A New Approach to Design Circularly Polarized Beam-Steering Antenna Arrays Without Phase Shift Circuits

A new approach to generate beam steering for the circularly polarized (CP) antenna array without phase shift circuits is proposed. The proposed approach is a low cost one compared with those with phase shifters. It is found that in spherical coordinate system (r, θ, and φ), for any constant r and θ, as φ varies from 0 to 2π, the phase of the CP antenna's copolarized far field will progress linearly by 2π, and the magnitude is constant. If a CP antenna is rotated around its own phase center by certain degrees, there is a phase difference between the copolarized electric far fields generated by the antenna before and after rotation. An N × N array with such CP antennas elements is analyzed. The array can generate beam steering with different rotation angles of adjacent elements. The beam-steering mechanism is discussed from the orthogonal electric current elements and array perspective. Then, a 4 × 4 planar spiral array is designed to verify the mechanism. The array has a good beam-steering characteristic within X-band. At the planes of φ = 0°, 45°, and 90°, the mainlobe can be scanned from -25° to +24°, -36° to +35°, and -24° to +25°, respectively.