Wideband Circularly Polarized Tightly Coupled Array

Tightly coupled arrays (TCA) have received considerable

interests recently. Although various TCAs have been reported, they are

limited to single or dual linear polarizations. Considering the importance of

circular polarization (CP) in various wireless systems, it is meaningful to

design a CP TCA with a simple configuration. This paper presents a

circularly polarized tightly coupled crossed dipole array (CP-TCCDA) with

wide overlapped impedance bandwidth and axial ratio (AR) bandwidth. A

tightly coupled crossed dipole unit cell is investigated and the comparison

with an isolated crossed dipole of the same size indicates that the VSWR<3

bandwidth is increased from 3:1 to 7.1:1 while the 3-dB AR bandwidth is

increased from 1.3:1 to 2.1:1. Analysisis given to explain the principles of AR

bandwidth improvement and is verified by the comparison of radiated Efields

between a CP-TCCDA and a conventional crossed dipole array. To

verify the design concept, a 4×4 CP-TCCDA with feeding network is

fabricated and measured. The measured results confirm that the proposed

array achieves VSWR<3 bandwidth from 2.06GHz to 6.46 GHz (3.14:1) and

3-dB AR bandwidth from 2.35GHz to 5.6GHz (2.38:1), which are much

wider than the bandwidth of an isolated element and a conventional array

using the same element.