This invention discloses a
hybrid transmission line 3dB coupler and its design method, comprising a first conductor layer, a first
dielectric layer, a second conductor layer, a second
dielectric layer, and a third conductor layer stacked sequentially. A first
coupling line is disposed within the first conductor layer, a second
coupling line is disposed within the second conductor layer, and a reference
ground plane is disposed within the third conductor layer. The first and second
coupling lines share the reference
ground plane as their reference ground. Perpendicular to the stacking direction, the projections of the first and second coupling lines overlap, and the
orthographic projection of the second coupling line completely falls within the
orthographic projection of the first coupling line. This invention employs a shared reference ground and a full projection coverage structure, ensuring that the area of the coupling lines facing each other is largely unaffected by PCB layer alignment errors, improving the consistency of
mass production performance, while simplifying the stacking structure and reducing costs.