MAS6179 데이터 시트보기 (PDF) - Micro Analog systems

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MAS6179

AM Receiver IC

Micro Analog systems 

ANTENNA TUNING CONSIDERATIONS

The ferrite bar antenna having inductance LANT and

parasitic coil capacitance CCOIL is tuned to three

reception frequencies f1, f2 and f3 by parallel

capacitors CANT1, CANT2 and CANT3. The receiver

input stage and internal antenna capacitor switches

have capacitances CRFI, COFF2, COFF3 which affect

Frequency f1 (highest frequency):

CTOT1=CCOIL+CANT1+CRFI+COFF2+COFF3

1

f1 =

2π L ANT ⋅ CTOT1

Frequency f2 (middle frequency):

CTOT2=CCOIL+CANT1+CANT2+CRFI+COFF3

1

f2 =

2π LANT ⋅ CTOT 2

Frequency f3 (lowest frequency):

CTOT3=CCOIL+CANT1+ CANT2+ CANT3+CRFI

1

f3 =

2π LANT ⋅ CTOT 3

DA6179.000

22 January, 2007

the resonance frequencies. COFF2 and COFF3 are

switch capacitances when switches are open. When

switches are closed these capacitances are shorted

by on resistance of the switches and they are

effectively eliminated. Following relationships can

be written for the three tuning frequencies.

5 (10)

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