Main Length; Filtering; Mirrored Spectrums; Time-Domain Corrections - Agilent Technologies 89410A Operator's Manual

Wideband CDMA Concepts (Options B73, B79, and 080)

Main Length

The number of slots that the analyzer demodulates is set by the [ Instrument Mode ],
[ demodulation setup ], [ main length ] softkey. This softkey is also located under the [Time]
hardkey for convenience.
Main length must be entered as an integer number of slots. You can enter from 8 to
20 slots. You can also enter main length using units of seconds. If you use seconds,
the analyzer automatically increments your entry as necessary to obtain an integer
number of slots.

Filtering

The analyzer always uses a root-raised cosine filter to demodulate W-CDMA
signals. Unlike Digital or Video Demodulation, you cannot change the filter—you
can only control the filter's alpha.
To change the filter's alpha, press [ Instrument Mode ], [ demodulation setup ], [filter alpha]. You
can select a filter alpha from 0.05 to 1.0 in increments of 0.01.

Mirrored Spectrums

The Wideband CDMA instrument mode provides a feature that lets you configure
the analyzer's demodulator to conjugate the complex time-domain waveform. This
has the effect of flipping the spectrum around the analyzer's center frequency. This
feature is useful when the W-CDMA signal is inverted, or flipped due to an IF
downconversion. To enable this feature, select the Wideband CDMA instrument
mode, then press [ Instrument Mode ], [ demodulation setup ], [ freq spectrum mirror].

Time-Domain Corrections

As shown in the general block diagram earlier in this chapter, the analyzer's digital
demodulator uses time-domain data. Because of this, the analyzer automatically
enables time-domain corrections when you select the Wideband CDMA instrument
mode. For details about time-domain corrections, see online help for [System
Utility], [time domain cal].
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