A broadband surface-micromachined 15-45 ghz microstrip coupler

A broadband elevated microstrip coupler has been designed and implemented on the soda-lime glass with surface micromachining technology. The coupler is elevated by 200 μm and fed by a combination of epoxy-core metal post and coplanar waveguide, which helps eliminate the conventional air/dielectric interface problems. By this method, frequency dispersion and attenuation due to the substrate can be effectively reduced. A 10 dB return loss and a 12.5 dB coupling is measured in our experiment over 15-45 GHz. The proposed structure can be implemented on very lossy substrates, such as standard CMOS substrate and thus can be applied into the integration of high performance RF components with digital or optical functions/subsystems on low-cost low-resistivity silicon wafers.