K850
1203-2528 rev. 1
FUNCTIONAL OVERVIEW
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Block diagram of the GSM/EDGE Transceiver
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 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 LNAs for each
band and a common quadrature mixer. The front-end block is followed by a baseband block
with active antialiasing 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.
RX Frequency and Channel Range
GSM 850:
Frequency Range: 869,2 MHZ – 893,8 MHZ
Channel Range: 128 – 251
GSM 900:
Frequency Range: 935,2 MHZ – 959,8 MHZ
Channel Range: 1 - 124
EGSM 900:
Frequency Range: 925,2 MHZ – 934,8 MHZ
Channel Range: 975 – 1023
Technical Description
SEMC Troubleshooting Manual
68
(101)
