A microstrip patch phased array antenna with parasitic elements and reactance-tuned coupling

A new approach to parasitic phased array antennas is presented. A symmetric two-layer, single input inexpensive three-element array at 1 GHz employing varactors as tuning mechanisms is designed, fabricated and measured. The driven element is mutually coupled to two parasitic elements in the H-plane, and the mutual coupling is tuned by open-circuited microstrip stubs on the feed layer. The varactors are used to break the symmetry of the structure, resulting in beam scanning, and to maintain resonance at 1 GHz. A symmetric scanning range of -20 to +20° is measured with maintained impedance matching and radiation pattern integrity. The low cost of this array is advantageous to applications in point-to-point communication systems, weather and target tracking radar systems.