TDA7333

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Figure 7. Phase Response of the RDS Bandpass Filter

The output sample of the bandpass filter is picked up from a linear interpolator with sinc2 characteristics. The

interpolation factor is 32. A zero cross detection is simply formed by taking the sign bit of the interpolated signal.

This signal which contains only phase informations is processed by the RDS Demodulator.

7.5 Demodulator

– The demodulator includes :

– RDS quality indicator with selectable sensitivity

– Selectable time constant of 57kHz PLL

– Selectable time constant of bit PLL

– time constant selection done automatically or by software

Figure 8. Demodulator Block Diagram

5.6

5.65

5.7

5.75

5.8

x 10

4

3

2

1

0

1

2

3

Phase of RDS Filter

Frequency [Hz]

to RDS group and block synchronisation

module:

from RDS group and block synchronisation

module:

RD

RDSDAT

RDSQUAL

AR_RES

mclk

(8,550 or 8,664 MHz)

MPX

Input-stage

(digital Filter)

ARI-indicator

57 kHz PLL

frequency

offset comp.

Clock Generator

Half Wave

Integrator

Half Wave

Extractor

RDS Quality

Extractor

RDS Data

Extractor

1187.5Hz

PLL

mclk

Sine comp.

Cosine comp.