# Comprehensive Review of RF MEMS Switches in Satellite Communications
## 3 Strategies for Optimizing RF MEMS Switch Performance
### High Reliability
#### 3.1.1 Reducing the Impact of Shocks  
In RF MEMS switch applications, significant impacts can accelerate the degradation of contact surfaces and creep, reducing the performance of the dielectric layer [83; 84]. This amplifies the likelihood of failure due to adhesion. Increased impact velocity can strengthen contact bouncing and residual vibrations [67; 85; 86], mainly due to the inertial momentum of the movable electrode and the elastic energy stored in its structure [85; 87]. This bouncing can last for an extended period and does not stop until a stable contact is achieved. High-intensity contact impacts can cause electrical discontinuities, material damage, and dielectric charging [86], detrimental to lifespan and reliability. Therefore, taking measures to eliminate or reduce the speed of an electrode bounce to enhance the reliability of these switches is necessary. Various corrective strategies have been developed to mitigate the effects of contact, including open-loop [88] and closed-loop [89] control schemes. The overall dynamic characteristics of the switch can be improved by modifying the electromechanical and electromagnetic modeling of the switch's geometry, as well as thenumber and size of its holes. The switches shown in Figure 4a [90] are manufactured on a Pyrex glass substrate using a four-layer mask surface micromachining process. These MEMS switch designs require only a low actuation voltage of 4.8-6.2 V. They achieve bounce-free switching during contact and quickly stabilize after release. Customized pulse drive waveform schemes, widely applied to minimize velocity issues related to contact impact, are used [91; 92]. A solution based on command shaping [93], developed through the application of energy conservation, force balance, and elliptical integrals, is shown in Figure 4b. Experimental validation indicates that this approach achieves rapid positioning by suppressing motion-induced vibrations, thus reducing the contact effects on MEMS devices. However, even minor deviations in parameters may result in significant changes in the force, due to the highly nonlinear characteristics of electro  
Figure 4: (**a**) Schematics of three designs of capacitive RF MEMS switches. (i) Design 1: T-support, (ii) Design 2: parallel-support, and (iii) Design 3: L-support beams [90]. Reprinted/adapted with permission from [90], 2017, IEEE. (**b**) Illustration of the nonlinear command shapers for electrostatically actuated MEMS systems. (i) Two-step nonlinear shaping method for positioning and (ii) shaper for contact force minimization [93]. Reprinted/adapted with permission from [93], 2011, IEEE. (**c**) Softlanding by patterning the electrode upper/lower or dielectric. Electrode upper/lower can be a (p1) rectangular plate, (p2) array of cylinders, or (p3) array of spheres, and dielectric can be (p4) an array of linear slots or (p5) a fractal of linear slots [88]. Reprinted from [88], with the permission of AIP Publishing. potentially leading to serious collisions. Therefore, the design of excitation pulse waveforms is particularly sensitive to parameter deviations, which might not be the best choice for mass-produced devices. To address this issue, [PERSON] et al. [89] proposed a novel method of adaptive stiffness. This approach enhances inherent stiffness adaptively in the area near the closed position, improving the robustness of mass-produced switches against parameter deviations. When the actuation voltage is slightly increased, constant stiffness switches convert more electrostatic energy into collision energy for the movable plate compared to adaptive stiffness switches. This new method effectively offsets the significant changes in electrostatic force caused by parameter deviations. [PERSON] et al. [88] proposed a dynamic soft landing scheme that effectively reduces impact velocity without affecting other performance characteristics such as actuation voltage and actuation time.