Patent attributes
A directional coupler includes a first to a fourth port, a main line connecting the first port and the second port, a first and a second subline section configured to be electromagnetically coupled to the main line, and a phase shifter. The first subline section, the phase shifter, and the second subline section are arranged in this order in series between the third port and the fourth port. The phase shifter outputs a signal that is phase-delayed relative to an input signal. The phase delay amount of the output signal of the phase shifter relative to the input signal increases with increasing frequency of the input signal. A frequency twice as high as the frequency of the input signal at which the phase delay amount is 90 degrees is lower than the frequency of the input signal at which the phase delay amount is 180 degrees.
