Characteristics of a small planar loop antenna

Small planar-type loop antennas used in pagers have fixed directivity patterns. As a result, the received signal strength depends on the orientation of the antenna. A new type of small planar loop antenna (PLA) is, therefore, proposed. The position of the conductor posts can be changed and MOSFETs are adopted for switching the conductor posts. If the positions of the posts can be switched at will, then the dependence of the received signal on the orientation of the antenna can be minimized. Fundamental experiments were performed in order to investigate the characteristics of polarization switching. Polarization directivity was measured while switching each conductor alternately. The receiving characteristics are affected by a cable connected to the receiver. Therefore, the transmission characteristics are measured by using an internal oscillator. As a result, meaningful results were obtained and the possibility of polarization diversity was shown.