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Test & Measurement World: Testing the tester components

Peregrine Semiconductor builds a range of RF switches and other devices based on its UltraCMOS solid-state SOS (silicon-on-sapphire) process, which integrates ultra-thin silicon CMOS circuitry on a dielectric sapphire substrate. The company’s SOS devices operate beyond 10 GHz and at power levels greater than 40 dBm. They target applications ranging from high-volume consumer electronics to high-reliability test equipment and military and aerospace systems.

The test-equipment market is a key one for Peregrine. And because the company’s switches can be used in test equipment, they must deliver levels of performance that exceed that which can be economically and accurately measured by commercially available test systems. To overcome this limitation, Peregrine’s engineers have developed unique approaches to perform device characterization and high-volume production test.

Christian Steele, product-development section manager at Peregrine, said the company’s parts can appear to be deceptively simple ones that might seem to be easily testable. The parts tend to be low-pin-count, 6- to 20-lead devices, but he pointed out that when it comes to measuring specs like linearity, the challenges immediately become apparent. “When we try to measure harmonics or IP3 [third-order intercept point] or the 1-dB compression point,” Steele said, “it’s very challenging and can’t easily be done using traditional test techniques.” Similarly, he said, insertion loss might be guaranteed within a 0.1- or 0.2-dB range from part to part. “If a typical maximum variation is 0.1-dB wide, the test equipment that we are using to collect a distribution of data has to be very repeatable. That challenges our test capabilities and makes us rethink how we perform functions like de-embedding.”

Mark Schrepferman, director of communications and industrial products at Peregrine, explained that the test challenges that Steele’s team faces help the company develop parts for the testequipment market. Those parts include the PE42552 absorptive SPDT (singlepole, double-throw) switch, which operates to 7.5 GHz with a 1-dB compression point of 34.5 dBm and exhibits an insertion loss of 0.65 dB at 3 GHz. Also for test-equipment applications, the company complements the PE42552 switch with the PE43703 7-bit digital step attenuator.

When testing its own products, Peregrine faces different test challenges in characterization and production test. Steele focuses on characterization, and he noted that many people perform characterization with a bigbox ATE system, a relatively quick approach that can simplify the development of production-test programs. But, Steele said, “A big-box tester is not going to offer anywhere near the performance and repeatability that we need to measure our parts. So, what we have had to do is design individual automated test systems (Figure 1) that will measure one or two parameters in a very accurate, repeatable manner. Each part that gets characterized may go through four different stations as we measure harmonics, S-parameters, switching time, IP3, 1-dB compression point, and so on, with each station giving us the highest performance that we can possibly get for one or two specific parameters, without being limited by ATE.”