Calibration of antenna pattern and phase errors of a cross-loop/monopole antenna array in high-frequency surface wave radars

High-frequency surface wave radar has now been widely used as a regular instrument in remote sensing of sea states. To solve the contradiction of the array pattern beamwidth and array aperture, multiple cross-loop/monopole (CM) antennas are used as sub-arrays to form a uniform linear array, which is called the CM-uniform linear array (ULA). Adaptive beamforming via virtual interferences is used to synthesize the desired pattern and a half beamwidth of about 20° is achieved by a two-unit CM-ULA with a spacing of 0.75λ (λ is the radar wavelength). A novel iterative method is proposed to calibrate the array errors, including the individual antenna pattern distortions and the channel gain/phase errors, without resorting to any known signals such as a beacon or transponder signal. Simulations are executed and the results show the validity of the proposed method.