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.

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.

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In this paper, a new microstrip stepped‐impedance hairpin resonator (SIHR) slow‐wave bandpass filter (BPF) using a dielectric‐supported air‐gapped microstrip line (DAML) via 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. The proposed slow‐wave band‐pass filter is designed to produce a passband of 10% at the fundamental frequency of 60 GHz. It exhibits insertion loss of 2.23 dB, return loss of better than 15 dB, and a stopband greater than 35 dB. This filter is useful for many millimeter‐wave system applications. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 86–89, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21089

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