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A tunable LTCC fourth‐order bandpass filter with high selectivity for L‐band satellite applications
Author(s) -
Zhang Jun,
You Chang Jiang,
Jiao Zhuofan,
Zhu Jianhua,
Xiao Qian,
Cai Jingye
Publication year - 2021
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.32709
Subject(s) - stripline , band pass filter , varicap , resonator , capacitive coupling , capacitance , materials science , filter (signal processing) , optoelectronics , m derived filter , electronic engineering , electrical engineering , physics , engineering , filter design , voltage , electrode , quantum mechanics
This Letter presents a varactor‐loaded double‐layer coupled stripline resonator to implement compact fourth‐order tunable bandpass filter. The whole structure of the proposed resonator consists of two strongly coupled striplines, a metal post and a varactor with bias circuit. Strong capacitive coupling between the striplines at different layers is introduced to significantly reduce the resonator size. A detailed investigation on the relationship between the transmission line length and loading capacitance is presented. The stripline is connected to the varactor by the metal post so that the resonant frequency can be tuned. Through cross‐coupled technology, transmission zeros are introduced in the upper and lower out‐of‐bands of the filter using combline structure for high selectivity. One prototype bandpass filter has been designed to validate the principle, and the measured results show good agreement with the simulated ones. The designed fourth‐order filter has a size of <0.1 λ g × 0.1 λ g and a steep frequency response with the shape factor <1.7.