Design of mechanically rotatable microstrip patch antennas using an asymmetric polariser for adaptive polarisation adjustment

This paper proposes the design of a microstrip patch antenna with an asymmetric polariser for adaptive polarisation adjustment. The asymmetric polariser is placed in the outer perimeter of a circular radiating patch and is mechanically rotated from 0 degrees to 360 degrees to adjust the axial ratio (AR) and the tilt angle (TA). To verify the operating principle of the proposed antenna, its radiating properties are theoretically formulated based on the cavity model, and three sample antennas with different shapes of the polariser are fabricated to measure their antenna characteristics. Then, a field test is conducted to observe variations of the received signal strength for incoming signals with time-varying polarisation properties. The results demonstrate that the mechanical rotation of the polariser is suitable to minimise the polarisation mismatch with improvement of the received signal strength from -44.0 to -30.3 dBm in a harsh multipath environment.