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 concep t concerns a microstrip line loaded with varactor diodes serving the d ual purpose of phase shifter and feeder for a linear travelling wave a rray. 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 b eam scanning response, and the antenna construction are other design a spects discussed. An array at 7.5 GHz containing 24 varactor diodes de monstrates that some 20-degrees of beam scan is achievable before the travelling wave action is disrupted, and confirms the usefulness of th e concept for applications demanding modest beam scan range and a simp le low cost construction. The second concept introduced is a novel mic rostrip patch element with embedded diode and polariser enabling mixer action to take place. The theoretical and practical design of this an tenna mixer element, and its deployment in an eight element linear bea m scanning array at 2.92 GHz, is presented. Other mixer configurations , using additional diodes offering superior suppression of spectral pr oducts, are noted and the possible influence of the polariser on inter -element mutual coupling investigated. Computations and measurements s how that coupling effects are not significantly increased and confirm the usefulness of the antenna mixer element concept in beam forming ar ray applications where no premixer low noise amplification is demanded .