| 摘要 |
These types of modulation distortion have previously been measured with constant modulation. The invention allows them to be measured modulation-dependently over the link. The section under test is supplied with a test signal with constant weak amplitude modulation percentage, the amplitude of which is swept between an (adjustable) maximum value which approximately corresponds to the modulation limit of the relevant section under test, and a minimum value, which is a fraction (about 10 %) of the maximum value in accordance with a known time variation, and an output signal of the section under test is examined for modulation-dependent variations of its phase modulation index and of its amplitude modulation percentage. In microwave links operated with QAM, the said types of modulation distortion can result in complete signal corruption. Their accurate knowledge is therefore of particular importance in this case. <IMAGE> |
