Abstract
In the signal acquisition of complete orthogonal frequency alternating acquisition system, we need to transform the broadband input signal to baseband through analogue orthogonal demodulation. Thus, the IQ imbalance errors will inevitably exist, including amplitude imbalance error and phase imbalance error, resulting in distortion deterioration of reconstruction signals. This paper makes an in‐depth study on such IQ imbalance errors and mathematically deduces the mathematical expressions of imbalance errors and the spurious frequency distribution caused by them, which shows that the positions where the spurious signals appear are closely related to the frequency of input signal and the tuning frequency of analogue quadrature demodulation. Meanwhile, the amplitude and phase imbalance parameters of the channels I and Q are also calculated. Finally, the spurious effects caused by imbalance errors are verified by simulation experiment, and the verification results are consistent with the theoretical derivation results.
Highlights
Sampling rate and bandwidth are two key indicators to evaluate the performance of a set of data acquisition systems, and the two indicators are directly reflected in the performance of analogue-to-digital converter (ADC)
Its concept is that the input signal is uniformly divided into several sub-bands in terms of frequency spectrum characteristics, each sub-band is moved to the baseband by analogue IQ quadrature demodulation, and the various baseband signals are sampled using the ADC and the carrier frequency of these baseband signals is recovered with the help of the digital IQ quadrature modulation algorithm, so as to achieve the purpose of reproducing the characteristics of input signal
As this structure involves the two characteristic links of analogue IQ quadrature demodulation and digital IQ quadrature modulation, it is known as a complete orthogonal frequency alternating acquisition structure
Summary
Sampling rate and bandwidth are two key indicators to evaluate the performance of a set of data acquisition systems, and the two indicators are directly reflected in the performance of analogue-to-digital converter (ADC). Its concept is that the input signal is uniformly divided into several sub-bands in terms of frequency spectrum characteristics, each sub-band is moved to the baseband by analogue IQ quadrature demodulation, and the various baseband signals are sampled using the ADC and the carrier frequency of these baseband signals is recovered with the help of the digital IQ quadrature modulation algorithm, so as to achieve the purpose of reproducing the characteristics of input signal As this structure involves the two characteristic links of analogue IQ quadrature demodulation and digital IQ quadrature modulation, it is known as a complete orthogonal frequency alternating acquisition structure.
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