Rigorous analysis of transient radiation mechanism of small Multi Sector Monopole Yagi-Uda array antenna using FDTD method

The Multi Sector Monopole Yagi-Uda Antenna (MS-MPYA) can be used to realize low profile, multi-sector antennas. The MS-MPYA has an interesting feature; we can sharpen the beams by using the adjacent array effect if we set metallic fins between the arrays so as to hide the excitors. otherwise, without the fins, undesired radiation from the adjacent arrays causes beam division. This paper shows the radiation mechanism by using transient solutions in the time domain calculated by the FDTD method to examine how electromagnetic waves interact with the directors, adjacent arrays, and fins in real time. We introduce the transient solutions for three types of MS-MPYA: with adjacent array and with fins, without adjacent array but with fins, and with adjacent arrays but without fins. The transient solutions show that the adjacent array's action is changed by the existence of the fins and caused beam division. Without fins, the adjacent arrays act as directors of the active array and cause beam division. With fins, the adjacent arrays reflect the wave coming from the main array and sharpen the beam.