Design of a novel structure capacitive RF MEMS switch to improve performance parameters

Abstract

This study reports the design and analysis of novel step structure RF micro-electromechanical system (MEMS) switch for low pull-in voltage, low insertion loss and high isolation by using uniform single meander. The central beam of the membrane is designed with 0.5 µm lower than the side beams to form a step-down structure which reduces the pull-in voltage. Stress analysis, electromechancial, switching time, quality factor and RF analysis have done to understand the behavioural characteristics of the proposed step-down switch. The analysis has been carried out for different beam and dielectric materials among them switch with gold material exhibits low pull-in voltage of 4.7 V, low insertion loss <1 dB and high isolation of −38.3 dB at 28.2 GHz for silicon nitride. The switch also shows good quality factor of 0.95 for gold material along with high capacitance ratio of 132. The upstate capacitance of 56.8 pF contributes low return loss and made the switch to transmit the signal up to 26.2 GHz and provides 7.2 pF of downstate capacitance to produce high isolation at 26.2 GHz which is efficiently used for Kband satellite applications.

Ultrabroadband (DC–80 GHz) RF MEMS DC/capacitive load shunt switch

“…σ 0 is the residual stress at room temperature. Equation (9) shows that ν Eα (1 − ) bs is an essential parameter to observe pull-in voltage variation against temperature. Hence, the material with low ν Eα (1 − ) bs should be used to provide robustness against temperature.…”

“…Thus far, a single switch has not achieved high isolation from DC to the millimeter frequency range. [8][9][10] Shunt capacitive contact switches operate based on the capacitance that is determined by the combined overlapping area of both the top and bottom electrodes. The area of the bottom electrode and the dielectric present on top of this bottom electrode are fixed.…”

A comprehensive overview of recent developments in RF-MEMS technology-based high-performance passive components for applications in the 5G and future telecommunications scenarios

“…Targeting K-band satellite applications, [22] introduces a simple and effective design on silicon nitride, simultaneously achieving low actuation voltage (4.7 V) and Insertion Loss (-0.3 dB) up to 45 GHz. Capitalising on meandered beams, a traditional rectangular perforated membrane with stepped profile, and 1.7 μm air gap, a structure with 175 μs switch-on time and high capacitance ratio (132) is obtained.…”

“…From the structural point of view, multiple and large holes on the movable membranes are a wise option, since they increase the speed of actuation by reducing the damping of air. This is one of the criteria behind the design of the membrane reported in [22]. Another option consists in modulating the amplitude of the biasing waveform, as discussed in [27].…”

“…The spring constant of the movable structure can be lowered by adopting folded or meandered beams with reduced thickness, as in [20] [22]. The negative consequence of a reduced spring constant of a structure is an attenuation of its restoring force, which, in turn, determines an increased risk of stiction (missed release of the actuated membrane after the zeroing of the actuation voltage).…”