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AS3930

Data Sheet - D e t a i l e d D e s c r i p t i o n

In case the maximum amplification at the beginning is a drawback (e.g. in noisy environment) it is possible to set a smaller starting gain on the

amplifier, according to the Table 14. In this way it is possible to reduce the false frequency detection.

8.4.2 Antenna Damper

The antenna damper allows the chip to deal with higher field strength, it is enabled by register R1<4>. It consists of shunt resistors which

degrade the quality factor of the resonator by reducing the signal at the input of the amplifier. In this way the resonator sees a smaller parallel

resistance (in the band of interest) which degrades its quality factor in order to increase the linear range of the channel amplifier (the amplifier

doesn't saturate in presence of bigger signals). Table 15 shows the bit setup.

8.5 Demodulator / Data Slicer

The performance of the demodulator can be optimized according to bit rate and preamble length as described in Table 16 and Table 17.

Table 14. Bit setting of Gain Reduction

R4<3>

R4<2>

R4<1>

R4<0>

Gain reduction

0

0

0

0

no gain reduction

00

0

1

n.a.

0

0

1

0 or 1

n.a.

0

1

0

0 or 1

-4dB

0

1

1

0 or 1

-8dB

1

0

0

0 or 1

-12dB

1

0

1

0 or 1

-16dB

1

1

0

0 or 1

-20dB

1

1

1

0 or 1

-24dB

Table 15. Antenna Damper Bit Setup

R4<5>

R4<4>

Shunt resistor (parallel to the resonator at 125 kHz)

00

1 k

Ω

01

3 k

Ω

10

9 k

Ω

11

27 k

Ω

Table 16. Bit setup for Envelop Detector for Different Symbol Rates

R3<2>

R3<1>

R3<0>

Symbol rate [Manchester symbols/s]

0

0

0

4096

0

0

1

2184

0

1

0

1490

01

1

1130

1

0

0

910

1

0

1

762

1

1

0

655

1

1

1

512