Using a Predefined FIR Filter

Custom Arb Waveform Generator

Working with Filters

middle, and total attenuation at high frequencies. The width of the middle frequencies is defined by the roll off factor or Filter Alpha (0 < Filter Alpha < 1).

•Gaussian is a Gaussian pre- modulation FIR filter.

•User FIR enables you to select from a Catalog of FIR filters; use this selection if the other

predefined FIR filters do not meet your needs. For more information, see Define User FIR, below.

•Rectangle is a rectangular pre- modulation FIR filter.

•APCO 25 C4FM is an APCO 25- specified C4FM filter; this is a Nyquist filter with an alpha of 0.200 that is combined with a shaping filter.

Filter Parameters

•Define User FIR is available for when the predefined FIR filters do not meet your needs. You can define FIR coefficients and set the oversample ratio (number of filter coefficients per symbol) to be applied to a custom FIR filter.

•Filter Alpha enables you to adjust the filter alpha for a Nyquist or root Nyquist filter. If a Gaussian filter is used, you will see Filter BbT; this softkey is grayed out when any other filter is selected.

•(Custom Realtime I/Q Baseband Only) Optimize FIR for EVM ACP enables you to optimize a Nyquist or root Nyquist filter for minimized error vector magnitude (EVM) or for minimized adjacent channel power (ACP); the softkey is grayed out when any other filter is selected.

•Restore Default Filters replaces the current FIR filter with the default FIR filter for the selected format.

Selecting a Predefined FIR Filter
1.	Preset the instrument: Press Preset.
2.	Press Mode > Custom > ARB Waveform Generator	> Digital Mod Define	> Filter	> Select
	or
	Mode > Custom > Real Time I/Q Baseband > Filter > Select >
3.	Select the desired filter. If the filter you want is not in the first list, press More (1 of 2).
Adjusting the Filter Alpha of a Predefined Root Nyquist or Nyquist Filter
1.	Preset the instrument: Press Preset.
2.	Press Mode > Custom > ARB Waveform Generator	> Digital Mod Define	> Filter	> Filter Alpha
	or
	Mode > Custom > Real Time I/Q Baseband > Filter	> Filter Alpha
3.	Enter a new Filter Alpha value and press Enter.
Adjusting the Bandwidth-Bit-Time (BbT) Product of a Predefined Gaussian Filter
1.	Press Mode > Custom > ARB Waveform Generator	> Digital Mod Define	> Filter	> Select > Gaussian
	or
	Mode > Custom > Real Time I/Q Baseband > Filter	> Select > Gaussian

2.Press Filter BbT.

3.Enter a new Bandwidth- Bit- Time (BbT) product filter parameter and press Enter.

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E8267D PSG, E8257D PSG specifications

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Agilent Technologies E8257D PSG Using a Predefined FIR Filter, Selecting a Predefined FIR Filter

Models: E8267D PSG E8257D PSG

Filter Parameters