Precise frequency and bandwidth control of microstrip switchable bandstop filters

Abstract

AbstractIn this article two switchable bandstop filters able to switch precisely between two different center frequency and bandwidth states are presented. The filter topologies allow precise control over the design parameters frequency and bandwidth, achieved by choosing adequate resonator sections switched by PIN diodes. Center frequency control was obtained by modifying resonator length. Bandwidth control was achieved by choosing a resonator width and controlling the normalized reactance slope parameter of the decoupling resonators by means of switchable resonator extensions. Both filters were designed to have a 32.5% center frequency tuning range at L band between a low and high filter center frequency. One topology focuses on producing an 8% fractional stopband bandwidth for both filter states. The second filter topology focuses on producing 7 and 9% fractional stopband bandwidths for the low and high filter center frequency states, respectively. Measured results show a very good agreement with the simulations, for the first topology a 32.2% measured center frequency tuning range was obtained with 8.1 and 8.75% fractional stopband bandwidths for the low and high filter center frequency states, respectively. The second filter topology showed a 31.2% measured center frequency tuning range with 6.94 and 9.66% fractional stopband bandwidths for the low and high filter center frequency states, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2573–2578, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24679