A 60-GHz-Band planar dielectric waveguide filter for flip-chip modules

A planar dielectric waveguide filter with coplanar waveguide (CPW) I/O ports suitable for flip-chip bonding is proposed and is demonstrated for 60-GHz-band applications. The filter is formed incorporating metallized through holes in an alumina substrate. In order to improve stopband rejection, short-circuited CPW resonators with a half-wavelength are added to waveguide-to-CPW transitions. A fabricated four-resonator filter exhibits an insertion loss of 3.2 dB with a 3-dB bandwidth of 3.0 GHz and rejection of 35 dB at 3-GHz lower separation from a center frequency of 59.5 GHz. The filter is mounted by using flip-chip bonding in a multilayer ceramic package with structures to suppress parasitically propagating electromagnetic waves. No degradation of the stopband rejection is observed from 50 to 80 GHz.