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Multi-band CMOS cellular transceiver integrates LNA

Posted: 06 Feb 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Janine Love? Quorum Systems? CMOS? Sereno? QS1000?

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GSM is a standard that has truly earned the name of "standard." GSM users, although interested in additional functionality and bands, will simply not tolerate anyone messing with the performance of their proven, reliable, GSM handset. So, what should you do when you want to design a multi-band transceiver to enable worldwide cellular coverage in a single handset? You do it very carefully, the team at Quorum Systems will tell you.

Quorum began developing multi-band CMOS chips for voice and data platforms in 2003, and their portfolio already includes the Sereno QS1000 (GSM/GPRS + EDGE) and Sereno QS2000 (WiFi+GSM). Now, they have released the Sereno QS3000, which simultaneously covers seven bands, including all 3GPP frequency bands as well as 800MHz and 1,700MHz. An on-chip software switch controls which bands are in use.

While other manufacturers have been working on devices covering these bands, Quorum added a bit more to the mix by integrating the low noise amplifier (LNA) on chip. In the end, the QS3000 transceiver not only covers the necessary bands, it also supports on-chip DCXO calibration, suppressed and non-compressed mode, and features the on-chip LNA.

One of the key specifications for a part of this type is current consumption. When evaluating multimode transceivers, be sure to compare accurately. For instance, the QS3000 features an on-board LNA and consumes 120mA in full duplex mode or 53mA in GSM receive mode. "The need for an off-chip LNA adds to the real current consumption of other transceivers, as well as system footprint and cost," said Steve Brown, VP of product management of Quorum.

Another important specification for a cellular transceiver is size, and the QS3000 measures in at 7-by-7mm. In terms of performance, the device hits performance targets of -110dBm sensitivity for WCDMA. "This chip is designed for high-performance, advanced radio functionality, and it offers significant savings for the entire system," explained Quorum CTO Lon Christensen.

It's no small task to design a multi-band radio in CMOS, and the team relied on techniques and system blocks it had developed for low-cost bulk CMOS with the QS1000 and QS2000, as well as new innovations to complete the design of the QS3000. "One of the greatest design challenges was discovered when we began integrating early designs into real handsets, and we learned that it was imperative to minimize the interaction between the baseband in WCDMA when transmit performance is critical," added Christensen. "So, we use on-chip digital processing to minimize interactions with the baseband. And, by incorporating the LNA and eliminating the need for a transmit SAW filter, we have optimized the entire system."

Another challenge for the team was to ensure the transmit functionality across a 90dB dynamic range without any external calibration. For this, they borrowed IP and techniques developed for earlier Sereno designs.

So, what's next? This is an energized and committed design team, and they plan on making more product announcements very soon. While they are keeping the details quiet, with cellular and wireless data under their belts, you can bet they are looking at services such as digital video and Bluetooth. In the meantime, if you are looking for a transceiver for a wireless handset, give Quorum Systems a second look.

The QS3000 transceiver is priced at $8.15 in quantities of 10,000 units.

- Janine Love

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