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Tackling test for next-gen WLAN RF ICs

Posted: 16 Jan 2004 ?? ?Print Version ?Bookmark and Share

Keywords:wlan? rfic? wireless? lan? radio frequency?

The emerging generation of WLAN chips would accelerate the demand for more differentiated WLAN RFICs, believes Credence System's Larry DiBattista

Larry DiBattista is VP and GM of Credence Systems Corp.

An emerging generation of WLAN chips promises to fuel an explosion of new applications, accelerating demand for more differentiated WLAN RF ICs. However, for WLAN semiconductor companies, spiraling device complexity threatens to drive up test times and costs, potentially stalling growth and limiting the revenue opportunities anticipated for this evolving segment.

To deal with the formidable test challenges associated with RF ICs, semiconductor companies will need improved WLAN test methods that deliver high throughput and lower cost-of-test, while providing the flexibility needed to address changing product mixes and next-generation devices.

Advanced process technologies permit semiconductor companies to integrate RF, analog and digital circuits on a single die, providing the capability to implement complex RF ICs with interference-resistant signaling methods like DSSS and complex modulation protocols like OFDM and n-n-QAM.

Serving as the foundation of key WLAN standards such as 802.11a, HiperLAN2, 802.11b and 802.11g, signaling methods like DSSS, OFDM and n-QAM offer greater data throughput at lower transmission rates. However, with their wide bandwidth and high dynamic range, these approaches present significant challenges to companies seeking to be first to market with more sophisticated WLAN devices.

Traditional test methods and test equipment created for narrowband (<100KHz) single-carrier designs lack the performance characteristics needed to deal with emerging WLAN devices for 2.4GHz and 5GHz bands. Because active devices behave differently under sinusoidal and modulated stimuli, traditional test methods that rely on simple sinusoidal measurements provide misleading results.

If tuned and tested with sinusoidal waveforms, these designs will perform differently with the modulated signals present in actual applications, risking field failures in devices that seem to pass performance tests in the factory. As a result, RF designers increase guardbands, trading yield, and ultimately profit, for reduced risk of device failures.

To deal with this situation, RF IC companies are replacing traditional sinusoidal measurements with more relevant modulated signals measured using modulated vector network analysis methods. With these modulated methods, RF designers can apply the same underlying model for interpretation of results used in earlier approaches.

Since the device-under-test is stimulated with modulated signals, however, the results more faithfully reflect real-world performance. In turn, designers can use the more accurate results to reduce guardbands, resulting in improved yield and higher profit.

With the increasing test complexity, WLAN RF IC manufacturers face continuing challenges for high throughput and cost-effective test. Test equipment must provide the ability to compress RF test times and maximize throughput, handling multiple WLAN characterizations often on several devices in parallel. Using distributed parallel-processing subsystems, advanced RF IC test systems like the ASL 3000RF are capable of acquiring data streams with high precision and at high sample rates and complete multiple independent RF measurements from a single acquisition.

At the same time, semiconductor manufacturers must be able to quickly adapt their equipment to changing requirements, easily creating RF, analog and digital test configurations to address specific test needs of varying product mixes. The emergence of scalable test-system architectures promises to provide a cost-effective path for adapting and upgrading equipment as new RF, analog and digital test requirements come out. The inherent flexibility of this approach will enable companies to adapt WLAN test equipment to the exact configuration needed to take on a specific RF IC test challenge.

For RF IC companies, leading-edge WLAN devices present increased test challenges that demand improved test methods and test architectures. By providing a measurement environment well-matched to real-world applications, more sophisticated test methods and advanced RF IC test systems will be able to deliver the high levels of accuracy and throughput needed to meet emerging test challenges.

- Larry DiBattista


Credence Systems Corp.

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