MINI-LINK BAS 5-12
Technical Description EN/LZB 111 0542 P2B
DC/DC Converter
The DC/DC converter provides stable voltages for the microwave
sub-units as well as for the radio interface unit.
Transmitter Oscillator
The frequency of the transmitter is controlled in a Phase Locked Loop
(PLL), a sample of the VCO signal is fed to a divider and further on to
a programmable phase detector. The error signal is controlled by the
integrated control and supervision system through a serial bus. An
unlocked VCO loop generates a transmitter frequency alarm.
Multiplying and Filtering
The VCO signal is amplified, frequency multiplied and filtered.
Final Amplifier
The transmitter output power is controlled by adjusting the gain of the
final amplifier. The output power is set in steps through the operation
and maintenance system (EM). The transmitter can be turned on or off
by switching the final amplifier.
Power Detector
The transmitted output power it's checked for supervision, output
power alarm.
RF Loop
An attenuated replica of the transmission signal is mixed with a shift
oscillator signal and is fed into the receiver for test purposes.
Branching Filter
On the transmitting side, the signal is fed to the antenna via a
branching filter and a circulator. On the receiving side, the circulator
feeds the received signal to an input branching filter.
Receiver
The received signal is fed from the input branching filter into a low
noise amplifier and a down-converter to a first IF step. After bandpass
filtering and amplification, the signal is down-converted to the second
IF of 140 MHz.
Receiver Oscillator, Multiplier and Filter
LO signals for the two down-conversions are generated in the same
way as for the transmitted signal. A frequency control signal from the
indoor parts (AFC) is fed to the receiver oscillator via the control and
supervision processor.
A double superheterodyne receiver with a high first IF, is
implemented enabling frequency selection over a wide frequency
band, with an excellent receiver of spurious and image rejection.
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