Methods of reducing spectral leakage due to I-Q imbalance within a transmitter are disclosed. The method includes the transmitter receiving a data stream of coefficients of a multi-carrier modulation signal. The data stream is pre-processed by processing a set of the coefficients that correspond with selected notch frequencies to reduce the effects of I-Q imbalance of the transmitter, wherein at least a portion of the set of coefficients corresponds to non-symmetrical notch frequencies. The pre-processed data stream is multi-carrier modulated. The multi-carrier modulated pre-processed data stream is I-Q modulated before transmission.