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ENABLING MULTIMODE COMMUNICATIONS
The team of RF architects at Sequoia Communications realized that
a new vision of cellular transceivers would enable the development
of a truly breakthrough RF device. For the receiver, this means
a level of integration that is unprecedented in today’s products;
for the transmitter, this means a single, unified transmit architecture.
A
key challenge is to build on the industry-standard, direct-conversion
receiver architecture and further reduce the current power consumption,
cost and board area. Integration of all low noise amplifiers
(LNAs) and WCDMA image reject filters is essential to creating the
industry’s
first monolithic receiver.
Polar modulation is the most promising approach to efficiently integrating shared transmit circuitry, especially when incorporating WCDMA. Polar modulation splits the signal into its phase and amplitude components, and is the basis for most GSM and EDGE phones. By extending the polar architecture to WCDMA, it is possible to eliminate the redundancies within the transceiver chip inherent to today’s approaches, which require completely separate transmit paths for WCDMA and EDGE.
More significantly, polar modulation offers a method for dramatically
increasing the efficiency of the power amplifier (PA) by implementing
a feedback loop from the PA output and using the amplitude component
to linearize the PA at its input. The opportunity for reducing current
consumption increases with higher peak-to-average ratio envelope
variations, which occur in
WCDMA and OFDM systems (such as WiFi and WiMAX). Decreasing the
total current consumed by the RF system will not only increase battery
life, but will also diminish thermal issues, which may have otherwise
constrained handset size reduction.
Sequoia Communications has introduced the SEQ7400 which delivers
the highest levels of integration by using a common transmit
architecture and the industry’s first monolithic receiver.
Click here for more information.
IEEE Communications Magazine
Sept. 2007
Polar Transmitters for Wireless Communications
» Read the article
March 2008
A Multimode Cellular Radio
» Read the article |
