2005YDC

簡業達 (Ye-Da Chien)

Design, Simulation and Fabrication of Miniaturized RF-MEMS Filter

微小化共面波導濾波器之設計、模擬與製作

A compact-size coplanar waveguide (CPW) lowpass filter is designed, simulated, fabricated and measured. The purpose of this thesis is to investigate the performance of miniaturized CPW lowpass filter which is a fifth-order semi-lumped uniplanar Butterworth filter. Our design utilizes transmission line lumped elements consisting of interdigital capacitors and meander line inductors. These filters with different metal thickness (up to 20μm) are successfully fabricated by surface micromaching and copper electroplating technologies. The miniaturized CPW lowpass filter has a rather small circuit size operating at 4 GHz. This circuit area with 2x2.3 mm^2 is reduced by 98% when compared with conventional stepped-impedance filter (24.6x11.6 mm^2)

Besides, Sonnet software which has lossless and thick metal model conductor is used for investigating the performance of miniaturized lowpass filter with different metal thickness. Good agreement has been found between the simulation and experimental results. The experimental results show that the cutoff frequency of lowpass filter can be adjusted by varying the meander length and the metal thickness. By periodically cascading this lowpass structure, we can improve the characteristics in the stopband.