Polarization, phase and frequency agility in varactor diode loaded patches

Independently biased varactor diodes fitted to radiating edges of microstrip patches afford independent control of the input impedance and resonant frequency. Square patches with varactor diodes fitted to each radiating edge can be adjusted to radiate linear polarization with the electric vector in any one of three planes, or circular polarization, (left or right hand). Similarly, equilateral triangular patches with diodes mounted at the vertices and the feed probe located symmetrically at the centre can be adjusted to radiate linear polarization in any of the three axes with marginal control over the orientation of the cross-polar null, and the facility of switching the radiated phase in any plane from zero to 180 degrees. Input match optimisation and frequency agility is possible in both antenna geometries