Micro Digital Satellite Receiver Manual de usuario descargar pdf (Pagina 4)

AN2677/D

4 Digital Satellite Equipment Control (DiSEqC ) using MC68HC908QT/QY

Figure 1 shows the signal block diagram. There are two universal LNBs used,

receiving signals from satellite A and B respectively. The ODU

(MC68HC908QT4 and some other components) receives the command data

signal from the IDU. The commands are sent in the DiSEqC data format

(modulated 22 kHz) through the high frequency coaxial cable.

Figure 1. Signal Block Diagram

Figure 2 shows the functional block diagram. The satellite receiver is

connected by the coaxial cable to the pin called “IF-Out” (4).

This cable carries:

• Supply voltage +13 V or +18 V at 0.5 A max from the satellite receiver

to the LNB switch and the target LNB (LNB-A or LNB-B)

• DiSEqC or non-DiSEqC commands from the satellite receiver to the

LNB switch and the target LNB

• High-frequency television signal in the IF band (950 MHz to 2150 MHz)

from that LNB through the LNB switch to the satellite receiver

The universal LNBs are controlled by:

• Supply voltages

– +13 V — vertical polarization

– +18 V — horizontal polarization

• 22-kHz signal superimposed on those voltages

– 22-kHz signal is present — high band (11.7 GHz to 12.75 GHz) is

received

– 22-kHz signal is not present — low band (10.7 GHz to 11.7 GHz) is

received

SAT A

HF SIGNAL

TO IDU

MC68HC908QT4

DiSEqC LEVEL 1.0

COAX CABLE:

dc SUPPLY

22 kHz

COMMANDS FROM IDU

UNIVERSAL LNB

SAT B

UNIVERSAL LNB

ODU

Freescale Semiconductor, I

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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Freescale Semiconductor, I 1

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Micro Digital Satellite Receiver Manual de usuario Pagina 4

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