K-band quasi-planar tapped combline filter and diplexer

• Published in: IEEE transactions on microwave theory and techniques 1993-02, Vol.41 (2), p.215-223
• Main Authors: Wen-Teng Lo, Tzuang, C.-K.C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Band pass filters; Bars; Circuit optimization; Circuit properties; Coupling circuits; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Fasteners; Frequency; K-band; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave filters; Resonator filters; Stripline
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/22.216459

Quasi-planar realizations of a combline bandpass filter and diplexer using multiple coupled suspended substrate striplines (MCSSSs) have demonstrated good performance at K-band without any tuning. The N MCSSSs excite N zero-cutoff-frequency quasi-TEM modes. A computer-aided filter design approach employing a rigorous spectral domain approach and 2N-port microwave circuit theory accounts for the effects of the N quasi-TEM modes, the couplings through nonadjacent MCSSSs, and cover height. Two 19.5-20.5 GHz MCSSS combline filters with different cover heights have been built and tested to compare their filter characteristics. The reduction in cover height has been found to decrease the amount of nonadjacent coupling through MCSSSs and to result in better filter stopband performance. An 18.5-19 GHz and 20-20.5 GHz MCSSS diplexer is also presented. All the measured results for the combline filters and diplexers agree well with the theoretic calculations.< >