Antenna position

Measurements shall be made on the left and right sides of the vehicle.

The horizontal distance is from the reference point of the antenna to the nearest part of the vehicle body.

Multiple antenna positions may be required (both for 10 m and 3 m antenna distance) depending on the vehicle length. The same positions shall be used for both horizontal and vertical polarization measurements. The number of antenna positions and the position of the antenna with respect to the vehicle shall be documented in the test report.

- if the length of the vehicle is smaller than the 3 dB beamwidth of the antenna, only one antenna position is necessary. The antenna shall be aligned with the middle of the total vehicle (see Figure 1)

- If the length of the vehicle is greater than the 3 dB beamwidth of the antenna, multiple antenna positions are necessary in order to cover the total length of the vehicle (see Figure 2). The number of antenna positions shall allow to meet the following condition :

With:
N: number of antenna positions.
D: measurement distance (3 m or 10 m).
2×β: 3 dB antenna beamwidth angle in the plane parallel to ground (i.e. the E-plane beamwidth angle when the antenna is used in horizontal polarization, and the H-plane beamwidth angle when the antenna is used in vertical polarization).
L: total vehicle length.

Depending of the chosen values of N (number of antenna positions) different set-up shall be used:
if N=1 (only one antenna position is necessary) and the antenna shall be aligned with the middle of the total vehicle length (see Figure 1).
if N>1 (more than one antenna position is necessary) and multiple antenna positions are necessary in order to cover the total length of the vehicle (see Figure 2). The antenna positions shall be symmetric in regard to the vehicle perpendicular axis.

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