Carrier-phase synchronisation in the demodulation of UQPSK signals
Carrier-phase synchronisation in the demodulation of UQPSK signals
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DOI：
10.1049/ip-i-2.1989.0053
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发表时间：
1989-10
期刊：
影响因子：
--
通讯作者：
A. Clark;A. Aftelak
中科院分区：
文献类型：
--
作者：
A. Clark;A. Aftelak
本文描述了一种新的载波相位同步过程，该过程已开发用于在卫星链路上运行的数字通信系统中，并采用不平衡的四元相移键控（UQPSK）信号。这颗卫星不是地球同步卫星，至少在其轨道的一部分上可能会接近地球表面。正确的载波相位同步需要在卫星升到地平线以上时实现，在此期间，它正在传输数据信号，因此不需要使用已知的训练信号。在这些条件下，数字信号以低信噪比和存在严重的多普勒频移的方式接收。正确的载波相位同步必须在卫星经过头顶时保持，直到它再次接近地平线。因此，同步电路也必须容忍多普勒频移的高变化率，尽管在更高的信噪比。同步算法分为两个独立的部分，它们按顺序运行，并且都是非数据辅助的。第一部分从接收信号中去除多普勒频移，然后第二部分实现载波相位同步，这在传输的其余部分保持。本文描述了这些新算法，并给出了一系列计算机仿真测试的结果来评估它们的性能。
The paper describes a novel carrierphase synchronisation process that has been developed for use in a digital communication system operating over a satellite link and employing unbalanced quaternary phase shift keyed (UQPSK) signals. The satellite is not geostationary and may travel close to the surface of the earth over at least a part of its orbit. Correct carrier phase synchronisation needs to be achieved here as soon as the satellite rises above the horizon, during the time it is transmitting data signals, and therefore without the use of a known training signal. Under these conditions the digital signal is received at a low signal to noise ratio and in the presence of a severe Doppler shift. Correct carrier phase synchronisation must then be maintained as the satellite passes overhead and until it approaches the horizon again. Thus the synchronisation circuits must tolerate also a high rate of change of Doppler shift, albeit at a higher signal to noise ratio.The synchronisation algorithm is in two separate parts that operate sequentially and are both non-data aided. The first part removes the Doppler shift from the received signal and the second part then achieves carrier phase synchronisation, which is maintained over the rest of the transmission.The paper describes the new algorithms and presents the results of a series of computer simulation tests to assess their performances.