Electronically Switchable Bandpass Filters Using Loaded Stepped-Impedance Resonators
Journal
IEEE Transactions on Microwave Theory and Techniques
Journal Volume
54
Journal Issue
12
Pages
4193--4201
Date Issued
2006
Author(s)
Abstract
Stepped-impedance resonators with diodes loaded at one end are used to develop switchable bandpass filters in this paper. The loaded diodes are used to switch the resonance conditions of the stepped-impedance resonators. The equations for resonance conditions of the stepped-impedance resonators with different loads at one end are derived and discussed. With these derived equations, the switchable filters can be easily designed and synthesized using the coupled-resonator filter theory. When the switchable filter is switched on, a bandpass filter response with a wide stopband rejection is achieved by making the on-state coupled resonators have the same fundamental resonant frequency, but different higher order resonant frequencies. When switched off, a high and wideband isolation is obtained by properly misaligning the resonant modes of the off-state resonators. The design concept is demonstrated by two single-pole-single-throw fourth-order Butterworth-type switchable microstrip bandpass filters, which utilize two and three switched stepped-impedance resonators, respectively. Finally, a compact single-pole-double-throw switchable microstrip bandpass filter using common resonators is demonstrated for wireless communication applications. © 2006 IEEE.
Subjects
Coupled-resonator bandpass filter; Stepped-impedance resonator; Switch; Switchable filter
Type
journal article