This document describes techniques, apparatuses, and systems utilizing a high-isolation transition design for differential signal ports. A differential input transition structure includes a first layer and a second layer made of a conductive metal and a substrate positioned between the first and second layers. The second layer includes a first section that electrically connects to a single-ended signal contact point and to a first contact point of a differential signal port. The first section includes a first stub based on an input impedance of the single-ended signal contact point and a second stub based on a differential input impedance associated with the differential signal port. The second layer includes a second section that electrically connects to a second contact point of the differential signal port and to the first layer through a via housed in a pad. The second section includes a third stub associated with the differential input impedance.

This document describes techniques, apparatuses, and systems utilizing a high-isolation transition design for differential signal ports. A differential input transition structure includes a first layer and a second layer made of a conductive metal and a substrate positioned between the first and second layers. The second layer includes a first section that electrically connects to a single-ended signal contact point and to a first contact point of a differential signal port. The first section includes a first stub based on an input impedance of the single-ended signal contact point and a second stub based on a differential input impedance associated with the differential signal port. The second layer includes a second section that electrically connects to a second contact point of the differential signal port and to the first layer through a via housed in a pad. The second section includes a third stub associated with the differential input impedance.

An antenna includes a radiator and a balun structure. The radiator includes a first branch for a first current to flow through and a second branch for a second current to flow through. The first branch and the second branch are arranged on two opposite sides of the balun structure. A direction of the first current is at least partially opposite to that of the second current. The first branch is spaced from the balun structure by a first slot. The second branch is spaced from the balun structure by a second slot. The first slot is configured to form a first horizontally-radiated electric field by the first current and a current on the balun structure. The second slot is configured to form a second horizontally-radiated electric field by the second current and the current on the balun structure.

An antenna includes a radiator and a balun structure. The radiator includes a first branch for a first current to flow through and a second branch for a second current to flow through. The first branch and the second branch are arranged on two opposite sides of the balun structure. A direction of the first current is at least partially opposite to that of the second current. The first branch is spaced from the balun structure by a first slot. The second branch is spaced from the balun structure by a second slot. The first slot is configured to form a first horizontally-radiated electric field by the first current and a current on the balun structure. The second slot is configured to form a second horizontally-radiated electric field by the second current and the current on the balun structure.

A balun includes an unbalanced terminal; first and second balanced terminals; first and second main lines; first and second sub-lines; and a parallel line. The first main line has an end connected to the unbalanced terminal. The second main line has an end connected to another end of the first and second end that is open. The first sub-line is connected between the first and a reference potential, and is coupled to the first main line. The second sub-line is connected between the second balanced terminal and the reference potential, and is coupled to the second main line. The parallel line is connected in parallel with a part of the first sub-line. The line length of a specific portion of the first sub-line that is connected in parallel with the parallel line is different from the line length of the parallel line.

A balun includes an unbalanced terminal; first and second balanced terminals; first and second main lines; first and second sub-lines; and a parallel line. The first main line has an end connected to the unbalanced terminal. The second main line has an end connected to another end of the first and second end that is open. The first sub-line is connected between the first and a reference potential, and is coupled to the first main line. The second sub-line is connected between the second balanced terminal and the reference potential, and is coupled to the second main line. The parallel line is connected in parallel with a part of the first sub-line. The line length of a specific portion of the first sub-line that is connected in parallel with the parallel line is different from the line length of the parallel line.

A folded Marchand Balun includes a first, a second, a third port, and a first transmission line being folded into a first and second intermediate transmission lines, the first intermediate transmission line disposed on a first signal plane and electrically connected through metal vias to the second intermediate transmission line disposed on a second signal plane. The first transmission line has one end as the first port and an opposite end as an open circuit. The Balun includes a second transmission line disposed on the first signal plane and is adjacent to the first intermediate transmission line. The second transmission line has one end as the second port and an opposite end grounded. The Balun includes a third transmission line disposed on the second signal plane and adjacent to the second intermediate transmission line. The third transmission line has one end as the third port and an opposite end grounded.

A folded Marchand Balun includes a first, a second, a third port, and a first transmission line being folded into a first and second intermediate transmission lines, the first intermediate transmission line disposed on a first signal plane and electrically connected through metal vias to the second intermediate transmission line disposed on a second signal plane. The first transmission line has one end as the first port and an opposite end as an open circuit. The Balun includes a second transmission line disposed on the first signal plane and is adjacent to the first intermediate transmission line. The second transmission line has one end as the second port and an opposite end grounded. The Balun includes a third transmission line disposed on the second signal plane and adjacent to the second intermediate transmission line. The third transmission line has one end as the third port and an opposite end grounded.

A balun includes: first wiring that has a first end connected to a first balanced line and a second end connected to a second balanced line; second wiring that has a grounded first end and a second end; third wiring that has a first end connected to the second end of the second wiring and a second end connected to an unbalanced line and is electromagnetically coupled to the second wiring; a first capacitor that has a first end connected to the first end of the third wiring and a grounded second end; and a second capacitor that has a first end connected to the second end of the third wiring and a grounded second end. The first wiring is electromagnetically coupled to at least one of the second wiring and the third wiring.

A balun includes: first wiring that has a first end connected to a first balanced line and a second end connected to a second balanced line; second wiring that has a grounded first end and a second end; third wiring that has a first end connected to the second end of the second wiring and a second end connected to an unbalanced line and is electromagnetically coupled to the second wiring; a first capacitor that has a first end connected to the first end of the third wiring and a grounded second end; and a second capacitor that has a first end connected to the second end of the third wiring and a grounded second end. The first wiring is electromagnetically coupled to at least one of the second wiring and the third wiring.