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Chapter 3
Schottky Noise
In this chapter, the Schottky noise will be introduced. The chapter is
strictly theoretical, containing quite a lot of mathematics and signal analysis. Only the principles of signal behaviour is introduced. Considering
the complete signal behaviour would involve too many parameters, to be
performed in a nice analytical way. Such complete analysis’ are left for the
simulators to do.
At first the signal source is introduced, then the way it is detected.
Following is a the main part of this chapter, going through the analysis of
these four types of signal. The system noise contributions to these signals
is only just mentioned. Then the signals are analysed from a power spectral
density point of view. This including the effect of a noise floor. This part
is statistical and considers the effect of averaging spectra. The windowing
function is introduced and the effect of it, applied to the power spectral
density calculation. Finally the timing of such signal detection, is gone
through. This finishes with a sheet containing a draft of the analysis timing.
3.1
What is Schottky noise
The name Schottky noise signal, is a bit misleading. It is not really noise, as
we are used to think of it. Ordinary noise has uncorrelated nature, whereas
Schottky noise is a bit different. Schottky noise, is an addition of many
coherent signals, but individually uncorrelated in phase and frequency. In
our system the coherent signals appear, when the same particle passes the
same pick-up successively in a systematic way. However about 50 million
other particles are doing likewise, but with no correlation to each other.
Special techniques is thus needed to observe the signal, in order to derive
the Schottky noise information.
We do not detect single particle behaviour, but a kind of very detailed
behaviour of the beam. Each passage of particles does add information that
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