the stopband. Excellent coincidence of the computed and measured responses of the realized filter-obtained without any post-manufacturing tuning-is achieved.