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同相/正交(In-phase/Quadrature,I/Q)解调技术广泛应用于射频信号相位控制系统。I/Q器件存在固有误差,如直流偏置、幅度不平衡、相位不平衡和电路长度不等。这些误差会导致输出的I/Q轨迹呈椭圆,相位为非线性,影响相位鉴别的精度。为减小误差带来的影响,提出一种基于I/Q解调技术的软件校准方法,并将此方法在自制基于贴片式芯片集成的I/Q解调印刷电路板上验证。测试表明,输出的I/Q信号经校准后相位误差≤±0.15°,幅度稳定度≤±1%,通道延时≤10 ns。此板卡设计和校准方法已在新升级的上海光源储存环高频束流丢失分析系统中的射频信号前端预处理中使用,各项指标均满足束流丢失分析系统中射频信号监测的要求。
In-phase / quadrature (I / Q) demodulation techniques are widely used in RF signal phase control systems. I / Q devices have inherent errors such as DC offset, amplitude imbalance, phase imbalance, and circuit length. These errors cause the output I / Q trajectory to be elliptical and the phase to be non-linear, affecting the accuracy of phase discrimination. In order to reduce the influence of error, a software calibration method based on I / Q demodulation technology is proposed and verified on a homemade I / Q demodulation printed circuit board based on chip-on-chip integration. Tests show that the output phase I / Q signal after calibration phase error ≤ ± 0.15 °, amplitude stability ≤ ± 1%, channel delay ≤ 10 ns. The board design and calibration method has been used in the RF signal front-end preprocessing in the newly-upgraded high-frequency beam current loss analysis system of Shanghai Light Source Storage Ring. All the indexes meet the requirements of radio frequency signal monitoring in the beam current loss analysis system.