A Digital Microwave Network Analyzer

A new method for amplitude and phase measurements of time harmonic microwave signals is presented. By means of a harmonic mixer the HF signal is mixed down to an IF frequency, sampled and then processed digitally in a minicomputer. As the IF signal is processed digitally it is not necessary that the IF frequency is fixed, which means the local oscillator need not be phase locked. The accuracy of the analyzer depending on the signal-to-noise ratios of the test and reference signals is considered. With the aid of a special signal processing hardware amplitude and phase can be measured at a few hundred frequencies per second. Finally a simple version of the analyzer using a two-channel sampling oscilloscope is shown.