SP-QPSK: a new modulation technique for satellite and land-mobile digital broadcasting

A new modulation technique, SP-QPSK (sinusoidal shaped π/4-QPSK), suitable for land-mobile and satellite digital-broadcasting systems applications is introduced. In digital data and/or sound broadcasting systems, which may have a relatively low bit-rate transmission requirement, the residual phase noise introduced by the Doppler shift of moving vehicles presents a high bit-error floor in coherently demodulated systems. The overall performance of noncoherent systems is frequently superior in a mobile radio environment. In addition, to satisfy the high-power and spectral-efficiency requirements of emerging digital-broadcast systems, nonlinear saturated amplifiers may become essential subsystems. The performance of the new generation of SP-QPSK systems is investigated experimentally and by computer simulations. Digital signal processing implementation techniques have been used in the experimental prototype design. The authors demonstrate that nonlinearly amplified SP-QPSK has a 10-dB-lower out-of-band radiated power than conventional QPSK and it is suitable for differential and discriminator detection