Abstract. A fast four channel network analyser is introduced to measure S-parameters in a frequency range from 10MHz to 4GHz. The measurement period of this kind of network analyser is short in comparison with a conventional one, which becomes possible by using highly linear analogue frequency ramps, realized with fractional divider phase locked loop circuits. The settling time for the discrete frequency points, which is typical for a conventional network analyser, is nearly eliminated by the use of frequency ramps.

To achieve the necessary bandwidth of 4 GHz in the baseband, a heterodyne principle is applied. A VCO-signal from 5 to 9 GHz is down converted to the baseband with a fixed frequency generator of 9 GHz. The structure of the following network analyser is similar to the structure of a conventional four channel network analyser and therefore all known calibration techniques are suited for the fast network analyser.

The intermediate frequency, which is necessary for the evaluation, carries the required information. However a special analysis technique is necessary. This technique is based on two Fourier transformations.