RadiMation Application Note 103
How to determine the antenna diagram of an antenna
This [[::Category:RadiMation Application Note|Application Note]] will explain how measurements can be done in RadiMation® to determine the antenna diagram of an antenna on one or more frequencies. RadiMation® is not designed to perform antenna diagram measurements, but due to its flexibility it is possible to perform this type of measurement.
Overview
Fixed and stable signal applied to antenna. Can be a signal generator, or an EUT that contains the antenna that generates a stable signal Measure it depending on the turntable angle.
Hardware configuration and preparations
The antenna of which the antenna diagram that should be determined, should be placed on the turntable. It is also possible to connect the antenna on the turntable
It is required that the used RadiMation® license contains the Radiated Emission module.
Create a new EUT that represents the antenna that is being measured. This EUT file is also used to store and maintain the measurements results.
In RadiMation a testsite should be selected that has the - Turntable: - Antenna: The receive antenna - Spectrum analyzer: - (optional) cables: to correct for cable loses - (optional) preamplifier: an external preamplifier between the receive antenna and the spectrum analyzer to amplify the received signal All corrections that are selected in the selected equipment will be taken into account when the measurement results are shown. The transmit antenna (of which the antenna diagram is being determined) is not included in the testsite. The transmit antenna is represented
In this application note we used a virtualized setup, which uses the Virtual Spectrum Analyzer and the virtual Turntable. This virtualized setup has a signal on .... MHz, which fluctuates depending on the turntable angle. It can be used to demonstrate the capability of RadiMation® to determine the antenna diagram. This same measurement can also be performed on any RadiMation® installation
Frequency measurement to determine the frequency
Multiband emission, applicable frequency range Measure on the turntable angle on which the highest antenna gain is expected. No need to specify a limitline Detect a single peak. Ensure that it is listed in the table of peaks Only necessary to use the peak detector. Also for final measurement. Short measure time for final measurement.
- screenshot of TSF setup -
Verify if the correct peak is selected. Select a single peak that should be measured. A peak can be selected by clicking with the mouse on the signal in the graph. RadiMation® will then automatically mark the clicked signal as a new peak to the list of detected peaks.
- screenshot with frequency graph with selected peak -
Performing the angle measurement
Switch to the Polar graph. It will show the amplitude and the turntable angle on which the value was measured. Ensure that only the peak final measurement detector is activated. Activate the continuous measurement mode.
- screenshot of polar graph. No polar trace yet -
Press the Turn CW and Turn CCW buttons. Pressing the Turn CW or Turn CCW button again while it is pushed, will stop the turning. Can have benefit to first turn to a start angle (for example -180 degrees), and then start the 'continuous measurement mode' by pressing the Continuous measurement mode button. Then press the Turn CW which will start a complete turntable rotation. During the turntable movement, the continuous measurement on the selected peak will be performed and the measured data will be updated in the polar graph. The antenna diagram will be determined and shown in the polar plot dynamically.
Multiple rotations of the turntable can be performed, however due to the speed of the turntable and spectrum analyzer this very often results in measurements at slightly different turntable angles. If also the amplitude of the signal generator has changed, this can cause that the measurements are shown as a triangle wave. In this situation it is best to press the Clear Results button, which clears the measurement data of the selected peak. This will cause that the polar plot becomes empty again, and a new measurement can be performed.
After the measurement is finished, press the Continuous measurement mode button to stop the continuous measurement.
- Screenshot of polar graph, showing a complete antenna diagram of the peak -
Multiple frequencies
Measurement of multiple frequencies and the antenna diagrams for those frequencies is also possible within the same test. Just select additional peaks in the frequency graph. The polar plot only can show the measurement results of a single peak. The information of the peak that has the selected checkbox in the list of detected peaks will be shown. When multiple peaks are added to the list of peaks, the rotation of the turntable with an activated 'Continuous measurement mode' should be repeated for each peak.
Automated measurement of multiple frequencies
If multiple frequencies should be measured, it is also possible to perform the measurement automatically. The TSF can be configured to perform measurements on multiple angles. The measurement results at these different angles are also used to determine the results as it is shown in the polar plot. It is for example possible to perform a measurement on every 10 degrees of the turntable. The peaks can be automatically detected by RadiMation® or manually selected in the frequency graph. For all of the determined peaks a polar plot with a 10 degrees accuracy will be available. This polar plot of the peaks can then always be further improved by performing the 'Continuous measurement mode' manually, for the relevant turntable range.
- screenshot of TSF with multiple angle measurement -
Reviewing the measurement results
The measurement results are automatically saved when the test is closed. When the test is reopened from the EUT File, it is possible again to switch to the polar plot graph on the Polar tab. The antenna diagram of the antenna for the selected peak frequency will then be shown again.
