ViaSat VBM-1400, Инструкция по установке и эксплуатации

Страница: 75 / 81

VBM-1400 Broadband Modulator Installation and User’s Guide
Glossary
Rev. 002 1018360
C-3
msec – millisecond
MSPS – Megasymbols per second (also Msym/s)
ODU - Outdoor Unit
PC - Personal Computer
PLL - phase-locked loop
Protocol - a rigidly defined set of rules for communication across a network.
PSK - phase shift keying; a modulation technique for converting an information stream to a
sinusoidal RF waveform by varying the phase of the RF carrier; each information symbol is contained
in a constant time interval with constant frequency and amplitude; the variation in phase determines
which symbol is being transmitted
QAM - Quadrature Amplitude Modulation; an encoding method that combines amplitude modulation
and phase modulation to create a constellation of signal points, each representing one unique
combination of bits that can be identified with one possible state that the carrier wave can be in.
QPSK - Quadrature Phase Shift Keying; a type of PSK modulation using four phases: 1/2 pi, pi, 3/2
pi, and 2 pi (zero) radians; binary message symbols are grouped in twos to give four possible values,
{0,1,2,3}; each of the four values is transmitted as the carrier wave with the corresponding phase
shift.
8PSK – 8-value Phase Shift Keying
RF - radio frequency
RMA – Return Material Authorization
spectrum - a signal’s frequency domain description
synchronous transfer - an I/O transfer in which data bit timing information (bit boundaries) is not
included in the data stream; data bit timing is provided by separate clock signals at the transfer
source and destination
TXB - Transmitter, Block converter. A transmitter and block converter combined into a single LRU.
TX - Transmit
VAC - Volts, Alternating Current
VDC - Volts, Direct Current