Transceiver Module; Ad6548 ) - LG -A120 Service Manual

3.3 Transceiver Module (AD6548)
3.3.1 General Descriptions
The AD6548/9 provides a highly integrated direct conversion radio solution that combines, on a
single chip, all radio and power management functions necessary to build the most compact GSM
radio solution possible. The only external components required for a complete radio design are the
Rx SAWs, PA, Switchplexer and a few passives enabling an extremely small
cost effective GSM Radio solution.
The AD6548/9 uses the industry proven direct conversion receiver architecture of the OthelloTM
family. For Quad band applications the front end features four fully integrated programmable gain
differential LNAs. The RF is then downconverted by quadrature mixers and then fed to the
baseband programmable-gain amplifiers and active filters for channel selection. The Receiver
output pins can be directly connected to the baseband analog processor. The Receive path
features automatic calibration and tracking to remove DC offsets.
The transmitter features a translation-loop architecture for directly modulating baseband signals
onto the integrated TX VCO. The translation-loop modulator and TX VCO are extremely low noise
removing the need for external SAW filters prior to the PA.
The AD6548/9 uses a single integrated LO VCO for both the receive and the transmit circuits.
The synthesizer lock times are optimized for GPRS applications up to and including class 12.
To dramatically reduce the BOM both TX Translational loop and main PLL Loop Filters are fully
Figure.3-3-1 AD6548 FUNCTIONAL BLOCK DIAGRAM
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