Phase Optimized Constant Envelope Transmission (POCET) and the Method of Phantom Signals

Philip A. Dafesh and Gourav K.  Khadge

Peer Reviewed

Abstract:	The phase optimized constant envelope transmission (POCET) method was developed as an approach to optimally combine any number of component signals into a single constant envelope waveform [1], or composite signal. The POCET method modulates a carrier signal utilizing a finite set of signal phases to generate a constant envelope composite signal, where the finite set of signal phases are determined through an optimization process that minimizes the constant envelope (or power) of the signal, subject to intra-signal constraints on the component signals, and inter-signal constraints between the component signals. In prior work, the intra-signal constraints have been expressed as two or more constraints on the component signal power levels and relative phase relationships [2-4] and the solution was constrained to have a symmetric constellation. Although symmetric constellations are generally desirable to prevent carrier tracking performance degradation [5], Zhang has shown that by allowing POCET to arrive at asymmetric constellations, the POCET optimization can arrive at more power efficient solutions [6]. In this paper, we have developed the method of phantom signals, which allows for symmetric constellation solutions which are not outperformed by asymmetric designs. In the method of phantom signals, a POCET solution is computed using symmetry constraints described in [1] and [2], but with the addition of one or more unconstrained phantom signals. The signals are called phantom signals because their sole purpose is to increase the degrees of freedom in the optimization problem resulting in a more efficient solution. We will also show the “Phantom POCET” solution space is convex and is guaranteed to arrive at the optimal efficiency solution for a given set of fully specified constraints on desired signal power levels and relative signal phases.
Published in:	Proceedings of the ION 2017 Pacific PNT Meeting May 1 - 4, 2017 Marriott Waikiki Beach Resort & Spa Honolulu, Hawaii
Pages:	100 - 117
Cite this article:	Dafesh, Philip A.,  Khadge, Gourav K., "Phase Optimized Constant Envelope Transmission (POCET) and the Method of Phantom Signals," Proceedings of the ION 2017 Pacific PNT Meeting, Honolulu, Hawaii, May 2017, pp. 100-117. https://doi.org/10.33012/2017.15041
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