Design of small printed multiband loop antennas for short range wireless (SRW) applications

Worldwide application of wireless IoT and telemetry solutions are more cost effective if they are inherently able to operate in multiple frequency bands as these units require lower logistics and manufacturing cost. Moreover, interferences in the highly crowded available frequency bands enhances the advantages of multiband operation wireless system. However, one major bottleneck is the difficulty of the multiband antenna design. In this paper, investigation, design and measured results of multiband, high impedance, small, printed loop antennas are presented. The built antennas are inherently tuned with only two or more discrete capacitors to properly terminate the applied high impedance, highly efficient switched current power amplifier (PA) in two or more UHF bands. The presented design method is applicable for higher frequency bands as well.