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)