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A triband omnidirectional circularly polarized dielectric resonator antenna with a top-loaded modified Alford loop for GSM, WLAN, and WiMAX applications is proposed. Fed by an axial probe, the DRA (dielectric resonator antenna) radiates like a vertically polarized electric monopole. The top-loaded modified Alford loop provides an equivalent horizontally polarized magnetic dipole mode at triband. Omnidirectional CP (circular polarized) fields can be obtained when the two orthogonally polarized fields are equal in amplitude with phase quadrature. The antenna has been successfully simulated, fabricated, and measured. The experimental and numerical results exhibit that the antenna can obtain usable CP bandwidths of 1.925–1.955 GHz, 2.36–2.48 GHz, and 3.502–3.53 GHz with return loss larger than 10 dB and axial ratio less than 3 dB. In addition, over the three bands, the antenna obtains very good omnidirectional CP radiation patterns in the azimuth plane. Moreover, an average CP gain in the azimuth plane of 1.2, 1.6, and −1.5 dBic for the lower, middle, and upper bands has been obtained.

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Abstract-A simple dual-port sum-difference beam antenna with high isolation is proposed. A Tshaped slot is utilized to achieve both sum-difference beam pattern and high port-isolation. The slot coupling feeding structure simplifies the feeding network and avoids complicated fabrication. The proposed antenna is simulated, fabricated and measured. Experimental validations confirm that the antenna has 10-dB impedance bandwidths of 10.2% (4.82-5.33 GHz) for the sum port and 2.0% (4.95-5.05 GHz) for the difference port, respectively. In addition, high port-isolation better than 50 dB is achieved covering a wide band from 4.0 GHz to 5.5 GHz. The proposed antenna exhibits a measured peak gain of 6.3 dBi for the sum beam and a null depth better than −26 dB for the difference beam. Measured results agree well with simulated ones.

A wideband and high-gain uniform circular array with calibration element for smart antenna application is presented. This letter focuses on the feasibility of substituting calibration element for calibration network to achieve wide bandwidth and high gain. The proposed array antenna with 15 array elements and a calibration element is designed and fabricated. Good agreement between simulated and measured results is observed. Simulation and measurement results reveal that the proposed array element can provide an impedance bandwidth of 38.3% (3.95-5.82 GHz) and a radiation pattern bandwidth of 12.8% (4.4-5 GHz). The impedance bandwidth of the calibration element is 15.4% (4.39-5.12 GHz). Additionally, within the pattern bandwidth, the radiation pattern of the array element has horizontal deviation angles in E-planes ranging from -5° to 6°, 3-dB beamwidths in E-planes from 25° to 35° and element gains from 7 dBi to 7.85 dBi. Compared with the conventional array, the proposed method can be able to increase the average array gain of 1.2 dB and to decrease the average normalized side lobe level (SLL) of 4.2 dB. In addition, over the operating band, the phase and amplitude matching of the coupling coefficients between the calibration element and 15 array elements are from 3° to 7.2° and 0.6 dB to 1.2 dB, respectively.