RF Central RFX-BRK Spécifications télécharger pdf (Page 10)

RFX-BRK Issue 1 page 10 of 19

5 CIRCUIT DESCRIPTIONS

RFX-BRK Simplified block diagram

The complete RFX-BRK board; individual functions of the PCB are as follows:

5.1 Audio / Video Encoder

The Encoder has the following main functions :

• Analogue to Digital Video Converter, 10 bit over sampling ADC

Takes Composite Video in either PAL / NTSC format and converts to an 8bit

parallel digital video bus.

• Audio Analogue to Digital Converter, 48kHz, 24 bit

Two high impedance analogue inputs at Line level. The audio channels are

converted into digital signals and passed to the MPEG2 Encoder.

• MPEG2 Encoder

Compresses the video and audio. The encoder uses a suite of MPEG2

compliant compression techniques, where the data bit rate is reduced by

processing over multiple picture frames. The RFX-BRK MPEG encoder

operates at MP@ML (4.2.0) only. Low data rates down to 4 Mbps, can be

achieved.

The encoding parameters are loaded into the encoder at power up. These are

selected by the ‘preset’ rotary switch position. See 6.2

COFDM modulator

Power supply

Power

amplifier

TX RF

out

Encoder

Video/

audio

processing

MPEG coder

Power

supply

Transport

stream

Composite video

Analogue audio 1, 2

DC in

USB port

CDT TX

Simplified block diagram

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RF Central RFX-BRK Spécifications Page 10