Digital Modulation: Quadrature Phase-Shift Keying (QPSK) Signal Constellation and Eye Diagrams
Digital Modulation: Quadrature Phase-Shift Keying (QPSK) Signal Constellation and Eye Diagrams
A digitally modulated signal is represented by its equivalent complex low-pass or base-band signal. The real and imaginary parts of this signal are called the quadrature components (t) and (t). The figure shows the signal constellation in the complex plane and the eye diagrams of the quadrature components for QPSK (quadrature phase-shift keying). The eye diagram shows how the waveforms used to send multiple bits of data can potentially lead to errors in interpretation. You can change the roll-off factor of the base-band pulse-shaping filter to see the effect of an amplitude or phase imbalance of the modulator.
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