Abstract: A high-frequency front end circuit includes a duplexer, a phase adjustment circuit, and a power amplifier. The phase adjustment circuit is connected between the power amplifier and a transmission filter of the duplexer. The phase adjustment circuit carries out phase adjustment so that a quadrant in which an impedance ZRX (fr0) seen from the transmission filter toward the power amplifier at the fundamental frequency of a reception signal is present and a quadrant in which an impedance ZTX (fr0) seen from the power amplifier toward the transmission filter at the fundamental frequency of the reception signal is present are not in a conjugate relationship with respect to the phase.

Abstract: A built-in-circuit substrate includes a substrate body, an electrical circuit including inner electrodes provided inside the substrate body and to which an RF signal is input, outer electrodes which are provided on the substrate body so as to be connected to the electrical circuit and which each include an underlying metal layer and a nickel layer covering at least a portion of the underlying metal layer, and a permanent magnet which is arranged on the substrate body. Thus, noise caused by intermodulation distortion generated in the nickel layers of the outer electrodes is prevented.

Abstract: A built-in-circuit substrate includes a substrate body, an electrical circuit including inner electrodes provided inside the substrate body and to which an RF signal is input, outer electrodes which are provided on the substrate body so as to be connected to the electrical circuit and which each include an underlying metal layer and a nickel layer covering at least a portion of the underlying metal layer, and a permanent magnet which is arranged on the substrate body. Thus, noise caused by intermodulation distortion generated in the nickel layers of the outer electrodes is prevented.