User's Manual

EMS Wireless Operator’s Manual
MirrorCell II CDM 812, CDM1912 Series
608112-1, Rev C
22
Reflector (Dish) Donor
Antenna
Sectorized Panel Server
Antenna
Signal Generator,
approx. 1 watt
output (+30 dBm)
Spectrum
Analyzer
+30 dBm
-70 dBm
Isolation = +30 dBm - (-70
dBm) = 100 dB
Figure 5: Antenna Isolation Measurement Set-up
1. Mount the server antenna at the initially chosen location to obtain the desired
coverage.
2. Inject a known signal within the bandwidth of operation into the server antenna. An
unused channel within the band should be used. The signal should be at least 1
watt to allow for an accurate measurement of isolation. If a 1 watt (+30 dBm) test
source is not available, the repeater and a low-power signal generator can be used
in series to generate a signal of sufficient strength. The repeater will add
approximately 60 – 90 dB of gain, depending upon the repeater model, and how
much attenuation is added to the repeater.
3. Connect a signal measurement device, such as a spectrum analyzer, to the donor
antenna. Measure the received signal level. The RF power difference between the
output of the signal generator and the input to the spectrum analyzer is the antenna
isolation. (Note that the gain of each antenna is not used in the calculation.) This
test should be done once using downlink frequencies and once using uplink
frequencies. Generally both measurements will be similar, but as much as 10 dB
difference can occur. The final result should be the lower of the two measured
values.
Antenna isolation should be measured once the donor and server antennas have been
mounted at their initially desired location. Isolation measurement is important in
properly setting up a repeater. Although isolation can be approximately calculated, an
actual measurement is strongly recommended in most applications.