Distortion produced by RF MEMS varactors on digital communication signals

This paper presents a study of the nonlinear effects introduced by MEMS varactors when excited with digitally modulated RF signals (QPSK and 16 QAM). The study is based on simulating a nonlinear model of the MEMS device using harmonic-balance and envelope solvers, and on experimental measurements of the wave reflected by the on-wafer MEMS device. It is shown that the adjacent-channel power ratio (ACPR) and error-vector magnitude (EVM) of the digital signal suffer a degradation due to the device nonlinear distortion.Peer Reviewe

Characterization of dynamics and power handling of RF MEMS using vector measurement techniques

This paper proposes a new method to measure dynamics and power handling of RF microelectromechanical systems (MEMS) devices based on a mobile membrane. The method uses in-phase/quadrature demodulation of an RF signal proportional to the reflection coefficient of the measured device, which contains information of its mechanical properties, such as actuation and release times and instantaneous position of the mobile membrane. Both one-port (capacitors) and two-port devices (switches and extended tuning-range capacitors) can be measured. Its main advantage is the capability of obtaining information from both magnitude and phase variations of the device reflection coefficient to characterize its dynamics and power handling. It is shown that detecting phase is advantageous in high quality factor capacitors, where the magnitude of the reflection coefficient is nearly constant for any position of the mobile membrane. Open-short-load calibration of the system is provided in order to obtain absolute measurements, which are necessary for power-handling characterization. The performances of the proposed method are demonstrated by comparison to systems based on detection of the magnitude of the reflection coefficient. A MEMS capacitor is characterized in terms of dynamics-actuation and release times, and mechanical resonance frequency and in terms of power handling-membrane instantaneous position and phase and tuning range variation.Peer Reviewe

Nonlinear actuation model for lateral electrostatically-actuated DC-contact RF MEMS series switches.

In this work, a nonlinear model to predict actuation characteristics in lateral electrostatically-actuated DC-contact MEMS switches is proposed. In this case a parallel-plate approximation cannot be applied. The model is based on the equilibrium equation for an elastic beam. It is demonstrated that the contribution of fringing fields is essential. The model relies on finite-difference discretization of the structures, applying boundary conditions and is solved with a Gauss- Seidel relaxation iteration scheme. Its usefulness is demonstrated in a series MEMS switch with lateral interdigital electrostatic actuation.Peer Reviewe

Electrothermally actuated RF MEMS switches suspended on a low-resistivity substrate

This paper presents an electrothermally actuated lateral resistive-contact switch for application to low-gigahertz-band communication systems. It was manufactured on a standard low-resistivity substrate, and its RF performance was improved by suspending the structures 25 μm from the substrate, which is a strategy for future integration with active devices in the system-on-chip concept. Measured insertion losses are−0.26 dB at 1 GHz and −0.65 dB at 6 GHz, return losses are −29 dB at 1 GHz and −25 dB at 6 GHz, and isolations are −52 dB at 1 GHz and −26 dB at 6 GHz. The device is driven by a metal electrothermal actuator, which achieves large displacements and contact forces at much lower temperatures than traditional polysilicon electrothermal actuators. The RF power handling characteristics are also addressed and measured.Peer Reviewe

Study of intermodulation in RF MEMS variable capacitors

This paper provides a rigorous study of the causes and physical origins of intermodulation distortion (IMD) in RF microelectromechanical systems (MEMS) capacitors, its analytical dependence on the MEMS device design parameters, and its effects in RF systems. It is shown that not only third-order products exist, but also fifth order and higher. The high-order terms are mainly originated by the nonlinear membrane displacement versus applied voltage and, in the case considered in this study, with an additional contribution from the nonlinear dependence of the reflection coefficient phase on the displacement. It is also shown that the displacement nonlinear behavior also contributes to the total mean position of the membrane. In order to study these effects in depth, an analytical frequency-dependent IMD model for RF MEMS based on a mobile membrane is proposed and particularized to the case of a MEMS varactor-a device for which IMD can be significant. The model is validated, up to the fifth order, theoretically (using harmonic balance) and empirically (the IMD of a MEMS varactor is measured). To this end, a two-tone IMD reflection measurement system for MEMS is proposed.Peer Reviewe

Tunable dual-band filters based on capacitive-loaded stepped-impedance resonators

This paper proposes the design of tunable dual-band filters for multi-band multi-standard systems. The main objective is to provide frequency tunability in the second band while maintaining the first band fixed. To this end, the capacitive-loaded stepped-impedance resonator is used. The work is divided into two main parts. In the first part, a deep analysis of the capacitive-loaded stepped-impedance resonator structure is done, which provides analytical closed-form design equations which eases their design in front of the several approaches available in the literature up to now. The analysis is also particularized for the case of the capacitive-loaded uniform resonator. In the second part, resonators are integrated in two dual-band tunable filters.Postprint (published version

Desfassador banda dual basat en híbrid multibanda per aplicacions wireless

El primer objectiu del projecte és l'estudi i disseny d'un desfassador bi - banda reconfigurable per integrar en sistemes d'antenes intel·ligents i amb aplicació a sistemes dual band WLAN operant en els marges freqüencials 2.4 - 2.5 GHz i 5.15 - 5.35GHz. El desfassador que es proposa realitzar està basat en un acoblador híbrid multibanda, diplexors i circuits reconfigurables commutats amb díodes PIN. El segon objectiu del projecte és l'aprenentatge de la metodologia de disseny de circuits d'RF i més concretament les següents etapes: estudi i disseny teòric (analític), simulació circuital (ADS), simulació electromagnètica (Momentum), cosimulació circuital-electromagnètica i fabricació, així com les diferents interacions i mecanismes d'optimització entre aquestes etapes

A low-power-consumption out-of-Plane electrothermal actuator

This paper proposes a new vertical electrothermal actuator. It can be considered as a hybrid between the traditional in-plane buckle-beam actuator and the vertical hot-cold actuator. It is here referred to as vertical buckle beam. At identical dimensional and bias conditions, it features a displacement larger than that of other vertical electrothermal actuators proposed so far in the literature. The actuator performance is demonstrated by means of an analytical model along with finite-element analysis. It is applied as a driving element in parallel-plate capacitors, where it is validated and its advantages in terms of power consumption are demonstrated empirically.Peer Reviewe

Distortion produced by RF MEMS varactors on digital communication signals

This paper presents a study of the nonlinear effects introduced by MEMS varactors when excited with digitally modulated RF signals (QPSK and 16 QAM). The study is based on simulating a nonlinear model of the MEMS device using harmonic-balance and envelope solvers, and on experimental measurements of the wave reflected by the on-wafer MEMS device. It is shown that the adjacent-channel power ratio (ACPR) and error-vector magnitude (EVM) of the digital signal suffer a degradation due to the device nonlinear distortion.Peer Reviewe