Bias effects in nonlinear adaptive servomechanisms

In many adaptive servomechanisms, a gain is varied as a function of some noisy measured quantitity. If the measured quantity (or another quantity depending on it) is an input to the variable gain, then the noise in the gain will be correlated with the noise in its input producing rectification and an undesired (dc) component in the output. This effect is analyzed and analytic bounds for the magnitude of the bias are computed for some typical cases. An example is also worked out in detail.