A Microstrip Patch Electronically Steerable Parasitic Array Radiator (ESPAR) Antenna With Reactance-Tuned Coupling and Maintained Resonance

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 are designed, fabricated, and measured. The driven element is mutually coupled to two parasitic elements in the H-plane. The varactors are used to control the mutual coupling and beam scanning and to maintain resonance at 1 GHz. A continuous scanning range of -15 + 15° is measured with maintained impedance matching and radiation pattern integrity. The low cost of diode varactors, used in place of expensive phase shifters, allows for more economic fabrication. This is advantageous to applications in point-to-point communication systems, weather, and target tracking radar systems.