A Metamaterial-Based Circularly Polarized Antenna and Its Phased Array Application

In this paper, a millimeter waves (mmW) metamaterial-based circularly polarized antenna and its 1×4 phased array is proposed. Excited by a triple crossed slot, a slotted patch can act as a metamaterial-based radiator. The feeding line beneath the coupling slot were designed as a notched ring. By adjusting the length of three coupling slots and the angle of notch, the proposed antenna can generate circularly polarized radiation. Single antenna element operating at 43GHz shows an impedance bandwidth operating from 39.3 to 47.7 (19.5%) and an axial ratio (ARs) bandwidth from 39.5 to 48.2 (20.2%). Then an 1×4 phase array based on the proposed antenna element is designed, which exhibits a combine bandwidth of 13.75% and the scanning range at 40GHz reaches ±30°, thus making the proposed CP array a promising candidate for mmW applications.

I. Introduction

Recently, due to the abundant spectrum resource, millimeter-wave frequencies have gathered more and more attention, various technologies have applied in this band, such as multi-beam antennas system [1]–[3], Low Earth Orbit (LEO) satellite communication [4]–[6], and synthetic aperture radar (SAR) [7]–[9]. In several application fields, using linearly polarized antenna array may cause unexpected mismatch and loss because of the misalignment between receiving end and transmitting end. Thus, different kinds of circularly polarized (CP) antenna have been studied and fabricated over the past decades. The principle of CP radiation is to generate two orthogonal polarized waves with a 90° phase difference and identical amplitude distribution, based on this rule and changed antenna structure nimbly, researchers from different countries using various methods to generate CP radiation. In [10], a magneto-electric (ME) dipole CP antenna is proposed, by adding a connection strip and cutting the corners of the patches, the CP radiation is realized. Based on 3× 3 metasurface patch, [11] reported an CP array system for LEO satellite communication, unique antenna structure promising a ±60° scanning potentiality. With the characteristics of low profile, an endfire CP array is reported in [12], tapered radiating wedge and electric dipole are exciting orthogonal electric-field components respectively, phase difference controlled by integral structure parameters. Fig. 1.

The configuration of single CP antenna element.

Fig. 2.

Development steps of patch and its corresponding S-parameter and AR. (Wpatch = 3.3mm, Wgap = 0.15mm, Wp =1mm, Wcro = 0.15mm, Lcro = 3mm)

Fig. 3.

Structures of feeding lines and crossed slot. (L_s1 =2.4mm, L_s2 = 2mm, L_s3 =1.6mm, W_s1 = 0.15mm, W_s2 = 0.15mm, W_s3 = 0.15mm, W_ring1 = 0.2mm, θ_ring1 = 70°, R_ring1 = 0.7mm, W_trans = 0.7mm)

Fig. 4.

Simulated radiation patterns of single antenna element at 43GHz (which plane).