Electrically-Steerable Parasitic Array Radiator (ESPAR) antenna design for arrays with two and three parasitically-coupled elements

Two- and three-element microstrip patch ESPAR arrays are presented, operating at 2.5 GHz and 1 GHz, respectively. Both ESPAR structures are driven using a single element which is coupled to the parasitic antennas. Mutual coupling between the driven and parasitic elements replaces the traditional feed system and eliminates phase shifters. Tunable varactors are utilized to control the beam scanning. Both arrays are simulated with a full-wave solver, while the three-element array is fabricated and measured. Impedance match at the operating frequency is consistently maintained, as the resonance is controlled by tunable reactive loading. Phase shifter elimination results in inexpensive fabrication, allowing widespread use in point-to-point communication systems such as automobile receivers for satellite and GPS.