Agilent Technologies manual Differences from 89600 VSA operation, Full rate, User rate

This table summarizes the difference in approach to alias protection between the various sample modes:

Table 5. Varying approaches for alias protection

Full rate	Both in-band and out-of-band aliasing are prevented through use
	of the maximum sample rate and an appropriate lowpass filter.
User rate	You are responsible to avoid in-band aliasing through appropriate
	selection of sample rate based on center frequency and span. To
	ensure no in-band aliasing is present the digitizer sample rate (FS)
	must be selected to meet this criteria:
	Baseband: FSTOP ≤ FS/2.56
	Zoom: (n*FS)/2 ≤ FCENTER - (1.28 * FSPAN)/2
	AND
	((n+1)*FS)/2 ≥ FCENTER + (1.28 * FSPAN)/2
	where n = 1,2,3,4…
	Out-of-band aliasing is minimized through use of appropriate
	low-pass filter. Use of Alias Checker macro (Section 6) is required
	to detect other unwanted out-of-band signal aliasing.
	(Note: aliasing of unwanted signals can be eliminated through use
	of appropriate bandpass filter.)

Another concern in user rate mode is that you may see unwanted amplitude variability in two channel measurements. This can occur if any part of the mea- surement frequency span falls within the regions defined by:

(2*n+1) x FS/2 ± 0.1 x FS where n = 1, 2, 3, 4 …

where FS is the actual digitizer sample rate. Make sure you choose a sample rate where such overlap does not occur.

4.3 Differences from 89600 VSA operation

•No Magnitude Trigger (however, Channel Trigger is available).

•Possible limitation of movement on the operating region curve to avoid alias corruption of the measured signal. This depends on the settings of Center Frequency, Span, Sample Mode, and Number of Frequency Points. There is also potential interference due to the alias products of out-of-band signals. (See Section 6.)

•No built-in wideband calibrator. The frequency response corrections are determined from factory data.

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