Abstract
Due to their excellent quality factor in microwave frequency range, microelectromechanical (MEMS) varactors are an attractive choice for wireless communication engineers for building high performance telecommunication circuits. Significant progress in the technology of MEMS varactor has been reported over the past few years; however a comprehensive design methodology for the varactors based on some performance specifications is not reported. Also, it has been found that for the varactors fabricated with multi user processes (MUMPs), the measured capacitance deviates widely from the predicted value. In this work, it has been shown that a substrate-induced capacitance can change the expected capacitance of the varactor widely and can justify the deviation of the measured values to a good degree of accuracy. Here, a quantitative account of this difference has been presented. The capacitance profile of the varactor fabricated in PolyMUMPs process has been measured and the results show good agreement with the design values; thus indicating a clear influence of substrate induced capacitance on the varactor. Finally, a systematic design methodology of the varactor for a voltage controlled oscillator (VCO) application has been given.
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Acknowledgments
The authors would like to express their profound gratitude to Prof. Navakanta Bhat and his research group in the Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore for their help in characterizing the devices using their facilities. This work is funded by National Programme on Smart and Micro Systems (NPMASS), Govt. of India.
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Bhattacharya, A., Chakraborty, S. & Bhattacharyya, T.K. A top-down design methodology of MEMS varactor for RF applications based on a substrate-induced capacitive model. Microsyst Technol 17, 1589 (2011). https://doi.org/10.1007/s00542-011-1337-4
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DOI: https://doi.org/10.1007/s00542-011-1337-4