• JSTS:Journal of Semiconductor Technology and Science
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• 제2권4호
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• pp.237-245
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• 2002

A new type of RF MEMS switch for low voltage actuation, high broadband application and high power capability is presented. Mechanical and electromagnetic simulations of this new RF MEMS switch type are shown and the fabrication process and measurement results are given. The switching element consists of a cantilever which is fixed by a suspension spring to the ground of the coplanar line. The closing voltage is 16V. The switches exhibit low insertion loss (<0.85dB@30GHz) with good isolation (>22dB@30GHz).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.282-283
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• 2007

본 논문에서는 저전압에서 구동 할 수 있는 압전구동 방식의 RF MEMS 스위치를 설계하였다. 설계는 유한요소기법(FEM)을 지원하는 시뮬레이터 (ConventorWare)를 사용하여 수행하였고, 이를 바탕으로 deflection, contact force, stress 등 기계적인 해석을 함으로써 최적화된 설계를 할 수 있었다. 이번 설계에서는 적절한 contact force를 유지하면서 hinge에서 받는 stress를 최소화하기 위하여 구동기를 2개 사용한 듀얼형식의 모델을 제안하였고, hinge의 모양은 'ㄷ'로 하여 deflection을 향상시켰다. 이 듀얼형식의 최적화된 모델은 signal line과 contact pad 간의 gap이 3.4${\mu}m$일 때, 최초 2.8V에서 contact이 이루어졌으며, 5V에서 12.4${\mu}N$의 contact force와 116MPa의 stress를 얻었고, 차후, SP4T나 SP6T 등의 설계시 공간 효율이 높은 다양한 형태의 구조를 설계할 수 있다.

• 한국인터넷방송통신학회논문지
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• 제18권5호
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• pp.223-228
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• 2018

본 논문은 동축 공동 공진기를 이용한 레인센서를 설계하고 제작한다. 선형적으로 빗방울을 감지할 수 있는 레인센서는 전압 제어 발진기 (VCO), 동축 공동 공진기, RF 스위치, RF 검출기, A / D 컨버터, DAC 및 마이크로 컨트롤러로 구성되었다. 설계된 레인 센서의 작동 주파수 범위는 2.5GHz ~ 3.2GHz이며, 입력 전압과 전류 소스는 24 [V / DC]와 1 [A]이다. 설계된 센서 회로는 VCO, RF 스위치, 고주파수 3GHz에서 소자의 주파수 특성을 변화시키는 RF 검출기를 포함한다. 센서 회로의 주파수 특성에 대한 오차를 교정한다. 이를 위해 공진기에 신호를 보내지 않고 RF 검출기로 신호를 직접 전달하는 기준 경로를 만든다. 시뮬레이션 및 측정 결과에 따르면 시뮬레이션된 공진기 주파수와 제작된 공진기 주파수 사이에 0-50MHz 차이가 있음을 알 수 있다.

• ETRI Journal
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• 제34권1호
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• pp.1-8
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• 2012

This paper proposes a reconfigurable beam-steering antenna using a bended dipole and a loop. The radiation patterns of the two antennas are cancelled or compensated, and headed towards a specific direction when the dipole and loop antenna are combined at a reasonable ratio. The proposed antenna can steer the beam directions by controlling the operation of two artificial switches. The proposed antenna was manufactured on a PCB (FR-4) and a flexible PCB (polyimide). In the case of the antenna that was fabricated on a PCB, the maximum beam directions were $+50^{\circ}$, $0^{\circ}$, and $-50^{\circ}$ in the azimuth direction using the two artificial switches, and the antenna gain was 1.96 dBi to 2.48 dBi in the operation bandwidth of 2.47 GHz to 2.53 GHz. Also, the antenna was fabricated on a flexible PCB and measured under various bending conditions for wearable applications.

• Transactions on Electrical and Electronic Materials
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• 제14권5호
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• pp.225-230
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• 2013

This paper presents a novel shunt radio frequency microelectromechanical system switch on a quartz substrate with stiff ribs around the membrane. The buckling effects in the switch membrane and stiction problem are the primary concerns with RF MEMS switches. These effects can be reduced by the proposed design approach due to the stiffness of the ribs around the membrane. A lower mass of the beam and a reduction in the squeeze film damping is achieved due to the slots and holes in the membrane, which further aid in attaining high switching speeds. The proposed switch is optimized to operate in the k-band, which results in a high isolation of -40 dB and low insertion loss of -0.047 dB at 21 GHz, with a low actuation voltage of only 14.6 V needed for the operation the switch. The membrane does not bend with this membrane design approach. Finite element modeling is used to analyze the stress and pull-in voltage.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권5호
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• pp.675-681
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• 2016

A 41dB gain control range $6^{th}$-order band-pass receiver front-end (RFE) using CMOS switched frequency translated impedance (FTI) is presented in a 40 nm CMOS technology. The RFE consists of a frequency tunable RF band-pass filter (BPF), IQ gm cells, and IQ TIAs. The RF BPF has wide gain control range preserving constant filter Q and pass band flatness due to proposed pre-distortion scheme. Also, the RF filter using CMOS switches in FTI blocks shows low clock leakage to signal nodes, and results in low common mode noise and stable operation. The baseband IQ signals are generated by combining baseband Gm cells which receives 8-phase signal outputs down-converted at last stage of FTIs in the RF BPF. The measured results of the RFE show 36.4 dB gain and 6.3 dB NF at maximum gain mode. The pass-band IIP3 and out-band IIP3@20 MHz offset are -10 dBm and +12.6 dBm at maximum gain mode, and +14 dBm and +20.5 dBm at minimum gain mode, respectively. With a 1.2 V power supply, the current consumption of the overall RFE is 40 mA at 500 MHz carrier frequency.

• 한국통신학회논문지
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• 제35권11A호
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• pp.1091-1096
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• 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.

• 한국통신학회논문지
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• 제34권2A호
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• pp.139-146
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• 2009

본 논문은 TDD(Time Division Duplex) 배열안테나 시스템에서 빔형성을 할 때와 송신 전력을 할당하는 경우에 필요한 송수신 RF 단의 진폭과 위상 오차를 교정하는 평균자동내부순환교정 방법을 제안한다. 제안된 기술은 기존의 부가적인 내부 신호발생기나 외부의 기준신호를 필요로 하지 않으며 송수신기 내부의 스위치와 커플러를 이용하여 배열안테나 RF단을 교정할 수 있는 방법이다. 또한 한 개의 송수신 RF단을 사용한 교정에 의한 오차를 줄이기 위해서 평균송수신 RF단 교정 방법을 제안하였다. 전산모의실험을 통해 DOA(Direction of Arrival)추정 빔형성 알고리즘이 송수신 RF단 교정에 의해 정확한 빔형성이 되는 것을 보였고 송신 전력 할 당시에도 제안된 교정에 의해 비트오류율이 낮아짐을 보였다.

• 한국소음진동공학회논문집
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• 제21권6호
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• pp.553-561
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• 2011

A theoretical approach is carried out to predict the quality factors of flexible modes of a microcantilever on a squeeze-film. The frequency response function of an inertially-excited microcantilever beam is derived using an Euler-Bernoulli beam theory. The external force due to squeeze-film phenomenon is developed from the Reynolds equation. Slip boundary conditions are employed at the interfaces between the fluid and the structure to consider the gas rarefaction effect, and pressure boundary condition at both ends of fluid analysis region is enhanced to increase the exactness of predicted quality factors. To the end, an approximate equation is derived for the first bending mode of the microcantilever. Using the approximate equation, the quality factors of the second and third bending modes are calculated and compared with experimental results of previously reported work. The comparison shows the feasibility of the current approach.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2395-2397
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• 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.