How Do RF Circuits Resist Mechanical Stress?

RF Circuits Resist Mechanical Stress

RF circuits are electronic circuits that operate at radio frequencies, typically between 10 kHz and 100 GHz. They are used for transmission and processing of signals in communication systems like mobile phones, wireless networks, medical diathermy machines and radars. They are also found in measurement equipment, electrical power distribution and lighting fixtures. The physical structure of RF circuits is quite sensitive to mechanical stress, especially when it comes to shock and vibration. Hence, they require advanced techniques and materials to resist mechanical destabilizing effects.

Compared to analog rf circuit, which operate at audio and baseband frequencies, RF circuits are much more complex in terms of wave properties, signal propagation and electromagnetic radiation. RF design requires knowledge of specialized components, layout techniques to control wave interaction effects and impedance matching networks. Keysight PathWave enables rapid RF design using an intuitive interface for schematic entry, signal integrity simulation and electromagnetic (EM) simulation.

Electromagnetic radiation is the energy that electric currents in conductors radiate into space. The energy from a time-varying signal can leak into adjacent circuitry and disturb its proper functioning. This is referred to as electromagnetic interference (EMI). It can be caused by both intentional and unintentional sources.

How Do RF Circuits Resist Mechanical Stress?

Both the transmitter and receiver in an RF system generate EMR. The transmitter converts baseband signal inputs to higher frequency RF outputs, and it uses components like oscillators, mixers and power amplifiers. The RF signals are then transmitted through a communication channel like air, waveguide or cable to the receiver. The receiver captures the RF signals, amplifies them and filters out any unwanted noise. The signals are then processed and stored as data for further use.

Unintentional EMI can be caused by equipment such as electric motors and generators, lightings, rectifiers, inverters and satellites. These devices have large electrical currents that switch on and off frequently. This causes electromagnetic fields to leak into the surroundings, disrupting nearby equipment and causing interference.

On the other hand, intentional EMI can be generated by electronic devices designed to emit electromagnetic energy for specific purposes such as radars and jamming devices.

RF MEMS switches are often the source of unintentional EMI. They have suspended membranes or cantilevers fixed at one end and fixed lower electrodes at the other. These microstructures are subject to mechanical destabilizing forces such as shock and vibration, which can cause the lower electrodes to hit the membrane or cantilever, resulting in stiction and short-circuit problems [76]. Moreover, a strong external magnetic field can induce electromagnetic coupling between the circuit and its enclosure. This can lead to malfunction of the RF MEMS switches or even their failure. To prevent this, various protective measures can be applied, including the sublimation of wax to prevent movement during a mechanical shock. In addition, certain methods of collision prevention and control can be employed to improve the reliability of RF MEMS switches.