Electronic Design

Network Vector Analyzers Set New Performance Standards

Instruments significantly improve automation, throughput, and ease of use.

When Hewlett-Packard introduced the HP 8753 in 1986, RF designers finally had an automatic network vector analyzer to call their own. The 8753 followed its higher-frequency counterpart, the HP 8510, which was introduced in 1983. The 8510 combined the power of microprocessors with the world's most advanced microwave hardware, bringing new levels of accuracy and ease of use to network analysis. These same capabilities were extended to lower-frequency measurements by the 8753, which soon became the standard for network analysis throughout the world.

Now comes a breakthrough as significant as the 8510 and 8753—the Agilent (formerly Hewlett-Packard) PNA series of network vector analyzers (Fig. 1). Instruments in this series combine exceptionally fast sweep speeds and dynamic range, low trace noise, four measurement re-ceivers with direct access, and 9-GHz coverage. In addition, the analyzers incorporate Microsoft's Windows 2000 Professional Operating System.

This gives them the full power of network connectivity and the ability to em-ploy a variety of tools for automated tests, like COM/DCOM and programming languages, as well as Microsoft applications for the postprocessing of measurement data. Ease-of-use features include electronic calibration (ECal), online and context-sensitive help, and robust built-in tutorials and manuals.

Four mixer-based receivers provide a standard low-noise floor of −118 dBm (−133 dBm by direct access). They also feature TRL calibrations for fixture and wafer applications direct-receiver access. Options are available for configurable test-set domain applications.

Measurement challenges that manufacturers of RF products face today provide clear goals for instrument manufacturers. Greater accuracy, higher measurement speed, a powerful but simplified operator interface, and the ability to integrate fully into a networked corporate environment are all essential ingredients in the design of today's state-of-the-art instruments. The PNA series of analyzers was designed to meet just such needs for both R&D and production environments.

Sweep speed, for ex-ample, illustrates just how great an advance the Agilent PNA se-ries is over both of its predecessors and competitive instru-ments. Furthermore, it shows how the instruments in this series don't compromise measure-ment speed to achieve wide-dynamic range. Measurements re-quiring 100 dB of instrument-dynamic range can be made with a 35-kHz bandwidth, rather than the 1-kHz bandwidth of the Agilent 8753ES, thereby producing sweep speeds that are 16 times faster than those of the 8753.

For measurements that require 120 dB of dynamic range, the PNA series is 35 times faster than the 8753ES. Sweeps that take 43 seconds on the 8753ES only take 1.2 seconds on PNA instruments. By removing the front-panel RF jumpers to directly access the measurement receivers (bypassing the internal directional couplers), more than a 143-dB dynamic range can be achieved. This provides insight into a component's performance that before was simply unavailable.

With a 35-kHz IF bandwidth, the PNA series can sweep six times faster than the 8753ES, updating a measurement 80 times per second. With a 10-Hz bandwidth, the PNA series achieves over 128 dB of dynamic range at the test-set ports, with an insignificant 0.0005-dB rms trace noise.

At a 10-Hz bandwidth using a reversed two-port coupler, the PNA series features a typical, average noise level of −147 dBc. This is much lower than the typical, −115-dBc average noise level of the older 8753 (Fig. 2).

Unparalleled Connectivity
The PNA series of network analyzers has the power to connect seamlessly with other instruments and an entire enterprise network. Windows 2000 endows these instruments with features typically found on PCs and brings a PC personality to network analyzers.

Several choices are available to save instrument states or measurement data. For local storage, operators can use either the analyzer's internal hard-disk or 3.5-in. diskette drive, or an optional USB-compatible CDRW drive. The Windows network-drive mapping features and a LAN interface allow data to be saved directly to remote PCs or file servers, making it easier to develop statistical process-controlled manufacturing environments. Users can generate hard copy either by any printer on the LAN, or else locally via a USB port or a parallel interface.

The LAN, serial, parallel, or GPIB interfaces also can be used to control other equipment, such as power meters, signal sources, and spectrum analyzers in the test station, directly from the network analyzer. Test software can employ Windows-based programs like Visual Basic, Visual C++, LabVIEW, or Agilent VEE. The LAN interface additionally makes it possible to conduct remote troubleshooting by reviewing measurement results and controlling the analyzer from anywhere on the LAN—or anywhere in the world via the Internet.

Agilent made automation a priority in the PNA series. Windows 2000 allows programs or applications to be run directly on the analyzer without an external PC. For example, a group of network analyzers on the production floor can each run test programs to control their individual test stations. The data collected at each test station can be stored locally on the network analyzer, or on a remote file server that's accessible via the LAN. For computation-intensive programs or programs that require considerable memory resources, the application can run on a fast external computer that also controls the instrument. Or, some data processing can be performed on the network analyzer and some on an external computer.

Engineers can create test processes using familiar SCPI or COM commands and execute them over a LAN interface or within the instrument. Additionally, SCPI can be executed over the GPIB. The analyzer's firmware provides many programmable objects, or automation "entry points." These respond directly to COM statements. COM programming and IntelliSense make it easier to write test code on multiple hardware or software platforms and also make the source code much easier to understand and debug. Plus, programs in COM can transfer data up to five times faster than SCPI.

In addition to their exceptional RF performance, the instruments have a powerful COM-based automation environment, simplified calibration through ECal and CalWizard, and many features designed to streamline the test process. If a segmented sweep is employed, the analyzer will measure the device's response only at defined frequency segments. It skips unneeded data and delivers high-frequency resolution where desired, like in a filter passband. Variable IF bandwidths enable wide bandwidths and fast sweeps to be performed in segments that require little dynamic range, while narrow IF bandwidths can be used in segments requiring high dynamic range.

The new instruments can improve test throughput when used to evaluate devices that need up to four instrument setups for complete characterization. The PNA series provides up to four measurement channels, each with its own stimulus and response parameters. Instead of recalling separate instrument states, one instrument state, containing all of the measurement channels, can be recalled. Only one instrument state, therefore, has to be recalled for an entire production run, rather than four per device. When these recall time savings are multiplied by a large number of device measurements, overall test throughput increases dramatically.

Price & Availability
The Agilent PNA series of RF network vector analyzers is available now. The E8356A 300-kHz to 3-GHz model is priced at $43,000, while the 300-kHz to 6-GHz E8357A model costs $49,000, and the 300-Hz to 9-GHz E8358A model costs $55,000.

Agilent Technologies Inc., Test and Measurement Organization, 5301 Stevens Creek Blvd., MS54LAK, Santa Clara, CA 95052; (800) 452-4844, ext. 7127; www.agilent.com.

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