K850
1203-2528 rev. 1
FUNCTIONAL OVERVIEW
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WCDMA Radio Module
N1210 (Mammoth)
In WCDMA the differential transmit outputs from the WCDMA transceiver are filtered by an
external SAW filter. The SAW filter cleans up the spectrum and also provides a single ended
drive signal to the power amplifier. Two power amplifier modules are used one for Band I and a
dual power amplifier for Bands II and V. For power control, a sample of the transmit output is
taken by a directional coupler and converted to a DC level by the power detection circuit. This
signal is used to control the transmitter output power. The transmit signal passes through an
isolator and then a duplexer. The duplexer output is selected by a switch in the N1200 (Thor)
module for connection to the antenna. In WCDMA receive mode the signal from the antenna is
switched by the N1200 (Thor) module to the correct duplexer. The output from the duplexer is
amplified by one of the low noise amplifiers in the LNA/SAW module, then filtered by an
integrated receive SAW filter. The SAW filter converts the unbalanced receive signal to a
differential signal required by the WCDMA receiver. The N1200 (Thor) module supplies the
N1210 (Mammoth) module with a 26 MHz clock and the antenna switch functionality. The
module is shielded using fence and lid technology. The main components in the design are a
Transceiver ASIC, two PA modules, LNA/SAW filter module, power detector, 2 couplers, 3
duplexers, 3 isolators, and 3 cleanup filters.
Frequency Generation
The transmitter and receiver frequency synthesizers and the VCOs are fully integrated in the
WCDMA radio circuit. The signal from the crystal oscillator is used as a reference for the
synthesizers. The two synthesizers are controlled through the serial bus from the access
subsystem of the digital baseband controller.
WCDMA Transceiver
The WCDMA transceiver uses differential analog in-phase and quadrature-phase Interfaces;
that is, an IQ-interface, both in the receiver and transmitter information path. The receiver part
of the transceiver consists of an RF front end, a channel filter, and Automatic Gain Control
(AGC), and the transmitter part consists of an analog voltage baseband I and Q interface, an up
mixer and an RF VGA. Each part has an RF VCO and an RF fractional-N synthesizer PLL. All
functions are controlled by a 3-wire serial programmable bus.
Three bands is covered in a single application:
Band I (TX 1920 – 1980 MHz, RX 2110 – 2170 MHz)
Band II (TX 1850 – 1910 MHz, RX 1930 – 1990 MHz)
Band V (TX 824 – 849 MHz, RX 869 – 894 MHz)
WCDMA Transceiver Block Diagram
Transmitter
The TX IQ modulator has differential voltage I and Q inputs. It converts input signals to RF
output frequency and is designed to achieve LO and image suppression.
The transmit output stage provides at least +5 dBm at maximum power control at the
differential output. Gain is set through the 3-wire bus. Two 10-bit DAC are used to control the
DC/DC converter and the PA gain. Those DACs are controlled through the 3-wire-bus. One 11-
bit DAC is used to control the variable gain output of the transceiver chip. The transceiver chip
output feeds the constant gain power amplifier, which means that the transceiver chip sets the
phone’s output power.
Receiver
The receiver converts the antenna RF signal down to a Zero Intermediate Frequency (ZIF). The
first stage after the duplexer is a single-ended LNA with a 23 dB gain step. This LNA is followed
by a SAW filter. The LNA and SAW filter are integrated in the LNA/SAW module. The output
from the LNA/SAW module goes to the input of the N300 circuit (Inside the Mammoth module)
and is buffered by an amplifier and then sent to the IQ down-mixer, which consists of two
mixers in parallel driven by quadrature phase LO signals. The In phase (I) and Quadrature
phase (Q) ZIF signals are then low pass filtered to provide protection from high frequency offset
interferer and fed into the channel filter.
Technical Description
SEMC Troubleshooting Manual
69
(101)
