Design of Multi-Band, Compact Parasitic Array With Twisted, Helical Directors

A new design for compact parasitic array is suggested in order to achieve multiple bands. The driver is folded for close spacing between the driver and the directors, and the directors are twisted in helical shapes with different radii and heights. The three proposed compact parasitic arrays have two, three, and four helical directors, and the number of directors results in the same number of resonances. At all generated resonances, the maximum measured realized gains in the direction of the directors are greater than 8.6 dBi, and the front-to-back ratios are greater than 9 dB. Both results are similar to those in a conventional two-element Yagi antenna, whilst the proposed design offers multiband operation and smaller overall volume.