8

4694E–AUTO–08/05

ATA5282

3.5

Signal Conditioner

The signal conditioner operates on the demodulated output signal of all three channels.

Figure 3-5.

Function of Signal Conditioner

The AGC reduces the gain of all 3 channels with reference to the signal with the highest ampli-

tude. This automatically reduces the gain of channels with medium or low input signal

amplitudes which results in the suppression of further process of these channels. The logical

combination of the 3 demodulated output signals mostly represents the signal with the highest

input amplitude.

3.6

Preamble Detection

To prevent the circuit from unintended operations in a noisy environment, the preamble is

checked to consist of 192 periods minimum. Three consecutive periods missing do not disturb

counting. With this check passed, the circuit starts the internal oscillator at the end of the pre-

amble (Figure 3-9 on page 12). The AGC needs a maximum of 256 steps for full range tuning

of amplifiers.

Medium signal strength

High signal strength

Low signal strength

Signal

conditioner

output

(NDATA)

Internal signals

Input

Channel 1

Internal GAP

Input

Channel 2

Internal GAP

Input

Channel 3

Internal GAP