A circuit for interfacing a balanced radio frequency power amplifier with an unbalanced load

A circuit interfacing balanced RF Power Amplifier (1) with unbalanced load (15) has first shunt inductor (5) and series capacitor (6) connected to first output (2) and first shunt capacitor (17) and series inductor (7) connected to second output (3) of amplifier, and comprises second shunt inductor (9) connected to second output and feeding current to this output. First shunt capacitor may correspond to sum of capacitors required to resonate with series inductor and second shunt inductor. Second shunt inductor may exceed value to resonate with capacitance of first shunt capacitor less capacitor required to resonate with series inductor, by same amount as first shunt inductor exceeds value to resonate with series capacitor. Circuit may further comprise second shunt capacitor (27) connected to first output, whereby first shunt capacitor exceeds sum of capacitors required to resonate with series inductor and second shunt inductor.