Noise spectrograph apparatus

In both A and B channels, the random voltage n t) delivered by the sample is amplified (frequency range 0-300 kHz), then filtered at a frequency V (1 Hz v lOOkHz) with a bandwidth dv = 0.05v. Then the signal is detected through a multiplier-integrator built in our laboratory and transmitted to a computer. 

Amplifiers A and B exhibit their intrinsic noncorrelated electronic noises [denoted by n t) and a(t)] and also independent of n t). 

In each channel of the spectrograph, the total noise signal is 

Because n, n, and ng are noncorrelated noises, the last three terms, denoted L, are negligible therefore the above relation becomes 

by a cross-correlation technique, it is possible to obtain the noise properties of the sample with high rejection of the parasitic noise of the device. 

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