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微分增益失真(DG)和微分相位失真(DP)是两个重要的彩色电视信号失真参数。本文从电视信号的角度证明了一种用计算机软件进行的 DG、DP 的数字测量方法。这种方法的特点是所求的幅度和相位参量可以直接用四个取样点的样值的简单函数来表示,并且不要求取样点必须在指定的位置上,因而简化了软件算法和外围定时系统。文中接着分析了使用这种方法时系统分辨率的极限情况,并指出了安排取样位置的原则。最后,本文还给出了在这种方法下采用不同的 ADC编码位数时系统分辨率的实际计算值。由于 DG、DP 的测量事实上归结为用很少的取样点获取正弦波的幅度和相位信息,因而本文的结论对数字测量技术具有一般的意义。
Differential Gain Distortion (DG) and Differential Phase Distortion (DP) are two important parameters of color TV signal distortion. In this paper, a digital measurement method of DG, DP by computer software is demonstrated from the perspective of television signal. The characteristic of this method is that the desired amplitude and phase parameters can be expressed directly as simple functions of the samples of the four sampling points and the sampling points must not be required to be in the specified positions thus simplifying the software algorithm and the peripheral timing system . The paper then analyzes the limits of the system resolution when using this method and points out the principle of arranging sampling locations. Finally, this article also gives the actual calculation of the system resolution when using different bits of ADC coding in this method. Since the measurement of DG and DP actually comes down to obtaining the amplitude and phase information of the sine wave with a few sampling points, the conclusion of this paper is of general significance to the digital measurement technique.