High speed signal averager for characterizing periodic signals in the time domain

Abstract

A new data‐acquisition and averaging system is described which rapidly digitizes and averages periodic signals of known frequency. Each acquisition channel has a programmable gain input amplifier, track and hold amplifier, 12 bit analog to digital converter, 4K by 32 bit memory buffer, and an arithmetic logic unit which adds the converter output directly to the contents of the current memory location. In the present implementation, two channels are used in parallel with a common sampling clock at rates up to 1.35 MHz. With real time ‘‘add to memory’’ capability, signal averaging can be continued to any desired degree in order to improve the signal‐to‐noise ratio and reject contributions from harmonics and asynchronous frequencies. This type of acquisition system is most suitable where a periodic signal of known frequency is applied to an experimental device and the system’s response, at the same frequency, must be accurately determined. The phase resolution of better than ±0.001° which this system provides, is particularly important for analysis of a ‘‘drive and response’’ experiment of this type.