LeCroy 6000 SERIES, Руководство оператора

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Operator's Manual
200
ISSUED: October 2003 WR6K-OM-E Rev A
The opposite may be true if the noise is mostly at lower frequencies. SNR improvement due to
the removal of coherent noise signals -- feed-through of clock signals, for example -- is
determined by the fall of the dominant frequency components of the signal in the pass band. This
is easily ascertained using spectral analysis. The filters have a precisely constant zero-phase
response. This has two benefits. First, the filters do not distort the relative position of different
events in the waveform, even if the events' frequency content is different. Second, because the
waveforms are stored, the delay normally associated with filtering (between the input and output
waveforms) can be exactly compensated during the computation of the filtered waveform.
The filters have been given exact unity gain at low frequency. Enhanced resolution should
therefore not cause overflow if the source data is not overflowed. If part of the source trace were
to overflow, filtering would be allowed, but the results in the vicinity of the overflowed data -- the
filter impulse response length -- would be incorrect. This is because in some circumstances an
overflow may be a spike of only one or two samples, and the energy in this spike may not be
enough to significantly affect the results. It would then be undesirable to disallow the whole trace.
The following examples illustrate how you might use the instrument's enhanced resolution
function.
In low-pass filtering: The spectrum of a square signal
before (left top) and after (left bottom) enhanced
resolution processing. The result clearly illustrates how
the filter rejects high-frequency components from the
signal. The higher the bit enhancement, the lower the
resulting bandwidth.
To increase vertical resolution: In the example at left,
the lower ("inner") trace has been significantly enhanced
by a three-bit enhanced resolution function.