IQ Meas Spec and IQ Ref Spec (1xEVDO)

When 1xEV-DO Demodulation is enabled, Comp IQ Meas Spec and Comp IQ Ref Spec is the spectrum of the Composite IQ Meas Time or Composite IQ Ref Time trace data respectively. The VSA produces the spectrum by Windowing and FFTing the composite I/Q measured or composite I/Q reference signal. The spectrum represents the signal AFTER filtering.

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 Measurement Interval and Measurement Offset parameters have no effect on this measurement.

For forward link measurements, the Time Division nature of the signal produces non contiguous composite time data when specifying an Analysis Channel. To include the entire slot and therefore have useful FFT Fast Fourier Transform: A mathematical operation performed on a time-domain signal to yield the individual spectral components that constitute the signal. See Spectrum. information, select the Combine TDM channels for composite results parameter.

Marker Frequency Correction

The VSA's demodulator removes carrier-frequency error. Therefore, in the composite error vector spectrum display, add the carrier-frequency error to marker readouts to obtain exact frequency information. The carrier-frequency error (Freq Err) is shown in the Composite Error Summary trace data.

By default, the VSA shows the log(dB) magnitude when IQ measured spectrum is selected. The same is true for I/Q reference.