Modified planar Luneburg lens millimetre-wave antenna for wide-angle beam scan having feed locations on a straight line

摘要

This study presents the design and characterisation of a modified planar Luneburg lens antenna operating at 30 GHz. A parallel plate lens structure with varying separation between the metal plates realises the required variation of phase velocity of the guided TE mode in the device. The focal points for different beam radiation directions are all placed on a straight line, thus simplifying the mechanical setup for steered beam and multi-beam systems. A planar slotline radiator excites the TE mode in the parallel plate structure. An optimisation process leads to best compromise between large directivity, large maximum scan angle and small side-lobes. As a result, measurements show that by moving the feed radiator on a straight line over ±40 mm, the beam maximum can be steered over more than ±35° with a gain drop of <;3 dB. While scanning the beam from broadside direction towards ±35° scan angle, the worst-case side-lobe level deteriorates from 15 dB to about 10.5 dB. The proposed antenna shows peak directivity of 15.2 dBi and a large simulated power efficiency of 95%.