两个矢量合成调相电路的等价分析

阿姆斯特朗调相和双调幅矢量合成调相都是“高频电子线路”课程中的矢量合成调相电路。由于先天的缺陷，阿姆斯特朗调相存在相位非线性失真和寄生调幅等问题，只有当调相指数较小时，相位失真和寄生调幅才显得不突出，因此这种方法是一种近似的方法。双调幅矢量合成调相与阿姆斯特朗调相看似是两种完全不同的电路，且一般教材中也不指出双调幅矢量合成调相存在的问题。以数学方法证明两个电路是完全等价的，据此可以断定双调幅矢量合成调相也存在与阿姆斯特朗调相同的问题，且完全可以用后者来替代。

The Equivalent Analysis of Two Vector Composing PM Circuits

The Armstrong Phase Modulation （PM） and Double Amplitude Modulation （AM） vector composing PM both are vector composing style circuits in the course ＂Radio Frequency Circuits＂. Due to having innate defects of nonlinear phase distortion and parasitical AM, the properties of Armstrong PM are not good unless the modulation exponent is small enough. Therefore, the Armstrong PM is an approximate circuit. The double AM vector composing PM is a different circuit from the Armstrong PM in structure, and its defects are not pointed in general teaching material. The equivalence of two circuits are proved in this paper by mathematical method. So, the double AM vector composing PM has same problems with Armstrong PM and can be replaced with the latter completely.