Measurement and model for correlating phase and baseband 1/f noise in an FET

Phase noise in solid state oscillators arises in part from residual phase noise in the active device that provides gain. The device´s residual phase noise is usually attributed to baseband noise on the bias that upconverts via a mixing process to generate phase noise around the carrier signal. This conclusion is consistent with the observation that baseband and carrier noise sources both have 1/f spectral properties. However, similar spectral properties are not sufficient to prove that the baseband and carrier noise are fully-correlated. Experimental results presented here for a heterojunction FET show less than 40% correlation. To account for these observations a new 1/f noise model is presented. This model is used to accurately predict the phase noise when a bias feedback circuit is added to stabilize the baseband fluctuations