Bandwidth and Storage Capacity of Oscilloscope
1. How important is bandwidth to oscilloscopes?
Engineers also mentioned categories, that is, bandwidth is not the only measure. High bandwidth also means more noise. How to deal with this problem?
In fact, oscilloscopes with the same bandwidth exhibit different rise times because the bandwidth is determined at -3 dB without providing any information about the linearity of the frequency response or phase response. Different amplifier characteristics (filter characteristics) lead to a more or less sharp decline in frequency response at high frequencies, which will lead to considerable fluctuations in the available bandwidth of the amplifier. However, for applications, errors occurring along the rising edge of measurement are critical. In addition, in data signals, the influence on the opening of eye maps is also significant. For this reason, the rise time index is very important for the equipment (oscilloscope) that performs the measurement in the time domain. Through this indicator, users can understand the measurement data more easily.
Noise depends not only on the bandwidth, but also on the steepness of the descent beyond the bandwidth limit. It is necessary to achieve a good balance between linear frequency response, moderate drop, ideal pulse characteristics and noise. In our device, you can limit the available bandwidth of a given application, and greatly reduce noise by adjusting the bandwidth of the DSP (Digital Signal Processing) in the vertical menu.
2. What does maximum storage mean? Current standards do not use maximum storage capacity, but which applications do?
The maximum storage capacity determines the recording time of the oscilloscope. The storage capacity of 250M points and the sampling rate of 100 GS/s (= 10 ps/point) will produce the maximum recording time of 2.5 Ms. This time can only be improved by reducing the sampling rate. The oscilloscope using DSP frequency response correction technology is not allowed to do so, so the measured signal may be misunderstood. In our instrument, we can activate the DSP and reduce the sampling rate to Nequist frequency (sampling rate > 2 times input bandwidth); we can also turn off the DSP and select arbitrary sampling rate, which can significantly improve the recording time.
For jitter measurement, recording time determines the lower limit of jitter frequency for correct measurement. At 50 GS/s and 250 MB, the jitter frequency decreases by about 600 Hz. For most standards and applications, 30 MB of storage capacity is usually sufficient.
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