Multichannel Cross Modulation in CATV Amplifier

The Volterra series approach is used to derive a simplified expression relating the single channel and multichannel cross modulation in a CATV amplifier. The cross modulation from n unwanted carriers synchronously modulated is seen to be dependent upon the phase versus frequency variation of the third-order Volterra transfer function of an amplifier. Only when the phase is constant for any frequency of interest is the increase in the magnitude of the cross-modulation vector given by 20 log n, n being the number of synchronously modulated carriers.