A capacitive power sensor based on the MEMS cantilever beam fabricated by GaAs MMIC technology

Abstract

In this paper, a novel capacitive power sensor based on the microelectromechanical systems (MEMS) cantilever beam at 8-12 GHz is proposed, fabricated and tested. The presented design can not only realize a cantilever beam instead of the conventional fixed-fixed beam, but also provide fine compatibility with the GaAs monolithic microwave integrated circuit (MMIC) process. When the displacement of the cantilever beam is very small compared with the initial height of the air gap, the capacitance change between the measuring electrode and the cantilever beam has an approximately linear dependence on the incident radio frequency (RF) power. Impedance compensating technology, by modifying the slot width of the coplanar waveguide transmission line, is adopted to minimize the effect of the cantilever beam on the power sensor; its validity is verified by the simulation of high frequency structure simulator software. The power sensor has been fabricated successfully by Au surface micromachining using polyimide as the sacrificial layer on the GaAs substrate. Optimization of the design with impedance compensating technology has resulted in a measured return loss of less than −25 dB and an insertion loss of around 0.1 dB at 8-12 GHz, which shows the slight effect of the cantilever beam on the microwave performance of this power sensor. The measured capacitance change starts from 0.7 fF to 1.3 fF when the incident RF power increases from 100 to 200 mW and an approximate linear dependence has been obtained. The measured sensitivities of the sensor are about 6.16, 6.27 and 6.03 aF mW −1 at 8, 10 and 12 GHz, respectively.

Bent cantilever radio frequency microelectromechanical system power detector with improved linearity up to 1 W

“…The authors found that the grounded gold membrane would reach saturation when input power is >600 mW. For now, the reported maximum input power of the linear region is no more than 400 mW [6,9,10] (see Table 1). It is discovered that the beams they used prefer regular shapes, which is considered to be a potential factor for the nonlinearity.…”

“…They showed good microwave performances but the power capability was not mentioned. Therefore, Yi and Liao [9] presented a cantilever beam power sensor at X-band. The authors discussed the cantilever displacement under different power levels.…”

Compact nanomechanical plasmonic phase modulators

“…While we emphasize that very high modulation frequency is not required for the envisioned on chip optical switching and reconfiguration applications, the mechanical resonance frequency scales as ~t/L 2 and is able to increase up to 100 MHz with fixed beam thickness and drive voltage. Furthermore, non-plasmonic nanomechanical cantilever devices of similar dimensions have been made operating up to 1GHz with careful material choice, 30,31 and such a fast, yet ultrasmall modulator can potentially operate at low voltage with the use of piezoelectric actuation. [32][33][34] Considering the negligible power dissipation of its electrostatic-drive, actuation voltages at the level of the smallest high speed transistors, its length scale and feature size at the level of CMOS metallization layers, its broadband optical operation and its reasonable speed, we argue 9 that a GPPM can play a unique and important role as a building block for optoelectronic integration.…”

Inline capacitive RF power sensor based on floating MEMS beam for GaAs MMIC applications

“…Introduction: Radio frequency (RF) microelectromechanical systems (RF MEMS) power sensors have become important tools for signal power measurements. Recently, capacitive RF MEMS power sensors have been widely studied owing to their small temperature influence and high dynamic range [1][2][3][4], compared with thermoelectric power sensors [5][6][7]. However, these capacitive sensors must be grounded anchors of MEMS beam as a capacitor's electrode so that it is impossible to adopt a balanced-bridge impedance technique for an accurate measurement of capacitance change.…”

“…Fernandez et al [2] and Dittmer et al [8] have reported two capacitive MEMS power sensors fabricated on the glass substrate, where anchors of the MEMS beam are not connected with ground lines, but they are not compatible with the traditional GaAs or Si process. Furthermore, operation frequencies of these capacitive sensors are up to 1 GHz [8], up to 4 GHz [1,2] and 8-12 GHz [3,4].…”