WiMedia test tools emerge
By Richard A. Quinnell, Contributing Technical Editor -- Test & Measurement World, 10/1/2006
Promoters of ultrawideband (UWB) communications using multiband orthogonal frequency division multiplexing (MB-OFDM) have recently scored a double victory in the standards game. The MB-OFDM UWB approach, designated WiMedia and slated for use in the proposed WiMAX networking scheme, has also been chosen as the radio standard for two additional wireless efforts: Certified Wireless USB and next-generation Bluetooth. This expanded adoption promises to turn WiMedia into a multifunction radio base for all the key wireless systems of a PC.
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| Certified Wireless USB and next-generation Bluetooth. This expanded adoption promises to turn WiMedia into a multifunction radio base for all the key wireless systems of a PC. |
Testing WiMedia radio, however, poses a significant challenge. The radio’s scheme calls for frequency hopping among as many as 16 radio bands with center frequencies ranging from 3.4 GHz to 10.3 GHz. Further, the radio must conform to strict power spectral emission standards set by a variety of international regulatory agencies.
As a result, testing has two components. One is the measurement of spectral power to ensure regulatory compliance. The other is the measurement of the error vector magnitude (EVM) for the demodulated signal. The EVM may be measured as a function of the full multiband signal, of a single subcarrier, or of the symbol that the frequency hopping encodes.
Fortunately, commercial test equipment that can make such measurements has already begun to appear. Agilent Technologies, for instance, has added MB-OFDM UWB analysis capability to its 89600 Series vector signal-analysis tools. Tektronix has added wideband spectral analysis capability to its TDS 6000C Series oscilloscopes with its TDSUWB software, and the company has developed TDSUWB+WiMedia software to provide additional capabilities addressing WiMedia band groups.
One of the most recent introductions comes from LeCroy, which has released MB-ODFM UWB compliance software for its Wavemaster oscilloscope and Serial Data Analyzer (SDA) product lines. With the software, either instrument can capture signals directly from the transmitter and then down-convert and demodulate them, providing access to both the full RF signal and its modulation details in a single tool. James Mueller, chief technologist for LeCroy’s serial data division, explained that in addition to performing precompliance tests, the software also provides tools for tracking down compliance problems.
Offering compliance test tools when the standards are not yet finalized may seem premature, but Mueller noted that test-equipment vendors have been refining their tools at the WiMedia interoperability trials that have been run during the last several years. “We don’t have an official standard yet, but we have a candidate, and it is converging,” he said. “We are at draft version 1.0.” Mueller pointed out that the interoperability tests have provided equipment vendors with the opportunity to compare results with one another. “We all now have good test tools that agree with the results of other vendors’ tools,” he said.
The availability of these tools can accelerate the introduction of WiMedia radio devices by easing the certification process. Currently, the tools are primarily of interest to semiconductor device developers, but systems developers may find them useful when creating systems that incorporate certified radio components—once those components are available. By verifying that an integrated system meets regulatory and industry requirements before submitting a design for compliance and certification testing, test engineers can minimize the chances of failure and can help speed their WiMedia products to market.
