Differentiator. The ideal differentiator is a high pass filter that shifts phase by 90 degrees and its’ frequency response would be
linear from DC to 0.5. Since this is not easily realized, the filter provided in the library makes a good differentiator for the
frequency range of DC to 0.45.
Figure 30: Frequency response of the differentiator filter
This section describes the ASCII file format for storing filters for use in the Tektronix oscilloscope waveform math section. A filter
menu function allows the user to specify a disk file name containing the filter. A single file format allows the user to specify a
different set of coefficients for each sample rate that the filter operates at. If the desired sample rate is not in the file list, then the
filter will not be applied to the data. The file format also allows the user to specify that the set of filter coefficients is normalized.
This allows the same set of filter coefficients to operate at all sample rates.
The ASCII file format is specified as follows:
# Comments are preceded by # symbol
< sampleRate > coef1, coef2, …. coefN
< sampleRate > coef1, coef2, …. coefN
| |
| |
< sampleRate > coef1, coef2, …. coefN
Each set of filter coefficients in a file are specified in one row preceded by the sample rate value at which that set will operate. If
the user specifies the @ symbol for the sample rate then the filter will operate at all sample rates. If the @ symbol is specified
then there should only be one set of filter coefficients in the file. However, the user may have other rows with sample rates
specified and they will be ignored. There will be a separate row for each sample rate the filter is to operate at. Each row may
have a different number of coefficients with a maximum of 1000. The file may contain up to 20 rows.
An example of file content for a normalized filter is shown below. This example is the contents of the smooth5.flt file:
@ 0.2, 0.2, 0.2, 0.2, 0.2
Oscilloscope reference
792 DPO70000SX, MSO/DPO70000DX, MSO/DPO70000C, DPO7000C, and MSO/DPO5000B Series
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