Hello,
Iam using the N9010A-EXA-Analyzer with the 89600 VSA Software.
When i demodulate a digital modulation for example a QPSK with IQ imbalance (the I-signal has a higher amplitude than the q-signal), the vector diagramm don't shows a constant constellation. The expected "rectangle" is there, but changes its state all the time. Sometimes the I-Signal has the higher amplitude, sometime the Q-signal. So the Software switches the phase of the demodulated signal all the time and the allocation of the I- and Q-Signal is faulty.
This effect i have all the time.
The RF modulated signal is done by the Agilent N9310A RF Signal Generator, which gets an external I/Q-Signal.
Iam using the N9010A-EXA-Analyzer with the 89600 VSA Software.
When i demodulate a digital modulation for example a QPSK with IQ imbalance (the I-signal has a higher amplitude than the q-signal), the vector diagramm don't shows a constant constellation. The expected "rectangle" is there, but changes its state all the time. Sometimes the I-Signal has the higher amplitude, sometime the Q-signal. So the Software switches the phase of the demodulated signal all the time and the allocation of the I- and Q-Signal is faulty.
This effect i have all the time.
The RF modulated signal is done by the Agilent N9310A RF Signal Generator, which gets an external I/Q-Signal.
The VSA software does not have a phase reference and what you are seeing is a phase ambiguity that occurs with non-differential modulation formats. To correct for this you can use the constellation sync search if your signal contains a sync word during a specified time period. For more details see http://wireless.agilent.com/wireless/he ... ncsrch.htm
Regards -