Research On Compensation Algorithm Of IQ Imbalance In OFDM System

Orthogonal frequency division multiplexing(OFDM)technology has good anti-multipath interference capability and efficient spectrum utilization.This can meet the needs of high-speed data transmission.It has become a key technology for the physical layer of broadband high-speed wireless communication systems.With the continuous development of chip integration technology,direct conversion receivers have received widespread attention and commercial applications in recent years due to their simple structure,easy integration,low cost and power consumption.The combination of OFDM and direct conversion receiver is of great significance to the miniaturization of wireless broadband transmission terminals.However,the direct conversion receiver will introduce a more serious IQ imbalance due to the imperfect analog front end.As a result,the orthogonality between the sub-carriers of the OFDM system is destroyed,which leads to a decrease in system performance.Therefore,it is very important to study the estimation and compensation of IQ imbalance in OFDM systemsA common method of compensating IQ imbalance is to use high-performance analog devices.Although high-performance analog devices can fundamentally suppress the effects of IQ imbalance.However,high-performance analog devices are generally larger and more expensive,increasing the power consumption and price of mobile transceiver equipment.In addition,high-performance analog devices cannot fully compensate for IQ imbalance.In different environments(temperature,humidity,etc.),the ability to suppress IQ imbalance will be different,so it is not very practical to compensate IQ imbalance in the analog domain Furthermore,it is a better choice to suppress and compensate IQ imbalance in the digital domain through digital signal processing.This article is based on the second-order statistical characteristics of the carrier signal.We give two IQ imbalance compensation algorithm and simulation analysis.The main work is as follows:First of all,compared with advantages and disadvantages of the direct conversion receivers and superheterodyne receivers,the time domain and frequency domain model of IQ imbalance are established to describe the received signal under IQ imbalance.On this basis,the second-order statistical characteristics of multi-carrier modulated signals are analyzed and their spectral interpretations are given.Next,the IQ-imbalance leads to the destruction of the second order statistical properties of the complex signal.Demonstrated the non-ideal effects of other factors on the regularity of the complex signal.These will serve as a theoretical basis to provide support for subsequent algorithm constructionNext,according to the compensation principle of the existing IQ imbalance compensation algorithm,a frequency-independent IQ imbalance compensation algorithm is given.The solution process is simplified to reduce the computational complexity of the algorithm simulation results show that the algorithm performance to meet the needs of the theory According to the second-order statistical characteristics of the carrier signal,a frequency-dependent blind compensation algorithm for IQ imbalance is presented.It is implemented through FPGA design and combined with Matlab for joint simulation analysis to verify the feasibility of the implementation method.