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- Title
A Miniaturized Tunable Bandpass Filter with Constant Fractional Bandwidth.
- Authors
Liangzu Cao; Guangwen Li; Jian Hu; Lixia Yin
- Abstract
This paper presents a miniaturized tunable bandpass filter, consisting of two coaxial dielectric resonators and a pair of parallel-coupled lines. A coaxial dielectric resonators and a microstrip line form a new step-impedance resonator (SIR), which is different from a conventional SIR. Varactor diodes are connected to SIRs to tune the center frequency. The gap between parallel-coupled lines controls the inter-stage coupling coefficient. Lumped inductors used for coupling to I/O ports can reduce design complexity. The variations of coupling coefficient and external quality factor with tuning frequency are analyzed using HFSS software. A appropriate coupling coefficient which satisfies with constant fractional bandwidth within the tuning range is available. A tunable filter has been made of dielectric ceramics with dielectric constant of 38, fabricated on dielectric substrate and measured using Networks analyzer. Center frequencies vary from 0.43GHz to 0.78GHz, 3 dB fractional bandwidth from 6.4% to 6.8% when bias voltages are applied from 0V to 10V. The measured results validate the approach and agree with the simulation.
- Subjects
BANDPASS filters; DIELECTRIC resonators; MICROSTRIP transmission lines; CERAMICS; SUBSTRATES (Materials science); BANDWIDTH research
- Publication
Progress in Electromagnetics Research C, 2015, Vol 57, p89
- ISSN
1937-8718
- Publication type
Article
- DOI
10.2528/pierc15032701