User Manual

MBF, Multi Band Repeater
PRODUCT DESCRIPTION AND USER'S MANUAL
© Axell Wireless Ltd A 200 93 00, rev E 13 (105)
where the BTS signal strength is large enough to be usable by the system. Ideally the repeater’s donor
antenna should have line of sight (LOS) contact with the BTS antenna. If the signal strength is high enough,
LOS may in some cases not be necessary.
The signal generated by the BTS is picked up at the repeater site via the donor antenna. The repeater filters
and amplifies the signal before retransmitting it at the same frequency over the server antenna.
The isolation between the antennas at the repeater site has to be high in order to prevent degradation of signal
quality and risk of oscillation. Ways to achieve this can be large physical separation between the antennas,
usage of highly directional antennas with good front-to-interference ratio or external shielding between the
antennas. Another option is to use a Frequency Translating repeater (see description below).
Channel selective repeaters may have higher output power per carrier and typically have better spurious
rejection than band selective repeaters. The maximum output power per carrier can be several watts.
1.2.2 Band Selective Repeaters
Band selective repeaters have the same functionality as channel selective repeaters. The difference is that
band selective repeaters do not separate out specific carriers but amplify and retransmit all signals within a
defined frequency band.
The risk for intermodulation distortion leads in most cases to a lower output power per carrier in a band
selective repeater than in a channel selective repeater.
1.2.3 Frequency Translating Repeaters
A frequency translating repeater provides output power levels comparable to a base station. The concept
allows for high gain without the high antenna isolation required for channel selective repeaters.
The frequency translating repeater consists of two units; one donor unit and one remote unit.
Donor Cell
Base Station
Remote unit
Server antenna
F4
F4
F1
Donor unit
RF Link Path
F1
Link antennas
Repeater units
The donor unit is mounted at the base station site where the signal enters the repeater via a directional
coupler. In the donor unit, the signal is translated into another frequency, the link frequency, amplified and
transmitted via a link antenna. At the remote site, a link antenna picks up the signal and feeds it to the remote
unit. The signal is translated back into the original frequency and retransmitted over the server antenna.
Only 2 guard channels are needed between the radio frequency and the link frequency.
The isolation between antennas at the remote site seldom needs to be more than 75dB. This value that can be
achieved with a limited antenna displacement, often as low as 3 meters. The relatively modest isolation
requirement allows the use of omni-directional antennas for the service area.
Important applications for frequency translating repeaters are road coverage, rural coverage or for
transferring capacity from a base station to another area.