The charging of the dielectric used for the actuation in microelectromechanical system (MEMS) devices is one of the major failure sources for switches based on this technology. For this reason, a better understanding of such an effect is vital to improve the reliability for both ground and space applications. In this paper, the expected response of MEMS switches to unipolar and bipolar dc actuation voltages has been measured and modeled. Two configurations of MEMS switches, namely, an Ohmic series and a shunt capacitive one designed for microwave applications, have been studied as a test vehicle for charging effects related to the dc actuation pads. The recorded data have been interpreted mainly through the Poole–Frenkel effect due to charge injection when a high voltage is applied to the dielectric layer. Metal-Insulator-Metal (MIM) structures have been also considered as a complementary information for the response of the dielectric material.

This paper presents the experimental results obtained on a digital phase shifter based on RF MEMS coplanar shunt switches for radar, beam forming applications. A new design approach is proposed for the design of digital distributed MEMS phase shifters, and the image parameter representation of two port networks is used to develop an analytic model for this component. Vector Network Analyzer measurements have been performed by recording the scattering (S) parameters of the reflected and transmitted signals, and they have been elaborated to get the signal phase shift around the frequency F = 13.7 GHz used for the design. Actually, good performances of the phase shifter have been obtained with respect to the expected ones.

Packaged MEMS devices for RF applications have been modelled, realized and tested. In particular, RF MEMS single ohmic series switches (SPST) have been obtained on silicon high resistivity substrates and they have been integrated in alumina packages to get single-pole-double-thru (SPDT) and true-time-delay-line (TTDL) configurations. As a result, TTDLs for wide band operation, designed for the (6-18) GHz band, have been obtained, with predicted insertion losses less than 2 dB up to 14 GHz for the short path and 3 dB for the long path, and delay times in the order of 0.3-0.4 ns for the short path and 0.5-0.6 ns for the long path. The maximum differential delay time is in the order of 0.2 ns.

In this paper, a circuit model to predict the microwave response of a shunt-connected capacitive microelectromechanical coplanar switch is proposed. The numerical values of the lumped elements composing the equivalent circuit are computed by means of a fully analytic approach. In particular, the contribution of resistive and inductive parasitic elements has been evaluated by using closed-form expressions. Configurations characterized by different technological solutions have been obtained and modeled. Simulations performed with the proposed approach correlate very well with actual measurements.

The technology for the realization of RF MEMS ohmic series switches on LTCC substrates has been set up for their implementation in true time delay line configurations. Alumina and LTCC structures for validating the technological process on the individual switches have been obtained and characterized. Static delay lines on LTCC have been manufactured and tested to get the expected electrical performances for the final configuration.

A novel circuital model for a shunt connected RF MEMS coplanar switch, based on a fully analytical approach, is presented. The numerical simulations performed with the proposed new model are in good agreement with experimental measurements.

Coplanar wave-guide grounded lines (CPWG) have been designed for being realized by micromachining of high resistivity silicon wafers. Actually, different configurations have been compared between them by changing the dimensions of micromachined via-holes, as well as their number and separation, to get the optimal electrical matching conditions for CPWG lines. Wide-band matching and low losses have been predicted up to 30 GHz, and preliminary experimental results about the technology have been obtained.

Experimental results obtained for a binary distributed phase shifter based on RF MEMS coplanar shunt switches are presented. A new approach based on the image parameter representation of two-port networks is proposed for the modelling of this structure. Vector network analyser measurements have been performed by recording the scattering parameters of the device, obtaining a differential phase shift of 180 degrees at a frequency f(0) = 13.7 GHz, very close to the theoretical one f(theo) = 14 GHz. A very low number of switches has been used for the realisation of the component.

RF micromechanical switches are fabricated using dry releasing techniques. LTCC is used as substrate. Amorphous silicon, as an alternative sacrificial layer to silicon dioxide, has been used followed by dry plasma release. The silicon deposition has been optimized to obtain low mechanical stress and allowing thick sacrificial layer deposition. The use of amorphous silicon extends the flexibility of the design of the devices and of the packaging procedure.

In this paper a new approach to manufacture low losses coplanar waveguide (CPW) lines for microwave and millimeter wave signal processing is presented. A photolithographic process is performed by using SU-8 thick negative photo-resist on low resistivity silicon wafers, to obtain CPW lines elevated with respect to the substrate, in order to take advantages, in terms of propagation losses, from transmission line structures which are almost on-the-air.

RF MEMS shunt switches in coplanar waveguide (CPW) configuration have been designed, realized and tested for wideband isolation purposes. SU-8 negative photo-resist technology has been introduced for improving the bridge mechanics and the RF performances of the device. The polymeric material is used to elevate the ground planes of the CPW structure, with minor consequences on the electrical matching and an improvement in the bridge ends definition. The EM design has been followed by a sixstep photolithographic process on a 4" oxidized high resistivity silicon wafer, up to the release of the bridge by using a plasma etching technique.

In this paper a new approach to obtain low losses coplanar waveguide (CPW) lines is described. A photolithographic process is performed by using SU-S thick negative photo-resist on low resistivity silicon to obtain CPW lines elevated with respect to the substrate to get the advantages from transmission line structures which are almost on-the-air.

Microelectromechanical (MEMS) switches have been recently considered as building blocks of phase shifters to be used in microwave applications for radar systems up to 40 GHz. In this paper, a novel methodology is proposed for the design of loaded line phase shifters based on RF MEMS shunt switches with evident improvements on the insertion loss level with respect to conventional design criteria and an optimization in the number of switches to be used.

Cascaded, two- and three-stages band-pass filters based on fixed-fixed beam micromechanical resonators have been designed for central frequencies F/sub 1/=10 MHz and F/sub 2/=20 MHz. Quality factors Q=500 have been predicted, under vacuum conditions, for a 3-dB bandwidth BW=0.2%. Insertion losses in the order of 1 to 2 dB have been evaluated.