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RF MEMS Switches Provide Superior Performance Over Solid-State Switches

RF MEMS

RF MEMS switches outperform solid-state RF switches

Technology is booming, and the size of electronics is shrinking. As a result, research and development in the field focuses on delivering world-class technology in the most miniaturized size possible. 

A new development in technology miniaturization, RF micromechanical structures (RF MEMS) are small, have virtually no mass, and require no power supply. The performance of RF MEMS is superior to its solid-state counterparts, which is why they are utilized in applications such as IoT, defense, and wireless communications

Let’s take a closer look at RF MEMS technology and the advantages of using RF MEMS switches in circuits.

What Are RF MEMS?

RF MEMS are miniature mechanical systems that utilize state-of-the-art integrated electronics technology. RF MEMS technology provides a range of elements for microwave and RF applications such as: 

Due to their superior performance, RF MEMS are replacing conventional RF and microwave devices in smartphones, radars, and satellites. They offer advantages including:

MEMS devices are a millimeter or less, with tiny movable parts that can bend, stretch, deform, or connect together. RF MEMS are closely associated with low-loss applications at very high frequencies, as shown in the table below.

RF MEMS Devices

Frequency

RF MEMS switches, inductors, and varactors

DC-120 GHz

High Q resonators, filters, antennas, and micromachined transmission lines

12-200 GHz

Thin film bulk acoustic resonators (FBAR)

Upto 3GHz

RF micromechanical resonators and filters

0.1-3GHz

RF MEMS Switches

Circuit designers use RF MEMs switches in low-noise and low-power circuits due to their low-loss switching. RF MEMS switches are also widely used in portable wireless systems. 

RF MEMS switches are manufactured on low-cost silicon or glass substrates, which provide very low up-state capacitance and a very high capacitance ratio compared to PIN diodes and FETs. As a result, the cut-off frequency of RF MEMS switches is around 30 to 50 times that of GaAs switches.

RF MEMS switches require virtually zero power once the switch is actuated. Biasing is provided through low resistance aluminum or gold lines supplying current for the switching cycle. 

RF MEMS Switch Sections

There are two parts to RF MEMS switches: the mechanical section and the electrical section.

  1. The Mechanical Section

The mechanical movements of RF MEMS switches are governed by electrostatic, magnetostatic, piezoelectric, or thermal forces, though electrostatic actuation is the most prominent. Electrostatic actuation requires high actuation voltage, and the CMOS upconverter raises the low input voltage to actuation voltage. 

RF MEMS move either vertically or laterally. Vertical movement is typically seen in small size devices compared to lateral movement.

  1. The Electrical Section

RF MEMS switches are configured as series-connected or shunt-connected. In both configurations, either metal-to-metal contact or capacitive contact makes the electrical connection. The series configuration of RF MEMS switches with metal-to-metal contact provides low up-state capacitance and is suitable for DC-50GHz applications. Capacitive contact series configuration is used in 10-50 GHz systems and shunt configured metal-to-metal contact RF MEMS delivers low inductance to the ground. 

RF MEMS switches provide: 

  • Outstanding isolation 
  • Reduced insertion loss 
  • Low intermodulation 
  • Superior performance over solid-state switches

These characteristics enable RF MEMS switches to allow network switching in communication systems. Single-port N-throw switches in filter and amplifier circuits are built using RF MEMS switches. 

In the era of downsizing and miniaturization, RF MEMS switches are an exciting new development with a promising range of possibilities for use in RF and microwave circuits. Cadence’s software offers a design suite that allows designers to construct circuits with RF MEMS devices. 

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