STLC2500A View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STLC2500A' PDF : 37 Pages View PDF
Functional description
5
Functional description
STLC2500A
5.1
Transmitter
The transmitter uses the serial transmit data from the Bluetooth Controller. The transmitter
modulator converts this data into GFSK modulated I and Q digital signals. These signals are
then converted to analogue signals that are low pass filtered before up-conversion. The
carrier frequency drift is limited by a closed loop PLL.
5.2
Receiver
The STLC2500A implements a low-IF receiver for Bluetooth modulated input signals. The
radio signal is taken from a balanced RF input and amplified by an LNA. The mixers are
driven by two quadrature LO signals, which are locally generated from a VCO signal running
at twice the frequency. The I and Q mixer output signals are band pass filtered by a poly-
phase filter for channel filtering and image rejection. The output of the band pass filter is
amplified by a VGA to the optimal input range for the A/D converter. Further channel filtering
is done in the digital part. The digital part demodulates the GFSK coded bit stream by
evaluating the phase information in the digital I and Q signals. RSSI data is extracted.
Overall automatic gain amplification in the receive path is controlled digitally. The RC time
constants for the analogue filters are automatically calibrated on chip.
5.3
PLL
The on-chip VCO is part of a PLL. The tank resonator circuitry for the VCO is completely
integrated without need of external components. Variations in the VCO centre frequency are
calibrated out automatically.
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