A Band-Reconfigurable Antenna Based on Directed Dipole

A novel reconfigurable directed dipole antenna operated in a wideband or four narrowband modes is presented. The wideband mode (0.83-2.5 GHz) is based on a folded bowtie-shaped dipole while the four narrowband modes are based on a length-reconfigurable thin dipole. A rectangular cavity is introduced to provide the antenna with well-controlled unidirectional radiation patterns. PIN diodes are used as switches at specific locations for choosing different modes. The design procedure is presented in details which maybe a useful guideline. A fully functional prototype is developed and tested, which exhibits good performance. The unidirectional patterns and frequency selective feature make the antenna potentially suitable for fixed facilities in cognitive radio.