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

When 1xEV-DO Demodulation is enabled, the Chan IQ Meas Time and Chan IQ Ref Time traces are the demodulated time data results sampled at the chip times, for the specified code channel (Walsh Code Number) and code layer (Walsh Code Length). Chan IQ Meas Time is the data results for the measured input signal. Chan IQ Ref Time trace data is the data results that would be derived from an ideal input signal (reference signal).

Available only for reverse link direction channels.

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 and burst amplitude-droop compensation, filtering and system gain normalization to the incoming signal.

IQ reference signal

IQ reference signal is the ideal signal that the VSA generates from the IQ measured signal demodulated data bits. 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.

Online help for Digital Demodulation includes a block diagram that shows how I/Q measured and I/Q reference data are generated.

Time-Domain Displays

The VSA's demodulator produces time-domain data. The VSA shows the I/Q measured signal in the time domain when Chan IQ Meas Time is selected. Likewise, the VSA shows the I/Q reference signal in the time domain when Chan IQ Ref Time is selected.

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)).

If normalization is OFF, the VSA shows the instantaneous magnitude. If normalization is ON, the VSA scales the IQ measured and IQ reference traces to map them onto the unit circle, which yields a unitless y-axis.

For further details about normalization, see online help for Normalize IQ Traces.

The following parameters affect how the VSA shows the I/Q measured and I/Q reference signals:

Result Length determines the number of slots in the measurement.
Measurement Interval and Measurement Offset determine which slots will be displayed