Negative capacitance tuning in an acoustic filter circuit

An acoustic filter circuit comprising:

• an acoustic resonator coupled between an input node and an output node and configured to:
• resonate in a series resonance frequency to pass a signal from the input node to the output node;
• and
• block the signal between the input node and the output node in an operating frequency range comprising a plurality of operating frequencies nonoverlapping with the series resonance frequency;
• and
• a tunable negative capacitance circuit coupled in parallel to the acoustic resonator and configured to present a plurality of negative capacitances each tuned to cancel an electrical capacitance inherently caused by the acoustic resonator at a respective one of the plurality of operating frequencies.

A wireless device comprising an acoustic filter circuit, the acoustic filter circuit comprises:

• an acoustic resonator coupled between an input node and an output node and configured to:
• resonate in a series resonance frequency to pass a signal from the input node to the output node;
• and
• block the signal between the input node and the output node in an operating frequency range comprising a plurality of operating frequencies nonoverlapping with the series resonance frequency;
• and
• a tunable negative capacitance circuit coupled in parallel to the acoustic resonator and configured to present a plurality of negative capacitances each tuned to cancel an electrical capacitance inherently caused by the acoustic resonator at a respective one of the plurality of operating frequencies.