Abstract
A broadband circularly polarized (CP) antenna with enhanced gain and low profile is proposed. Two identical dipoles with full wavelength are placed orthogonally to generate radiation waves with equal amplitude and orthogonal polarization. The arms of the dipoles are designed as stepped patches to enlarge the impedance matching bandwidth and axial ratio (AR) bandwidth. Crossed-dipoles with full wavelength are utilized as the main radiators to provide a wide operating bandwidth and enhanced gain, and an artificial magnetic conductor (AMC) structure is introduced as the reflector to reduce the profile of the whole antenna. Due to the introduction of the AMC structure, the antenna profile is reduced from 12.8 to 6.9 mm, that is, reduced to 0.14λ0 (where λ0 denotes the wavelength corresponding to the center frequency of the passband, 4.0–8.5 GHz). A simulation and experiment were carried out to verify the performance of the proposed antenna. Experimental results showed that the antenna realized an impedance bandwidth of 74%, an AR bandwidth of 67.7%, a peak gain of 12.1 dBic, and an average gain of 10.69 dBic.
Highlights
Polarized antennas have been widely used in communication systems because of their advantages of resisting multipath distortion, polarization mismatch losses, and Faraday rotation effects
Several means have been utilized to improve the impedance matching and axial ratio (AR) bandwidths of microstrip circularly polarized (CP) antennas, such as microstrip antennas based on a reactive impedance surface [1], stacked patches [2], antenna arrays with a sequential feeding network [3], and multilayered structures [4]
An artificial magnetic conductor (AMC) structure was further introduced as the reflector
Summary
Polarized antennas have been widely used in communication systems because of their advantages of resisting multipath distortion, polarization mismatch losses, and Faraday rotation effects. A crossed dipole-based CP antenna with a low profile was proposed in [19]; an impedance matching bandwidth of 66.3% and a 3 dB AR bandwidth of 44.7% were achieved, and the profile was reduced to 0.12λ0. A compact dual-polarized full-wavelength dipole antenna was proposed in [23], which has a significantly wider bandwidth of 78% These studies demonstrate that, if the impedance matching issue can be solved, the fullwavelength dipoles potentially exhibit higher directivity and wider bandwidth compared with half-wavelength dipoles. Rather than feeding a single full-wavelength dipole, four full-wavelength dipoles are connected in parallel and matched with a standard coaxial cable in [24] This method solves the impedance matching problem and reduces the antenna elements for the same gain, which assists in the production of a low-cost and high-efficiency antenna array. The proposed antenna provides an example of the design of a broadband CP antenna with enhanced gain and low profile
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