Compact hybrid couplers having strong broadband coupling for base station antenna systems

A four-port radio-frequency (RF) hybrid coupler, comprising:

• a substrate;
• first through fourth power dividers having respective first through fourth input ports, which correspond to first through fourth ports of the coupler, and first through fourth pairs of output ports, on the substrate;
• a first primary trace electrically connecting a first output port of the first power divider to a first output port of the second power divider, on the substrate;
• a second primary trace electrically connecting a first output port of the fourth power divider to a first output port of the third power divider, on the substrate;
• a first coupled trace electrically connecting a second output port of the first power divider to a second output port of the third power divider;
• and
• a second coupled trace electrically connecting a second output port of the fourth power divider to a second output port of the second power divider.

A coupled-line coupler, comprising:

• a substrate;
• first and second side-by-side primary traces, which are spaced apart from each other along their length by an air-gap, on a top surface of the substrate;
• a ground plane on a bottom surface of the substrate, said ground plane having a slot therein extending opposite the first and second side-by-side primary traces;
• and
• a linear coupling trace on the bottom surface of the substrate, said linear coupling trace extending within the slot and opposite at least a portion of the air-gap between the first and second side-by-side primary traces.

A coupled-line coupler, comprising:

• a substrate;
• first and second side-by-side primary traces, which are spaced apart from each other along their length by an air-gap, on a top surface of the substrate;
• a ground plane on a bottom surface of the substrate, said ground plane having a slot therein extending opposite the first and second side-by-side primary traces;
• and
• a pair of linear traces extending side-by-side within the slot on the bottom surface of the substrate, said pair of linear traces including a first linear trace extending opposite the first primary trace and a second linear trace extending opposite the second primary trace.