模拟正交调制技术是合成孔径雷达(SAR)宽带激励信号产生中最常用也是最重要的技术手段之一，随着雷达系统瞬时带宽越来越大，模拟正交调制的IQ一致性特性无法仅依靠器件的对称特性来保证，而IQ不平衡在宽带雷达发射系统中带来的杂散失真会随着链路逐级恶化。针对上述情况，提出一种数字预失真补偿方法，通过对整个发射通道进行系统误差建模并搭建测试系统，能够提取包含正交调制IQ不平衡在内的整个发射链路上的所有幅相误差，并将幅相误差映射到数字基带信号输出的IQ支路上，通过数字预失真的方式补偿发射通道的幅相失真，使得输出的雷达激励信号具有接近理想的幅相特性。最后结合实际的雷达发射系统，利用预失真算法对整个发射链路进行失真校正，给出校正前后的测试对比结果，通过测试表明方法的有效性。
Analog I/Q modulation technology is one of the most commonly used and important technical means in broadband synthetic aperture radar (SAR) exciter design. With the increasing instantaneous bandwidth of radar system, the amplitude-phase consistency of analog I/Q modulation can not be completely guaranteed by the symmetrical characteristics of devices, and the spurious distortion caused by the IQ imbalance in broadband radar transmission system will deteriorate progressively. This paper proposes a digital predistortion method which can extract all amplitude-phase errors on the whole transmission channel， mainly including IQ imbalance， by modeling the system error and building a test system, map the amplitude-phase errors to the IQ branch of digital baseband signal output, and compensate the amplitude-phase distortion of the transmission channel. Finally, combined with the actual radar transmitting system, the distortion of the whole transmitting link is corrected by using the predistortion method. The test results before and after correction are given， demonstrating the effectiveness of the method.
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