Overview
As an important type of connector and port for RF and microwave testing, Waveguide is used in a wide range of applications. Among the test applications of vector network analyzers, waveguide interfaces, especially rectangular waveguide types, are one of the common interfaces.
The calibration of the vector network analyzer is the prerequisite and necessary condition for ensuring the accuracy of the test. This paper mainly describes the Rohde & Schwarz vector network analyzer, the introduction method of the calibration component parameters and the precautions in the calibration when applying the waveguide port.
Rectangular waveguide
Cutoff frequency of rectangular waveguide fc=149.9/a (GHz)
Common rectangular waveguide parameters
| Main mode frequency range (GHz) | Inner section size (mm) | TE10 cutoff frequency fc (GHz) | ||||
| Interface model | Starting frequency 1.25fc | Termination frequency 1.9fc | Basic width a | Basic height b | ||
| WR-90 | 8.2 | 12.5 | 22.86 | 10.16 | 6.557 | |
| WR-75 | 9.84 | 15 | 19.05 | 9.525 | 7.869 | |
| WR-62 | 11.9 | 18 | 15.799 | 7.899 | 9.488 | |
| WR-51 | 14.5 | twenty two | 12.95 | 6.477 | 11.575 | |
| WR-42 | 17.6 | 26.7 | 10.668 | 4.318 | 14.051 | |
| WR-34 | 21.7 | 33 | 8.636 | 4.318 | 17.358 | |
| WR-28 | 26.3 | 40 | 7.12 | 3.556 | 21.053 |
Waveguide calibration method
Commonly used waveguide calibration methods are TRL and TOSM
| TRL |
| T:through, straight through, waveguide port directly docked R:Reflect, reflector, corresponding to the crowbar L: Line, transmission line, waveguide segment of known electrical length or time delay |
| TOSM |
| T:through, straight through, waveguide port directly docked O:Offsetshort, offset shunt S:short, short circuiter M: Match, matcher, waveguide load with return loss greater than 20dB |
Calibration data
The vector network analyzer must be calibrated prior to testing. Calibration data must be used in the calibration process to match the calibration components used. This is necessary to ensure the accuracy of the test data.
Import data file
Both Rohde & Schwarz calibrations are accompanied by data files (U disk or floppy disk) that can be imported directly into the vector network analyzer.
Custom calibration data
If there is no corresponding data file, such as a self-made calibration piece, or known calibration parameter data, but there is no electronic data file that the Rohde & Schwarz network analyzer can recognize, it needs to be manually set on the vector network analyzer.
New waveguide interface type
Line Type: Waveguide
Rel.Permittivity: 1.001
Cut off Freq. fc: Cutoff frequency, must be set according to actual parameters (see section 2.2)
New / edit calibration
New calibration piece:
Edit the existing calibration:
>>>Edit calibration parameters
In the Kit Standards window described in the previous section, select the calibration piece to be edited, set the start and stop frequencies (Min Freq / Max Freq), select the calibration piece to be edited, and click View/Modify to set the parameters.
Post-calibration verification
>>>Wavelength waveguide section test results
>>>Load test results
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