High-frequency filter, complex electronic component using the same, and portable radio apparatus using the same

摘要

A high-frequency filter (10) serving as a bandpass filter has three transmission lines (SL11 to SL13) side-coupled in three stages. The transmission lines (SL11 to SL13) are respectively connected in parallel to capacitors (C11 to C13). A first end of the input transmission line (SL11) is connected to an input terminal (Pi) through an input capacitor (C14). A first end of the output transmission line (SL13) is connected to an output terminal (Po) through an output capacitor (C15). Second ends of the transmission lines (SL11 and SL13) are connected and the connection point is connected to the ground through an inductor (Lg) for forming a pole in the transmission characteristic of the high-frequency filter. One end of the third transmission line (SL12) is connected to the ground.