Reconfigurable filters in a multiplexer

A filter for radio frequency (RF) signals, comprising:

• first resonators coupled in series between an input and an output;
• a second resonator coupled as a shunt between a node in the series and a reference voltage;
• and
• a first circuit coupled between the second resonator and the reference voltage, the first circuit including a first impedance in parallel with a series combination of a second impedance and a switch.

An apparatus, comprising:

• an antenna;
• a receiver path and a transmitter path coupled to the antenna;
• a filter disposed in the receiver path or the transmitter path, the filter comprising:
• first resonators coupled in series between an input and an output;
• a second resonator coupled as a shunt between a node in the series and a reference voltage;
• and
• at least one of:
• (1) a first circuit coupled in parallel with one of the first resonators, the first circuit including a first switch coupled in series with first impedance;
• and (2) a second circuit coupled between the second resonator and the reference voltage, the second circuit including a second impedance in parallel with a series combination of a third impedance and a second switch.