Signal averaging with a magnetic tape loop and boxcar integrator

Abstract

An analogue technique is described which recovers a de-noise, amplitude-averaged waveform from a noisy, synchronous signal of short duration. The system is advantageous where the changing or non-stationary nature of the event prevents signal averaging by slow scanning and 'real-time' analysis equipment is not available. If part of the noise is outside the signal bandwidth, the signal to noise ratio may be immediately improved by filtering. The remaining noise within the signal bandwidth must be removed by averaging. This is accomplished by recording several repetitions of the noisy signal on a loop of magnetic tape and then playing it back many times into a boxcar integrator which averages out the noise. Data are presented to show the capability of the system in recovering a signal which is non-stationary in amplitude and buried in noise. The technique has been used with an optical homodyne spectrometer to de-noise the Rayleigh spectrum of laser light scattered by biological samples which permit only brief experiments.