Open AccessContinuous frequency and bandwidth tunable combline cavity bandpass filters with internally mounted motors
Author(s) -
Parish James S.,
Somjit Nutapong,
Hunter Ian Charles
Publication year - 2018
Publication title -
iet microwaves, antennas and propagation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.555
H-Index - 69
eISSN - 1751-8733
pISSN - 1751-8725
DOI - 10.1049/iet-map.2018.5277
Subject(s) - insertion loss , passband , bandwidth (computing) , center frequency , band pass filter , materials science , resonator , return loss , optoelectronics , acoustics , optics , electrical engineering , physics , telecommunications , engineering , antenna (radio)
Novel design methods for implementing continuous centre‐frequency and bandwidth tunability are reported. Coupling bandwidths are tuned through the mechanical rotation of a metallic plate suspended between resonators. Centre‐frequency tuning is achieved via the vertical actuation of a moving part mounted within each resonator. In addition, each resonator and transformer is designed so that motors can be housed within them – adding tunability without compromising the overall filter volume. A second‐order filter, based on combline cavity structures, capable of bandwidth tunability of 49–67 MHz for all centre frequencies in the range of 1.751–1.998 GHz is presented. Passband insertion loss is kept below 1.2 dB for all tuning states with return loss above 10 dB. A five‐pole filter is also fabricated with centre‐frequency tunability of 14% from 1.764 to 2.015 GHz and 15 dB bandwidth tunability of 107% from 41 to 85 MHz. Midband insertion loss is kept below 1.4 dB in all tuning states. The five‐pole filter is compared to other tunable filters in the UHF range and is shown to reduce midband insertion loss by 36% from the next best filter (2.2–1.4 dB).