Robust Nonlinear Multichannel Amplifier Characterisation

A novel approach to the prediction of third order intermodulation distortion (IM3) in multichannel amplifiers is presented. The amplifier is viewed as a black-box nonlinear circuit and is characterised by carrying out an intermodulation distortion (IMD) test using 3 tones of equal amplitude. Then, by using linear interpolation and the Volterra-series approach, an IM3 prediction can be made for an arbitrary number of input tones of different amplitudes. To demonstrate and verify the capability of this technique predicted and measured results are compared for single and cascaded amplifier stages. This technique will be extremely useful from a system design viewpoint.