| The continued decline in the overall cost of monolithic microwave integrated circuits (MMIC), has made modular assemblies, such as amplifiers and transceivers, very popular. All of these modules are commonly build on microstrip, because this medium affords the most cost-effective and convenient method of integration to other planar circuits. However, the ideal form of power transmission at the millimetre waves frequencies is the rectangular waveguide, due to its low dissipation and low interface VSWR. There has been therefore a requirement for a low loss transition from waveguide to microstrip.; In the past, the usual type of transitions suffered from their mechanical complexity and even from precise positioning of waveguide back-short. Some of them can be rather large, comprised of several independent pieces that must be assembled in various steps or may require a multilevel conductors and substrates.; In our study, we have proposed a new concept that simplifies the transition geometry, while still maintaining a good level of electrical performance. In fact, a waveguide-to-microstrip transition has been developed using a new design methodology. A proof of the concept was achieved by implementing a K-band (f0 = 20GHz) design on duroid©.; The optimal coupling of the RIF power to and from the waveguide occurs by way of an E-plane rectangular resonant iris etched from the ground plane of the microstrip substrate. A cavity encloses the waveguide transition with the exception of the opening. The combination of the rectangular iris and the cavity enclosure shows to be one of the more distinguishable features of the present study; it ensures the transition independence from microstrip radiation, that could otherwise have detrimental effects on its performance. These features render our design readily integrable into typical MMIC multichip assembly. |
