| 摘要 |
Achieve favorable directivity in directional coupler even with low magnetic-field coupling coefficient. A directional coupler (1) includes a main line (2), a secondary line (3), and impedance conversion sections (4, 5). The main line (2) is connected between a signal input port (RFin) and a signal output port (RFout). The secondary line (3) is coupled to the main line (2) through coupling capacitance and mutual inductance. The impedance conversion sections (4, 5) are connected between the secondary line (3) and a coupling port (CPL) or an isolation port (ISO), and the impedance viewed from the secondary line (3) differs from the impedance viewed from a port side while both impedances viewed from the secondary line (3) are equal. |
