Abstract
As an important part of the communication system, synchronization technology is a communication system to run the correct protection, has been a hot topic in communication systems research. Four-phase phase shift keying (QPSK) circuit structure is relatively simple, and has a good band utilization, in the modern communication has a wide range of applications. Corresponding research on carrier synchronization for QPSK coherent demodulation is carried out. By comparing several carrier recovery loops, The quaternary loose tail loop is selected as carrier recovery loop. First of all, the core part of the digital phase-locked loop analysis and implementation, and finally through the tool Simulink to complete the realization of the system.
Highlights
With the rapid development of modern communication and network technology, wireless communication technology development in the direction of digital, broadband-oriented
QPSK technology is widely used in digital microwave communication systems, broadband access digital satellite communications systems, mobile communications and cable television systems
Carrier synchronization is known as carrier recovery, that is, through the receiving device to generate a carrier with the received signal synchronization in phase with the local oscillation, the receiver to do coherent demodulation [2]
Summary
With the rapid development of modern communication and network technology, wireless communication technology development in the direction of digital, broadband-oriented. QPSK demodulation generally uses coherent demodulation of the way, so there are high requirements on the performance of carrier synchronization [1]. Carrier synchronization is known as carrier recovery, that is, through the receiving device to generate a carrier with the received signal synchronization in phase with the local oscillation, the receiver to do coherent demodulation [2]. The self-synchronization method is a more desirable synchronization method than the external synchronization method, because all the power and bandwidth can be assigned to the signal transmission [3]. Since QPSK modulation is to suppress the modulation of the carrier, there is no carrier component in the modulated signal, and the carrier needs to be recovered from the received signal to achieve coherent demodulation. To recover the carrier from the received signal, the signal must be processed non-linearly to produce the corresponding carrier component, and filter out with a narrowband filter or phase-locked loop
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