Shielded microstrip aids V-band receiver designs

The recent development of thin, flexible, and relatively low dielectric-constant substrate materials (such as Cuflon) has simplified the design of shielded microstrip transmission media for millimeter-wave integrated circuits. Before such transmission materials were available, conventional millimeter-wave integrated circuits relied on fused-quartz-dielectric substrates. However they are expensive, break easily, and are difficult to drill. Moreover, fused-quartz circuits are small, and require greater precision in processing. Using Cuflon, a cost-effective V-band receiver module with shielded microstrip as the transmission media can be designed. The module consists of a Gunn-diode, dielectric-resonator-controlled local oscillator, an isolator, a directional filter, a single-diode mixer, and a waveguide-to-shielded-microstrip transition. Since all millimeter-wave circuits require metallic shielding to control higher-order modes, reduce radiation losses, and eliminate external electromagnetic interference, the receiver must have a rectangular magnetic shield. Together, the metallic shield and the shielded microstrip provide for improved millimeter-wave integrated circuits.