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TEMIC Semiconductors |
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U4276B
FM Multipath Noise Cancellation
Description
The U4276B is a bipolar integrated multipath noise cancellation circuit. It is designed for high performance car radio
applications.
Features
D Preparation of the fieldstrength signal
D Multipath noise cancellation
D Mute function controllable by microcomputer
D Suitable for analogue as well as digital processing
D Only a few external components necessary
Block Diagram
2
FSIN
BFSOUT
7
Buffer
VS
6
Bandgap
3
GND
AVFS
MPXIN
1
4
95 10619
Multipath
detection
Multipath
noise
cancellation
8
MUTE
5
MPXOUT
Pin Description
Pin Symbol
Function
1 AVFS Average of fieldstrength signal
2 FSIN Fieldstrength input
3 GND Ground
4 MPXIN Multiplex input signal
5 MPXOUT Multiplex output signal
6 VS Supply voltage
7 BFSOUT Buffered fieldstrength output
8 MUTE External mute input
AVFS 1
FSIN 2
GND 3
MPXIN 4
8 MUTE
7 BFSOUT
6 VS
5 MPXOUT
95 10632
TELEFUNKEN Semiconductors
Rev. A1, 05-Sep-96
Preliminary Information
1 (8)
U4276B
FSIN / BFSOUT
FSIN
40 mA
VS
BFSOUT
MPXIN / MPXOUT
50 kW
MPXIN
VS
50 kW
94 8647
All information about reception conditions is derived
from the fieldstrength signal. The fieldstrength signal at
FSIN is initially buffered so as not to impair the character-
istics of the IF IC and is available at BFSOUT.
AVFS
94 8649
VS
60 kW
MPXOUT
VS
40 mA
AVFS
94 8648
The fieldstrength signal at buffer output BFSOUT is aver-
aged over time and applied to input AVFS via an RC
low-pass filter with a large time constant.
60 kW
200 m A
94 8650
The MPX signal is fed directly from the FM demodulator
to input MPXIN and is available amplified by a factor of
1.5 at MPXOUT. The MPX signal is blanked out in the
event of multipath interference or when MUTE is acti-
vated externally in the circuit part MNC (Multipath Noise
Canceller). In all other cases, the MPX signal passes
through the IC unchanged.
MUTE
MUTE
94 8651
The function unit MNC can be controlled externally via
this pin. Blanking occurs when the voltage at the MUTE
pin falls below 1 V.
2 (8) TELEFUNKEN Semiconductors
Preliminary Information
Rev. A1, 05-Sep-96
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