磁光盘片载噪比特性的自动测试方法

Automatic Measurement of Carrier to Noise Ratio for Magneto-Optical Disks

分析了实现磁光盘载噪比CNR指标自动化测试的障碍和谱信号的特性，针对CNR测试中存在的特殊性，即测试精度依赖于对载波频率处的信号谱幅值和噪声谱幅值的测量误差，而与两者出现的时间无关．提出单轴等时间测试方法，最大限度地利用8098微控制器的内部资源，在保证测试精度足够的基础上实现了数据采集电路结构最简．

The difficulties met in the automatic measurement of the carrier to noise ratio (CNR) for magneto-optical disks is discussed, and the spectrum signature of the signals produced by spectrum analyzer is analyzed. According to the particularity in CNR test, the measurement accuracy is dependent only on the measurement error of the spectrum amplitudes of signal and noise at the carrier frequency, but not on the time when they are occurred. On the basis of comparison made between several data acquisition schemes, uniaxial identical interval sampling method is put forward. With the method, only the y-axis signals out from the frequency spectrograph are needed to be sampled. The optimum time to start and to end the sampling are determined by a sampling clock generator. The signal spectrum amplitude is found by software. The inside resource of type 8098 microcontroller is utilized in a best possible way, and the necessity to extend further A/D device is avoided. As a result, a simplest structure of the data acquisition module is obtained with a fairly high accuracy being guaranteed.