Duplexer with negative phase shifting circuit

A duplexer, comprising:

• a transmit filter connected in series between an antenna terminal and a transmitter terminal;
• a receive filter connected in series between the antenna terminal and a receiver terminal, the receive filter having a higher passband center frequency than the transmit filter;
• and
• a phase shifter connected in series between the antenna terminal and an input of the receive filter, the phase shifter comprising a capacitor connected in series between the antenna terminal and the input of the receive filter, a first inductor connected between a first end of the capacitor and ground, and a second inductor connected between a second end of the capacitor and ground, wherein the phase shifter provides a negative phase shift of an input impedance of the receive filter.

A duplexer, comprising:

• a transmit filter connected in series between an antenna terminal and a transmitter terminal;
• a receive filter connected in series between the antenna terminal and a receiver terminal, the receive filter having a higher passband center frequency than the transmit filter;
• and
• a phase shifter connected in series between the antenna terminal and an input of the receive filter, the phase shifter comprising first and second capacitors connected in series between the antenna terminal and the input of the receive filter, and one shunt inductor having a first end connected between the first and second series capacitors and a second end connected to a ground voltage, wherein the phase shifter provides a negative phase shift of an input impedance of the receive filter.