A novel feeding structure for second higher order mode excitation of microstrip leaky-wave antenna

This paper proposes a novel feeding structure for exciting the second higher order leaky mode of microstrip antenna. By properly designing the three excitation points at the input port, the second higher order leaky mode can be purely excited. The fundamental and first higher order leaky mode cannot be excited due to the unequal power amplitude and phase at different excitation points. The prototyped antenna achieves the beam scanning range 30° when the frequency is swept between 12.5 GHz and 13.7 GHz. The simulated peak gain is 13.2 dB and the gain flatness is 2.3-dB variation with the 9% return loss bandwidth. The measured 10-dB return loss is obtained over the leaky band with 13.1 dB peak gain.