Yagi antenna with improved out-of-band gain suppression

Presented is a Yagi antenna with improved out-of-band gain suppression to reduced the demands on the front end band filter. Two parasitics close to the fed element are used to increase the Q-factor of that element, and the length and position of the other directors and reflectors are optimised to suppress the out-of-band gain. Simulated and measured results show that the proposed antenna has the characteristics of a conventional Yagi antenna in the passband, albeit with a narrower bandwidth, whilst providing more than 10 dB of gain suppression to interference signals located outside the band.