Cobham Wireless
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Coverage
BSF0060 User Handbook
www.cobham.com/wireless
Document number: BSF0060HBK
Issue number: 5
Date: 14/05/2018
Page 23 of 43
3.6.5.
Digital Signal Processing (DSP) module
The DSP module is a wideband RF module that digitises factory set segments of the full bandwidth,
the setting of the segments of spectrum is performed at factory initialisation and is not field
adjustable. Once the equipment leaves the factory its operating bandwidth is already set by the
initialisation and the external duplexing filters used to separate and define the required Part 90 Tx
and Rx frequency bands.
The DSP module provides the initial gain in the DL path and the entire gain in the UL direction.
Internal ceramic filters provide UL and DL selectivity, in addition it provides attenuation control and
level control in both the UL and DL directions, the overall repeater has a defined maximum output
level, if the input signal amplified by the gain set exceeds the set output limit, an ALC loop is
activated in the DSP module which has a range of 20dB. This ALC ensures that the amplifier does not
add distortion to the radio signal.
3.6.6.
Multi Carrier Power Amplifier (MCPA)
The Downlink output MCPA provides 37dB of gain and has a P1dB of 47dBm and an IP3 of 68dBm.
The MCPA utilises high linearity class A techniques to minimise Intermodulation generation in the
presence of multiple carriers. The amplifier output power is limited to 36dBm (4W) composite power
to ensure high linearity to keep spurious products to a minimum.
3.6.7.
Bandpass Duplexer Module
The bandpass duplexer module is connected to a common output/input port for single antenna
operation. The purpose of the duplexer is to ensure that the equipment operating bandwidth is
limited to the band of frequencies required to be amplified/repeated. The filters in the duplexer
ensure that noise and any Intermodulation is limited to within the operating transmission band. The
filters must prevent any noise reaching the antenna port at the receiver frequencies as any noise at
this point will affect the ability to receive. The receiver input filter is used to ensure that only the
required input band of frequencies is presented to the DSP module. The filter also ensures that the
high level Downlink transmit output does not cause overload damage by blocking the receiver’s ability
to detect the wanted Uplink input frequencies.
3.6.8.
Reference Generator Board
The Reference Generator is used to provide an accurate stable 10 MHz Reference signal to the DSP
module to ensure that the channel selectivity is centred on the wanted channel frequency.
3.6.9.
Distribution Board
The Distribution board is used to connect the DC power and the RS485 control signals between the
associated modules and the PSU/Control Module.
