AS3933 datasheet(36/64 Pages) AMSCO

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ams Datasheet

Page 35

[v1-08] 2015-Sep-02

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AS3933 − Detailed Description

Figure 39:

Bit Setting of Gain Reduction

Antenna Damper

In case the chip needs to deal with higher field strengths the

antenna damper can be enabled. The antenna damper consists

of internal resistors which can be connected in parallel to the

external resonator as shown in Figure 40. It is possible to enable

the antenna damper with the bit R1<4> and the value of the

resistor can be chosen with the bits R4<5:4>. The shunt resistors

degrade the quality factor of the external 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). Figure 40 shows the bit setup.

Figure 40:

Antenna Damper Bit Setup

<3>

<2>

<1>

<0>

Gain

Reduction

No gain

reduction

n.a.

0 or 1

n.a.

0 or 1

-4dB

0 or 1

-8dB

0 or 1

-12dB

0 or 1

-16dB

0 or 1

-20dB

0 or 1

-24dB

R4<5>

R4<4>

Shunt Resistor

1 k

3 k

9 k

27 k

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