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) andquadrature (Q) components and between signal elements in each component. These encoding rulesimply 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.