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The general study is dedicated to Wireless Sensor Networks. The idea is to associate micro-mechanical and microwave communication functions to exchange information between a remote sensor and a base station [1]. A specific part of this project concerns the conception, realisation, and characterisation of a passive microwave frequency shifter used f...
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Context 1
... frequency shifter is made of two coupled capacitors integrated on the same micro-system moving in opposition at the low frequency rate. Electrostatic actuation is used to control the gap between two electrodes, see Figure 2. When connecting the two capacitors properly, see Figure 3, we collect a current I proportional to the product of the low frequency capacitance variations and the high frequency voltage time variations, which is the required mixing function [2]. ...
Citations
... There are other reported RF MEMS devices from France; mainly switches and their applications. These switches are, for example, purely thermal actuated [4], electrostatic seesaw type switches [5], ohmic shunt switches [6] and shunt capacitive single-pole double-throw switches [7]. Microsystems employing switches were also reported. ...
This paper presents a review of radio frequency microelectromechanical systems (RF MEMS) research within Europe. A tour of Europe is given, identifying the key institutions within France, Germany, Belgium, Switzerland, Sweden and the UK. Some of the activities from these institutions have been mentioned, with corresponding references cited. The European Union's Network of Excellence in RF MEMS and RF Microsystems, called AMICOM, is introduced. Finally, four RF MEMS research projects being undertaken at Imperial College London are briefly discussed. It will be seen that Europe has a very vibrant and healthy activity in RF MEMS research and this is expected to continue for the foreseeable future.
This thesis deals with the realisation of a frequency transposition block from 1 to 20 GHz based on MEMS components. It results in the design and fabrication of a new kind of tuneable RF MEMS capacitor based on a rotational gyroscope structure for the actuation part and on a surface variation for the capacitance change. Compared to other architectures published, this structure presents the advantage to have an actuation part (the MEMS part) and a RF part (the capacitor) that are electrically separated in order to avoid the phenomenon of self-actuation with RF signal crossing power. Another advantage of this structure is the possibility to simultaneously tune 8 different capacitors on a single chip, with only one actuation system. The fabrication of the chips requires the use of a SOI wafer for the MEMS part and a glass wafer for the RF part, which offers on chip packaging opportunity. This work also focused on the study of the pull-in effect in the case of curved comb-drives, highlighting the most critical physical parameters for the design. This parametric study has been used to improve the actuation structure and more particularly the topology of the curved comb-drives by variation of the finger width and gap. These modifications were done in order to push the pull-in effect out of the actuation operating range. This new tuneable capacitor has been integrated into a simple VCO circuit on alumina to validate the RF performances and could be associated to a RF mixer in order to realize the full frequency transposition block
This paper reports on an original rotating MEMS structure used to design RF tunable passive components operating in the X band. These components are either analog tuning MEMS variable capacitors or inductors, based respectively on surface variation or magnetic coupling variation. The choice of a rotating MEMS allows high displacements leading to high tuning ratios. A great advantage of the proposed solution relies in the possibility to integrate into the same chip several analog tuning RF MEMS (up to 8) on a surface reduced below 20mm2.
Wide range tunable components are a key point for high frequency performances. We have developed a novel RF MEMS rotational
capacitor based on surface variation and high displacement. This paper will present multiple designs with physical parameter
variations for comparative test with fabricated device measurements. The goal of this work is to prove the proper operation
of the devices according to fulfill target performances. The main parameters will be tunability, capacitance value, resonance
frequency and finally maximal actuation voltage allowed.
