A new wide tunability MEMS based variable capacitor using two separate electro-static vertical comb drive actuators

Document Type : Original Article


Electrical Engineering Department, Faculty of Engineering, Urmia University, Urmia, Iran


This paper presents a new MEMS variable capacitor to achieve high stable region and extremely wide tunability. The idea is based on increasing the stable region in the gap between the plates of the capacitor. It is done by combining the functionality of two different vertical comb drive actuator sets to takeover a unity air gap variation. The design of the structure is carried out so that the performance of these two actuator sets is fully independent of one another and without any destructive or damaging effect on each other. The advantage of this scheme is that adding the second mechanism of actuation does not change the overall structure thickness compared with when the structure uses a single actuation mechanism. Therefore, the tunability increases sharply. Aluminum is the structural material used for the designs. Comb actuators are widely used as MEMS motors due to their long range of linear motion, low power consumption and ease of fabrication. A full review of electrostatic actuator portion is done. The structure is calculated using MATLAB software. To verify, the calculated results are compared with simulated results using Intellisuite software. The natural frequency is 1.173 KHz. According to calculation and simulation results the achieved minimum tuning range is 2300%.


  1. Dec, A. and Suyama, K., "Microwave mems-based voltage-controlled oscillators", IEEE Transactions on Microwave Theory and Techniques, Vol. 48, No. 11, (2000), 1943-1949. DOI: 10.1109/22.883875
  2. Khodapanahandeh, M., Mirzajani, H. and Ghavifekr, H.B., "A novel electrostatically actuated high q rf mems tunable capacitor for uhf applications", in Electrical Engineering (ICEE), Iranian Conference on, IEEE. (2018), 11-16. DOI: 10.1109/ICEE.2018.8472482
  3. Rebeiz, G.M., Tan, G.-L. and Hayden, J.S., "Rf mems phase shifters: Design and applications", IEEE Microwave Magazine, Vol. 3, No. 2, (2002), 72-81. DOI: 10.1109/MMW.2002.1004054
  4. Saberhosseini, S.S., Ganji, B.A., Koohsorkhi, J. and Ghorbani, A., "Design and simulation of a variable mems capacitor for tunable hmsiw resonator", IET Circuits, Devices & Systems, Vol. 14, No. 5, (2020), 707-712. doi: 10.1049/iet-cds.2019.0511
  5. Reinke, J.R., "Cmos-mems variable capacitors for reconfigurable rf circuits", Carnegie Mellon University, Ph.D. Thesis (2011),
  6. Gong, Z., Liu, H., Guo, X. and Liu, Z., "Optimization of a mems variable capacitor with high linearity and large tuning ratio", Microsystem Technologies, Vol. 24, No. 7, (2018), 3169-3178. doi.org/10.1007/s00542-018-3844-z
  7. Gupta, P., Singh, P. and Srivastava, P., "Design and analysis of rf mems varactor for extended tuning range", in 2013 International Conference on Control, Computing, Communication and Materials (ICCCCM), IEEE. (2013), 1-4. DOI: 10.1109/ICCCCM.2013.6648915
  8. Mobki, H., Rashvand, K., Afrang, S., Sadeghi, M.H. and Rezazadeh, G., "Design, simulation and bifurcation analysis of a novel micromachined tunable capacitor with extended tunability", Transactions of the Canadian Society for Mechanical Engineering, Vol. 38, No. 1, (2014), 15-29. doi.org/10.1139/tcsme-2014-0002
  9. Mohabbatian, N., Abbaspour-Sani, E. and Ghasemzadeh, M., "An electrostatic tunable rf mems capacitor with improved quality factor", in 2014 22nd Iranian Conference on Electrical Engineering (ICEE), IEEE. (2014), 422-427. DOI: 10.1109/IranianCEE.2014.6999577
  10. Nguyen, H., Hah, D., Patterson, P.R., Piywattanametha, W., Wu, M.C. and Chao, R., "A novel mems tunable capacitor based on angular vertical comb drive actuators", in Solid-State Sensor, Actuator and Microsystems Workshop, Citeseer. (2002), 277-280.
  11. Rijks, T.G., Van Beek, J., Steeneken, P., Ulenaers, M., De Coster, J. and Puers, R., "Rf mems tunable capacitors with large tuning ratio", in 17th IEEE International Conference on Micro Electro Mechanical Systems. Maastricht MEMS 2004 Technical Digest, IEEE. (2004), 777-780. DOI: 10.1109/MEMS.2004.1290700
  12. Teymoori, M.M., Ahangarkolaei, J.M. and Sangrody, R.A., "Investigation and comparison of two movable plates electrostatic mems tunable capacitors", International Journal of Electronics Communication and Computer Engineering, Vol. 6, No. 3, (2015). 404-408.
  13. Feng, Z., Zhang, W., Su, B., Harsh, K.F., Gupta, K., Bright, V. and Lee, Y., "Design and modeling of rf mems tunable capacitors using electro-thermal actuators", in 1999 IEEE MTT-S International Microwave Symposium Digest (Cat. No. 99CH36282), IEEE. Vol. 4, (1999), 1507-1510. DOI: 10.1109/MWSYM.1999.7802401
  14. Lee, C.-Y. and Kim, E.S., "Piezoelectrically actuated tunable capacitor", Journal of Microelectromechanical Systems, Vol. 15, No. 4, (2006), 745-755. DOI: 10.1109/JMEMS.2006.878886
  15. Mehran, M., Rotani, E.Z., Shirazi, A.D.M. and Hakimi, A., "An electro-thermal mems variable capacitor", in 2020 28th Iranian Conference on Electrical Engineering (ICEE), IEEE. Vol., No. Issue, (2020), 1-5. DOI: 10.1109/ICEE50131.2020.9260576
  16. Shahi, M., "Development of tunable mems capacitor with dual-mode deformation to improve tunability and linearity", Southern Illinois University at Edwardsville, (2021), M.Sc. Thesis
  17. Nguyen, H.D., Hah, D., Patterson, P.R., Chao, R., Piyawattanametha, W., Lau, E.K. and Wu, M.C., "Angular vertical comb-driven tunable capacitor with high-tuning capabilities", Journal of Microelectromechanical Systems, Vol. 13, No. 3, (2004), 406-413. DOI: 10.1109/JMEMS.2004.828741
  18. Steeneken, P., Rijks, T.G., Van Beek, J., Ulenaers, M., De Coster, J. and Puers, R., "Dynamics and squeeze film gas damping of a capacitive rf mems switch", Journal of Micromechanics and Microengineering, Vol. 15, No. 1, (2004), 176.
  19. Li, Z. and Tien, N.C., "A high tuning-ratio silicon-micromachined variable capacitor with low driving voltage", in Proc. Solid-State Sensor and Actuator Workshop. (2002), 2-6.
  20. Ashoori, M. and Nabovati, H., "Wide tuning range and high quality factor mems variable capacitor with two movable plates in 0.18 μm cmos technology", Majlesi Journal of Mechatronic Systems, Vol. 3, No. 4, (2014). 25-31.
  21. Lee, H.S., Yoon, Y.J., Choi, D.-H. and Yoon, J.-B., "High-q, tunable-gap mems variable capacitor actuated with an electrically floating plate", in 2008 IEEE 21st International Conference on Micro Electro Mechanical Systems, IEEE. (2008), 180-183. DOI10.1109/MEMSYS.2008.4443622
  22. Li, X., Xia, Y., Liu, J., Yin, L., Liu, Y., Fang, D. and Zhang, H., "Tunable rf mems capacitor for wireless communication", in 2009 International Conference on Optical Instruments and Technology: MEMS/NEMS Technology and Applications, International Society for Optics and Photonics. Vol. 7510, (2009), 751002. https://doi.org/10.1117/12.845903
  23. Rais-Zadeh, M., Samarao, A., Monajemi, P. and Ayazi, F., "Low-voltage large-value tunable capacitors using selfaligned harpss", in 2008 IEEE 21st International Conference on Micro Electro Mechanical Systems, IEEE. (2008), 319-322. DOI10.1109/MEMSYS.2008.4443657
  24. Al-Ghamdi, M., Khater, M., Abdel-Rahman, E. and Nepomuceno, E., "Quasi-static pull-in: An instability in electrostatic actuators", Scientific Reports, Vol. 10, No. 1, (2020), 1-8. doi.org/10.1038/s41598-020-61534-w
  25. Azizi, A., Fard, N.M., Mobki, H. and Arbi, A., "Bifurcation behaviour and stability analysis of a nano-beam subjected to electrostatic pressure", Applied and Computational Mathematics, Vol. 7, No. 1-2, (2018), 1-11.
  26. Razeghi A., B. Azizollah Ganji; A. Abdipour; R. A. Jafari-Talookolaei., "A Novel Metamaterial Microelectromechanical Systems Phase Shifter with High Phase Shift and High Bandwidth", International Journal of Engineering, Transactions B: Applications, Vol. 32, No. 8, (2019) 1163-1168 doi: 10.5829/ije.2019.32.08b.12
  27. Pratiher, B., "Electrostatically driven mems resonator: Pull-in behavior and non-linear phenomena", Nonlinear Systems: Theoretical Aspects and Recent Applications, (2020), 241.
  28. Rezazadeh, G., Rashvand, K. and Madinei, H., "Effect of length-scale parameter on pull-in voltage and natural frequency of a micro-plate", International Journal of Engineering, Transactions C: Aspects, Vol. 27, No. 3, (2014), 375-384. doi: 10.5829/idosi.ije.2014.27.03c.04
  29. Zhang, W.-M., Yan, H., Peng, Z.-K. and Meng, G., "Electrostatic pull-in instability in mems/nems: A review", Sensors and Actuators A: Physical, Vol. 214, (2014), 187-218. doi.org/10.1016/j.sna.2014.04.025
  30. Afrang, S., Mobki, H., Sadeghi, M.H. and Rezazadeh, G., "A new mems based variable capacitor with wide tunability, high linearity and low actuation voltage", Microelectronics Journal, Vol. 46, No. 2, (2015), 191-197. doi.org/10.1016/j.mejo.2014.11.006
  31. Bakri-Kassem, M. and Mansour, R., "High tuning range parallel plate mems variable capacitors with arrays of supporting beams", in 19th IEEE international conference on micro electro mechanical systems, IEEE. (2006), 666-669. DOI: 10.1109/MEMSYS.2006.1627887
  32. McFeetors, G. and Okoniewski, M., "Performance and operation of stressed dual-gap rf mems varactors", in 2006 European Microwave Conference, IEEE. (2006), 1064-1067. DOI: 10.1109/EUMC.2006.281117
  33. Mobki, H., Sadeghi, M.H., Afrang, S. and Rezazadeh, G., "On the tunability of a mems based variable capacitor with a novel structure", Microsystem Technologies, Vol. 17, No. 9, (2011), 1447-1452. doi.org/10.1007/s00542-011-1327-6
  34. Rezazadeh, G. and Mobki, H., "Application of thau observer for fault detection of micro parallel plate capacitor subjected to nonlinear electrostatic force", International Journal of Engineering, Transactions B: Applications, Vol. 28, No. 2, (2015), 270-276. doi: 10.5829/idosi.ije.2015.28.02b.13
  35. Borwick, R.L., Stupar, P.A., DeNatale, J.F., Anderson, R. and Erlandson, R., "Variable mems capacitors implemented into rf filter systems", IEEE Transactions on Microwave Theory and Techniques, Vol. 51, No. 1, (2003), 315-319. DOI: 10.1109/TMTT.2002.806519
  36. Afrang, S. and Nematkhah, N., "A new mems based variable capacitor using electrostatic vertical comb drive actuator and auxiliary cantilever beams", Microsystem Technologies, Vol. 25, No. 9, (2019), 3317-3327. DOI: 10.1109/TMTT.2002.806519
  37. Chen, C. and Lee, C., "Design and modeling for comb drive actuator with enlarged static displacement", Sensors and Actuators A: Physical, Vol. 115, No. 2-3, (2004), 530-539. doi.org/10.1016/j.sna.2004.04.052
  38. Jaecklin, V., Linder, C., De Rooij, N. and Moret, J., "Micromechanical comb actuators with low driving voltage", Journal of Micromechanics and Microengineering, Vol. 2, No. 4, (1992), 250.
  39. Legtenberg, R., Groeneveld, A. and Elwenspoek, M., "Comb-drive actuators for large displacements", Journal of Micromechanics and Microengineering, Vol. 6, No. 3, (1996), 320.
  40. Rebeiz, G.M., "Rf mems: Theory, design, and technology, John Wiley & Sons, (2004).