Span Considerations (cdma2000/1xEV-DV)
When selecting a frequency span, select the narrowest span that includes all of your signal components (select a span that is slightly larger than the bandwidth of your signal). If you select a span that is too narrow, your measurement may have excessive errors or the VSA may lose carrier lock. If the span is less than (1+filter alpha) x chip rate, the VSA displays "DATA?" to indicate that the results may not be accurate.
For best results, the frequency span should be set according to the following formula (filter alpha is the filter characteristic of the Nyquist filter used to demodulate the cdma2000 signal):
Frequency Span ³ (1 + Filter alpha) x Chip Rate
If you select a span that is too wide, your measurement may be affected by excessive noise and slower speed. You may want to turn the demodulator OFF and set the span while viewing the spectrum of your signal.
Using the configuration settings will select a default span that should work well.
The following topics may help optimize your measurements and explain the reasons for changes made automatically by the VSA.
Measurement Speed Considerations
See Also
Setting Measurement Parameters
