High power reliability aspects on RF MEMS varactor design
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Joined: Nov 2010
16-11-2010, 03:35 PM
The switched varactor for high power RF signals is described in this article. This varactor can perform tuneable capacitor operations up to 10 GHz frequencies. The RF micro-electro-mechanical systems (MEMS) has become an atractive area of research in the recent. Devices like tuners, antenna beam forming networks and reconfigurable filters all will benefit from this.
In the case of RF MEMS which depend on the electrostatic actuation have a a small air gap in the micrometer range between their movable membrane and their actuation electrode. The disadvantage is that a temporary device failure may occur if power varies, as it shows higher sensitivity to RF power effects on the membrane dynamics.
The stiffness and the power exposed surface must be properly designed in order to overcome the electrostatic pressure induced by the RF signal. A specific cantilever structure consisting of two cantilever beams is used.
The proper on/off capacitance ratio is achieved in this design because of the improved capacitance contrast. The cantilever collapse is also prevented by the double step profile. The static risks posed by the air, humidity and organic
contaminants, etc is also overcome because of the small contact area.
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