A 20-dB directional coupler has been designed and fabricated on a thin
dielectric membrane using micromachining techniques. The fabrication
process is compatible with monolithic microwave integrated-circuit (MM
IC) techniques, and the coupler can be integrated into a planar-circui
t layout. Design of the asymmetric tapered coupled-line coupler relies
on simple quasi-static models and ideal transmission-line theory. The
use of membrane technology results in less than 0.5-dB insertion loss
in the coupler from 10 to 60 GHz. In addition, a micromachined packag
ing technique creates a shielded circuit, which is extremely compact a
nd lightweight.