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 MiniMEMS will introduce a novel device of MEMS switched capacitor in RF tuning applications which greatly mitigates the effects of dielectric charging and temperature effects and allows switching times one order of magnitude below the state of the art. This new device is a highly miniaturised version of the standard capacitive MEMS switch, resulting in enhanced mechanical properties and consequently leading to high-reliability, high-power and high-speed capabilities.The main objective of MiniMEMS is to develop the design methodologies and technological process to achieve the integration of the miniaturised switched capacitors in tunable filters and phase shifters, which will allow the demonstration of low cost and high yield adaptive receiver and reflect arrays antennas for weather and wake vortex detection radars. Two routes will be followed for the development of the miniaturised MEMS fabrication process : - Based on the existing know-how of the consortium, a secure and low-risk fabrication process will be developed to fabricated the demonstrators using standard MEMS. This process will be compliant with a short time-to-market transfer to the foundry UMS. - The second route will consist in developing the MiniMEMS process, adapted to the fabrication of miniaturised MEMS. It is more risky and challenging but the economic impact of such a successful process will be huge and will allow to address massive civilian markets. Low losses and high linearity are key drivers for microwave tunable filters and phase shifters. The insertion of miniaturised MEMS in such functions will bring them to unrivalled levels of agility and reliability. In the MiniMEMS project, tuneable (multi-bits) matching/ filtering circuits on silicon and GaN substrates will be implemented in order to realize a frequency-agile (multi-band) LNA using the technologies depicted above. 3-bit and 6-bit phase-shifting cells for X-Band reflect array antennas will also be fabricated on the basis of MiniMEMS process flows. Finally, three demonstrators will be fabricated in the framework of MiniMEMS by implementing these tunable filters and phase shifters respectively in: - Adaptive receiver for Air Traffic Management applications. Two architectures will be proposed for this demonstrator. The first one consists in the hybrid integration of a tunable filter with external limiter and LNA. The second architecture is based on the monolithic integration of the tunable filter and the LNA on the same GaN substrate. This second architecture will allow drastic improvements in terms of volume and robustness. The reliability and agility allowed by the use of miniaturised MEMS are very important for futur radar architectures in which the A/D converter will directly follow the front-end receiver. - Partial Reflect Array Antennas for weather radar and wake vortex detection radar (2 demonstrators). These radar antennas today are still traditional parabolic reflector antennas, mechanically scanned both in azimuth and elevation. The reflect array concept based on miniaturised MEMS phase shifter is very promising for this applications in terms of cost, reliability and beam agility. The consortium gathers all the technological skills necessary to the success of the project and covers all the value chain: from the component level to the system level. The process flows will be transferred to European foundries at the end of the project. |
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For the past ten years, RF-MEMS have received a lot of interest because of their promising performances such as low loss, high linearity, and very low dc power consumption. There are two different devices based on the capacitive approach: (i) the RF-MEMS capacitive switch, with a capacitance ratio 30-150 and (ii) the MEMS switched capacitor, with a ratio of 1.5–10. RF-MEMS switches are commonly used for routing purposes, while switched capacitors are mostly used in tunable filters and reconfigurable networks. Currently, the long-term reliability problems associated with RF-MEMS devices have delayed their use in commercial applications. There are two main problems associated with standard MEMS capacitive devices, which are: (i) dielectric charging and (ii) temperature sensitivity of the movable membrane, especially for fixed-fixed beam designs. The relatively low-temperature handling of fixed–fixed beams has also limited the available hermetic packaging techniques. Another drawback compared to their equivalent in solid-state technology (Pin diode, GaAs FET) is the switching time of the RF-MEMS which remains above 1 µs.
