A novel wideband and circularly polarized cross-dipole antenna

Abstract

In this paper, we present a novel wideband circularly polarized (CP) composite, called cavity-backed crossed dipole antenna for 2.45 GHz industrial, scientific, and medical (ISM) band wireless communication. To excite the CP radiation effectively, a curved-delay line providing an orthogonal phase difference among the cross-dipole elements is attached at corners of the sequentially rotated elements. By choosing a proper radius of the curved-delay line, a wide input impedance of the antenna can be realized. Unlike conventional cross-dipole antennas, the proposed cross-dipole antenna is designed with an open stub added to the radiating arms of the dipole so that both impedance and axial ratio bandwidths are enhanced. The antenna is center-fed by a 50-Ω coaxial cable and is placed above a cavity-backed reflector to obtain a directional CP radiation pattern. With the advantage of being center-fed, a symmetric CP radiation pattern can be achieved across the entire operating bandwidth. To further improve the directivity and the radiation pattern, a rectangular cavity-backed reflector is used. Simulated and measured results confirm that the proposed antenna has good CP characteristics. The proposed antenna obtains a broad 3-dB axial ratio bandwidth of 49% (1.20 GHz, 1.96-3.16 GHz) and an impedance bandwidth of 67.7% (1.66 GHz, 1.69-3.35 GHz) for reflection coefficient (S 11 ) ≦ À10 dB. It also yields an average CP gain of 9.2 dBic across the operating bandwidth and a peak CP gain of 10 dBic.

A Broadband Circularly Polarized Antenna Based on Cross-Dipoles

“…The initial design in Figure 2(a) used four small square radiating patches instead of wide open-ends, which could make the area of the surface of the substrate effectively utilized. Compared with the antenna proposed in [13], the AR bandwidth in this design is better. Then, the structure of radiating patches has been improved with the P 1 increment and the size of dipoles reduction, which is shown in Figure 2 Polarization for an antenna can be represented by surface current.…”

“…In [8][9][10][11][12], CP characteristics are produced by crossing two dipoles through a 90 • phase delay line of a vacant-quarter printed ring. Although the appropriate 3-dB AR bandwidth of the antenna in [13] is achieved, its impedance bandwidth is narrow and the gain of the antenna is not satisfactory.…”

Wideband Single-Feed Circularly Polarized Antenna

“…Recently, patch antennas have attracted increasing attention as an approach for realizing the circular polarization [1][2][3][4][5][6][7]. By using four sequential-rotation proximity-coupled L-probes, the antenna in [1] delivers a measured 3-dB axial ratio bandwidth of 82% from 1 to 2.4 GHz.…”

“…This antenna features a much wider axial ratio bandwidth of 19.4%. In [6], a novel cross-dipole and curved-delay feeding line are proposed. The antenna has a 3-dB axial ratio bandwidth of 27%.…”

“…Experimentally, the proposed antenna delivers an impedance bandwidth of 82.4% and a 3-dB axial ratio bandwidth of 56.2%. Compared with the single-feed patch antennas in [3][4][5][6][7], this antenna has a much wider axial ratio bandwidth of 56.2%. Figure 1 shows the structure and photograph of the proposed antenna.…”