The response characteristics of the oscilloscope will affect the waveform of the signal and change the calculation of the signal rise time. When Pentium 4 entered the gigahertz era, high-speed interfaces or buses such as Serial ATA and PCI Express also gradually surpassed Gbps. Choosing the appropriate probe is of course an important thing, but choosing the appropriate oscilloscope is also indispensable.
The measured waveform is sampled and signal processed from the input connector to be displayed on the screen while the data is saved. Once an inappropriate oscilloscope is selected, the waveform may be distorted. Especially when measuring waveforms of high-speed serial interfaces such as PCI Express, it is not only necessary to measure the sampling frequency and bandwidth, but also to understand the response characteristics of the oscilloscope. For example, when measuring very steep signal changes, there will be differences due to differences in the response characteristics of the oscilloscope.
The response characteristics of an oscilloscope generally refer to the "transmission characteristics" of the entire measurement system from the input connector to the screen display. Generally, it can be divided into two categories: Gaussian Response type reaction system and Brick-wall Response type reaction system. Brick wall response system is also called flat response.
To distinguish or compare the differences between these two types of systems, the easiest way is to look at the two basic parameters of "-3dB frequency characteristics" and "step waveform response".
When measuring the waveform of a high-speed serial interface, a real-time sampling broadband digital oscilloscope is generally used. This type of oscilloscope mostly uses a brick wall response type response system.
The response characteristics of the brick wall response type are also called "the highest flat response". The frequency response is extremely flat within the frequency band, but when it reaches the roll-off outside the frequency band, the signal is quite steep. With such ideal frequency characteristics, there will be no attenuation of the signal amplitude within the frequency band. Beyond the frequency band, the signal amplitude becomes zero.
