Druckschrift 99810454, New Broadcast Antenna Solutions for Digital ...

T-DMB
L-Band Antennas for Special Applications –
Omnidirectional Antenna using Dual-Polarized Panels
Especially with new services, such as DVB-H and T-DMB the broadcasters often face the problem of having only largediameter
mast sections free for additional UHF and L-Band antennas. However, such mast sections do not permit the
mounting of panels in a compact and centric way in order to create smooth omnidirectional patterns. The resulting deep
minima caused by runtime delays may lead to blank spots in the coverage area.
One adequate solution for avoiding this effect is the use of pairs of dual-polarized radiating elements, particularly for
mobile and portable services.
If the radiating elements are all polarized in the same way, the minima would be created by the runtime-delays of the
overlapping signals of the different panels – see Figure 1.
Figure 1: 4 panels vertically polarized mounted with radius of r/λ = 2
Where dual-polarized pairs of panels are used as illustrated below, no deep minima will show up, because of the
different polarizations in the overlapping zones. As a result, all variations of slant and elliptical polarization may be
created at different angles, which will always provide good signal levels, but with different polarizations – see Figure 2.
Figure 2: Two pairs of orthogonally polarized panels. This setup works
even for large mounting radii r/λ
Since the polarization varies in the coverage area, such an antenna system is especially suitable for
digital mobile and portable broadcasting services where the polarization of the receiving antennas is
not precisely defined.
10
–45°
r
+45° +45°
–45°
r
270 90
10
3
0
dB
0
180
270 90
10
3
0
dB
0
180
Models 750 10094 (+45°) and 750 10194 (–45°)
L-Band Antenna Panel with 70° half-power beamwidth,
3 ° electrical downtilt
Max. power 500 W, height 1302 mm