Broadband Circularly Polarized Printed Crossed-Dipole Antenna and Its Arrays for Cellular Base Stations

Abstract

This paper presents and investigates broadband circularly polarized (CP) printed crossed dipole antenna and its arrays. The proposed antenna comprises a pair of crossed fan-shaped dipoles, two kinds of parasitic elements, and a reflector with two vertical side walls. A three-quarter circular phase shifter connected to the fan-shaped arms of this antenna allows it to radiate CP waves due to the excitation of the arms and the creation of sequential phases in them. The significant contribution of this work is the creation of electromagnetic coupling between the crossed fan-shaped dipoles and parasitic elements to improve the purity of CP radiation and increase the axial ratio (AR) bandwidth. The proposed antenna has upgraded into 4-element and 8-element array models as cellular base station antennas for PCS/DCS/UMTS systems. The experiments indicate that the proposed CP antenna achieves an impedance bandwidth of 57% (1.47-2.65 GHz) for VSWR < 2, an AR bandwidth of 33% (1.65-2.3 GHz) for AR < 3 dB, and a gain of 7.8-8.7 dB. The implemented arrays of 1×4 and 1×8 arrangement achieve peak gains of 13.2 and 16.1 dB, respectively. The horizontal half-power beam widths (HPBWs), horizontal axial ratio beam widths (ARBWs), and front-toback ratios (FBRs) for antenna arrays are around 64° ± 3°, more than 90°, and higher than 25 dB, respectively.INDEX TERMS Antenna array, axial ratio, base station, circularly polarized, crossed-dipole.

A Wideband Circularly Polarized Dipole Antenna with Compact Size and Low-Pass Filtering Response

“…The filtering CP dipole antenna designs have been rarely proposed. In [5][6][7][8][9][10]17,19,20,22,24], the antennas have wide axial ratio bandwidths but occupied large antenna sizes or heights. In [16,18,21] folded cross dipole arms and shorted circuit radiator patch were used to realize compact CP antenna function.…”

“…In order to broaden the axial ratio bandwidth, the crossed dipole arms can be changed into wide rectangular [4], wide ring [5], bowtie [6], and the divided wide dipole arms [7]. Or, using the folded microstrip lines instead of annular delay line phase shifters [8], or parasitic units [9][10][11] around the dipole arms, the axial ratio bandwidth can be expanded to 25%-90%. However, for these designs, wide axial ratio bandwidth is usually obtained with increasing antenna size or height, or unstable radiation patterns.…”

A Wideband Circularly Polarized Dipole Antenna with Compact Size and Low-Pass Filtering Response

“…The filtering CP dipole antenna designs have been rarely proposed. In [ 5 , 6 , 7 , 8 , 9 , 10 , 17 , 19 , 20 , 22 , 24 ], the antennas have wide axial-ratio bandwidths but occupy large antenna sizes or heights. For example, the antenna’s axial-ratio bandwidth exceeds 90% [ 6 , 9 , 10 ], yet its dimensions are substantially large, nearly double those of the proposed antenna.…”

“…Cross-dipole antennas have been widely studied for their ability to achieve good circular polarization [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. The traditional cross-dipole circular polarization antenna is connected by two annular delay-line phase shifters to the four narrow arms of the cross-dipole and fed through the coaxial line, which can achieve a 3 dB axial-ratio bandwidth of about 7% [ 2 , 3 ].…”

“…In order to broaden the axial-ratio bandwidth, the cross-dipole arms can be changed into wide rectangular [ 4 ], wide ring [ 5 ], bowtie [ 6 ] and the divided wide dipole arms [ 7 ]. Or, using the folded microstrip lines instead of annular delay line phase shifters [ 8 ], or parasitic units [ 9 , 10 , 11 ] around the dipole arms, the axial-ratio bandwidth can be expanded to 25–90%. However, for these designs, the wide axial-ratio bandwidth is usually obtained through increasing antenna size or height, or unstable radiation patterns.…”