Symmetric and Compact Single-Pole Multiple-Throw (SP7T, SP11T) RF MEMS Switches

This paper presents extremely compact single-pole multiple-throw radio frequency (RF) microelectromechanical system switches, SP7T and SP11T, based on a symmetric circular switch topology. The switch dimensions are 0.61 mm ×0.61 mm, which is smaller than typical CMOS Si-on-insulator switches. The SP7T and SP11T switches, which are insensitive to stress gradient effects, achieve simulated contact and restoring forces of 0.3-0.4 mN (per a switch) at 90-100 V. The SP7T and SP11T switches also achieve isolation levels of 50-19 dB and 50-17 dB, respectively, and insertion loss of 0.3-1.2 dB and 0.3-1.7 dB, respectively, at 0.1-10 GHz. The measured ON-resistance is 4.5-2.5 Ω at 75-100 V, respectively, in an open environment and limited by contact contamination. The measured switching time is 7-10 μs. Cold-switched reliability tests of SP7T and SP11T switches show greater than 10⁸ Hz with an RF power of 0.1-1 W, which is sufficient power handling capability for 3G and 4G systems.

I. Introduction

Single-pole multiple-throw switches are broadly utilized in modern communication systems requiring operation at 2G/3G/4G standards such as cell phones and tablets. This area has been dominated by solid-state switches such as Si-on-insulator (SOI), Si-on-sapphire (SOS), and GaAs switches due to their high-count SPNT switches (). SOI/SOS SPNT switches, while having excellent performance up to 2.7 GHz, quickly fail in terms of insertion loss and isolation above 3 GHz due to their inherent large off-state capacitance and low-pass tuning networks [1]–[5]. On the other hand, RF MEMS metal-contact switches have lower insertion loss and higher isolation and linearity in comparison to SOI/SOS switches.