ENCAP-4: an OQPSK-type modulation technique for digital radio

A class of OQPSK-type signals (offset quadrature phase shift keyed) is defined which generalises several well known modulation formats. These signals are generated by means of a set of encoding rules which introduce a controlled amount of correlation between the in-phase (I) and quadrature (Q) components and between signal elements in each component. These encoding rules imply the specification of four generating functions directly related to the eye diagram of the I and Q baseband signals. It is shown that the proposed signal representation provides an efficient means of design and performance evaluation. Advantageous trade-offs between spectral efficiency and power efficiency can be achieved with some of the proposed signals, making them suitable for digital radio applications.