Design of lead networks for A-C servos with carrier-frequency drift

In a-c servomechanisms tandem compensation is effected by the use of a-c notch-type networks, which operate on the modulating envelope by virtue of being resonant at, and sufficiently symmetrical around, the carrier frequency. However, if carrier frequency drifts away from the notch, the two sidebands of suppressed-carrier-modulated signal around it are no longer symmetrical. The adverse effects of such drifts have been analyzed by a number of authors. This problem is of great importance in air-borne installations where closely regulated carrier-frequency supply would increase the weight, cost, space, and complexity of the equipment. It would be most economical to design a network which would provide satisfactory compensation for a predetermined carrier drift.