Electronic Design

Conflicting Needs Require Compromises In Test

Four key needs are pushing the test field—bandwidth of measurement, speed of testing or throughput, usability, and cost of test. It’s difficult to achieve all of these in one instrument or test solution without some tradeoffs, so you have to focus on the most critical needs.

Bandwidth: Bandwidth refers, of course, to the frequency of operation and the bandwidth of the signals being processed. RF circuits operate at higher and higher frequencies as more and more services push up into the microwave regions. And, digital circuits and processors continue to operate at higher and higher clock frequencies with super-fast serial data buses to carry the data. To properly test the products with these higher-frequency signals and data streams, the instruments must have the bandwidth along with the higher sampling rates. The trend shows we can see signals up to 20 GHz today, with greater bandwidth on the way.

Speed: In this venue, speed refers to how fast you can make a test. While test speed really isn’t an issue in engineering, it’s hypercritical in production testing. Testing cell-phone handsets is the best example. Here is one of the most complex pieces of electronic equipment ever developed, and companies are building over 1 billion per year. To keep prices competitive, manufacturing costs (including test) must be low. As handsets become more complex with multiple multimedia functions, multiband operation, multiple processors, cameras, and other features, test equipment costs increase to make the necessary advanced measurements as well as shorten testing time.

Decreasing the test time has a huge impact on the cost of the product—more than you may think. Even shortening the test cycle by seconds or even fractions of a second can bring test savings. This complexity/test time problem has also become prevalent in many other electronic products with advanced integration and multiple functions. The trend is test times being sliced from hours to minutes to seconds, with faster testing on the horizon.

Usability: Today’s more complex test requirements require more advanced instruments. Such equipment thus becomes harder to use. Multifunctions with many test options greatly improve instrument application at the price of operational complexity. And, much of that complexity is related to the increased use of software. While the software helps you perform tasks quicker and more automatically, there’s still a learning curve to any new instrument or solution. So the trend in this case is status quo—essentially no improvement or decline in usability.

Cost: High-speed, wide-bandwidth test instruments are far more complex and expensive. Faster sampling is required along with the analog bandwidth to achieve the necessary precision of measurement. All of this costs more. Building test instruments that can make measurements faster also costs more. So more often than not, any test solution is a compromise to balance these factors in the target situation. The trend is clearly toward faster instruments with greater functionality—and heavier price tags.
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