GUNN-LOADED ACTIVE PATCH ANTENNAS

Abstract

The quasi optical power combining arrays have emerged as an alternative to the vacuum tube sources at millimeter wave spectrum. An approach, to quasi optical power combining involves arrays of weakly coupled individual oscillator elements. It has numerous advantages. An active microstrip patch antenna, integrating microstrip patch with a solid state source, is a prime choice for such arrays. In this work, Gunn-loaded active patch antennas have been experimentally studied. Two configurations of single diode active patch antennas have been used. In one case the diode was located centrally along the non resonant length of the patch at a distance x' calculated for impedance of 9n, from one of the radiating' edges. Whereas in the other case diode was slightly displaced from this central position along the non resonant length over which impedance remained constant. Two configurations of dual diode antennas have also been studied. In one case, the two diodes were placed symmetrically along the resonant length whereas in other case they were placed symmetrically along the non resonant length of the patch. Results have been reported here on radiation patterns and operating frequencies at different bias voltages. The symmetry of the structure, in case of dual diode patch antennas has resulted in a dramatic decrease in H-plane crosspolarisation, improved copolarisation patterns and 'high power as compared to the single diode patch antennas.