Comtech EF Data SDM-650B Especificaciones descargar pdf (Pagina 336)

100

101

SDM-300L3 Satellite Modem Revision 0

Specifications MN/SDM300L3.IOM

15–14

Using vector analysis of the constellation pattern, QPSK represents a symbol with the

carrier phase angle at 45°, 135°, 225°, or 315°. The 1/2, 3/4, and 7/8 rates encoded provide

the desired input/output bit rates.

Code Rate Symbols/Bit Bits/Hz

1/1 1 2

1/2 2 1

3/4 1.5 1.33

7/8 1.143 1.75

15.6.2 OQPSK Encoding

The modulator PCB converts the transmitted baseband data into a modulated OQPSK

carrier within the same parameters as QPSK.

The OQPSK modulation is mainly different from QPSK by offsetting the I and Q channel

modulation signals. This offset prevents the RF envelope from going through zero. Under

certain conditions, this may allow less back-off in the High Power Amplifier (HPA)

system. The 1/1, 1/2, 3/4, and 7/8 rates encoded provide the desired input/output bit rates.

Code Rate Symbols/Bit Bits/Hz

1/1 1 2

1/2 2 1

3/4 1.333 1.5

7/8 1.143 1.75

15.6.3 8PSK Encoding

The modulator converts transmitted baseband data into modulated 8PSK carrier at the

following parameters:

Using vector analysis of the constellation pattern, 8PSK represents a symbol with carrier

phase angles at 22.5°, 67.5°, 112.5°, 157.5°, 202.5°, 247.5°, 292.5°, and 337.5°. The rate

encoding provides the desired input/output bit rates.

Code Rate Symbol/Bit Bit/s Hz

2/3 1.5 2

3/4 1.333 2.25

1 2 ... 331 332 333 334 335 336 337 338 339 340 341 ... 433 434

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Comtech EF Data SDM-650B Especificaciones Pagina 336

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