Abstract: A coupled resonator filter including a first parallel resonator including a first capacitance connected in parallel with a first inductance. The filter includes a second parallel resonator including a second capacitance connected in parallel with a second inductance and a third parallel resonator including a third capacitance connected in parallel with a third inductance. Magnetic coupling between the first inductance and the second inductance, between the second inductance and the third inductance, and between the first inductance the third inductance occurs in accordance with first, second and third coupling factors, respectively. A frequency response of the coupled resonator filter includes a notch when values of the first coupling factor, the second coupling factor and the third coupling factor satisfy predetermined conditions.

Abstract: The present disclosure relates to a radio frequency power amplifier system (200) comprising a first (114) and a second input port (121). The radio frequency power amplifier system (200) comprises a main amplifier (101) having an input (107) and an output (108) and a first (102) and a second auxiliary amplifier (122) having respective inputs (109, 129) and outputs (110, 128). The radio frequency power amplifier system (200) comprises an internal load (103) connected to the output (110) of the first auxiliary amplifier (102), a feedback network (104) having an input end (111) connected to the output (110) of the first auxiliary amplifier (102) and an output end (112) connected to the input (109) of the first auxiliary amplifier (102). The radio frequency power amplifier system (200) also comprises a feedforward amplifier (123) having an input (124) and an output (130).