Directional coupler, antenna device, and radar system

摘要

A directional coupler includes two non-radiative dielectric lines, each formed by a dielectric strip between flat conductive surfaces placed substantially parallel to each other, such that the two non-radiative dielectric lines are close to each other. The main transmission mode of electromagnetic waves at the frequency used is an LSE mode, the electromagnetic waves being propagated in the non-radiative dielectric lines. Therefore, the insertion loss due to mode switching in the coupling portion of the primary line and the secondary line which form the directional coupler can be reduced, and leakage of the electromagnetic waves from the gap between the primary line and the secondary line of the directional coupler when they are separated from each other can be suppressed.