Frequency adjustable microstrip annular ring patch antenna with multi-band characteristics

This study introduces a frequency-tunable dual-band microstrip annular ring patch antenna design for wireless local area network (2.45 GHz) and Worldwide Interoperability for Microwave Access (3.5 GHz) applications. The proposed antenna produces realisable gain higher than 5 dBi and return loss better than 10 dB for the stated applications. The antenna design consists of an annular ring patch loaded with a slot or gap. This loaded ring excites higher-order modes around the dominant mode (TM11) of the annular ring thus making this design capable of dual-band operation. This design is realised on a 1.57 mm thick polytetrafluoroethylene substrate using a coaxial probe feed. In this study, a novel technique for independent frequency tuning has also been introduced by cutting grooves on the periphery of the ring at the desired locations. Furthermore, the design capability of multi-band operation (2.45 GHz/3.5 GHz/5.5 GHz) has also been explained in the later part of the study. Antenna operation has been verified with the help of two commercially available EM solvers (CST Microwave Studio and Ansoft HFSS Designer) and measurements. A close agreement has been found between the simulated and the measured results.