Visualization of 4D QPSK and CEQPSK in Ideal Bandlimited Channels

This paper presents new visualization techniques for 4D Quadrature-Quadrature Phase Shift Keying (QPSK), Saha’s Constant Envelope (CE) QPSK, and Cartwright’s CEQPSK in ideal bandlimited channels. The signal diagrams analyzed are: time-signal eye patterns for 4D passband signals, 2D complex trajectory diagrams of baseband signals, and time-signal eye patterns for the 1D outputs of the baseband matched filter. These methods may be applied to other multidimensional modulation systems to obtain insight into the effects of noise, interference, and channel filtering.