Conception and realization of highly selective band-pass filters in Ka-band built on thin polymer films

A novel structure of high performance narrow band-pass filters on thin polymer film is reported in this paper. It's composed of two microstrip resonators placed between two via-free microstrip-grounded coplanar waveguide transitions. It combines therefore compactness, low-cost, fabrication easiness of microstrip lines and connection facility of coplanar pads. Narrow band-pass filters have been optimized by using HFSS software, realized and characterized, over the range of Ka-band frequencies. With the band-pass filter realized on thin BCB polymer (benzocyclobutene, relative permittivity er = 2.65 and loss tangent tanô = 0.0025) film of 60 μm thick, the performance obtained for a center frequency optimized at 30.5 GHz is 28.8 for quality factor and −1.4 dB for insertion losses, with very good agreement between simulation and experiment results.

I. Introduction

Microwave filters are essential to the operation of signal processing devices, transmission networks and detection systems, such as satellite communications, terrestrial microwave communications, astronomical observations, radars, molecular rotational spectroscopy. They permit detecting weak signals buried in noise and improving detection sensitivity. In space and terrestrial communication systems, band-pass filters are useful in both receivers and transmitters. They should in general satisfy the following technical requirements: high frequency selectivity, low insertion losses and good phase linearity. In addition, they are requested to be compact, light, low cost and easy to fabricate.