70 Chapter3
Making EDGE (with GSM) Measurements
Making the Phase and Frequency Error Measurement
The menus under the Span X Scale and Amplitude Y Scale keys are
context dependent upon the selected window (graph type). The
Span X
Scale parameters will be in units of time or bits, dependent on the view
selected. The
Amplitude Y Scale parameters will be in units of dB or
degrees, dependent on the view selected. All of the softkey labels are
blank when
I/Q Measured Polar Vector, or Data Bits are selected.
Changing the Display
The Display key will allow you to turn the bit dots on and off.
Troubleshooting Hints
Poor phase error indicates a problem with the I/Q baseband generator,
filters, or modulator in the transmitter circuitry. The output amplifier
in the transmitter can also create distortion that causes unacceptably
high phase error. In a real system poor phase error will reduce the
ability of a receiver to correctly demodulate, especially in marginal
signal conditions. This ultimately affects range.
Occasionally, a Phase and Frequency Error measurement may fail the
prescribed limits at only one point in the burst, for example at the
beginning. This could indicate a problem with the transmitter power
ramp or some undesirable interaction between the modulator and
power amplifier.
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