Integration of three-dimensional high-Q filters with aperture antennas and bandwidth enhancement utilising surface waves

Seamless integration of three-dimensional cavity filters with a new antenna is presented. The antenna consists of an open-ended waveguide aperture mounted on a ground plane. The energy coupling between the last cavity resonator and free space, which is related to the external quality (Q) factor of the integrated filter/antenna system, can be significantly enhanced. The low external Q factor (Q_ext), which is necessary for the design of wide-band filter/antenna systems, is due to the excitation and radiation of surface waves. A three-pole cavity filter integrated with the proposed antenna is demonstrated at X band. The centre frequency and fractional bandwidth of the filter/antenna system are 10.2 GHz and 34.0%, respectively, in simulations. A prototype filter/antenna system is fabricated and measured. Good agreement between the simulated and measured results is observed.