Experience in developing Ka-band waveguide filter with HTS E-plane insert

This paper presents the results of the design and testing of seven-pole BPF Ka band with bilateral HTS insert in the E-plane rectangular waveguide. Study of the possibility of reducing the insertion loss in the E-plane filters with HTS inserts compared with losses in the filters with normal metal inserts is a purpose of the work. HTS insert is a single crystal MgO substrate of 0.5 mm thickness, of which the two surfaces are coated with superconducting YBCO films. By photolithography method, identical insert portions of the superconducting layers were removed on both sides of a substrate and thereby "window” chains were formed with a height equal to the height of the standard rectangular waveguide of 7.2x3.4 mm² section. The lengths of all "windows" and the distance between them along the axis OZ were calculated as a result of designing the filter. Therefore, individual resonators of seven-pole BPF are rectangular waveguide sections with dielectric MgO plates in the E-plane. The mutual coupling between the resonators and the coupling of the first and the last resonators with matched waveguide are carried out by means of pairs of the below-cutoff waveguide sections formed by the original walls of the waveguide and the conducting YBCO layers. It is clear that the principle of operation of the filter with HTS insert analogous to the principle of BPF widely used in practice with normal metal E-plane inserts.