Sony Ericsson W890 Troubleshooting Manual page 86

Radio Part
GSM/GPRS/EDGE
The GSM/GPRS/EDGE transceiver use a digital interface that is shared between receive
and transmit data. The receive interface is based on I and Q data and the transmitter
interface is based on envelope and frequency data. The quad band GSM/GPRS/EDGE
transceiver has the following general features:
The GSM/EDGE transceiver has the following features:
• Individual low-noise amplifiers for the 850, 900, 1800 and 1900 MHz frequency bands
with a common quadrature mixer
• Fully integrated VCO with dividers to generate both receive and transmit frequencies
• I and Q baseband receive channel amplifiers with on-chip antialiasing filtering
• I and Q receiver sigma-delta A to D converters
• Digital interface for the receive I and Q channel
• Multi modulus prescaler for direct VCO modulation in transmit mode
• Integrated phase detector with programmable charge pump
• Transmit output buffer with controllable output power level
• Transmit baluns integrated
• Digital interface for the transmit frequency and amplitude modulation
• 3-wire serial bus interface for control, configuration, and test
• Deep power down function
• Programmable power level to power amplifier (PA)
Block diagram of the GSM/EDGE Transceiver
FUNCTIONAL OVERVIEW Technical Description
Frequency Generation
The 26 MHz reference signal is used as the reference for the on-chip synthesizer. To
cover the required frequency range, the integrated Voltage Controlled Oscillator (VCO)
operates at twice the frequency for band 1800/1900, and at four times the desired
frequency for band 850/900.
Transmitter
The transmitter block consists of the following sub-blocks:
A separate block is used to convert the digital bit streams from the baseband into parallel
words to be used in the DAC-s and the Sigma Delta modulator. This block also includes
programmable delays for optimizing delays between the different modulation paths. The
combined DAC and LP-filter is used to convert the digital words of the digital block into analog
signals. The second FM-path is used to add the high frequency part of the FM to the VCO. It
also includes an auto-tuning block that compensates VCO gain variations. The AM-block
converts the differential voltage from the DAC to a single-ended output that drives the PA.
The output is scaled according to the desired output power, and an offset can be added for PA
linearization. The TX-buffer is used to drive the PA with the correct power level. A divide by 2
or 4 block is used to generate the correct output frequency from the 4 GHz VCO.
TX Frequency, Channel and Power Level Range:
GSM 850:
Frequency Range: 824,2 MHZ – 848,8 MHZ
Channel Range: 128 – 251
Power Level: Min: 19 – Max 5
GSM 900:
Frequency Range: 890,2 MHZ – 914,8 MHZ
Channel Range: 1 - 124
Power Level: Min: 19 – Max 5
EGSM 900:
Frequency Range: 880,2 MHZ – 889,8 MHZ
Channel Range: 975 - 1023
Power Level: Min: 19 – Max 5
DCS 1800:
Frequency Range: 1710,2 MHZ – 1784,8 MHZ
Channel Range: 512 – 885
Power Level: Min: 15 – Max 0
PCS 1900:
Frequency Range: 1850,2 MHZ – 1909,8 MHZ
Channel Range: 512 - 810
Power Level: Min: 15 – Max 0
Receiver
The receiver is a homodyne receiver with direct conversion of the received radio channel
to baseband I and Q channels. The analog signals are converted to digital bit streams in a
sigma delta A/D converter. The receiver block consists of a front-end with separate LNA-s for
each band and a common quadrature mixer. The front-end block is followed by a baseband
block with active anti aliasing filters that also suppress blocking signals and interferers. After
the baseband block is a fully integrated Analog to Digital Converter of sigma delta structure
with high dynamic range. The digital output signals are sent over a serial interface to the
digital base-band circuit for further processing and detection.
SEMC Troubleshooting Manual
W890
1217-3942 rev. 1 86 (119)