Miniaturization of ESPAR antenna using folded monopoles and conical central element

Miniaturized Electronically Steerable Array Radiator (ESPAR) antenna with folded parasitic monopoles and conical central element is proposed. ESPAR antenna is able to cover a bandwidth from 2.35GHz to 2.55GHz. Folded monopole structure with conical central element is employed to reduce the size of antenna. Height of antenna monopoles is reduced to 1/12 wavelength and its radius is reduced to 1/4 wavelength, making it three times smaller than conventional ESPAR antenna. Central element is made conical to improve bandwidth and return loss. In spite of its compactness antenna achieves gain of 7dBi and return loss of -25dB at designed frequency of 2.45GHz. Antenna main beam can be steered in the horizontal plane across a range from 0-360 degrees by opening shorting parasitic elements. The proposed ESPAR antenna has compact size, beam steering ability and in spite of its compactness antenna achieves almost the same gain as that of standard ESPAR antenna.