The quasi-coherent QPSK modulator
Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
This article presents the results of the development of the new quasi-coherent QPSK (quadrature phase shift keying) signal modulator structure, compared to traditional schemes of quasi-coherent QPSK signal former it has complex of improved parameters: increased locking range and holding range, the minimum synchronization time, improve accuracy and stability of the manipulation phase in the presence of destabilizing factors affecting the parameters of the device.
In the article, it is shown a block diagram the device. The description of the operating modes are given. Phase portraits of the device, timing diagrams of transient processes for mode of initial synchronization and mode of synchronous operation are shown. The results of the device simulation in MATLAB / Simulink are presented.
The dependence of the frequency synchronization time on initial frequency detuning were obtained for developed device and QPSK signal modulator based on traditional phase locked loop (PLL) (transfer function described by a differential equation of order 2), in Matlab / Simulink.
The results obtained during the study show a significant extension of the locking range of the developed device compared to the considered conventional scheme of quasi-coherent QPSK signal modulator. Time frequency synchronization of developed device has also significantly reduced and slightly changed in the all considered range of frequency detuning. The new structure of quasi-coherent signal modulator QPSK presented in the paper are promising for use in practical applications such as the reference oscillations using signals received from distant sources of standard time and frequency scales.
Keywords:quasi-coherent modulation, QPSK modulation, phase portraits, timing diagrams of transient processes, simulation
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