What is Alias Free Zone and How Does it Calculate?
In VNAs the bandwidth is limited when the Fourier transform is done from band limited frequency samples. The transformation is a periodic signal in time domain which is a continuous signal. Measurements are accurate if maintained in the alias free range which is the inverse of the step frequency divided by 2. The smaller the step frequency gives you a wider alias free range, whereas the wider the bandwidth will give you a finer resolution. This video shows the frequency starts at 10 MHz to 20 GHz with 2000 points that translates to a 10 MHz step frequency. In this case the alias free range is 50 ns. This video will go into more details on the alias free range and calculations.