Ericsson MINI-LINK TN R3 ETSI, Техническое описание

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MINI-LINK TN R3 ETSI
Multiplexing
The three different data types together with check bits and frame lock bits are
sent in a composite data format defined by the frame format that is loaded into
a Frame Format RAM. The 12 frame alignment signal bits are placed at the
beginning of the frame. Stuffing bits are inserted into the composite frame.
Scrambling and FEC Encoding
The synchronous scrambler has a length of 2
17
–1 and is synchronized each
eighth frame (super frame). The FEC bits are inserted according to the frame
format and calculated using an interleaving scheme.
5.3.1.5 Modulator
The composite data stream from the Radio Frame Multiplexer is modulated, D/A
converted and pulse shaped in a Nyqvist filter to optimize transmit spectrum.
C-QPSK (Constant envelope offset Qaudrature Phase Shift Keying), an
offset QPSK modulating technique, is used. It has a high spectrum efficiency
compared to other constant envelope schemes.
The Modulator consists of a phase locked loop (VCO) operating at 350 MHz.
For test purposes an IF loop signal of 140 MHz is generated by mixing with a
490 MHz signal.
5.3.1.6 Cable Interface
The following signals are frequency multiplexed in the Cable Interface for
further distribution through a coaxial cable to the outdoor RAU:
• 350 MHz transmitting IF signal
• 140 MHz receiving IF signal
• DC power supply
• Radio Communication Channel (RCC) signal as an Amplitude Shift Keying
(ASK) signal
In addition to the above, the cable interface includes an over voltage protection
circuit.
5.3.1.7 Demodulator
The received 140 MHz signal is AGC amplified and filtered prior to conversion
to I/Q baseband signals. The baseband signals are pulse shaped in a Nyqvist
filter and A/D converted before being demodulated.
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