First of all to choose the appropriate bandwidth of the device. If the bandwidth is too narrow, the measured edge rate will be very low.A lower along - speed translates the amplitude noise into more time - domain errors.However, if the band is too large, it will only increase the thermal noise and particle noise in the test and thus improve the noise bottom.In terms of NRZ code stream, a rule of thumb is to select a bandwidth 1.8 times the code rate.
Next, the sampling rate should be improved to avoid aliasing due to undersampling. In theory, the sampling rate is at least twice the signal's highest fundamental frequency.In fact, the analog signal shaping and data transformation during the capture process will leave a margin, so the oscilloscope really needs a sampling rate of 2.5 to 3 times the highest fundamental frequency.Therefore, the bandwidth sampling rate ratio of the oscilloscope is about 1 to 3.
It is important to increase the longitudinal resolution of the instrument to reduce ADC quantization errors.Adjust the voltage/scale knob until the graph enters the vertical range of the screen.Excessive ADC changes will saturate, and dissatisfaction will reduce SNR.
It is also important to measure the TIE dithering base Settings because this is equivalent to an adjustable high-pass filter. The time base sets the minimum TIE frequency at time of capture (oscilloscope bandwidth determines the highest dithering frequency).
Similarly, make sure that the test data pattern contains the correct spectrum component range and only the real spectrum component. When using the PRBS code, the code length should be long enough to ensure that the low-frequency component is captured without exceeding the storage range of the instrument.
Always reduce the delay between the trigger and the first sampling point.After the signal is triggered, the timing uncertainty is proportional to the length of the time base waiting for the sampled data.Reducing latency reduces this uncertainty and therefore reduces the measured jitter value.
Avoid oscilloscope homogenization waveform, select sin (x) /x interpolation between data points, and use large fast trigger.Finally, the trigger level is set to match the actual system receiver threshold level, otherwise it is set to half the waveform value.