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Startup preps chip support for China 3G

Posted: 01 Mar 2007 ?? ?Print Version ?Bookmark and Share

Keywords:RDA Microelectronics? TD-SCDMA? GSM? 3G? PHS?

It's still in startup mode, but China's RDA Microelectronics is aggressively pursuing several applications for its RF and power amplifier chips, including 3G, PHS and FM tuners.

In 2005, Shanghai-based RDA got its feet wet with an SCDMA transceiver and power amplifier. A year later, it followed with a transceiver for PHSstill a popular technology in China, with some 90 million users. Now, with a TD-SCDMA/GSM transceiver and power amplifier (PA), the company hopes to cash in on another distinctly local market and then branch out with an FM tuner that will sell in products mostly shipped abroad.

Many companies are betting that TD-SCDMA, China's 3G standard, will do well now that the government appears set to license it to China Mobile, the country's largest mobile provider. "We are already selling lots of TD-SCDMA PA modules to telecom equipment maker ZTE, so the infrastructure is going up quickly," said Vincent Tai, chief executive of RDA Microelectronics.

China has over 400 million mobile users, with millions more signing up every month. Spending on its 3G market will easily run into the tens of billions of dollars over the next few years as networks are fully built out. But China has held back on issuing licenses because of the immaturity of its local standard, leaving confounded chip and gear makers to await the spending spree's start.

In the meantime, RDA is working with baseband partners to verify its design. The offering consists of the RDA8212 PA and RDA8205 transceiver.

The single-chip transceiver operates in the dual-band ranges of 1,880-1,920MHz and 2,010-2,025MHz for TD-SCDMA, as well as the dual bands of 900MHz and 1,800MHz for GSM. The company has achieved a high level of integration, eliminating the IF surface acoustic wave filter and bringing most of the external componentssuch as the RF voltage-controlled oscillator, loop filters and tuning inductorsonto the chip. It comes in a 48-pin 7-by-7mm QFN package.

In TD-SCDMA mode, the receive path uses a zero-IF architecture, composed of an RF front-end (low-noise amp and mixer), an analog channel filter, an analog programmable gain amplifier and a sigma-delta ADC. A digital processing unit handles digital filtering, digital PGA and DC-offset cancellation. The transmit is a direct upconversion architecture, integrating a low-pass baseband filter, a highly linear I/Q modulator, a large dynamic range RF variable gain amp and a driver for external PA

GSM/GPRS parts will propel much of RDA's revenue growth this year. "The PA market alone is huge," explained Tai. "Many of the people who are buying MediaTek basebands and transceivers are using TriQuint or RFMD PAs, so I can break into that market. There is no China company making PAs right now. I am the only game." In addition, the company does its own switch, RDA ES04.

Much of China's demand is still in the 2/2.5G market, and for that, RDA has its quad-band RDA6205. The receive path uses a digital low-IF architecture, segmented into two sections. The RF front-end integrates three differential-input LNAs and an image-reject mixer. It amplifies the signal from the antenna and then downconverts it to a low IF of 100kHz.

The second section is the IF, which amplifies the chosen channel and performs gain control to adjust the output level to the desired value. The IF gain range can vary over more than 100dB.

In transmit, the RDA6205 uses a direct upconversion modulation block, an offset-PLL block and preamplifier block. The IF mixer upconverts the baseband signal to IF. Then the offset PLL block translates the IF modulation signal to the RF band and filters out noise.

The RDA6205 comes in a 32-pin, 5-by-5mm QFN and is moving into volume production now. The RDA8205 single-chip transceiver is sampling.

- Mike Clendenin
EE Times

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