A compensation method and device for IQ imbalance in a transmitter

Abstract

The present invention proposes a compensation method and device for IQ imbalance in the transmitter, which estimates and compensates the phase difference between the I channel and the Q channel generated by the IQ imbalance through the long training sequence and the short training sequence received by the OFDM transmitter and magnitude difference. The IQ imbalance compensation method and device proposed by the present invention allow frequency selectivity of the channel, and are suitable for situations where the channel environment is poor; with the increase of the signal bandwidth, the frequency selection characteristics of the channel gradually appear, and the frequency domain of the present invention is more The advantages of joint estimation of tap channel and IQ imbalance are becoming more and more obvious; in addition, the present invention has strong practicability and portability.

Description

technical field [0001] The present invention relates to an IQ imbalance compensation method and device in an OFDM transmitter, in particular to an IQ imbalance compensation method and device using a preamble sequence. Background technique [0002] Many wireless communication terminals use analog superheterodyne transmission and reception schemes to down-convert RF (radio frequency) signals into baseband signals or low intermediate frequency signals through multiple mixers and IF (intermediate frequency) stages. [0003] The superheterodyne system generally improves its performance by increasing the size and cost of the radio frequency selection filter. The performance of the filter determines the intermediate frequency that the system can achieve. In some systems, it is necessary to use multiple intermediate frequencies to amplify and selectively distribute To multiple intermediate frequencies, this will undoubtedly affect the performance and price of the product, so its str...

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Problems solved by technology

[0005] However, zero-IF receivers are very sensitive to I / Q imbalance, and it is difficult to ensure good I / Q balance with discrete I / Q modulators.

The existence of IQ imbalance will impose an image component on the original signal, resulting in image interference, and causing the error performance of the system to decline, while the indicators of error vector magnitude (EVM) and bit error rate (BER) will also decrease. For OFDM systems, IQ imbalance can also cause non-orthogonality between subcarriers

At the same time, the new generation of wireless communication systems tend to use high-order modulation and high-frequency carrier to increase the data transmission rate, and the introduction of high-order modulation and high-frequency carrier makes the wireless communication system more sensitive to IQ imbalance. Even an extremely small IQ imbalance may cause a significant decrease in the performance of the entire communication system

At present, there are already many IQ imbalance compensation methods. The traditional IQ imbalance compensation method is to feed back the IQ imbalance parameters estimated by the receiver to the transmitter, and then perform corresponding compensation, which inevitably brings Certain system overhead and time delay

In addition, most of the existing algorithms study the IQ imbalance of the receiver, and the research work on the IQ imbalance introduced by the transmitter is almost blank. In fact, the IQ imbalance of the transmitter is also a very important radio frequency index

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