Keysight E8663D, Руководство пользователя

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Keysight E8357D/67D & E8663D PSG User’s Guide 193
Custom Arb Waveform Generator
Working with Filters
The FIR filter is now optimized for minimum error vector magnitude (EVM)
or for minimum adjacent channel power (ACP). This feature applies only to
Nyquist and root Nyquist filters; the softkey is grayed out when any other
filter is selected.
Restoring Default FIR Filter Parameters
1. Preset the instrument: Press Preset .
2. Press Mode > Custom > ARB Waveform Generator > Digital Mod Define >
Filter > Restore Default Filter .
This replaces the current FIR filter with the default filter for the selected
modulation format.
Using a User–Defined FIR Filter
FIR filters can be created and modified by defining the FIR coefficients or by
defining the oversample ratio (number of filter coefficients per symbol) to be
applied to your own custom FIR filter.
To Modify Predefined FIR Coefficients for a Gaussian Filter Using the
FIR Values Editor
You can define from 1 to 32 FIR coefficients, where the maximum combination
of symbols and oversample ratio is 1024 coefficients. While the FIR Values
editor allows a maximum filter length of 1024 coefficients, the PSG hardware is
limited to 64 symbols for real–time and 512 symbols for arbitrary waveform
generation (the number of symbols equals the number of coefficients divided
by the oversample ratio).
If you enter more than 64 symbols for real–time or 512 symbols for arbitrary
waveform generation, the PSG cannot use the filter; it will decimate the filter
(throw away coefficients) until the required condition is met and then use the
filter, but fine resolution may be lost from the impulse response.
FIR filters stored in signal generator memory can easily be modified using the
FIR Values editor. In this example, you will load the FIR Values editor with
coefficient values from a default FIR filter (or, if one has been defined, a
user–defined FIR file that has been stored in the Memory Catalog), modify the
coefficient values, and store the new file to the Memory Catalog.
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) > Load Default FIR > Gaussian .
4. Press Filter BbT > 0.300 > Enter .
5. Press Filter Symbols > 8 > Enter .