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Article 8-7 2019

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DIGITAL AGC REFERENCE LEVEL CORRECTION IN A WIDEBAND QUADRATURE AMPLITUDE MODULATED RADIO RECEIVER

Aleksandr A. Prasolov,  Bonch-Bruevich Saint-Petersburg State University
of Telecommunications, St. Petersburg, Russia,  prasolov.alex@gmail.com

Abstract
Introduction. Currently, quadrature amplitude modulation is used in a large number of diverse communication systems, including digital television broadcasting, mobile communication systems, as well as in all the other systems with OFDM. When receiving signals with varying amplitude, such as BPSK, DQPSK or QAM, it is necessary to maintain the signal amplitude at the input of the demodulator in certain predetermined limits. Communication systems today are mostly digital. One of the tasks of automatic gain control in digital receivers is to maintain analog signals at a level that prevents saturation of the analog-to-digital converter. Therefore, automatic gain control plays an important role in modern communication systems. Objective. This paper examines the effectiveness of the digital automatic gain control reference level adjustment in wideband QAM receivers. Materials and methods. In this paper, mathematical model of the QAM receiver with two blocks of the automatic gain control unit and the reference level correction is suggested. Results. Using digital automatic gain control reference level adjustment when overloading an analog-to-digital converter allows you to more precisely adjust the signal level. Digital automatic gain control parameters ware estimated. Conclusion. An algorithm which allows to reduce the bit error probability in receivers with QAM due to the digital automatic gain control reference level correction is proposed. The results of this work are relevant in the tasks of developing digital receivers for communication systems for various purposes.

Keywords:digital AGC, reference level, bit error rate, quadrature amplitude modulation, control signal.

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Information about author:
Aleksandr A. Prasolov, Senior Lecturer, Department of Radio Communications and Broadcasting, The Bonch-Bruevich Saint-Petersburg State University of Telecommunications, St. Petersburg, Russia