Fm Radio Interface; Rf Description; Receiver (Rx) - Nokia RM-632 Service Manual

The BTHFM module is powered by VBAT and the regulated voltage VIO. For audio applications the Bluetooth
has a PCM data bus. In addition an UART (universal asynchronous receiver/transmitter) is used for data
communication and controls.

FM radio interface

The FM radio system is controlled by RAPU via the I2C bus. EM ASIC delivers the needed voltages and the clock
reference (32.768kHz SleepClk). EM ASIC also processes the analog audio.
The FM receiver fully supports reception over US/European (87.5MHz to 108MHz) and Japanese (76MHz to
90MHz) FM band. The FM receiver comprises an RF receiver with fully integrated VCO, a stereo FM demodulator
and a RDS demodulator.
A headset accessory is used as an external antenna. The headset is connected to the AV connector.
FM radio is physically integrated with Bluetooth in the BTHFM module ASIC, but from a functional point of
view FM radio and Bluetooth have nothing in common.

RF description

Receiver (RX)

An analogue signal is received by the phone's antenna. The signal is converted to a digital signal and is then
transferred further to the baseband (e.g. to the earpiece).
The receiver functions are implemented in the RF ASIC.
Signals with different frequencies take different paths, therefore being handled by different components.
The principle of GSM and WCDMA is the same.
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Figure 42 FM radio interface
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RM-632; RM-634; RM-699
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