FASTest RF

"Structural test" is one approach engineers have employed to cut test costs. With structural test, you apply input signals to a device under test and monitor the DUT's output signals. The inputs don't represent real-world signals; instead, they are carefully constructed to exercise a high percentage of a device's internal circuitry in minimal time.

Structural test has made headway in digital-device test. Automatic test-pattern generators (ATPGs) derive logic test-vector sets from design data, and low-cost ATE systems have evolved to apply those patterns quickly in a production-test environment (see the cover story on p. 12). In contrast, analog and RF components have required full functional tests, which require extensive test times on expensive ATE systems.

That's changing, though, as evidenced by the FASTest methodology developed by Ardext Technologies (Tucson, AZ; 520-797-1900; www.ardext.com). FASTest brings an alternative to functional test into the analog and RF realm.

FASTest RF exemplifies the multidimensional test (MDT) technique that Ardext applies to RF as well as analog IC test. FASTest RF generates RF device tests in three steps (Figure 1):

Figure 1

First, an MDT stimulus generator accepts a device's netlist and datasheet parameters as input. Using patented algorithms, it generates a set of compacted MDT vectors, which take the form of analog waveforms instead of the logic patterns you would expect from digital ATPGs.

In the second step, you apply the MDT waveforms to a set consisting, typically, of 100 to 200 training devices, whose RF performance you measure with traditional RF instruments. You then apply the training devices' MDT-waveform response and their measured RF parameters to FASTest RF's MDT optimizer and response calibrator. The optimizer and calibrator, respectively, generate optimal MDT stimulus vectors and normalized calibration information for use in production test.

In the final step, a production ATE system applies the optimal MDT vectors to a DUT, and it extracts DUT specifications based on calculations of a FASTest run-time system, which can operate on ATE from many of the vendors cited on p. 16.

Note that all FASTest signals are baseband signals. MDT-based production tests don't require specialized RF instruments such as spectrum analyzers and noise-figure meters. The only RF components required to perform the tests are up-converters and down-converters, which can reside within the host ATE system or on the load board.

FASTest RF can capture gain, power, efficiency, and harmonic and nonharmonic distortion values from a DUT in a single operation. Total device test times are typically 100 to 200 ms.

For more information, visit www.ardext.com/documents/FASTestRF/FASTestRF.htm.