A Simple Planar Polarization Reconfigurable Monopole Antenna for GNSS/PCS

The design of a simple planar polarization reconfigurable monopole antenna for the Global Navigation Satellite System (GNSS) and Personal Communications System (PCS) is presented. The antenna consists of two meandered monopoles, a feeding network using the Wilkinson power divider, two switchable 90
$^{0}$
-phase shifters implemented using
$\lambda/4$
-microstrip lines and a defected ground structure (DGS). The meandered monopoles resonating at about 1.55 GHz are placed perpendicular to each other. The input signal is divided into two signals with equal amplitude and phase by the power divider and fed to the meandered monopoles via the phase shifters. The two signals arriving at the two monopoles have a phase difference of 90
$^{0}$
,
$-90^{0}$
or 0
$^{0}$
, depending on the phase shifters controlled using six PIN-diode switches, hence generating a right/left-handed circularly polarized (CP) or linearly polarized (LP) signal. We propose a novel biasing technique to control the six PIN diodes using five voltages. Measurement results show that the antenna in CP has an impedance bandwidth
$({\rm S}11 < -10 ~{\rm dB})$
of 1.06-1.64 GHz and an axial-ratio bandwidth
$({\rm axial-ratio}< 3~{\rm dB})$
of 1.43-1.84 GHz, and in LP has an impedance bandwidth of 1.63-1.88 GHz. Simulated and measured results on S11, AR, radiation pattern, and gains show good agreements.