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Advanced Antennas for Radio Base Stations 153

4.8.2 Field Trial
The performance of a modular high-gain
antenna, as shown in Figure 4.15, was
verified in a field trial in a live GSM 1900
20
network. A cell with small terrain varia-
tions served by a base station with a 28m
high tower was selected for the trial. The
performance of two different antennas was
compared: a reference sector antenna with
18 dBi gain (with 2° electrical beamtilt)
and a dual-subpanel modular high-gain
sector antenna with 22.8 dBi gain.
Figure 4.16 shows a sample of measured
received signal strength on downlink along
a radial road emanating from the trial site
for a 22km long measurement segment. A
very small part of the cell, the first kilo-
meter of the measurement segment near
the base station, experiences better signal
strength from the reference antenna. Even
so, in this part of the cell, the high-gain
antenna provides a very good signal with
approximately –60 dBm or better signal
strength, in part as a result of radiation Figure 4.15 Three-sector modu-
pattern null-filling. Test results show an lar high-gain antenna with two
subpanels installed in a tower

Figure 4.16 Measured downlink received signal strength for reference sector
antenna and modular high-gain sector antenna (MHGA). The modular high-
gain antenna coverage at small radii is maintained by null-filling.