Analysis and design of microstrip-slot line for phase shifting applications

The analysis and design of printed phase shifters based on the microstrip line are described. A spectral-domain analysis is presented where the necessary Green's functions are formulated using the transmission matrix technique. The nonreciprocal characteristics for single-layer and multilayer structures are studied. Microstrip-slot in a multilayer structure of ferrite and high-dielectric material is found to have considerably more nonreciprocity than microstrip-slot for microstrip in a single-layer structure. Over 65 degrees /cm is predicted for certain optimized designs. This, in addition to the 50- Omega design capability of the line, makes the microstrip-slot line a suitable choice for phase shifting applications. A multilayer microstrip-slot line was constructed on a rectangular ferrite toroid. Differential phase shifts of roughly 45 degrees /cm were measured over a 6.0-8.5-GHz frequency range. These results are in good agreement with the analysis.< >