微波幅相接收机的低中频正交优化结构

为解决微波毫米波幅相接收机的频率偏移超过中频带宽的问题,提出了一种低中频正交接收机结合双边带抑载的优化结构.利用频率误差对消的方法,获得了稳定的低中频信号,不包含微波本振源的频率偏移且保持了2路输入信号之间的相位关系.它的2路中频通道不对称,其中一路用一个晶体振荡器产生的正弦波预调制,对消过程用模拟乘法器和正交解调器在第1中频实现.与频率误差跟踪不同,它避免了锁相环引入的寄生调制和复杂性.分析了其性能,包括I/Q幅相不平衡的误差和校正.概述了一个实际的基于此结构的微波接收机,该接收机的特点是电路结构简单、成本低和小型化,性能测试结果和实际应用表明其具有较高的灵敏度和精度.

Optimal low-IF quadrature architecture for microwave amplitude and phase receivers

To solve the problem of frequency offset out of intermediate frequency(IF) bandwidth for microwave and millimeter wave amplitude and phase receivers, an optimal architecture of low-IF quadrature receiver combining with double-sideband suppressed-carrier(DSBSC) was presented. The frequency error canceling method was employed to achieve stable low-IF signal, which excluded the frequency offset from microwave local oscillator and kept the phase relationship between two input signals. Its two IF channels are asymmetric in that one of them was pre-modulated by a sine wave generated by a crystal oscillator. The canceling process was fulfilled by an analog multiplier and a quadrature demodulator at the first IF. Differing from frequency error track, it avoid spurious modulation and complexity caused by phase-locked loops. Its performances, including error and correction of I/Q imbalance, were analyzed. A practical microwave receiver based on this architecture was outlined. The results of performance test and practical application show high sensitivity and accuracy of the receiver, characterized by simplified circuits, low cost and miniaturization.