Baek-Seok Ko

Hybrid ring coupler for W-band MMIC applications using MEMS technology

The hybrid ring coupler was designed and fabricated on a GaAs substrate using surface micromachining techniques, which adopted dielectric-supported air-gapped microstrip line (DAML) structure. The fabrication process of DAML is compatible with the standard monolithic microwave integrated circuit (MMIC) techniques, and the hybrid ring coupler can be simply integrated into a plane-structural MMIC. The fabricated hybrid ring coupler shows wideband characteristics of the coupling loss of 3.57 /spl plusmn/ 0.22dB and the transmission loss of 3.80 /spl plusmn/ 0.08dB across the measured frequency range of 85 to 105GHz. The isolation characteristics and output phase differences are -34dB and 180/spl plusmn/1/spl deg/, at 94GHz, respectively.

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.

A millimeter-wave micromachined slow-wave bandpass filter using compact microstrip stepped-impedance hairpin resonator

In this paper, a new microstrip stepped-impedance hairpin resonator with inter-digital capacitor (IDC) slow-wave band-pass filter (BPF) using dielectric supported air-gapped microstrip line (DAML) of surface micromachining on GaAs substrate is proposed. The slow-wave periodic structures utilize the parallel and series resonance characteristics of the resonators to construct a band-pass filter. Unlike conventional slow-wave filters, the proposed bandpass filters are designed to produce a narrow passband at the fundamental mode of the resonators. Using IDC, this filter provides small size and sharp shirt characteristic. The proposed slow-wave band-pass filter with IDC is designed to produce a passband of 7.7 % at the fundamental frequency of 56 GHz. It shows the insertion loss of 3.37 dB, the return loss of better than 15 dB, and the stopband characteristic of greater than 31 dB within 37.03 /spl sim/ 45.51 GHz.