Abstract
A novel broadband circularly polarized (CP) antenna with wide axial ratio (AR) beamwidth is proposed. It is composed of two curved arms shaped like an inverted “S.” The mechanisms of wideband CP operation and wide AR beamwidth are explained. To validate the concept, a prototype at C-band is manufactured and measured. Experimental results confirm that the antenna achieves an impedance bandwidth of 63% and a CP bandwidth of 42%. Furthermore, maximum AR beamwidth of 140° is achieved and wide AR beamwidth can be maintained in a frequency bandwidth of 35% in nearly all elevation planes. In addition, the antenna has the advantage of being easily extended to arrays. A four-element array using the proposed antenna is investigated through both simulations and experiments, and achieves 60% CP bandwidth and wide AR beamwidth. The proposed inverted-S antenna can realize wide CP bandwidth and wide AR beamwidth, and can easily form wideband CP arrays.
Highlights
CIRCULARLY POLARIZED (CP) antennas are widely deployed in various wireless systems due to their advantages of the mitigation of multipath fading, the reduction of ‘Faraday rotation’ and the immunity of polarization mismatching between transmitting and receiving antennas [1]
Compared with other reported wideband wide axial ratio (AR) beamwidth CP antennas, another advantage of the proposed antenna is that it can be extended to an antenna array
The small element space was chosen in this design helps enhance the bandwidth of the antenna array, which is observed in sub-wavelength array [24] and can be explained by the cancelling of the imaginary part of mutual impedances [25]
Summary
CIRCULARLY POLARIZED (CP) antennas are widely deployed in various wireless systems due to their advantages of the mitigation of multipath fading, the reduction of ‘Faraday rotation’ and the immunity of polarization mismatching between transmitting and receiving antennas [1]. Besides improving the AR bandwidth, widening the AR beamwidth of CP antennas was received increasing interest due to their applications in global navigation satellite systems (GNSS) [7] and wide-angle CP beam-scanning array [8] Several researches on this topic were reported including a square-ring slotted patch antenna [9], an asymmetric microstrip antenna with integrated circular-patches [10] and an elliptical vertical patch antenna backed by an elliptical air cavity [11]. The antenna presented in [17, 18] can achieve wideband CP radiation with wide angular CP coverage in the two main planes, it is not clear whether wide AR beamwidths can be maintained in other.
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