Heart shaped reconfigurable band-notched ultra-wide band antenna using electromagnetic band-gap structure and varactor diodes

Abstract

Heart shaped reconfigurable band notched UWB microstrip line fed monopole antenna using two mushrooms like electromagnetic band gaps (EBGs) loaded by two varactor diodes has been developed, examined and fabricated. The effect of EBG dimensions, on the notch frequency, was first examined. A notched frequency of 5.3 GHz is obtained when two square EBGs with rectangular slits are used with length equal 7.5 mm and gap, g = 0.5 mm. The EBGs is loaded by a varactor diode to achieve re-configurability. The notch frequency covers WiMAX when varactor capacitance C = 0.7 pF and covers WLAN when C = 0.1pF. Also, the notch can be easily eliminated by decreasing the capacitance below 0.1 pF. A prototype of the proposed antenna using single capacitor elements with capacitances 0.6 pF is fabricated and S11 is measured. Notch frequency at 4 GHz is obtained in both simulated and measured antenna structures. The antenna with EBG has a directive radiation pattern in E-plane and omnidirectional pattern in H-plane. Also, the gain is suppressed in the notched frequencies. The group delay is nearly stable in the UWB frequency range, except at the notch frequencies, which is distorted sharply. FEM and FIT are hired to simulate the proposed antenna structure using HFSS and CST respectively. Very good agreement between both results has been obtained.