Fast convergence method for cross-correlation based modulation quality measurements

A measurement system for determining a modulation quality measurement, the system comprising:

• a processor coupled to a memory;
• a splitter configured to receive a modulated waveform from a source;
• a first vector signal analyzer (VSA) coupled to the splitter;
• a second VSA coupled to the splitter;
• wherein the system is configured to:
• receive, by the splitter, the modulated waveform from the source a plurality of times;
• transmit, by the splitter, the plurality of received modulated waveforms to each of the first VSA and the second VSA;
• by the first VSA, and for each of the plurality of received modulated waveforms, demodulate the received modulated waveform to obtain a first error vector;
• by the second VSA, and for each of the plurality of received modulated waveforms, demodulate the received modulated waveform to obtain a second error vector;
• by the processor:
• for each of the plurality of received modulated waveforms, perform a cross-correlation calculation on the respective first error vector and the respective second error vector to obtain a respective cross-correlation measurement, wherein each cross-correlation measurement comprises a real component and an imaginary component;
• average over the real components of the cross-correlation measurements corresponding to each of the plurality of received modulated waveforms to obtain an averaged cross-correlation measurement;
• determine the modulation quality measurement based at least in part on the averaged cross-correlation measurement;
• and
• store the modulation quality measurement in the memory.

A method, comprising:

• receiving, by a measurement system, a plurality of modulated waveform from a source;
• transmitting the plurality of received modulated waveforms to a vector signal analyzer (VSA);
• by the VSA, demodulating the plurality of received modulated waveforms to obtain a plurality of respective error vectors;
• performing a plurality of cross-correlation calculations on respective pairs of error vectors of the plurality of error vectors to obtain a plurality of respective cross-correlation measurements, wherein each cross-correlation calculation comprises multiplying a first error vector of the respective pair of error vectors by a complex conjugate of a second error vector of the respective pair of error vectors, wherein the cross-correlation measurements each comprise a respective real component and a respective imaginary component;
• averaging over the real components and not the imaginary components of the cross-correlation measurements to obtain an averaged cross-correlation measurement;
• and
• determining a modulation quality measurement based at least in part on the averaged cross-correlation measurement.