DOUBLE STUB AND TRIPLE STUB RF MEMS IMPEDANCE TUNERS
M. UNLU, H.I. ATASOY, S. DEMIR, O.A. CIVI, S. KOC, T. AKIN

Abstract. This paper presents two different reconfigurable RF MEMS impedance tuners. One of them is a double stub tuner with ohmic contact switches for 1-6 GHz applications and the other is a triple stub tuner with capacitive contact switches for 10-20 GHz applications. The double stub tuner is designed for impedance and noise matching of a two-stage low noise amplifier for 1.8-1.9 GHz, 2.1-2.2 GHz, and 4.9-5.9 GHz bands which correspond to the DCS1800, UMTS, and WLAN bands, respectively. 15 ohmic contact, series MEMS switches are used, each having a measured insertion loss of better than 0.2 dB and an isolation of better than 30 dB in 1.8-5.9 GHz band. The double stub tuner has a worst-case VSWR of 1.48:1 and an average VSWR of 1.2:1 in the operation bands. The triple stub tuner is designed to cover the maximum area on the Smith Chart in 10-20 GHz band with 10 capacitive contact MEMS switches on each stub. Electrical length of each stub is λ g/2 centered at 18 GHz. Simulations present an almost uniform coverage of the whole Smith Chart in 10-20 GHz. Both impedance tuners are fabricated using an in-house process developed at Microelectronic Facilities of Middle East Technical University. Measured performance of the fabricated tuners are in good agreement with simulations.