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REVIEW: Tiny package packs 2.4-GHz RF deck

RF Arrays, Inc. Delivers World's Smallest Wi-Fi Integrated Front End

3×3 mm package enables complete front end capability with LNA, PA, power detector and switch

PORTLAND, Ore.—RF Arrays, Inc. announces the world's smallest front end solution for Wi-Fi systems. The RWF111 delivers industry-leading performance for both Power and Low Noise Amplifier and antenna switch in a 3×3 mm package and an external component count of just 2 bi-pass capacitors. The ultra small footprint also reduces Power Amplifier power consumption significantly vs. currently available solutions, making it ideal for embedding Wi-Fi capability into portable, battery-powered consumer electronics.

The device addresses the growing demand for embedded Wi-Fi capability in electronic equipment where board space is at a premium and power consumption needs to be minimized. Target devices include PDAs, VoWi-Fi handsets, cameras, cellular handsets, computer peripherals, and automotive devices.

“As Wi-Fi technology is becoming ubiquitous more and more devices are looking to add WiFi connectivity, in the same form factor. This is putting pressure on the design community both in terms of board real-estate and power budget. The RWF111 provides an effective solution for mobile electronics when adding WiFi connectivity,” said Rupert Prince, Executive Vice president, RF Arrays, Inc. “With this new Front end device, RF Arrays is enabling OEMs to embed Wi-Fi in a series of challenging new applications while simultaneously shrinking form factors, extending battery life and meeting aggressive cost targets.”

The ultra compact front end features a power amplifier with a current draw of less than 100 mA whilst transmitting 802.11g signal at 15 dBm output with a EVM of better than 4%. The MMIC includes a high gain very low noise LNA which will greatly improve the link budget in most systems (LNA Gain = 15 dB, NF < 1.0 dB), as well as a power detector and biasing circuitry in a miniature 16-pin 3 x 3 x 0.5 mm QFN package. The FEM is fully matched internally to a 50 ohm output and input impedance.

Availability and Price

The RWF111 is in production now, priced at US $1.10 in 10k unit quantities.

For further information please contact sales@rfarrays.com or call +1 (503) 287 5238

Hardly a day goes by without news of an integrated RF device of one sort or another. Just this past week Infineon Technologies released its SmartiWiMax dual-band all-CMOS RF transceiver. Likewise, Texas Instruments continued trumpeting its CC1020 single-chip narrowband UHF transceiver chip in full-page advertisements in the trade press. These are monolithic devices.

Obviously a single-chip approach is ideal—or is it?

For device makers, monolithic devices have always been the goal. Nonetheless, the argument for non-monolithic devices is compelling, especially if the price is equivalent to a monolithic chip.

There's still a place for hybrids and modules. In use, many hybrid or multi-chip components can be treated as monolithic ICs anyway.

Partitioning Your Design

If you're designing an RF system, you're well aware that partitioning your design can be critical to its success. Some designs demand low NF (noise-figure), while others shoot for good third-order intercept performance, or low added EVM (error vector magnitude). Some designers prefer using bipolar devices in some parts of a design, while others may choose GaAs (gallium arsenide).

While the tradeoffs and choice are seemingly infinite, there are companies that are striving to integrate vital blocks in ways that can help a designer clarify what's needed, and cut cost in the process.

The RWF111 front-end chip from fabless semiconductor maker RF Arrays, Inc . (shown on an evaluation board, above) is one of these products. At a price of $1.10 a pop in large quantities, it may well fill the bill for a block of circuitry that would otherwise require discrete components and a large bill-of-materials.

RF Arrays's press release mentions that only two “bi-pass” capacitors (sic) are needed. These bypass caps (one each on the PA and LNA Vcc lines), are only 27-pF in size.

Flat-Lead QFN Packaged

Now, consider the RWF111's size. At 3 x 3-mm (0.12 x 0.12-in.), a flat-lead QFN16 -packaged RWF111 is reasonably small. This form-factor in a rather complete integrated front-end/output-amp may give you a route to faster time-to-market, as well as the freedom to focus on your unique value-added engineering.

As RF Arrays's press statement (on the left) indicates, its single-chip device is slated for IEEE-802.11b/g applications in the 2.4-GHz through 2.5-GHz band. Using it gives you a 40-mW/80-mW PA (power amplifier) stage for your transmitter section (RF output depends on whether it's working in an 802.11g or 802.11b system).

Supporting 64-QAM RF

Typically, a wireless LAN PA has a lower efficiency than those in low peak-to-average digital radios. In operation, the RWF111 can support 64-QAM (quadrature amplitude modulated) OFDM (orthogonal frequency division multiplexed) digital systems operating at data rates to 54-Mbits/s.

That's significant, as 54-Mbit/s transmissions spell high peak-to-average power ratios. To support high power transmission at these data rates, the PA needs to be over-designed by 7-dB to 9-dB to ensure distortionless amplification on signal peaks.

The RWF111 also provides a cascode architecture LNA (low-noise amplifier) for the transceiver's Receive section. Low-noise operation accrues to the use of an internal GaAs PHEMT (pseudomorphic high electron-mobility transistor) front-end.

The RWF111's a solid-state SPDT changeover switch affords 22-dB of T/R isolation. The T/R switch uses a shunt and series FET for the transmit path. In the active path the shunt FET is turned off and the series FET is turned on.

The PHEMT GaAs switch ensures low insertion-loss and high isolation. Insertion loss is better than 1-dB, yet the power handling capability of the switch is better than 27-dBm. Return loss is better than 15-dB.

Voltage-Compensated Circuitry

You also get on-chip voltage-compensated bias circuits and power detector circuitry, and all inputs and outputs are matched to 50-Ω loads. Finally, this device will operate over a range of DC source voltages, from 2.9-V to 4.5-V.

If you look at the company's Web site, you'll find a number of LNAs, PAs, and amplifiers using a variety of HEMT, CMOS, and FET technologies and processes. The RWF111 is the present culmination of the company's expertise.

For more details, contact Rupert Prince at RF Arrays,
Inc., 1722 NW Raleigh St., Suite 404, Portland, Ore. 97209. Phone: 503-287-5238. E-mail: sales@rfarrays.com.

RF Arrays , 503-287-5238, www.rfarrays.com

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