Millimeter-wave T-junction with Controllable Multiple Reflection Nulls and Its Application

A millimeter-wave air-filled waveguide T-junction with multiple reflection nulls is proposed in this paper. The numbers of the reflection nulls and their frequencies can be controlled by adjusting the positions of the additional irises and stepped waveguides. By utilizing the multiple reflection nulls of the T-junctions to weaken the strong reflection caused by the in-phase superposition of small reflections in the feed network, a large-scale antenna array with wide bandwidth performance can be achieved. Satisfying performance of the antenna array, including a bandwidth of 48.4% for VSWR < 2, a gain up to 34.5 dBi and stable radiation patterns, demonstrates the effectiveness of using controllable reflection nulls to enhance the bandwidth of the array. Benefitted from good performance, the arrays using T-junctions with multiple reflection nulls would be a good candidate for future millimeter-wave wideband communication systems.