Erwan Fourn

MEMS switchable interdigital coplanar filter

This paper presents a tunable interdigital coplanar filter with tapped-line feedings. Microelectromechanical systems capacitors are used as a high contrast capacitive switch between a quarter-wavelength resonator and an open-ended stub to perform the frequency shift. A two-pole tunable filter with a 13% relative bandwidth has been designed, fabricated, and measured. The center frequency can be switched from 18.5 to 21.05 GHz with low return losses (less than 15 dB) and low insertion losses (3.5 dB).

Bandwidth and central frequency control on tunable bandpass filter by using MEMS cantilevers

This paper deals with a tunable bandpass filter topology which controls independently and simultaneously both the central frequency and bandwidth. This tunable filter results from the association of MEMS cantilevers, used as variable capacitors, with an original passive topology. The latter is based on dual behavior resonators (DBRs), each of them is constituted of low- and high-frequency open-ended stubs. The associated filter electrical response is characterized by tunable frequency transmission zeros. A millimeter bandpass filter with central frequency and relative bandwidth tunability of about 10 and 75%, respectively, is presented.

Experimental determination of microwave attenuation and electrical permittivity of double-walled carbon nanotubes

The attenuation and the electrical permittivity of the double-walled carbon nanotubes (DWCNTs) were determined in the frequency range of 1–65GHz. A micromachined coplanar waveguide transmission line supported on a Si membrane with a thickness of 1.4μm was filled with a mixture of DWCNTs. The propagation constants were then determined from the S parameter measurements. The DWCNTs mixture behaves like a dielectric in the range of 1–65GHz with moderate losses and an abrupt change of the effective permittivity that is very useful for gas sensor detection.

Reconfigurable Planar SIW Cavity Resonator and Filter

A new reconfigurable frequency cavity compatible with planar technology has been designed, manufactured and measured. An original tuning solution is proposed, based upon the insertion of vertical capacitive posts integrated within SIW cavities. One extremity of each post is connected to a floating metallic ring, located on the substrate supporting the SIW cavity. The frequency agility is obtained once the metallic ring is connected to the ground plane by short-circuited the corresponding annular slot using surface actuators. Such combination of volumetric cavity and planar activation leads to reconfigurable filters with high Q values and simplified tuning control conditions

Millimeter wave carbon nanotube gas sensor

This Letter reports experimental observations regarding the significant changes in the transmission modulus and phase of the propagating microwave signals up to 110 GHz in a micromachined coplanar waveguide supported on a dielectric membrane with a thickness of 1.4 μm filled with a mixture of carbon nanotubes when exposed to nitrogen gas. These large shifts of amplitude and phase of microwave signals due to gas absorption represent the experimental basis on which a miniature wireless gas sensor could be implemented.

Minimization of MEMS Breakdowns Effects on the Radiation of a MEMS Based Reconfigurable Reflectarray

We present an investigation of MEMS breakdowns effects on the radiation pattern of a MEMS based reconfigurable reflectarray. In addition, a correction procedure is proposed to minimize phase errors due to breakdowns. It takes advantage of the numerous possibilities offered by the refectarrays cell to achieve a given phase shift. Furthermore, a systematic methodology is proposed to assess cells robustness to breakdowns by defining a cumulative root mean square error accounting for any possible MEMS failure. It is shown to provide a convenient means of comparing different possible cell topologies. Finally, it is also used to minimize the number of MEMS in the cell while preserving the necessary redundancy to limit phase errors.

A new method of dielectric characterization in the microwave range for high-k ferroelectric thin films

In this paper we propose a new method of dielectric characterization of high-k thin films based on the measurement of coplanar capacitor inserts between two coplanar waveguide transmission lines. The measurement geometry is deposed on the thin film which is elaborate on an insulating substrate. The thin film permittivity is extracted with the help of a mathematical model describing the capacitance between two conductor plates deposed on a 2-layers substrate. A simple correction is proposed in order to enhance the matching between the model and the full wave simulation. The results of the proposed measurement method are compared to those of a classical characterization technique using parallel plate capacitor geometry.

Carbon nanotubes-based microwave and millimeter wave sensors

The aim of this paper is to experimentally demonstrate the applications of carbon nanotubes as microwave and millimeter wave sensors. In this respect, two different sensors are presented. The first sensor is a microwave mass sensor termed as RF nanobalance able to detect 1 ng (10-9 g) of matter. The nanolabalance consists in a GaN membrane bulk acoustic wave resonator covered with a thin film of carbon nanotubes. The second sensor is a gas sensor which is a micromachined coplanar waveguide filled with carbon nanotubes. When exposed to gas, significantly changes in the modulus and phase of the transmission as observed for a wide range of frequencies up to 110 GHz.

MEMS IC concept for Reconfigurable Low Noise Amplifier

This paper investigates the MEMS IC concept for reconfigurable Low noise amplifier. A dual band demonstrator has been chosen and obtained through a very compact architecture that uses a MEMS network and a SiGe LNA. The system features gain larger than 11 dB and noise figure lower than 2.5dB. The concept has been validated on a first prototype, where a bond wire process has been used. Next generation will use an hybrid above IC method

A simple phase-shifting cell for reflectarray using a slot loaded with a ferroelectric capacitor

A tunable reflectarray phase-shifting cell, designed for a resonance frequency of 5.6 GHz, is presented. The cell is based on a simple slot topology and loaded by a ferroelectric thin film capacitor of 60% tunability under 400 kV/cm bias electric field. The cell provides 245 degrees of phase-shifting.