Beam scanning microstrip arrays using diodes

The feasibility of using diodes in linear microstrip antenna arrays to facilitate electronic beam scanning is investigated. The first concept concerns a microstrip line loaded with varactor diodes serving the dual purpose of phase shifter and feeder for a linear travelling wave array. Theoretical and practical results provide antenna design data on the number and type of diodes, optimisation of the radiating elements and temperature effects. Likely noise figure degradation, transient beam scanning response, and the antenna construction are other design aspects discussed. An array at 7.5 GHs containing 24 varactor diodes demonstrates that some 20° of beam scan is achievable before the travelling wave action is disrupted. The second concept introduced is a novel microstrip patch element with embedded diode and polariser enabling mixer action to take place. The theoretical and practical design of this antenna mixer element, and its deployment in an eight element linear beam scanning array at 2.92 GHz, is presented. Other mixer configurations, using additional diodes offering superior suppression of spectral products, are noted and the possible influence of the polariser on interelement mutual coupling investigated