Highly Efficient Encoded OQPSK Signals: Emission and Reception Design Aspects

The ENCAP-4^N (encoded amplitude and phase-4^N), related with a vast class of OQPSK (offset quadri-phaseshift keying) type signals, can be advantageous when it is important to achieve good tradeoffs between spectral efficiency and envelope fluctuations when a nonlinear amplification is employed. This paper presents a simplified representation of FQPSK (Feher-Patented quadrature-phase shift keying), showing also the potential improvement in power efficiency, without sacrifice of spectral compactness. Usually, the coding rule for ENCAP-4^N format is based on the complex envelope decomposition in pulses with bit duration T, directly related with the 4^N generating functions set. In this paper, it is proposed a new interpretation based in this signal format that results in a coding rule, based on a complex envelope description as function of pulses with duration 2T. The signal, in accordance with the foregoing coding rule, can be viewed as a trellis coded modulation with 2^2N+2 states and pulses shapes