Currently, methods of direct modulation using complex signals are widely used. A complex signal consists of in-phase I (In-phase) and quadrature Q (Quadrature) components. When a signal passes through a communication channel and a receiving path, mismatches of the signal components occur as a result of interference. The mismatch, in turn, leads to increase in bit error rate (BER) during signal demodulation. The quality of the received signal is expressed in terms of bit error rate. The article considers phase imbalance of the quadrature components of a complex signal. Phase imbalance occurs in the receive path and depends on the quality of the receiver's local oscillators, on the operating temperature and the difference in propagation time of the I and Q components. The article shows an algorithm for estimating the phase imbalance of the quadrature signal components for digital modulation methods. Examples of signal constellation distortions in case of phase imbalance of quadrature signal components are considered. The phase imbalance estimation is based on the modulation constellation method for measuring signal parameters. Formulas for calculating the angle of phase error and the magnitude of quadrature error are given. Formulas for compensating the phase imbalance are also given, taking into account the calculated quadrature error. A mathematical model of the transmitter, communication channel and receiver has been developed to study the method for estimating and compensating for phase imbalance. The mathematical model is built in the Matlab software environment and is an m-script software model. With the help of the mathematical model, method for estimating and compensating for phase imbalance has been studied. In the course of the study, relationships of error probability due to the mismatch of the quadrature components of the signal were obtained. The noise immunity of the receiver paths with and without compensation for the phase mismatch of the quadrature signal components is compared. Based on the results of the study, diagrams of the error probability and the phase mismatch of the receiver's local oscillators were obtained. The study shows that phase mismatch of the receiver local oscillators at a fixed signal-to-noise ratio leads to an increase in the probability of received bit errors. But when applying the phase imbalance compensation method, the error probability remains fixed as the phase mismatch of receiver local oscillators increases at a fixed signal-to-noise ratio.
The method of direct modulation using complex signals is used to implement signal paths of transmitters in base stations of cellular communication systems. In the process of modulation, there are mismatches of the gain coefficient and the phase of the quadrature components of the signal. Mismatch degrades the Error Vector Magnitude (EVM) at the receiver, which in turn results in an increased Bit Error Rate (BER). The quality of the received signal is expressed in bit error rate. The mismatch of the amplitude and phase of the quadrature components is one of the most important factors making the greatest contribution to the amplitude of the error vector, and which must be investigated. The paper presents a research of the influence of the mismatch on the OFDM (Orthogonal frequency-division multiplexing) and UFMC (universal filtered multi-carrier) technologies. A model of the transmitter, communication channel and receiver for OFDM and UFMC signals has been developed. The model was built in the MatLab software environment. In the work, by studying the simulation model, the dependence of the noise immunity of technologies was studied by changing the parameters of the communication channel, such as the amplitude and phase mismatch of the quadrature components of the signal, as well as the signal-to-noise ratio. Also, a comparative analysis of such signal parameters as the occupied bandwidth, peak to average ratio, frequency of occurrence of bits with an error was carried out. Based on the results of the study, graphs of the dependence of the error probability and the signal peak to average ratio on the mismatch of the quadrature components were obtained for two technologies, OFDM and UFMC. The study allows us to highlight the advantages of UFMC technology, which are expressed in spectral efficiency, noise immunity and the level of the signal peak to the average ratio.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.