frequency domain reflectometry
In frequency domain reflectometry, a sweep of the transmission line input frequencies is performed. The reflected signals are then reconstructed by converting them to the time domain using Inverse Fast Fourier Transform (IFFT). Compared to TDR measurements, one advantage of this measurement method is that it does not involve as much power as would be required for a single pulse, because the energy of the injected signal is spread over a longer period of time. Thus, in many cases, a greater measurement coverage can be achieved. In addition, the risk of damaging components in the measured system due to the pulse power introduced is reduced.
There is a separate device category for FDR measurements, but these can also be carried out with the aid of a vector network analyzer (VNA).