While we get the scope’s bandwidth from the vendor, as soon as we add a cable, probe, or amplifier to the scope, we decrease the system bandwidth. The new system bandwidth is as important to know as the scope’s bandwidth, but it is generally difficult to measure except in a calibration lab. We offer a simple method of evaluating the transfer function and system bandwidth of any probing system using a wide band noise source. This method not only gives us information about the probes and interconnects, but it also tells us how the scope responds to the measurement system, information which cannot be measured by a VNA alone.
