Soon-Koo Kim

Fabrication of new micromachined transmission line with dielectric posts for millimeter-wave applications

This paper describes a new GaAs-based surface-micromachined microstrip line supported by dielectric posts and with an air gap between the signal line and the ground metal. This new type of dielectric post and air-gapped microstripline (DAML) structure was developed using surface micromachining techniques to provide an easy means of air-bridge connection between the signal lines and to achieve low losses in the millimeter-wave frequency band with a wide impedance range. Each DAML is fabricated with a length of 5 mm. By elevating the signal lines from the substrate using micromachining technology, the substrate dielectric loss can be reduced. Compared with conventional microstrip transmission lines, which show over 10 dB cm−1 loss, the loss of a DAML can be reduced to 1.1 dB cm−1 at 50 GHz.

The Fabrication of the Low Loss Transmission Line and Low Pass Filter using Surface Microelectromechanical Systems Technology

In this study, we first fabricated a new GaAs-based dielectric-supported air-gap microstrip lines (DAMLs) by the surface microelectromechanical systems (MEMS) technology, and then fabricated the low-pass filter (LPF) for the Ka-band using those DAMLs. We elevated the signal lines from the surface in order to reduce the substrate dielectric loss and to obtain low losses at the millimeter-wave frequency band with a wide impedance range. We fabricated LPFs with DAMLs for Ka-bands, and we were able to reduce the insertion loss of LPFs by reducing the dielectric loss of the DAMLs. Miniaturization is essential for integrating LPFs with active devices, so we fabricated a LPF with the slot on the ground metal to reduce the size of the LPF. We compared the characteristics of the LPF with a slot and the LPF without the slot.

Fabrication of Millimeter Wave Radiometer

Abstract We have manufactured a close range Dicke type radiometer which consists of two stage low noise amplifier and diode detector. Frequency range of this system is 35 GHz. And this is used for studying temperature calibration on specific objects. We have present millimeter-wave radiometers thermal calibration method and its characteristics. From absolute temperature 299K to 309K, in proportion to increase temperature, output voltages are linearly increased. In this case, undefined objects can be measured thermal noise temperature relatively. Overall from absolute temperature 214K to 309K, we have obtained relation of temperature and output voltage;V= 0.03601K - 10.70517. Key Words : Dicke type radiometer, Millimeter-wave radiometer, Thermal noise, Calibration * 정회원, 상지대학교 이공대학 응용물리전자학과접수일자 2010.9.4, 수정완료 2012.5.15게재확정일자 2012.6.8.Received: 4 September, 2010, Revised: 15 May, 2012Accepted: 8 June, 2012 * Corresponding Author:kookim@dongguk.eduDept. of Applied Physics & Electronics, Sangji University, Korea

Studies on the pull-up RF MEMS switch for the lower actuation voltage and high speed using double electrode

We report a pull-up type RF MEMS switch using double electrode without elastic deformation of the cantilever involved in the actuation. At a voltage of 4.5 V, reliable actuations are achieved such that the movable lower contact pad is pulled up by the electrostatic force to make contact with the upper pad. At a frequency of 50 GHz, an insertion loss of 0.7 dB and an isolation of 50.7 dB are obtained from the switch. The measured transient times for switch-on and switch-off are 120 and 80 ns, respectively.

Negative Magnetoresistivity from Electron–Electron Interaction Effect in Modulation Doped n‐Channel Si/Si1—xGex Quantum Well Structures

Magnetoresistivity measurements are made on the two-dimensional electron gas in a Si/Si 0.7 Ge 0.3 modulation-doped quantum well. The temperature (T)-dependent negative magnetoresistivity, observed below 0.1 T, clearly shows the effect of electron-electron interactions.