Frequency-Scanning Multipolarization Antennas

This article proposes a new multipolarization antenna, and its multiple states of polarization are realized by scanning the operating frequency. The proposed antenna is based on a fixed configuration and fed by a single port. This is extremely simple and attractive in many applications, such as frequency-agile radar systems and multipolarization target identification systems, especially for those operating at higher microwave and millimeter-wave frequencies. The multipolarization antenna is realized by combining a bidirectional planar antenna with a carefully designed polarization rotating reflector. The reflector reflects and rotates the wave radiated from the bidirectional antenna. Then, two orthogonal waves of the same magnitude, including the reflected wave and the wave radiated directly from the bidirectional antenna, are obtained. Furthermore, the designed reflector helps to tune the phase difference between two orthogonal waves ranging from 90 degrees to -180 degrees with a monotonic continuous variation. The conceptual design of the proposed antenna is analyzed in detail, and a prototype is designed, fabricated, and experimentally tested to validate the design procedure.