| Modern communication systems are essential to use large bandwidth and high order modulation in order to achieve higher transmission rate, but the signal distortion generated by the transceiver has become the bottleneck of further improvement of data rate. In most of the existing zero intermediate frequency structure, in-phase/quadrature (I/Q) imbalance and frequency offset of the transceiver are main sources of signal distortion.In addition, the filters in the transmitter and receiver have non-ideal amplitude response and phase response, which also bring influence on system performance. In this paper, we study IQ imbalance, non-ideal filters and frequency offset in the 5G transceiver, analyzing their influence on the high-order modulated 5G system, and propose a compensation scheme.This paper is organized as follows:1. Analyzing the principle of IQ imbalance, describing the models of transmitter with IQ imbalance, receiver with IQ imbalance and receiver with both frequency and IQ imbalance. Then, discussing the non-ideal filters and give its mathematical model. Finally, give out the system model with the non-ideal transceiver.2. Analyzing the deterioration of the signal property caused by the non-ideal factors in the transceiver. A MATLAB simulation platform is established to study the influence of IQ imbalance, fruequency offset and non-ideal filter on the signal property. Furthermore, an experimental platform is established to verify the signal distortion caused by the non-ideal factors.Then, establish a 5G simulation platform with MATLAB, and study the influence of IQ imbalance and non-idealfilter to the 5G system. Finally, a simulation. of combined non-ideal factors on the 5G simulation platform is carried out to study the combined effect.3. An estimation algorithm is proposed and simulations are carried out on the 5G MATLAB simulation platform. Simulations includethe algorithm performance of different IQ imbalance parameters, different filter parameters, AWGN channel and Rayleigh channel. Then an experimental platform is established and experiment is carried out for algorithm verification.4. This paper does an in-depth analysis of the non-ideal filter in the transceiver on signal quality. The simulation and experimental platform tests show that the non-ideal filter has a great impact on the high-bandwidth system. When designing a system, we should choose a filter with smooth passband response and phase response closer to the linear response. Meanwhile, the estimation algorithm in this paper is designed for high order modulation 5G system, when the system is affected by transceiver IQ imbalance, frequency offset and non-ideal filter at the same time, the algorithmcan effectively improve the performance of the system. |
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