# Analytical Approach in the Development of RF MEMS Switches
## 1 Introduction  
Radio frequency (RF) electronics of high-frequency (HF) and ultra-high-frequency (UHF) microwave electronics have always needed switches that make low losses in the open state and provide high isolation in a closed state with high permissible signal power and low control power. The first switches fully meet the requirements of steel electromagnetic relays. After many years of improvement modern RF relays provide low on signal loss and high isolation in the off state, but they have such disadvantages as large overall dimensions, high cost and limited resource (from hundreds of thousands to tens of millions of cycles). The switch on PIN-diodes and field-effect transistors based on GaAs have a number of advantages over the RF relay, consisting in high speed operation, small size and weight, as well as low-power control. However, they introduce higher losses into the microwave transmission line and, therefore, cannot replace electromechanical switches in a number of applications. Further research led to the development of RF switches based on microelectromechanical systems (MEMS), which combined some of the advantages of semiconductor and relay devices. The comparative characteristics of semiconductor switches are based on PIN-diodes and field-effect transistors, MEMS switches and electromechanical switches of the UHF signal [1]. Micromechanical microwave switches were first demonstrated by [PERSON] as cantilever beams using electrostatic actuation [2]. According to the forecast of MEMS devices market development, published in 2015 in [3], the following areas of MEMS technologies are noted for high growth: pressure sensors, inertial measurement systems, microfluidic devices and systems. Nevertheless, RF MEMS devices have showna significant growth from 2014 to 2020, which have great market potential and have been declared as one of the main applications of MEMS technologies. The RF MEMS segment consisting of filters based on volume acoustic waves and switches boost the income level of the entire MEMS area as a whole with estimated revenues in 2022 at 10 billion dollars [4]. Driven by the complexities associated with the move to 5G and the higher number of bands it brings, there is an increasing demand for RF filters in 4G/5G, making RF MEMS the largest-growing MEMS segment. This market will probably soar from US $2.3B in 2017 to US $15B in 2023. Excluding RF MEMS market will grow at 9% over 2018-2023. With RF MEMS the CAGR is 17.5% [4]. With the miniaturization of RF chips and the growing need to improve their functions, the trend towards integration of RF MEMS and CMOS devices for RF applications will only increase. RF MEMS switches utilize various actuation designs including electromagnetic [5; 6; 7; 8], magnetostatic [9], electrostatic [10], thermal-electric [11] and various structural designs including a rotating transmission line [12], surface micromachined cantilevers [13; 14; 15; 16; 17], multiplesupported or membrane based designs [18; 19], bulk micromachined or wafer bonded designs [20; 21; 22], diamond cantilever and contact [23], polysilicon switch [24], mercury micro-drop contact [25; 26] and bistable microrelays [27; 28]. All switches designs have their advantages and disadvantages. The micromachined electrostatic switches or relays are the most widely studied devices to date. RF MEMS switches with electrostatic activation mechanism are characterized by their own power consumption of the order of several mW, which is considerably lower in comparison with other type of RF MEMS switches. Therefore, most of the developed RF MEMS switches have an electrostatic activation mechanism. At the technological level of electrostatic control it does not require the deposition of specific materials, for example, with piezoelectric or ferromagnetic properties which simplifies the manufacturing technology and, therefore, reduces the cost of finished devices.