Comp IQ Meas Time and IQ Ref Time (1xEVDO)

When 1XEV-DO Demodulation is enabled, the Comp IQ Meas Time and Comp IQ Ref Time trace data are the time data results of 1XEV-DO demodulation for the composite signal. Comp IQ Meas Time trace data is the data results for the measured input signal. Comp IQ Ref Time trace data is the data results that would be derived from an ideal input signal (reference signal).

Composite, forward link, trace data results are computed from the first measured slot. Composite, reverse link, trace data results are computed from the first measured half (0.5) slot. The and parameters have no effect on this measurement.

Concepts

The VSA's demodulator produces two signals: I/Q Measured and I/Q Reference.

IQ measured signal

The IQ measured signal is the result of resampling the data to one point per chip and applying carrier locking, symbol locking, IQ origin offset compensation, filtering and system gain normalization to the incoming signal.

IQ reference signal

I-Q reference signal is the ideal input that the VSA generates from IQ measured signal. The VSA detects bits from the measured IQ signal and reconstructs a sequence of ideal I and Q states. These are then treated as ideal impulses and are baseband filtered according to the reference filter and added together to form the IQ reference signal. The resultant IQ reference signal is then used compare and analyze against the IQ measured signal.

Time-Domain Displays

The VSA's demodulator produces time-domain data. If Comp IQ Meas Time is selected, the VSA shows the composite IQ measured signal in the time domain. Likewise, if Comp IQ Ref Time is selected, the VSA shows the composite IQ reference signal in the time domain.

The data can be displayed in a variety of trace data formats, including I-Q, Constellation, Q-Eye, I-Eye and Trellis-Eye formats (see Trace Formats (Digital Demodulation)).

For forward link measurements, the segment of the signal included in the trace data depends on the Analysis Channel and Combine TDM channels for composite results parameter settings.

For forward link measurements, the trace background annotation indicates what segment of the 1xEV-DO frame is being analyzed. Change the trace display colors from the Display Preferences > Color tab.

Normalization

If normalization is OFF, the VSA shows the instantaneous magnitude. If normalization is ON, the VSA scales the composite IQ measured and composite IQ reference traces so that the RMS level is one, which produces a unitless y-axis.

For further details about normalization, see Normalize IQ Traces.