Wideband and High-Gain Uniform Circular Array With Calibration Element for Smart Antenna Application

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 band-width 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 degrees to 6 degrees, 3-dB beamwidths in E-planes from 25 degrees to 35 degrees, and element gains from 7 to 7.9 dBi. Compared to 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 sidelobe 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 degrees to 7.2 degrees and 0.6 to 1.2 dB, respectively.