User Manual

INSTALLATION GUIDE
Proprietary Information
Title: BEAMER Array System-
Assembly and Operation Manual
Doc. No.: 913000100 Rev.: 00
Page: 53 of 92
The BEAMER -Rx programming property offers the system integrator the tool for calibrating the
system gain, in full accordance with the above rules.
The proper trade-off between these rules should be found. As an example, if the two Rx channel are
very much unbalanced an excessive gain increase might be required at one channel, causing possible
interference susceptibility on that channel.
Since it is impossible to accurately calibrate the BEAMER system reverse link gain without removing
the antenna element (thus, effectively disassembling the array) the gain balance will be calibrated
using an external low power CW transmitter located at short range (50-100meters) away from the
array, transmitting at vertical polarization.
2.8.6.1. Estimating the Required Rx-ABT and BEAMER Rx Gain
The purpose of this procedure is to verify that the BEAMER system available gain is sufficient to
cover the expected RF losses, before starting the actual Rx calibration.
1. Measure or estimate, according to the RF cable's vendor specifications, the RF losses over the Rx
RF cable. Typical loss for ½" cable is 0.11db/meter or about 5.5dB/50meters. (L
RX-CABLE
)
2. Measure or estimate the minimum input power to the BTS down-converter required for the AGC
bias point at maximum BTS down-converter gain (P
BTS
)
3. Using G BEAMER =25dB, estimate the needed gain from the Rx-ABT:
G(Rx-ABT)=P
BTS
-(-120dBm+G BEAMER -0.5dB- L
RX-CABLE
)
4. If the estimated G(Rx-ABT) is higher than 6dB, increase G BEAMER to get (Rx-ABT)~6dB. The
maximum available BEAMER -Rx gain is 30dB. If this limit is reached, you should use a lower loss
RF cable.
5.If the estimated G(Rx-ABT) is lower than -3dB, reduce the Rx- BEAMER gain and increase the Rx-
ABT gain. To avoid affecting the system noise figure, do not reduce the Rx- BEAMER gain below
20dB.
6. Record the required G(Rx-ABT) and G BEAMER.
2.8.6.2. Calibrating the Actual Reverse Link Gain
Calibrating the Rx channels is straightforward, using the ABT-Rx programming feature. However,
testing the actual calibration is not immediate, since, unlike the Tx channel calibration, power level
monitoring is not available for the Rx channels.
Rx channel calibration is performed by measuring the received Rx channels RF level, using a
reference mobile CDMA transmitter, or by measuring the background noise level for each receiver
using the BTS built-in software and hardware level measurements aids. These procedures, although
not requiring special test equipment, do require some interaction within the BTS software and
hardware. We leave this procedure for the customer's engineering personnel. Celletra will provide the
customer the needed technical support for performing the tests.
Note, however, that both the ABT-Rx gain and the BEAMER -Rx gain are calibrated to ±1dB (a total
of ±2dB uncertainty). We can thus guaranty, with good confidence level, that the RF front-end gain is
balanced within ±2dB for both Rx channels.
1. Connect the BEAMER array to the ICU's ABTs, for both Rx channels.
2. Using a PC or the BTS controller software, set the Rx- BEAMER and both Rx-ABT gain to the
computed required gain.