Generalised ENCAP-4/sup N/ digital modulation technique

A class of encoding schemes for generating offset-QPSK-type signals is introduced. Each scheme supposes the specification of 4 ^N functions directly related to the eye-diagrams of the in-phase and quadrature signal components. The main features of the proposed modulation format are described, namely its connections with well known modulation formats. It is shown that the new signal design method provides a unified representation of all OQPSK-type (MSK-type) signals recommended so far (IJF-OQPSK, TFM, GMSK, XPSK, 12PM3X, etc.), and allows the generation of a large variety of new signals. The conditions under which a linear filter and a nonlinear amplifier preserve the proposed format are discussed. It is also pointed out that, in most practical situations, the encoding rules can be modified so as to allow the transmission of a nonlinearly amplified signal of the proposed class, having a variable envelope.<>