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RF signal generator will be LXI-compliant

Posted: 27 Jan 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Alex Mendelsohn? Keithley Instruments? LXI? LAN eXtensions for Instrumentation? RF signal generator?

LXI RF signal generator

Test-and-measurement house Keithley Instruments Inc. is introducing a new LXI (LAN eXtensions for Instrumentation) RF signal generator, and is pre-announcing some related RF test gear that will debut later this year. Coverage will span 400MHz to 2.5GHz

These automated LXI products are slated for use in the lab, as well as on the factory floor, where they will support the physical, programmatic, LAN and Web portions of the LXI standard.

The first product to debut in this family, with availability expected in March, is Keithley's Model 2910 RF vector signal generator. Based on an SDR (software-defined radio) architecture, this instrument will use a patent-pending synthesizer and power-leveling scheme.

Related products
This summer, Keithley plans to roll out two related products: its Model 2810 RF Vector Signal Analyzer, and its Model 3500 Portable RF Power Meter. Designed to complement the Model 2910, the Model 2810 will provide high-speed measurement and modulation analysis. For its part, the Model 3500 power meter will be a handheld instrument for measuring average RF power.

Back to the precursor Model 2910. As an SDR design it's software will adapt it to your test requirements. What's more, Keithley claims its Model 2910 will make generation of RF signals simpler, even for novice users, thanks to an intuitive user-interface.

Reducing test time
Whether switching between frequencies, amplitude levels, or waveforms, Keithley claims its 2910 will also dish up switching speeds that will be 2x to 10x faster than its competitors. That will also be a production-line benefit, as faster execution time can increase throughput, permitting more tests to be conducted on a greater volume of devices.

The Model 2910 will enable this test-time reduction through a number of innovations and specs. For one, the 2910 will settle in just 1.5ms, and its sync-out source-settled indicator will only be set when a source is settled. This will eliminate the need to slow down tests by adding software wait-states to ensure the signal generator has settled.

Similarly, fast switching among waveforms is also a critical attribute for reducing test-time, especially for products embodying multiple wireless standards. Keithley's 64Msample arbitrary waveform generator (ARB) will support simultaneous loading of multiple signal waveforms and enable switching between these signals in less than 5ms.

Multiple file storage
The ARB will make use of volatile memory for storage of its complex samples. That will be complemented by 256MB of non-volatile memory for storing ARB files. This scheme will support multiple ARB files that can be loaded into memory at the same time.

Once ARB files have been loaded into volatile memory, switching from one ARB file to another will take only about 5ms. In addition, the 2910's built-in modulation personalities will be able to be copied to ARB memory, then selected to support programming of multiple different modulation formats. The generator will then switch between them quickly.

So, for example, a dual-mode cellphone may require tests with both GSM and WCDMA modulation formats. With some RF sources, the time required to switch modes may be so long that this type of test could be impractical in high-volume manufacturing scenarios. In those cases, separate generators are typically called into play for each modulation type. That can be costly, and add complexity to a test suite.

Adapt to changing needs
With its SDR-based architecture, the Model 2910 should prove to be adaptable as wireless standards evolve. As delivered, the 2910 will offer optional signal-generation software "personalities" for many cellphone formats, including GSM, GPRS, EDGE, W-CDMA, cdmaOne, and cdma2000. For signal formats not included in its initial release, the 2910's arbitrary waveform generator will support downloading of virtually any externally generated signal waveform, with up to 40MHz of bandwidth.

In addition, the 2910 will be able to generate an RF signal with up to a 200MHz bandwidth from analog baseband I/Q (in-phase and quadrature) signals provided by you.

A friendly user interface
A variety of other features will abound. The Model 2910 will use an intuitive touch-screen graphical user interface (GUI). The GUI will lend itself to both experienced RF engineers as well as novice users learning RF instrumentation for the first time.

Keithley points out that competing products often tend to have rows of buttons on the front panel, or multiple layers of so-called soft-keys. These are sometimes confusing to operate (of course, ultimately, only the day-in-day-out user can decide about the efficacy of a user interface).

Nonetheless, on the 2910 you will be able to choose between graphical or tabular methods to edit waveforms or create new ones. There will also be comprehensive Help documentation that will be accessible from the front-panel, or via the instrument's remote interface, or from a CD-ROM.

Remote control
If you decide to control the Model 2910 remotely, built-in 100Base-T Ethernet and USB interfaces will support high-speed programming and command transfer. There will also be an IEEE-488/GPIB (General Purpose Interface Bus) port, and the equipment will use the standard SCPI (Standard Commands for Programmable Instruments) syntax.

Moreover, the Model 2910's trigger input and sync output ports will be able to be used to provide hardware sequencing of a Model 2910 with other test equipment. There will be two modes for hardware triggering in Sweep and List modes. The first mode is to trigger a complete sweep or list. The second mode is to trigger each point in a sweep or list.

It may be desirable to provide a trigger to an RF analyzer or power supply in order to make a measurement after the source has settled to the new frequency or power level or at each point in a sweep or list.

If the Sweep/List mode is used and a hardware trigger is provided to go to the next point, the source will be settled and the sync output pulse will occur after only about 1.5ms. That's the kind of speed that can measurably improve production yields.

Price and availability
The Model 2910 RF Vector Signal Generator will be priced at about $14,500 when it rolls out at the end of March. Pricing for the Model 2810 and Model 3500 will be announced, and availability will be in the summer.

Finally, all of these boxes will come with a three-year warranty.

- Alex Mendelsohn

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