High-pass filter and multiplexer

A high-pass filter comprising:

• at least one capacitor located in a first pathway between an input terminal and an output terminal, the at least one capacitor being connected between the input terminal and the output terminal;
• at least one inductor, a first end of the at least one inductor being coupled to the first pathway, a second end of the at least one inductor being coupled to a ground;
• at least one first acoustic wave resonator located in a second pathway connected in parallel to the first pathway between the input terminal and the output terminal, the at least one first acoustic wave resonator being connected in parallel to the at least one capacitor;
• and
• at least one second acoustic wave resonator, a first end of the at least one second acoustic wave resonator being coupled to the second pathway, a second end of the at least one second acoustic wave resonator being coupled to a ground,
• wherein
• a resonant frequency of the at least one second acoustic wave resonator is lower than a passband of the high-pass filter,
• an antiresonant frequency of the at least one second acoustic wave resonator and a resonant frequency of the at least one first acoustic wave resonator are located within the passband, and
• the resonant frequency of the at least one second acoustic wave resonator is higher than the highest frequency among frequencies of one or more attenuation poles formed by the at least one capacitor, the at least one inductor, and the at least one first acoustic wave resonator.

A high-pass filter comprising:

• at least one capacitor located in a first pathway between an input terminal and an output terminal, the at least one capacitor being connected between the input terminal and the output terminal;
• at least one inductor, a first end of the at least one inductor being coupled to the first pathway, a second end of the at least one inductor being coupled to a ground;
• at least one first acoustic wave resonator located in a second pathway connected in parallel to the first pathway between the input terminal and the output terminal, the at least one first acoustic wave resonator being connected in parallel to the at least one capacitor;
• and
• at least one second acoustic wave resonator, a first end of the at least one second acoustic wave resonator being coupled to the second pathway, a second end of the at least one second acoustic wave resonator being coupled to a ground,
• wherein
• a resonant frequency of the at least one second acoustic wave resonator is lower than a passband of the high-pass filter,
• an antiresonant frequency of the at least one first acoustic wave resonator is located within the passband, and
• an antiresonant frequency of the at least one second acoustic wave resonator and a resonant frequency of the at least one first acoustic wave resonator are located within the passband.