CMOS RF Transceiver simplifies 3G radio design

Based on the proven Othello direct-conversion architecture and a novel low-noise transmitter, the AD6552 simplifies the development of the radio section of 3G wireless handsets by eliminating the SAW (surface acoustic wave) filters that are usually needed in the transmit path, reducing both cost and board space. In addition, the receiver section provides EVM performance that supports the requirements for HSDPA and includes a fully-automatic dc offset control. In addition, the AD6552 integrates virtually all of the necessary components for a handset radio design (VCOs, tank circuits, loop filters and power management) all on a single chip. Component count for a dual-band radio is reduced by almost 40% compared to the previous two-chip Othello-W single-band radio for TD-SCDMA.

Analog Devices is the only single source supplier of complete chipset solutions for the TD-SCDMA standard and the company's chipsets have been an integral part of the network trials in China over the past three years. Today, commercial TD-SCDMA networks are being deployed in 10 cities throughout China, with a total population estimated at more than 60 million, which is roughly equivalent to the entire population of the United Kingdom or France.

Analog Devices is the only company to offer a complete solution for TD-SCDMA and has built a broad portfolio of solutions for the standard over the past few years, said Christian Kermarrec, vice president, RF and wireless systems, Analog Devices Inc. Today, with networks being built that can reach 60 million potential subscribers,
TD-SCDMA interest is at an all-time high. The latest addition to our TD-SCDMA product family, Othello-3T AD6552, represents the industry's most complete and highly-integrated radio for TD-SCDMA handsets, and will enable both domestic Chinese and global handset OEMs to speed time to market and gain a position in China's emerging 3G market.

The Othello-3T AD6552 is part of Analog Devices family of direct-conversion RF transceivers. Othello was introduced as the first open-market direct conversion GSM radio in 1999 and the product family has since grown dramatically to support additional standards such as GPRS, EDGE, W-CDMA and TD-SCDMA. With Othello, a combination of patented circuit designs, architectures, and system knowledge were used to solve the historical problems associated with radio design such as self-detection, dc offset and VCO phase errors. Today, direct conversion has become the preferred approach for the design of wireless handset radios.

The Othello-3T AD6552 applies this same patented approach in a CMOS implementation and provides a complete transmit/receive solution for TD-SCDMA-based mobile terminals. The receiver section includes high-performance single-ended low-noise amplifiers (LNAs) covering the 1900 and 2000 MHz bands. A direct-down-converting quadrature mixer driven by an on-chip fractional-N PLL synthesizer deliver baseband I and Q (In-phase and Quadrature) signals to a variable-gain amplifier (VGA) and programmable low-pass filter stages with dc offset correction.

The transmitter section consists of a fractional PLL synthesizer, a high performance VGA and quadrature modulator driving a common wideband output stage, as well as a true-rms RF power detector and on-chip D/A converter (DAC) for power amplifier control.

Othello-3T AD6552 is sampling now in a 6 mm x 6 mm 40-lead lead-frame chip scale package.