Software based flexible measuring systems for analysis of digitally modulated systems

This paper describes modern software based flexible measuring systems for analysis of digitally modulated systems. The latest methods for evaluation of modulation parameters using new generation test systems based on PXI modular platform and graphical programming in LabVIEW are demonstrated. Authors concentrate on the most widely used modulation technique used in radio communication systems - QPSK. To achieve the best results, different measurements were performed, like measurement in the time domain, spectral measurements, vector diagram, and constellation diagram. Many results for definition of communication system quality were obtained like r (rho), DC offset, phase error, quadrature skew, IQ gain imbalance, bit error rate (BER), frequency deviation, burst timing measurements, modulation error ratio (MER) and error vector magnitude (EVM).