On the use of lumped filters for designing dual-band planar antennas with omnidirectional and directional radiation patterns

Modern 802.11 ac wireless systems are capable of dual-band operations in the 2.4 and 5 GHz bands to enhance bandwidth and data throughput. These systems typically employ separated radiators for the two bands, increasing cost and space requirements. In this paper, we describe two approaches that can be used to design a single planar antenna which can resonate at 2.4 and 5 GHz, as well as generate omnidirectional and directional radiation patterns. In the first approach, we used a single set of dual-band elements, where the two bands are separated through lumped inductors and capacitors. In the second approach, we designed two independent sets of elements for each band, connected to the central RF port by lumped diplexers. We discuss the designs and the measured results for these two approaches, highlighting the advantages and limitations of the respective radiation characteristics.