• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.2
• /
• pp.203-209
• /
• 2004

Compliant bi-stable mechanism allows two stable states within its operation range staying at one of the local minimum states of the potential energy. Energy storage characteristics of the bi-stable mechanism offer two distinct and repeatable stable states, which require no power input to maintain it at each stable state. This paper suggests an equivalent model of the chevron-type bi-stable microactuator using the equivalent spring stiffness in the rectilinear and the rotational directions. From this model the range of spring stiffness where the bi-stable mechanism can be operated is analyzed and compared with the results of the FEA (Finite Element Analysis) using ANSYS for the buckling analysis, both of which show a good agreement. Based on the analysis, a newly designed chevron-type bi-stable MEMS actuator using hinges is suggested for the latch-up operation. It is found that the experimental response characteristics of around 36V for the bi-stable actuation for the 60$mu extrm{m}$ stroke correspond very well to the results of the equivalent model analysis after the change in cross-sectional area by the fabrication process is taken into account. Together with the resonance frequency experiment where 1760Hz is measured, it is shown that the chevron-type bi-stable MEMS actuator using hinges is applicable to the optical switch as an actuator.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.2
• /
• pp.22-32
• /
• 2002

MEMS(Micro-Electro-Mechanical Systems)는 전기적인 구성요소와 기계적인 구성요소를 작게 조합하여 구성한 소자나 시스템을 말한다. RF(Radio Frequency) MEMS는 MEMS를 이용한 RF 소자나 시스템을 의미하며, 본 고에서는 RF 소자에 대하여 논의하고자 한다. MEMS는 RF 소자의 성능, 기능, 집적화 등을 높여 주고, 크기, 가격, 부피, 전력 소모 등을 낮추어 주므로 소자 개발에 대한 연구는 매우 다양하지만, 본 고에서는 움직이는 소자 중에서 가장 많이 연구되고 있는 mechanical RF switch에 대하여 중점적으로 다루고자 한다. 이에 대한 연구 동향, 특성, 응용 분야 등을 살펴보고, 상품으로서의 가치를 인정 받기 위하여 고려해야 할 점들을 논의 하겠다.

• Journal of Electrical Engineering and Technology
• /
• v.2 no.2
• /
• pp.263-266
• /
• 2007

We report a nickel optical MEMS switch, being able to rotate through a large angle and to accommodate multiple channels. The proposed optical switch consists of a thin nickel mirror and two torsion springs supporting the mirror. The torsion springs are designed using a finite element method (FEM) such that plastic deformation of the thin nickel is avoided during the large torsion actuation. For switching speed improvement, transient vibration of the released mirror is suppressed by optimizing the mirror design and a fast switching response of $200\;{\mu}s\;(pull-down)/300\;{\mu}s\;(pull-up)$ is demonstrated.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.54 no.6
• /
• pp.25-29
• /
• 2017

This paper presents a hetero-integration of electrostatically actuated RF MEMS Switch and step up DC-DC converter on a redistribution layer using commercial PCB process. RF characteristics of Duroid with $56{\Omega}$ impedance GCPW transmission line and that of FR4 with $59{\Omega}$ impedance CPW transmission line were analyzed. From DC to 6GHz, RF characteristics of Duroid were better than that of FR4, insertion loss was 2.08dB lower, return loss was 3.91dB higher, and isolation was 3.33dB higher.

• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.2395-2397
• /
• 2005

A low voltage operated piezoelectric RF MEMS in-line switch has been realized by using silicon bulk micromachining technologies for advanced mobile/wireless applications. The developed RF MEMS in-line switches were comprised of four piezoelectric cantilever actuators with an Au contact metal electrode and a suspended Au signal transmission line above the silicon substrate. The measured operation dc bias voltages were ranged from 2.5 to 4 volts by varying the thickness and the length of the piezoelectric cantilever actuators, which are well agreed with the simulation results. The measured isolation and insertion loss of the switch with series configuration were -43dB and -0.21dB (including parasitic effects of the silicon substrate) at a frequency of 2GHz and an actuation voltage of 3 volts.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.4
• /
• pp.381-391
• /
• 2010

In this paper, a novel frequency reconfigurable active array antenna(RAA) system, which can be reconfigurable for three reconfigurable frequency bands, is proposed by using commercial RF MEMS switches. The MEMS switch shows excellent insertion loss, linearity, as well as isolation. So, the system performance degradation of the reconfigurable system by using MEMS switches can be minimized. The proposed frequency reconfigurable active antenna system is consisted with the noble frequency reconfigurable front-end amplifiers(RFA) with the simple reconfigurable impedance matching circuits(RMC), reconfigurable antenna elements(RAE), as well as a reconfiguration control board(RCB) for MEMS switch control. The proposed RAA system can be reconfigurable for three frequency bands, 850 MHz, 1.9 GHz, and 3.4 GHz, with $2{\times}2$ array of the RAE having broadband printed dipole antenna topology. The validity of the proposed RFA as well as RAA is also presented with the experimental results of the fabricated systems.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.11a
• /
• pp.613-614
• /
• 2008

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.11A
• /
• pp.1091-1096
• /
• 2010

Stiction in microelectromechanical systems (MEMS) has been a major failure mechanism. Especially, in RF MEMS switches, moving parts often suffered in-use and release related stiction problems. Some materials and methods have been used to prevent this problem. Diamond-like carbon (DLC) has not only been used as a protective material owing to its good mechanical properties but also has been used as a hydrophobic material. Its properties could be controlled by post annealing treatment in various conditions. We synthesized DLC films using a radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gas. Then, the change of the hydrophobic property of the films was investigated undervarious annealing temperatures in nitrogen and in oxygen ambient. The films, that were annealed above $700^{\circ}C$ in nitrogen ambient, showed a high contact angle of water (> $90^{\circ}$) even though their mechanical property was sacrificed to some degree. The structural variation and the changes of the hydrophobic and mechanical properties of the DLC films were analyzed by Raman spectrum, contact angle measurement, surface profiler, and a nanoindentation test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.187-188
• /
• 2005

In this paper, big free standing metal structures for electrostatic MEMS switches are easily fabricated using photoresist sacrificial layer. The entire process sequence, through the removal of the sacrificial layer, is kept below 150 $^{\circ}C$ to avoid curing problem of photoresist sacrificial layer. Metal structure is fabricated by thermal evaporator and a self test electrode is fabricated underlying metal suspended structure for testing by electrostatic force. The new wet release process is considered using methanol rinse, general wet release process cause stiction problem by capillary force during drying, and the yield is dramatically improved than previous wet release process using DI water rinse. The fabrication becomes much simpler and cheaper with use of a photoresist sacrificial layer.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.4
• /
• pp.41-46
• /
• 2005

In this paper, a new method for suppressing microwelding on the RF MEMS (Radio Frequency Microelectromechanical System) direct contact switches is introduced. Two kinds of refractory metals, tungsten and molybdenum were coated onto the contact point of the switches and the effect of the coating was examined. The changes in insertion loss and isolation at the switch were measured by using network analyzer and power loss was evaluated by power measurement. The results revealed that while tungsten and molybdenum showed higher contact resistance than gold in low input power range, they enhanced the power handling capability and reliability of the switches in high input power region.