Amplifier system for a transmitter wherein a leakage signal from a local oscillator is minimised

An amplifier system for a transmitter comprise one or more signals (1) to input to a main signal path; a first upconverter stage comprising a first mixer (2) and a first local oscillator (3); a bandpass filter (4); a second upconvertor stage comprising a second mixer (5) and a second local oscillator (6); an amplifier (13) and error correction means. Wherein the error correction means comprises sampling means to sample the first local oscillator (LO) signal separate from the signal input and a third mixer (8) to upconvert the sampled LO signal by mixing with a signal from the second local oscillator(6). Whereby the upconverted sampled LO signal is used to minimise a leakage signal from the first local oscillator (3) in the transmitter. The leakage signal may be cancelled by either a feed forward or a feedback circuit arrangment.