Measurements of microwave circuits with the vector network analyzer
The goal of the exercise.
The goal of the exercise is to gain knowledge regarding the measurement capabilities of
vector network analyzers (VNA), with the emphasis on range and type of measurements
allowed to be performed. The above is obtained by:
getting the overall knowledge of the VNA’s principles of operation,
getting the knowledge of basic measurement procedures,
measurement of selected microwave circuits.
The description of a VNA can be found in e.g. Golio Mike, “The RF and microwave
handbook”, description of impedance matching can be found in Pozar D. “Microwave
Engineering”.
Exercise program.
Measurements of the scattering parameters (amplitude and phase characteristics) of the
following microwave components:
branch-line coupler,
coupled-line coupler,
band-pass filter,
low-pass filter,
band-reject filter,
1-port element.
The measurement rules
Caution. Connection of microwave components to the analyzer is done with strict
supervision of the tutor!
1. Frequency range set-up 45 MHz – 4 GHz.
2. Calibration of the VNA with the use of open short and matched load. Caution
calibration is valid only for the frequency range set-up for the calibration procedure.
Therefore, change of frequency range requires recalibration.
3. Connection of the measured device.
4. Measurement of the basic parameters of the devices such as: center frequency, cut off
frequency, attenuation is stop-band and pass-band, coupling, transmission, isolation,
directivity with the use of markers.
5. Saving the selected responses (S parameters) on the computer.
6. The measurement report shall consist of description of the measured devices with
emphasis on their properties. The saved characteristics shall be appropriately plotted
and commented. For the measured 1-port device a matching circuit shall be designed
at the frequency specified by the tutor. This task can be done in any freeware
microwave circuit analysis software such as Ansoft Designer SV, Serenade SV, or can
be performed in the lab using Microwave Office software.