Error Performance of Quadrature Pilot Tone Phase-Shift Keying

In this paper we exhibit the effect of the data sequence on the reconstruction of the reference (pilot) tone for a quadrature phase-shift keying (Q-PSK) system. This is a binary digital transmission system in which the phase of one quadrature component of the carrier tone is keyed, while the phase of the other component is unkeyed. The integration of several previous keying intervals provides a reference phase. A scheme of this type, called Kathryn, has been built by General Atronics Corporation. We find that the performance of a Q-PSK system is limited by self-noise unless certain message sequences can be avoided. It is concluded that a Q-PSK system can be used effectively only in a decision-directed mode which is also analyzed.