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Achieving a 30 Percent Reduction in Test Time by Migrating to the MXA Signal Analyzer

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The IL/PDL Engine also supports automated switching of multiple lasers for extended wavelength range.

Polarization averaged return loss can be measured at the same time.

Reference measurements from one power meter port for multiple ports, normalized for individual detector responsivity or reference from each port directly.

Measurements can be easily automated with the engine’s COM interface.

Devices with integrated photodiodes, like coherent receivers (ICR) can also be measured with the special N7745A-E02 with photocurrent inputs or B2900A Series source/measure unit in the same setup. The software engine will determine spectra of photocurrent and wavelength responsivity as well as TE vs. TM resolution. A bias voltage can also be applied to the photodiodes.

For devices with high polarization dependence like polarization beamsplitters and ICR for polarization-multiplexed signals, an additional routine for accurately measuring PER beyond 20 dB is included.

IL/PDL License available for purchase as N7700A-100.

 As handsets become more ubiquitous, manufacturers ind themselves under tremendous pressure to produce low-cost devices. This cost pressure is also passed along to their component suppliers. At the same time, device complexity grows as the demand for more functionality inside a multiband handset expands. To be successful, a supplier must not only be the irst to deliver requested parts, but also to meet all of the speciications in multiple frequency bands at the lowest cost possible. This article examines Skyworks’ real-world test strategy for characterizing power ampliiers using multi-test platform (MTP) testers. It will illustrate how a single change in this test strategy resulted in a reduction in test time of more than 30 percent.

 Reviewing the Existing Setup 

Skyworks is constantly working to improve its designs and costof- test in order to exceed its customers’ expectations. It currently uses the Keysight Technologies, Inc. PSA spectrum analyzer as a central tool in its MTP testers to perform characterization test on power ampliiers (PAs) used in cell phones. Skyworks requires a great deal of lexibility from its MTP testers. For example, each tester must be able to test multiple technologies and in any number of possible conigurations. Depending on its test requirements, a PA may require up to 16,000 readings. As an example, the number of frequency points tested may vary depending on the device. Single-band devices are tested at three frequency points, while dual-band and quad-band devices are tested at six and 12 frequency points, respectively. At each frequency, there could be literally hundreds of voltage/current points measured. Other test variables may include temperature, leakage current, RF measurements (e.g., gain, power out), modulation, power versus time (PvT), error vector magnitude (EVM), adjacent and alternate channel power ratios (ACPR), harmonics (up to the 13th), continuous waves (CW), pulsed, and more. 

Identifying the Major Requirements 

Within Skyworks, the task of performing a thorough characterization of PAs falls to its Test Development team. Each MTP tester used in its characterization test strategy is required to address six areas: – Support GSM, CDMA, WCDMA, EDGE, WiMAX, WLAN, LTE, and TD-SCDMA modulation formats – Enable harmonics measurements up to the 13th harmonic and up to 13.5 GHz – Measure CW and pulsed current with voltage and RF turned off – Sweep output power from –14 to +35 dBm as input varies from –60 to +10 dBm – Sweep input power while searching for output power in three modes: linear, saturation and eficiency (optimum operating point of device) – Conduct IP3 measurements 

Creating a Better Solution

 To realize improved test capabilities and lower cost-of-test, Skyworks needed a signal analyzer that could be easily incorporated into its existing test strategy and meet the requirements previously speciied. It conducted a thorough examination of various vendors’ speciications and an evaluation of their solutions. Keysight’s N9020A MXA signal analyzer proved to be ideal for this task. With an all-digital IF and preamps up to 26 GHz, the Keysight MXA provides high accuracy in a midrange analyzer and industry-leading measurement speed, enabling dramatic improvements in throughput and yields in manufacturing test. Skyworks selected the Keysight MXA solution because of the following three key criteria: – Reliability & Accuracy. In a characterization tester, the key lies in reliability and accuracy. Reliability is critical because the MTP tester cannot afford to be shut down. Having a spare instrument is not an option because it would increase the cost-of-test. Accuracy is equally important because the tester’s data helps to determine the design’s ruggedness and the product’s readiness for the market. The MXA solution is both highly reliable and accurate. – Reduction in test time. The MXA solution offers an immediate improvement of greater than 30 percent in test time over the Keysight PSA solution. – Support. According to Michael David, manager of Test Development at Skyworks, “Keysight continues to deliver excellent support.” To enable faster device characterization test times, Skyworks replaced the PSA spectrum analyzers in its MTP testers with the Keysight MXA signal analyzer. Alongside the MXA, Skyworks’ MTP tester now includes Keysight’s N5182A MXG vector signal generator, 33220A function/arbitrary waveform generator, E4417A EPM-P Series dual-channel power meter, and E932xA peak and average power sensors. The MTP tester also utilizes Keysight’s N6710B modular power supply system. 

Outlining the Beneits

 By replacing its existing Keysight PSA spectrum analyzers with the Keysight MXA signal analyzers in its characterization MTP testers, Skyworks achieved a greater than 30 percent reduction in test time. The transition to the MXA proved effortless since it is code-compatible with the PSA solution. While minor changes to the test code and test-plan optimization offered Skyworks additional reductions in overall test time, by far the most signiicant improvement came from migrating to the MXA signal analyzer. This is especially noteworthy given that it is not uncommon to take more than one day to completely characterize a power ampliier. As Skyworks’ Michael David explains, “A reduction in test time is critical to being irst to deliver the part that meets speciications—and gaining the business.” As an added beneit, because the system-ready MXA is LXIcompliant (www.lxistandard.org), Skyworks’ test system can be migrated from GPIB to LAN. In future test systems, this capability can eliminate the effort and expense of adding a GPIB card to each system controller, while also reducing the cost of system I/O cables. 

Conclusion 

While it may seem like a good idea to stick with a test strategy because it is “good enough”—or to tweak it slightly to reduce test time—meaningful reductions in test time usually come from migration to a faster signal analyzer. In this case, adoption of the world’s fastest signal analyzer, the MXA, brought the semiconductor manufacturer Skyworks an over 30 percent reduction in test times, in addition to more accurate results. 

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