Section 7: System Description
7-3
Moseley SL9003Q
602-12016-01 Revision J
internal sample rate clock (32, 44.1, 48 kHz selectable). For example, data could be
provided by a CD player at 44.1 kHz, while the internal sample rate to be transmitted across
the link is at 32 kHz (the default rate).
The digital audio is optionally compressed (using MPEG) in the Audio Encoder module to
allow for higher bandwidth efficiency (more audio channels per RF channel) at the expense
of aural masking compression disadvantages. However, some users may require the
compression algorithm for existing system compatibility.
Sine wave and “zeroes” test signal generators are available on the card (switch selectable)
for system testing. The stereo D/A converter transforms the signal back to analog for use in
monitoring the signal from the front panel. This conveniently allows for level monitoring of
the digital AES/EBU audio inputs on the bar graph.
The digital audio data (linear or compressed) and the auxiliary data channel are
subsequently coded into a single data stream. In a 2 channel system, this data stream is
sent to the QAM Modulator module directly.
7.2.2 Intelligent Multiplexer
The MUX is documented in a separate user manual. Typical broadcast applications are
described here:
6-Port Mux:
For discrete STL systems, the 6-port mux (with Ethernet option card) is
primarily used to interface and multiplex an Ethernet data stream for transmission as a data
channel.
7.2.3 QAM Modulator/IF Upconverter Daughter Card
BPF
70 MHz
BPF
6.4 MHz
IF Output
70 MHz
-10 dBm
PLL
Loop
Filter
VCO
76.4 MHz PLL
Data
Clk
Enbl
Ref
IF Input
6.4 MHz
-20 dBm
Synth Level
Synth
Lock
Exciter
Level
Figure 7-3. IF Upconverter Daughter Card Block Diagram
The QAM (Quadrature Amplitude Modulation) Modulator accepts the aggregate data stream
via the backplane. The module performs up to 256 QAM modulation at a carrier frequency of
6.4 MHz, adding FEC (Forward Error Correction) bits while interleaving the blocks of data.
The result is a very spectrally efficient, yet robust linear modulation scheme. This process
requires an ultra-stable master clock provided by an OCXO (oven controlled crystal
oscillator) that is accurate to within 0.1 ppm.
Summary of Contents for Starlink SL9003Q
Page 86: ...5 22 Section 5 Module Configuration Moseley SL9003Q 602 12016 01 Revision J ...
Page 90: ...6 4 Section 6 Customer Service Moseley SL9003Q 602 12016 01 Revision J ...
Page 110: ...A 10 Appendix A Path Evaluation Information Moseley SL9003Q 602 12016 01 Revision J ...
Page 118: ...D 2 Appendix D Microvolt dBm Watt Conversion 50 ohms Moseley SL9003Q 602 12016 01 Revision J ...
