User's Manual

Powerwave Fiber Optics

VM100 56/EN – User’s Manual Rev. P1A9-Draft 2004-11 4 - 3

Downlink RF Signal Path

The downlink RF modulated signal path, from the BTS to the repeater antenna, is shown

in Figure 4-2. The item numbers in the figure are described below.

Figure 4-2. Downlink RF transmission path

1. DC coupler

The DC coupler on the BTS antenna path picks up the BTS downlink signal with a fixed

coupling loss of 20dB.

The left figure shows the DC coupler connected to the BTS antenna path and the BTS

downlink amplifier with a typical noise figure of 5dB.

The values in the figure are typical values that can vary from one system to another.

2. DPX duplex filter

A Powerwave duplex filter separates the downlink and uplink signal frequencies

between the BTS antenna path and the separate input/output RF ports of the FON unit.

The Powerwave DPX filter has a typical loss of 1dB.

3. Power attenuator

An input 16dB/8W power attenuator is a security attenuator for the FON unit.

4. Software adjustable attenuator

The software adjustable 0 – 20dB attenuator is set manually via an O&M software. This

is described in the FON section of the VM100 01/EN, OM-Online, User’s Manual.

The attenuator should be set to a calculated value that attenuates the signal power to

0dBm to the following optical transmitter.

Example: Presume the typical values in the figures above are used, that is:

– BTS output = 40dBm

– DC coupler loss = 20dB

– DPX filter loss = 1dB

– power attenuator = 16dB

Set the attenuator to 3dB (40dBm – 20dB – 1dB – 16dB = 3dB).

BMU

FOR

TX RX

2 3 4 5 6 7 8 9 10 11

FON

NF 5dB

40dBm

20dB

BTS

BMU

16dB, 8W

0 – 20dB