Wideband Dual Feed Electromagnetically Coupled Circularly Polarized Microstrip Patch Antenna

Kshitiz Agarwal^a, G. Purnachandra Rao^a, M. V. Kartikeyan^a, M. Thumm^b,c

^aDepartment of Electronics and Computer Engineering

Indian Institute of Technology, Roorkee 247 667, India

(E-mail: kartkfec@iitr.ernet.in)

^bForschungszentrum Karlsruhe

Institut fuer Hochleistungsimpuls- und Mikrowellentechnik

Postfach 3640, D 76021 Karlsruhe, Germany

^cUniversitaet Karlsruhe, Institut fuer Hoechstfrequenztechnik und Elektronik,

Kaiserstraße 12, 76131 Karlsruhe, Germany

(E-mail: manfred.thumm@ihm.fzk.de)

Abstract

In this work we present a wideband dual feed circularly polarized microstrip patch antenna. The antenna uses a feed configuration that saves additional area required for incorporating a power dividing network. The antenna geometry uses three substrates. Below the first substrate a T-network is incorporated as a power dividing circuit. Above this substrate and below the second substrate a ground plane is sandwiched. Above the second substrate a conducting patch is placed. Above the second substrate and below the third substrate an air gap is used to enhance the bandwidth of the antenna. While on top of the third substrate there is another patch that is electromagnetically coupled with the first patch on the second substrate. The feed is connected to the lower patch by shorting the patch with the outputs of the T-network using shorted via holes through the substrates and the ground plane in between. The T-network power divider is incorporated below the patch area thereby saving the additional space as is required in conventional structures. The antenna is simulated using IE3D simulation software. It yields a high axial ratio bandwidth (AR<3dB) of 17.3% and an impedance bandwidth of 22.4% at a center frequency of 2.4 GHz. In the broadside direction, the antenna yields a gain greater than 8 dBi over the entire usable bandwidth of the antenna.