Partial $H$ -Plane Filters With Multiple Transmission Zeros

This paper presents partial H-plane filters with multiple transmission zeros using a narrow H -plane slot of open-ended evanescent waveguide. Each narrow H-plane slot operates as an admittance inverter and, simultaneously, provides the attenuation pole due to its resonance behavior at a particular frequency. Thus, the number of transmission zeros is equal to that of the H-plane slots. The filters with multiple transmission zeros are simply implemented without any additional coupling and extra modification of the filter structure. Two filters are designed by half- and quarter-wavelength resonators, respectively. The measured results are in good agreement with simulated results.