EMS Wireless DataNex Data-20, User'S Reference Manual

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1-5 System Description
DataNex EMS Wireless,
DATA-20
Digital Radio
Figure 1-4. Location of theDATA-20Backplane and Power Amplifier
The NMS/CPU card incorporates microprocessor and FPGA logic to configure and monitor the
overall operation of the system via front panel controls, LCD screen menus, status LEDs and the
bar graph display. Module settings are loaded into the installed cards and power-up default
settings are stored in non-volatile memory. LCD screen menu software is uploaded into memory,
providing field upgrade capability. A Windows-based PC interface is available for connection at
the rear panel DATA port.
1.5.2
QAM Modulator/IF Upconverter
INTERLEAVE
RAM
QAM
ENCODER
NCO
DIGITAL
POT
OCXO
12.8 MHz
FPGA
FPGA
EEPROM
uC
EEPROM
MICRO
CONTROLLER
LEVEL
TRANSLATOR
RS232
TRANSLATOR
QAM
DECODER
INTERLEAVE
RAM
RATE CONVERTER
PLL FIFO
SPI
IF
SYNTH
IF
STATUS
IF OUT
IF REF
CLK OUT
TRUNK
I/O
TXD
BUS
DATA & CLK
IN
BUS
REF CLK
OUT
BUS
I2C IN
RXD
IF IN
AGC
BUS
DATA & CLK
OUT
DEBUG
LED
STATUS
REF CLK
NO
CONNECTION
uC BUS
LEGEND
Figure 1-5. QAM Modem Block Diagram
The QAM (Quadrature Amplitude Modulation) Modulator is the transmit portion of the QAM
Modem card. The QAM Modem also houses the IF Up/Down Converter. The QAM Modulator
utilizes the upconverter portion of the IF daughter card.
The QAM Modulator accepts the aggregate data stream via the backplane (see Figure 1-5
above). The module performs 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