QPSK Signal Generation Based on Globally Linearized Synchronization System

Abstract

The paper presents a description of the quadrature phase shift keying (QPSK) signal shaping methodology based on the structure of a globally linearized synchronization system (GLSS). The results of simulation modeling of the QPSK-GLSS shaper, which performs the modulation process directly at the operating frequency in the microwave range, under conditions when the use of a programmable element base becomes ineffective, are presented. To synthesize the QPSK signal, the structure of the GLSS is supplemented with special control units that transform the phase portrait in such a way that the points of stable equilibrium of the system are located in steps equal to π/2 radians. The first control unit implements static shifts of the locations of the system stable equilibrium points equal to ±π/4 along the phase axis of the system phase portrait, depending on the polarity of the control signal. The second unit of binary control implements alternate synchronization of the GLSS system at two points of stable equilibrium located at a distance of $\boldsymbol{\pi}$ radians from each other. Joint combinations of control actions give a complete set of phase shifts of the system output signal relative to the reference oscillation, which corresponds to the QPSK manipulation: [-π/4; π/4; 3π/4; 5π/4]. The dynamic characteristics of the QPSK-GLSS shaper (modulator) are illustrated by the results of simulation when generating a signal directly at a frequency of 6.4 GHz and a data transfer rate equal to 300 Mbit/s.