The stabilization of nonlinear servomechanisms encountered in antenna instrumentation

This paper investigates the problem of compensating the loop-gain of instrument servos to provide uniform transient response over a wide dynamic operating range. Particular consideration is given to applications in the realm of antenna measurements. A distinction is made between situations where the nonlinearity results from characteristics of the follow-up device and where it results from the loop-gain being functionally related to an external variable. In the former case the loop-gain is made self-linearizing; in the latter the gain is effectively equalized with an auxiliary logarithmic servo. This necessarily requires a suitable slave potentiometer in the nonlinear loop, actuated by the logarithmic servo. Certain advantages resulting from the use of ladder attenuator as the slave component are described. It is shown how this combination logarithmic servo and ladder slave attenuator can make a loop-gain invariable which otherwise would be functionally related to a variable E by the equation N. The idea is extended to the generation of polynominal terms of the same form as .