An analog core memory for pulse-width modulated signal

This paper describes the results of studies on an analog core memory with the aim of applying them to the process controllers. The analog information is stored as the flux level of the square-loop magnetic core. The "write-in" and "read-out" of flux level are achieved by the pulse-width modulation techniques. The storage errors are introduced by the deviations from the ideal square-loop characteristics. However, improvements of stability and linearity are obtained by the following methods: 1) negative dc bias ampere-turn is applied to the square-loop magnetic core, 2) two magnetic cores are connected in the push-pull circuit configuration, 3) the pulse-width modulated (PWM) signal is employed as the "write-in" and "read-out" signal. The experimental results of this device show that the accuracy of analog information storage is better than 0.5 percent at the cycle-time of 1 ms. The PWM signal has both analog and digital characteristics and is suitable for the sequential analog arithmetic computation. An analog-digital hybrid computing control system is outlined to show how these devices can be utilized.