Ericsson MINI-LINK TN R3 ETSI, Техническое описание

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MINI-LINK TN R3 ETSI
4.2.2.3 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.
Two different modulations techniques are used:
• C-QPSK (Constant envelope offset Qaudrature Phase Shift Keying) is
an offset QPSK modulating technique. It has a high spectrum efficiency
compared to other constant envelope modulation.
• Square QAM (Quadrature Amplitude Modulation), consisting of two
independent amplitude modulated quadratures. The carrier is amplitude
and phase modulated. The technique doubles the spectrum efficiency
compared to C-QPSK.
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.
4.2.2.4 Cable Interface
The following signals are frequency multiplexed in the Cable Interface for
further distribution through a coaxial cable to the outdoor RAUs:
• 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.
4.2.2.5 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.
4.2.2.6 Radio Frame Demultiplexer
On the receiving side the received composite data stream is demultiplexed and
FEC corrected. The frame alignment function searches and locks the receiver
to the frame alignment bit patterns in the received data stream.
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