宽带I/Q平衡、低失真的微波光子正交混频理论与方法

Zero-intermediate-frequency (zero-IF) receiver based on a microwave quadrature mixer features the advantages of compact structure, easy integration and flexible working frequency. However, conventional microwave quadrature mixers suffer serious problems such as bandwidth limitation, electromagnetic interference, inphase/quadrature (I/Q) amplitude/phase imbalance, direct current (DC) offset, and even-order (mainly the second-order) distortion, and so the applications of the zero-IF receiver in electronic systems face difficulty. In this project, the microwave photonic theory and technology are introduced into zero-IF receiver. Taking the advantages of large bandwidth, low frequency-dependent loss, and immune to electromagnetic interference of the photonic technology, the theory and method of microwave photonic quadrature mixer with wideband I/Q balance and low distortion for zero-IF receiver are studied. The research mainly includes microwave photonic quadrature mixing with wideband I/Q amplitude/phase balance, balanced detection with suppressed DC and second-order distortion, and high-purity microwave photonic harmonic quadrature mixing. By exploring the characteristics and fine-tuning methods of the I/Q amplitude/phase, and the origin and variation rules of the DC offset and second-order distortion, we try to propose the solution of microwave photonic quadrature mixing with wideband I/Q balance and low distortion. This work may provide theoretical and technical supports for future electronic systems with large instantaneous bandwidth, wide working band, portable flexible, and immune to electromagnetic interference.

基于微波正交混频的零中频接收机具有结构紧凑、便于集成、工作频率灵活等优点，然而传统的微波正交混频器面临带宽受限、电磁干扰、I/Q幅相失衡、直流偏移和偶阶（主要是二阶）失真等严重问题，限制了零中频接收机在电子系统中的广泛应用。本项目将微波光子学这一新兴学科的相关理论和技术，引入零中频接收机，利用光子学大带宽、低频率相关损耗、无电磁干扰等优势，开展面向零中频接收的宽带I/Q平衡、低失真的微波光子正交混频理论与方法研究。具体通过研究宽带I/Q幅相平衡的微波光子正交混频、抑制直流与二阶失真的平衡探测，以及高频谱纯度的微波光子谐波正交混频理论与方法，阐明宽频带I/Q幅相特性及精细调控方法、直流和二阶失真的产生及变化规律，提出宽带I/Q平衡、低失真的微波光子正交混频的解决方案，为未来大瞬时带宽、宽工作频段、轻便灵活、抗电磁干扰的电子系统提供有力的理论和技术支撑。

为了解决传统微波正交混频器面临的带宽受限、电磁干扰、I/Q幅相失衡、直流偏移和偶阶失真等严重问题，本项目将微波光子学这一新兴学科的相关理论和技术引入零中频接收机，利用光子学大带宽、低频率相关损耗、无电磁干扰等优势，开展面向零中频接收的宽带I/Q平衡、低失真的微波光子正交混频理论与方法研究。.在宽带I/Q幅相平衡的微波光子正交混频研究中，研究了宽频带内幅度一致的微波光子双通道下变频，对两个下变频通道进行幅度和相位调控，实现了宽带I/Q平衡的微波光子正交混频。重点阐释了微波光子正交混频中I/Q幅相特性及精细调控方法，提出一种基于双平行马增调制器和波分复用器的微波光子I/Q下变频系统，在10-40GHz的工频带宽内实现幅相精细调控，相位不平衡小于1.3°，功率不平衡小于0.28dB。.在抑制直流与二阶失真的平衡探测研究中，深入探索了直流偏移和二阶失真的产生和变化规律，根据互补通道共模抑制机理，采用偏振分束器和偏振控制器实现了高效率的平衡探测，直流偏移和二阶失真明显得到抑制，转换增益、噪声系数和动态范围均有一定提升。.在高频谱纯度的微波光子谐波正交混频研究中，探索了微波光子谐波产生与混频过程中各阶光谐波随调制指数、调制器工作点、调制器消光比、偏振态等的变化规律，提出了基于偏振复用双平行马增调制器的微波光子I/Q下变频方案，实现二次谐波I/Q下变频，工作带宽10-40GHz，I/Q相位不平衡<1度，功率不平衡<0.7dB。.研究得到如下结论：微波光子正交混频可解决传统微波正交混频器面临的带宽受限、电磁干扰、I/Q幅相失衡、直流偏移和偶阶失真等问题，预期可有效应用于零中频架构的射频接收机，提高系统瞬时带宽、工作频段、轻便灵活度、抗电磁干扰能力，提升我国军民电子装备的性能。