W3020 Datasheet, PDF (4/44 Pages) Agere Systems – GSM Multiband RF Transceiver

W3020 GSM Multiband RF Transceiver
Advance Data Sheet
December 1999
Description
The W3020 is a highly integrated GSM transceiver
designed to operate in dual-band handsets or in
single-band handsets operating at 900, 1800, and
1900 MHz frequency bands (1900 MHz performance
is not verified in production). The IC architecture
allows the RF designer to provide solutions for three
different frequency bands with very few PCB changes,
thereby providing faster time to market and reduced
development time.
The W3020 RF transceiver and W3000 PLL have
been designed in conjunction with the SC1 (radio
interface and DSP) to provide a complete GSM
cellular solution. The W3020 interfaces to the W3000
UHF high-performance PLL IC. The W3020, in
combination with the W3000, provides the transmitter,
receiver, and frequency synthesizer. Adding a power
amplifier(s), filters, and VCO modules completes the
radio channel.
The baseband modulated signal is applied to the I/Q
double-balanced mixer in a differential manner. The
±45° phase-shifted local oscillator requires no trim to
achieve the required modulation spectral mask. Also,
I/Q input signals require no dc offset calibration to
achieve high phase accuracy signal. The IF signal
outputs from the I/Q mixers are summed and brought
out to an external filter that reduces the noise that
could be intermodulated into the receive band. This
signal is then applied to the low noise up-conversion
mixer and brought to the RF output.
The received signal is amplified through the low-noise
amplifier, which, combined with the preceding filter,
dominates the receiver sensitivity. The signal is then
passed through another external filter to attenuate the
image frequency to an acceptable level. The signal
passes through the RF down-conversion mixer to the
IF frequency. It is then filtered by an external surface
acoustic wave (SAW) filter to bring the in-band
blocking signals to an acceptable level. The signal is
amplified in the IF strip of the receiver. The IF strip
contains digital gain control (DGC) amplifiers at both
the IF and baseband frequencies and precision low-
pass filters. This allows the signal to be amplified
while in-band blocking signals are removed. The
precision I/Q demodulator splits the signal into its in-
phase and quadrature signals. The I/Q signals are low-
pass filtered and further amplified. The I/Q amplifier
contains integrated dc offset calibration circuitry. The
outputs (I/Q) are fed to the ADC for further signal
processing.
The second local oscillator (LO2), comprising a buffer
for the external voltage-controlled oscillator (VCO)
and a phase-locked loop (PLL), feeds the IF portions
of both the modulator and the receiver. An external
reference source, voltage-controlled crystal oscillator
(VCXO), is divided from 13 MHz to 1 MHz through a
counter. The 1 MHz is called the comparison
frequency. The VCO frequency of 540 MHz is also
divided down to 1 MHz. Both signals are fed into a
phase detector, and the resultant error signal is fed
through an external low-pass filter to the control input
of the VCO.
The RF receive and transmit mixers are driven by two
band-switchable external VCO modules and buffered
internally on the IC. The VCOs are both controlled by
a single W3000 PLL synthesizer and loop filter. Fast
band-locking is achieved using a proprietary scaling
technique integrated in the W3000 PLL.
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Lucent Technologies Inc.