Project Description
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Project Starting Date
03.07.2023
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Project End
01.08.2023
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Category
Research, RF measurement
Project Description
The radiation characteristics of the antenna system (AS) at the TWC Blatný Vrch site were measured using a Pixla 1 and a DJI Matrice 300 quadcopter. Measurements were performed on three frequencies of transmitters, grouped into AS.
The measurement was rather complicated, because the centre of the AS was not identical with the centre of the mast on which the AS was mounted together with other devices. First of all, it was necessary to accurately locate the centre of the mast and the centre of the AS and to correct the quadcopter flight program in both horizontal and vertical planes based on these two data. Several factors had to be taken into account when selecting the circling distance. First of all, the quadcopter must avoid any obstacles that were near the supporting mast. The distance from the centre of the AS must fall within the Franhouffer radiation zone and only the forward wave (no/minimal reflections) must be incident on the Pixla 1 measuring device. These requirements are quite stringent and therefore almost a full day of work was required to create the flight plan and position Pixle 1. The work was also complicated by the relatively low height of Blatný Vrch and its relatively flat topography, which allowed the existence of undesirable reflections.
The Challenge in the design
The measurement was carried out in the evening of 3.7.2023 at the transmitter Blatný Vrch near Lučenec. Three circular flybys of the tower were made at 72m, 90m and 170m. So too is the rotation of the quadcopter with the Pixla 1 around its axis at the geometric centre of the antenna system, rising to a height of 130m above the mast foot and dropping to a height of 20m above the ground in three azimuths of 15°, 55° and 330°. The azimuths were chosen based on the main radiating lobe of the AS and on minimizing reflections from the ground surface.
Three transmitters with RPM 10kW were measured. Data acquisition was performed every second, recording the position of the Pixla 1 device, the three strengths of the electric component of the electromagnetic field and the exact time of the measurement.
After the replacement of the system, a second measurement was carried out on 27.07.2023 in the morning hours. The second measurement was to confirm the correct placement of the antennas in the AS and the shape of the radiation characteristics identical to those in the Telecommunications Authority permit for the Blatný Vrch facility. After evaluating the data from the first, second measurement and the permit, we found a perfect match of the characteristic with the desired one, for all measured frequencies.
Results of directional characteristic measurement after statistical processing.
- We were able to simultaneously measure 3 directional characteristics
- Relatively data intensive – script/program needed to evaluate polar angle and relative electric field strength
- The measured directional characteristics have the expected shape (obtained from the permit)
- We have minimised the effect of reflections on measurement accuracy
