Patent ID: 9553349
Date: 2017-01-24
CPC Classifications: H01P,H03H

Claim:
1. A directional coupler comprising: a main line connected between a signal input port and a signal output port; a secondary line coupled to the main line through coupling capacitance and mutual inductance and connected between a coupling port and an isolation port; a first impedance conversion section provided between the coupling port and the secondary line and configured to perform impedance conversion; and a second impedance conversion section provided between the isolation port and the secondary line and configured to perform impedance conversion, wherein in the first impedance conversion section, an impedance viewed from a secondary line side differs from an impedance viewed from a coupling port side, in the second impedance conversion section, impedance viewed from the secondary line differs from impedance viewed from the isolation port side, in the first impedance conversion section, a ratio of impedance viewed from the secondary line side to impedance viewed from the coupling port side is substantially equal to a ratio of a magnetic-field coupling coefficient to an electric-field coupling coefficient, and in the second impedance conversion section, a ratio of impedance viewed from the secondary line side to impedance viewed from the isolation port side is substantially equal to the ratio of the magnetic-field coupling coefficient to the electric-field coupling coefficient.