Tracing Trends In RF Test Equipment

July 23, 2009
Some of the latest trends in RF/microwave test equipment include extended frequency ranges, nonlinear VNA measurements, and USB-powered portable measurement gear.

Demands on test equipment continue to increase as communications designers reach for more complex modulation formats. Several new instruments can be found in this issue, and some trends were apparent on the exhibition floor of the recent Microwave Theory & Techniques Society (MTT-S) event in Boston, MA: test-equipment specifiers want more power for their money and see low-cost solutions as Universal Serial Bus (USB) instruments to be practical.

Agilent Technologies introduced its model PSG E8257D signal generator with option 521 to provide from +24 to +28 dBm leveled output power from 250 MHz to 20 GHz, eliminating the need for add-on amplifiers to boost output power. The generator offers more than 1 W (+30 dBm) unleveled output power.

Giga-tronics unveiled its 2500B series of microwave signal generators, with total frequency coverage of 100 kHz to 50 GHz. Six models offer top frequencies of 2.5 GHz, 8 GHz, 20 GHz, 26.5 GHz, 40 GHz and 50 GHz. The agile sources feature frequency switching speed of typically less than 500 s for a 1-GHz step.

A great deal of interest at the show focused on nonlinear vector network analysis (NVNA), which makes twoand four-port measurements on highfrequency devices under compressed or saturated signal conditions. The results of such measurements, which have been termed "X-parameters" by Agilent, are actually modified scattering (S) parameters containing information about the nonlinear behavior of the device under test (DUT) at a given test frequency. The information is ideal for use in computer-aided-engineering (CAE) modeling tools, such as the Advanced Design System (ADS) from Agilent.

In support of the growing interest in NVNA measurements, Agilent showcased its latest VNAs, the PNA-X series with models operating to 13.5, 43.5, and 50 GHz (see Microwaves & RF, June 2009, Cover Feature). The analyzers (Fig. 1) feature two built-in test sources to simplify mixer measurements.

Earlier in the year, Anritsu Company introduced the industry's broadest-frequency VNA in a single unit, the VectorStar model ME7828A with frequency range of 70 kHz to 110 GHz. Its frequency coverage allows DC characterization of devices while also providing the higher-frequency extension to measure millimeter-wave devices, such as 60-GHz radar and communications devices.

Anritsu also supported a trend for smaller, more portable measurement power, by introducing its models MS2026B and MS2028B VNA Masters (Fig. 2). The former covers 5 kHz to 6 GHz while the latter operates from 5 kHz to 20 GHz. Although handheld units, these are capable two-port VNAs with fast tuning speed (750 s/ point sweep speed), for 12-term errorcorrected measurements.

An increasingly important trend in test is integration with software tools, and news from CAE software supplier Applied Wave Research (AWR) and test equipment leader Rohde & Schwarz reinforced this trend. The two firms announced AWR Connected for Rohde & Schwarz at the MTT-S, integrating the capabilities of the R&S WinIQSIM2 simulation software within the Visual System Simulator (VSS) system analysis software from AWR. This allows the modeling software to make full use of the full range of digitally modulated signals generated by R&S WinIQSIM2, along with those already present within the VSS platform.

One of the lesser-known test-equipment suppliers at the MTT-S, Oewaves, showed results for its high-performance automated phase-noise measurement system with standard carrier frequency range of 6 to 12 GHz and extended frequency range through 40 GHz. The homodyne system achieves absolute phase noise as good as -115 dBc/Hz offset100 Hz from carriers of 6 to 12 GHz.

In terms of USB test gear, LadyBug Technologies LLC offers an extensive line of USB power meters/sensors for pulsed and CW power measurements. They are controlled by a connection to the USB port of a personal computer (PC) and by a graphical user interface (GUI) software program running on the PC.

The PWR-6G+ USB power sensor from Mini-Circuits is suitable for CW power measurements from -30 to +20 dBm over a frequency range of 1 to 6000 MHz. Without calibration, it can provide 0.01-dB measurement resolution with typical linearity at room temperature of 0.1 dB.

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