Philips taps near-zero IF for GSM
radio
By Peter Clarke
EE Times
(01/19/00, 6:18 p.m. EST)
CAEN, France — Despite being an early
experimenter with direct-conversion RF
transceivers for communications applications,
Philips Semiconductors has nevertheless adopted a
near-zero intermediate frequency (N-ZIF)
architecture for its GSM transceivers.
The company has started sampling its first
single-chip RF section for GSM applications, the
UAA3535, based on the N-ZIF architecture.
The chip supports GPRS (General Packet Radio
Service) Class 12 functions that allow data rates of
as high as 56 kbits/second. Class 12 refers to the
ability to grab five time slots and assign as many
as four of them to receive or transmit a signal.
Triple-band support for carrier frequencies at 900
MHz, 1,800 MHz and 1,900 MHz allows the same RF
transceiver, and phones based on it, to cater to all
European, North American and Far East GSM requirements and roaming
among the regions.
"Essentially it is a dual-band front end — 900 and 1,800 or 900 and
1,900 — but with a few additional components, a switch and
wideband filter. It can be suitable for triple-band phones that in 2000
will be in high demand," said Yvan Droinet, international product
marketing manager for RF products at Philips Semiconductors.
Droinet said Philips Semiconductors would use the N-ZIF architecture
to address future developments in GSM, such as Edge (Enhanced Data
rates for GSM Evolution), and was likely to use it for third-generation
(3G) phones that will operate with carrier frequencies just above 2
GHz.
"It is strictly for GSM at the moment, but it would be no problem to
extend the architecture to 3G," he said. "We would certainly consider
near-zero IF for GSM/GPRS/Edge first and then for a GSM/Edge/UMTS
transceiver on a single die."
Philips said that it offers higher integration compared with traditional
double-conversion superheterodyne receiver architectures, as well as
advantages over direct conversion, also known as zero-IF.
A conventional IF configuration requires the use of an external SAW
filter, while a single-conversion alternative can be implemented
entirely on-chip.
"The intermediate frequency is 100 kHz, which provides an advantage
in integrating the IF channel filter," said Droinet. "Compared with a
zero-IF architecture, the advantage is that we don't need to [do] the
calculations for the dc offset."
The UAA3535, which operates at 2.5 V, interfaces to standard A/D
converters and requires few external components. Droinet said that
apart from three VCOs, available as single components, the design
only required a power amplifier, an RF antenna filter and three loop
filters composed of four or five capacitors and some decoupling
capacitors to complete the RF section.
The chip is being manufactured using Philips Semiconductors'
0.5-micron BiCMOS process. "The UAA3535 delivers all the advantages
demanded by today's handset manufacturers, excellent features, a
high integration level and low cost, for next-generation GSM mobile
phones," Droinet said.
He said future iterations of its GSM chip sets will integrate new
capabilities, such as Bluetooth, MP3 (Moving Picture Experts Group
Layer-3 Audio) and GPS (Global Positioning by Satellite), and will
directly address 3G standards.
The UAA3535 single-chip RF transceiver is currently sampling, with
volume production expected in July. It will be shown at the GSM World
Congress in Cannes, France, from Feb. 2 to 4.
eetimes.com
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Commentary on Philips near zero Triple-Band GPRS Transceiver by ChipCenter's Paul McGoldrick..
"This part follows on from the UAA3522
dual-band GSM transceiver announced
last year, a major enabling part. It is
extremely important that a company
like Philips has chosen to go ahead
with near-zero IF solutions rather than
the more elegant zero IFs avoiding
considerable the dc component and
filtering requirements that the latter
needs -- and will probably always need.
Those filters have caused problems for
many of us for 20+ years working on
zero-IF solutions.
The UAA3535 GPRS transceiver is a
complete solution that will be readily
adopted in triple-band handsets in the
GSM markets of the world. It is very
complete and the number of external
components needed is extraordinarily
small. In terms of the silicon additions
needed there would be the RF output
device(s), an RF switch and the
baseband module -- which is more than
likely to be a single chip. The next
product offering in this family will be one
that addresses enhanced data rates for
GSM evolution (EDGE).
The UAA3535 is sampling in an
LQFP-48 and is fabricated in Philips
QUBIC 3 BiCMOS. Volume production
will start in July 2000. As is
unfortunately normal with Philips' press
releases the U.S. operation does not
add prices to the European-originated
documents."
chipcenter.com |
