ViaSat VBM-1400, Инструкция по установке и эксплуатации

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VBM-1400 Broadband Modulator Installation and User’s Guide
General Theory of Operation
1018360 Rev. 002
5-2
•
Input Data Activity
•
Sync Bytes Detected
• RF PLL Status
•
RF Output Power Level
•
Modulator Closed Loop Power Control Status
•
Master Oscillator PLL Status
•
Frequency Reference Activity
•
FPGA Load Status
5.3 Reference Signal
The internal master clock signal is produced on the Modulator Board
using either an internally generated 10 MHz reference signal, or by
synchronizing to an external signal applied to the EXT REF IN jack.
Selection is made using the front panel menus. The unit will accept an
external balanced sine wave at 1 to 25 MHz in 8 kHz steps, from –20 to
0 dBm.
The reference signal may be daisy-chained to other units by connecting
to the REF OUT jack. Either the internal or external reference signal
may be selected using the front panel menus.
5.4 Signal Flow
The incoming baseband data is DVB-SPI, DVB-ASI, or M2P format. The
DVB-SPI or M2P input is applied to 25-pin D-Type subminiature
connector J1, while the DVB-ASI signal is applied to BNC-type
connector J2 on the rear panel.
The incoming signals are applied to the Baseband Interface Board
where, depending on the signal type, are processed and transformed
into multiplexed data for application to the Modulator Board.
The Modulator Board accepts the multiplexed data from the Baseband
Interface Board, and performs forward error correction (FEC), filtering,
symbol mapping, and digital-to-analog (D/A) signal conversion. The
final output consists of in-phase ( I ) & Quadrature ( Q ) analog
waveforms that are applied to the RF Board.
The RF Board provides the carrier frequency which is modulated by the
I and Q components and applied to the TX OUT jack on the rear panel.
The TX MON jack provides an attenuated sample of the transmit signal
at a -20 dBm level for external monitoring.