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Chapter 6 129
Custom Arb Waveform Generator
Working with Filters
To Create a User-Defined FIR Filter with the FIR Values Editor
In this procedure, you use the FIR Values editor to create and store an 8-symbol, windowed, sinc function
filter with an oversample ratio of 4. The Oversample Ratio (OSR) is the number of filter coefficients per
symbol.
You can define from 1 to 32 FIR coefficients, where the maximum combination of symbols and oversample
ratio is 1024 coefficients.
The FIR Values editor allows a maximum filter length of 1024 coefficients, but the PSG hardware is limited
to 512 symbols for arbitrary waveform generation, and 64 symbols for real-time waveform generation. The
number of symbols equals the number of coefficients divided by the oversample ratio. If you enter more than
the maximum number of symbols, the PSG cannot use the filter; it decimates the filter (throws away
coefficients) until the required condition is met and then uses the filter, but fine resolution may be lost from
the impulse response.
1. Press
Preset.
2. Press
Mode > Custom > Arb Waveform Generator > Digital Mod Define > Filter
or
Mode > Custom > Real Time I/Q Baseband > Filter
3. Press Define User FIR > More (1 of 2).
4. Press
Delete All Rows > Confirm Delete Of All Rows > More (2 of 2).
This brings up the FIR Values editor and clears the table of existing values.
5. Press
Edit Item.The Value field for coefficient 0 should be highlighted.