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Compact tunable cavity filter with high selectivity using double‐layer suspended stripline resonator
Author(s) -
Song Lei,
Wu Bian,
Xia Lei,
Guo Yongxin,
Chen Jianzhong,
Su Tao
Publication year - 2019
Publication title -
microwave and optical technology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 76
eISSN - 1098-2760
pISSN - 0895-2477
DOI - 10.1002/mop.31735
Subject(s) - resonator , materials science , varicap , optoelectronics , capacitor , capacitance , stripline , return loss , capacitive sensing , wideband , stub (electronics) , electrical engineering , optics , voltage , electrode , physics , antenna (radio) , engineering , quantum mechanics
A compact tunable cavity filter based on double‐layer suspended stripline resonator (DSSLR) is proposed. The DSSLR consists of a thin substrate suspended in an air‐filled cavity, a stepped impedance resonator loaded with interdigital capacitor on the top layer of the substrate, and a parallel‐plate capacitor series with a varactor at the bottom layer. The multiple capacitors not only achieve compact size by large capacitive loading, but also broaden the tuning range with a small capacitance variation of varactor. The internal coupling of two DSLLRs increases with the height of the inductive stub while decreases with the distance between two resonators. A fifth‐order wideband tunable cavity filter using a common bias voltage is designed, fabricated, and measured, which has a tunable frequency range of 67 MHz, constant bandwidth of 64 ± 7 MHz, low return loss of 15 dB, and high suppression of more than 40 dB.