Today's RF signal generators come in virtually every color and stripe. Although traditionalists conjure up images of heavy grey-painted bench-level boxes with vernier tuning dials and clicky step attenuators, signal generators these days range from miniature, portable, and modular sources, to software controlled PCI bus and PXI modules that use "soft" on-screen interfaces.

The top end of the mix is still dominated by bench-level and rack-mounted generators, but an innovation is so-called synthetic instrumentation. Synthesized RF generators (and related RF instruments) use re-usable basic building blocks to configure RF test systems.

The approach eschews dedicated instrument modules (the kind you'll find in virtual instrument assemblages), relying instead on more or less universal data converters, mixers, and translators. It's an idea whose time has apparently come (see eeProductCenter opinion article Synthetic test is the future of test, but the technology is available now).

One of the first companies to promote the technique is Aeroflex Inc. (Plainview, New York). Other players in the synthetic instrumentation game include Teradyne (North Reading, Mass.) and Honeywell Aerospace Electronic Systems (Olathe, Kansas), but Aeroflex's designs are arguably the first to target users working with RF circuitry. As part of its strategy to provide flexible and cost-effective RF test systems, Aeroflex recently announced its 3000 Series of PXI-based modular RF test gear.

Bob Vogel, Aeroflex's Test Solutions's VP of business development, says the company's strategy is to migrate to an industry-standard modular product development platform. "The 3000 Series PXI products are a first step to leverage modular designs into other systems and stand-alone instruments," says Vogel. "The core functions are portable, which lets us address rapidly changing testing needs."

Although software is key, much of Aeroflex's high-performance capability accrues to PXI modules and chasses. "PXI is an inherently flexible and cost-effective platform," avows Bill Burrows, the firm's product marketing manager.

Right now, Burrows says the 3000 Series comprises PXI modules and applications for signal generation and signal analysis, mostly for the hot GSM/EDGE and WCDMA/UMTS cellphone test markets.

For cellular test, applications include automated measurement of parametric performance of terminal transmitter and receiver characteristics, transmitter and receiver alignment, and performance characterization during manufacturing and R&D.

General Purpose, Too

Regardless of the initial cellphone thrust, Aeroflex contends its 3000 Series will expand PXI synthetic instruments into the realm of general-purpose wireless testing, too. There's no reason why an Aeroflex signal generator, for example, can't be used for general-purpose CW (continuous wave) and digital signal sourcing.

Presently, the Aeroflex PXI RF test suite includes a Model 3010, which is a 3-GHz single-slot 3U-sized synthesizer, and a Model 3020, a 2.5-GHz two-slot 3U generator. There's also a Model 3030 3-GHz two-slot digitizer, and a Model 3060 2.5-GHz single-slot 3U RF combiner.

Let's look at a few of the specs for a 3030 module, as it's a representative example of the level of performance that synthesized instrument makers are striving for. Although not strictly a signal generator per se, the 3030 is characterized by linearity and low noise.

A 3030 module can digitize many types of wireless signals, and output others. It will output amplitude- and phase-corrected digital IF or IQ data samples. Significantly, these samples have typical amplitude accuracy specs within a tight 0.5-dB.

A 3030 also accepts signals up to +10 dBm (input level-control uses fast electronic switched attenuators, selectable in 4-dB steps). The 3030 provides 75-dB of SFDR (spurious free dynamic range), and touts 75-dB intermodulation-free dynamic range.

Those kinds of RF specs make it possible to measure a 3G cellphone system's ACLR (adjacent channel leakage power ratio) to 68-dB. The module's 15-MHz wide digitized IF can also capture three channels of 3GPP WCDMA for ACLR measurement. Full-rate digital IF, or decimated IQ data can be output via an LVDS bus.

The 3030 is also repeatable, touting less than 0.1-dB level variance, an attribute that makes it suitable for production testing, where production yields may depend on repeatability.

The Softer Side Of Synthetics

Aeroflex supports its obsolescence-proof synthetic instrument hardware with what it calls IQ Creator waveform tools. In use, hardware modules are configured and controlled by device drivers implemented using NI-VISA (National Instruments Virtual Instrument Software Architecture). Each PXI module is provided with a software driver as both a DLL for use within the standard environment, and as a set of source code.

With the source code, you can adapt device drivers to your specific needs. In addition to the driver DLL and source, a so-called soft front panel is provided for each module.

Bench-Level Sources

In the realm of more conventional bench-level test equipment, there are myriad vendors of RF signal generators. It's an environment that forces RF test equipment makers to strive for exclusive niches and unique product offerings.

Anritsu Co. (Richardson, Texas), for example, has a synthesized RF generator that's billed as an all-in-one instrument. The firm's Model MG3690A combines the bandwidths of separate RF and microwave signal generators with the spectral purity and frequency stability of a phase-locked source.

The MG3690A's ability to achieve crystal-oscillator-like phase noise over a 0.1-Hz to 40-GHz frequency range makes it appealing for both laboratory and production applications that may previously have demanded separate RF and microwave synthesizers. Generating clean RF signals into the microwave regime, the MG3690A can be used for both CW and pulse modulation applications up to 40 GHz.

Architecturally Notable

Anritsu's microwave RF generator is also an impressive design, from the point of view of its RF chain and mixing architecture. The phase-noise specs of this box are especially impressive.

Noise is essentially a composite of synthesizer phase noise, amplifier noise, and spurious response noise---all things you don't want in a signal generator when you're trying to test low phase-noise communications designs, especially those that use various forms of phase-shift modulation.

The lower the phase noise of the RF source, the less error the generator introduces into the measurement. If, for example, you're using an MG3690A as a clock source for bit-error-rate testing (BERT), its low SSB phase-noise translates to precise clocks, with edges that are consistent period after period. The result is that you'll see a cleaner eye diagram that will show data transitions more accurately.

Below 10 MHz, Anritsu's RF instruments use a DDS (direct digital synthesizer) to achieve their ultra-fine frequency resolution and low phase-noise. From 10 MHz through 2 GHz, a digital down-converter option is needed, but the down-converter produces its frequencies by means of successive binary division, a technique that eliminates non-harmonic spurious signals that you sometimes get with mixer-based down-converters.

Above 2.2 GHz, Anritsu uses patented techniques that rely on as many as six nested PLLs (phase locked loops)! Nonetheless, the company claims this gives its RF generators better phase-noise specs than that of its competitor's models.

Anritsu also uses an yttrium-iron-garnet (YIG) oscillator, in conjunction with a special switched filter bank, to ensure spectral purity. In contrast, some RF sources rely on frequency multipliers for higher ranges, and these multiplier stages can be inherently non-linear, leading to spurious outputs. That translates into higher phase-noise, and possible unwanted harmonic energy.

Anritsu also offers an ultra-low-noise option for its Model MG3690A that can reduce SSB phase-noise even further. Other modules permit digital or analog down-conversion to generate low phase-noise signals from 0.01 GHz to 2.2 GHz. Another option gives the unit frequency resolution down to 0.1 Hz.

DC to Daylight

The menu-driven IEEE-488/GPIB talker/listener MG3690A synthesizer is available in three different versions. The three variations operate out to 20 GHz, 30 GHz, or 40 GHz respectively.

On the other end of the spectrum, by means of options, you can generate RF down to 10 MHz---or even down to audio frequencies as low as 0.1 Hz. Anritsu's sources come pretty close to living up to the old "DC to daylight" adage.

The MG3690 generators can also be operated remotely over an IEEE-488 bus using one of two external interface languages---either a native language or SCPI (Standard Commands for Programmable Instruments). The native language uses a set of product-specific commands for control of the generator.

Under GPIB control, more than 3,200 non-sequential frequency/power settings can be stored and then addressed as a phase-locked step-sweep in a MG3690A. These boxes are also fast, switching in less than 25-ms to within a kilohertz of a final frequency setting.

The MG3690A can also store front-panel settings and save them in nonvolatile RAM. Through the unit's big LCD, menus let you save and recall set-ups. Whenever the instrument is turned on, control settings come on at the same functions and values that were poked in when the instrument was last turned off.

Of course, this GPIB RF source also lends itself to ATE (automatic test equipment). While the performance of ATE is largely determined by hardware and hardware interfaces, software and/or instrument drivers can also be significant. In the case of the MG3690A, the use of IVI Interchangeable Virtual Instruments Foundation standard instrument driver models enables interchangeability and interoperability---without software changes.

Easier IVI Development

Anritsu's IVI drivers support application development languages such as VisualBASIC and Visual C++, as well as National Instruments's (NI) graphical LabVIEW programming environment.

The I/O model also supports Universal Serial Bus, Ethernet, and FireWire. Much to its credit, Anritsu uses COM-based IVI drivers. Anritsu's boxes also include firmware for diagnostics. Self-testing routines perform go/no-go tests of most of the internal circuit boards and assemblies.

As you'd expect, Agilent Technologies (Palo Alto, Calif.) also competes in the high-end RF signal source space. One of the company's latest microwave signal generators provides vector modulation up to 20 GHz, and like Anritsu's boxes, does that in a single instrument.

The Model E8267C Vector Signal Generator , a member of Agilent's Performance Signal Generator (PSG) series, features an I/Q modulation capability and internal baseband generator that enables the simulation of wideband complex waveforms. Like Anritsu's signal generator, it's also an IEEE-488/GPIB box.

Other models in the Agilent series include the E8257C Analog Signal Generator, and the E8247C CW Signal Generator, which feature an analog ramp-sweep capability for use with Agilent's 8757D Scalar Network Analyzer.

PSG vector signal sources pack dual-mode baseband generators. These combine the capabilities of a wideband (80-MHz) ARB with the coding power of a realtime baseband generator. Agilent says this duality ensures repeatable microwave signal generation, letting you solve many of the problems you might experience if testing with so-called golden devices, multiple RF instruments, and custom test gear.

Complex Pattern Generation

Today's generators don't just output CW either. Agilent's baseband generator's deep playback memory and waveform sequencing capability can even let you create signals such as complex radar test patterns. Arbitrary waveforms representing pulsed radar signals can be defined in the time domain using industry standard tools on a PC, such as MatLab, Agilent's Advanced Design System (ADS), or Signal Studio software.

These signals can then be played back using the generators' internal baseband generator. This technique enables custom pulse shaping, accommodates pulse compression, and eliminates many of the synchronization issues associated with pulsing modulated signals using analog techniques.

Custom Modulation Formats

Since some microwave systems aren't standardized, the PSG can also adapt to custom test needs. Agilent provides a suite of custom I/Q modulation formats for the purpose. These cover PSK, minimum shift keying (MSK), FSK, and quadrature AM (QAM), to name a few.

By selecting one of these formats and setting high-level parameters such as data type, filtering, and symbol rate, you can generate a test signal for most communications formats.

"As microwave systems increase in complexity, engineers working on broadband wireless and satellite communications systems are struggling to find a way to make measurements that truly simulate real-world environments," notes John Vink, general manager of Agilent's Signal Sources Product Generation Group.

"This vector signal generator not only breaks through the 6 GHz frequency barrier," adds Vink, "but also provides low phase-noise performance, high output-power, and a specified level or accuracy."

Okay, how much will one set your budget back? You can get a PSG E8267C vector generator for just under $67,000 (analog Model E8257C and CW Model E8247C spins cost from about $21,000 to $43,000).

An E8267C baseband generator option will add a bit less than $12,000 to the price tag. A 1-GHz extended bandwidth option will add less than about $11,000 more, and Agilent's Pulse Builder Signal Studio software will add just a bit over $15,000 to the total price tag.

Conventional Alternatives

Some RF sources---even those operating at microwave frequencies---are packaged as easy-to-implement modules. Nova Engineering's (Cincinnati, Ohio) NovaSource Programmable Synthesized RF Signal Sources, for example, are self-contained.

Models are available in bands from 45 MHz to 2.5 GHz, with a typical tuning resolution of 25 kHz to 100 kHz. The lower frequency modules are priced at less than $700 a pop. They include internal TCXO references, and software-attenuated buffered RF outputs that go to +10 dBm levels.

Nova's modules work in conjunction with a PC, too. Using a PC and bundled NovaSource Control Panel software, you can enter a desired frequency and select an RF output mode, whether it's continuous, momentary, or toggled.

Settings are also stored in non-volatile memory, so once configured, a NovaSource module is also a plug-and-play RF source. Additionally, a NovaSource's internal reference signal can be brought out, or an external reference signal can be used.

NovaSource modules can also be controlled continuously via serial inputs, which can be a boon during automated test applications, but can also ease deployment in product development, breadboarding, and for general lab use.

Niche Sources

NovaSources can also replace expensive signal generators, although these diminutive frequency-synthesized RF sources, sporting gold-plated SMA connectors that literally inspire certainty, are designed to fill a niche need for point-source RF signal generation. With their limited frequency ranges, each can be thought of as an alternative to dedicating a physically larger and more function-laden signal generator to a narrow application.

Nova's microwave generators are also serially programmable. The company's NovaSource G6 line of RF signal generators cover bands from 2.4 GHz to 5.875 GHz. G6 models are priced at less than $900 each. You can choose from five frequency bands: 2.4 GHz to 2.9 GHz, 3.4 GHz to 3.7 GHz, 3.7 GHz to 4.2 GHz, 5.15 GHz to 5.35 GHz, and 5.47 GHz to 5.875 GHz, with step sizes as small as 1 kHz.

The G6 models provide coverage for license-free ISM (industrial, scientific, medical) band designs, using standards such as IEEE-802.11a, IEEE-802.11b, and Bluetooth. It can also serve as RF sources in bands populated by U-NII, HiperLAN, and Wireless Local Loop designs. The ability to perform internal frequency modulation with a NovaSource G6 makes the module suitable for PCS and cellular development and test applications as well.

One of the NovaSource G6's neatest attributes is its portability, as it's about the size of a deck of playing cards. With a simple user interface and nonvolatile memory, a NovaSource G6 can go to work in the field, yet serve as an alternative to bench-level microwave generators, too.

The G6 also includes a frequency sweep function. That can come in handy for applications such as filter testing, or for searching for unstable spurious oscillations or mixing products, popularly called "birdies" by RF hounds.

"As design and development work grows in the higher frequency bands, it was natural to expand the NovaSource line to provide an alternative to large and expensive signal generators," avows Dave Jordan, the firm's Products Director.

Board-Level RF Generation

If you move from modules to board-level RF signal sources, your choices are many. National Instruments (NI---Austin, Texas), for one, has single-slot PXI plug-ins that let you digitally generate sine and clock outputs.

NI's Model PXI-5404 is a 100-MHz frequency source that can output sine and clock signals simultaneously, up to 100 MHz, with 1.07 µHz resolution and sine-level accuracy to within a very tightly controlled ±0.2 dB.

A PXI-5404 can generate low frequency signals (down to 9 kHz) too, with DC to 100 MHz clock generation, with 12 bits of vertical resolution.

Using a PLL, the device can also sync to PXI backplanes and other devices, such as high-speed digitizers. That makes this RF source useful for clocking options in ATE systems, as well as for sine-wave generation for basic analog stimulus. Its clock output levels can excite and drive both TTL and CMOS circuits. The simultaneous sine and clock outputs and sine-level accuracy make it useful for coherent sampling in ATE, functional testing, and design-validation applications.

For those of you working with ATE and test suites of multiple instruments, PXI also brings trigger-bus and reference clocking to the table. This is a feature that enhances multi-board synchronization. The spec defines a so-called Star Trigger Bus for precise system timing.

A PXI-5404's amplitude resolution (loaded resolution is 2,048 steps) is roughly 489 microvolts/step. With its very tight level-accuracy and 300-Msample/s DAC sample rate, a PXI-5404 is the essence of a state-of-the-art RF source.

DDS Silicon Magic

The level of performance NI gets in its PXI-5404 plug-in also rests with the use of an on-board DDS, which works in conjunction with the PLL. If you look closely at the circuit board, you'll find an Analog Devices Inc. (ADI--- Norwood, Mass.) Type AD9852 chip lurking quietly.

ADI's AD9852 is an all-CMOS 300-MHz DDS that packs its own 12-bit DACs and phase comparator. When referenced to an accurate clock source, this IC generates extremely stable frequency-, phase-, and amplitude-programmable sine-wave outputs.

This silicon is an example of state-of-the-art mixed-signal chip-level integration, and the NI board is a masterful design embedding it on a single-board RF source product. The AD9852's on-chip DDS and PLL combine to let you program and set amplitude, frequency, and phase of both the board's sine and clock outputs, as well as the duty cycle of the clock output.

Just look at the board's inherent phase range. It extends from zero to 359.978°, with a resolution of more than 16,000 steps. That gives you a resolution of 0.022°, which is remarkable in anybody's book. The plug-in feeds 50-ohm loads through a gold-plated SMB connector, where it will deliver up to 2-V (peak-to-peak) signals.

With those kinds of specs, the designers of the PXI-5404 surely considered noise and distortion too. For its sine output, the card touts an average noise density spec of just 0.126 µV (rms) per root-hertz. And, THD (total harmonic distortion) is -56 dB at 1 MHz, and still a respectable -36 dB at 100 MHz.

On the PC software side, the PXI-5404 sources come with virtual instrument IVI-compliant drivers. These ensure programming support for LabVIEW, LabWindows/CVI, VisualBASIC, and Visual C++.

A 125 Msample/s ARB

Another example of a PCI-based generator is Geotest-Marvin Test Systems's (Irvine, Calif.) arbitrary waveform generator (ARB). Its Model GC1300, priced at less than $4000, is a combination function generator, ARB, waveform synthesizer, and programmable sequencer.

Like NI's product, Geotest's GC1300's low phase-noise characteristics and carrier stability make it suitable for telecommunication and RF channel-separation applications.

With a sample rate of 125-Msamples/s, the GC1300 can be used as a modulation source for a variety of encoding schemes, but it also provides high-speed waveforms to stimulate things such as signal distortion or video signals. It will readily handle FSK, ramped FSK, FM, arbitrary FM, and sweeps.

The GC1300 also has the hooks for multi-instrument synchronization, so it can be a viable alternative to an IEEE-488/GPIB-based waveform generator in a PCI-based RF test system.

The GC1300 offers a 10-digit sample clock frequency setting, 1-ppm clock accuracy and stability, and 14-bit vertical resolution. It can also run sequences up to 4096 waveforms, thanks to its 2-Mpoint memory depth, backed by very fast waveform downloads using DMA.

Like NI's plug-in, the clock on the GC1300 board is derived from a smooth-running low-noise DDS circuit. That's what lets it support wide-band FM, signal wander, and linear and logarithmic sweeps.

PC Software

As with NI's PXI-5404, Geotest-Marvin also supplies PC hosting software for its GC1300 RF generator. The company's ArbConnection software can control all instrument functions, modes, and features. The software handles signal generation, waveform editing, and downloads of stored waveform definitions from a PC.

The bundled software also lets this unit switch between many different waveforms, and its sequencing function supports linking of up to 4096 waveform segments and/or bursts. Indeed, a segment can be repeated up to 128,000 times in burst mode. Sequences can also run continuously, or be initiated by a programmable TTL-compatible trigger.

The latter can kick off a single waveform, a burst of waveforms, or a sequence of different waveforms. Triggering can also be used to advance a sequence of waveforms one segment at a time. The GC1300 accepts hardware triggers from a front panel input, or via SCPI commands.

One of the nifty things about this environment is that you can mix continuous and triggered segments within a sequence. That lets you create complex waveforms and patterns. In use, sequences are created by writing a sequence table using the ArbConnection software (it writes to the board's registers without any overhead from a dedicated microcontroller).

Pulse Options

Standard waveforms supplied in Geotest's ArbConnection library include the expected sine, square, triangle, and ramp types, as well as a number of pulse options. The latter include Gaussian and exponential rise/decay pulses.

You can also generate noise---and even DC. The board's sine waves exhibit just 0.05% THD out to 100 kHz, with spurious signals down -55 dBc below 1 MHz, and -35 dBc down at 10 MHz.

Waveform coordinates can also be imported from sources as diverse as MatLab or ASCII files. Moreover, just about anything that you can show on one of ArbConnection's composer screens can be downloaded and generated.

An FM composer function in the software also puts the y-axis of a display in units of frequency, so waveforms can be set up to change frequency over time. This lets you create any arbitrary wave shape, or use an equation editor, to FM the board's main output.

There's even a nifty freehand sketch mode. It permits you to draw custom waveforms. Additionally, you can use a built-in equation editor to create your own functions. With this, you can do things such as add or subtract components of a Fourier series, or inject random noise into a signal.

If your demands are somewhat less stringent, Geotest-Marvin Test Systems also offers a number of slower PXI products. Its GX1200 and GX1201 boards, for example, are also all-in-one instruments, combining the role of function generators, ARBs, and programmable sequencers. These 14-bit products can also be cost effective alternatives to bench-type or VXI-based generators.

The GX1200 is a 50-Msamples/s product. The GX1201 is a 100 Msamples/s unit. Like the GC1300, these plug-ins have 10-digit sample clock settings, and 1-ppm stability. They also permit multiple board syncing. The price for either comes at about $750 less than that of a GC1300.

Packaged in the popular 6U PXI form factor, all of Geotest's plug-ins can save space on your bench, and compete favorably with VXIbus and IEEE-488/GPIB automated systems.

Faster Sampling

Sampling even faster is ZTEC, Inc.'s (Albuquerque, New Mexico) Model ZT500PXI, which is a 300-Msample/s ARB. As a 14-bit generator, it comes in a single-wide 3U PXI/CompactPCI (CPCI) card. You can pop a ZT500PXI board into either a CPCI or PXI system (PXI is a derivative of CPCI).

The only incompatibility might be due to the fact that the PXI standard reserves a few pins on its P2 connector for trigger, clock, and inter-card communication functions. You'll therefore have to ensure no bus-connector conflicts exist prior to firing up a ZTEC board in your particular host.

In any case, the ZT500PXI plug-in generates low-harmonic-distortion sine waves and square waves over a range extending from 20-Hz audio out to 150-MHz RF, with a frequency resolution within 0.5-ppm. Here's the plug-in's block diagram.

These signals can also be modulated as FM, QPSK, QAM16, or chirped, and square-wave duty cycles can be adjusted from 0.1% to 99.9%. For triangle waves, the system generates signals out to 30 MHz.

Once installed, and with NI LabVIEW software up and running, the board's output channel can deliver low-drift signals, developing as much as 7-V (peak-to-peak) into high-Z loads, or 3.5-V into 50-ohm or 75-ohm loads.

These outputs are adjustable in fine 1 mV increments, too, with the onboard 14-bit D/A converter operating at sample rates of 40-Msamples/s, 80-Msamples/s, 100-Msamples/s, 160-Msamples/s, 200-Msamples/s, or 300-Msamples/s---backed by the product's 2-million-point memory.

On-Board DSP

An onboard Texas Instruments TMS320VC5409 DSP chip supports a standard waveform library for the ZT500PXI, as well as algorithm-based waveform generation, and user-defined custom synthesis algorithms. Waveform entry and editing is simplified with Windows drivers and an NI LabVIEW application.

This plug-in's high-bandwidth and dynamic range make it suitable for many synthesis applications, including general-purpose function generation, communications, and video signal generation. Like the Geotest-Marvin boards, its 2-Msample memory supports memory segmentation and sequencing. Continuous, realtime segment sequencing also supports infinite looping capability.

The ZT500PXI also provides programmable trigger and clock sources. It can also readily sync to other modules in a cardcage, thanks to its triggering and gating functions that permit it to be synchronized to external events, primarily using a PXI backplane's clock and trigger lines.

ZTEC offers four versions of this board-level product. You can select a 50-ohm or 75-ohm output version, or one for high resolution, or one specializing in video generation. These plug-ins range in price from about $4,200 for a standard version, to about $5,600 for the video spin.

What's It Look Like? >

As you can see, the definition of what comprises an RF signal generator can depend on who is using it, and for what purpose. Arguably, Schaffner-Chase EMC Ltd.'s (Dorking, Surrey, United Kingdom) High-Frequency Radiating Reference Standard, also known as the Comparison Noise Emitter CNE6507, doesn't look like a conventional signal generator. However, the CNE6507 is most certainly a complete high-frequency broadband source.

It can be used to make evaluations of anechoic chambers, as well as open-area test-site EMC measurements. The CNE6507 noise source, with its internal battery pack and self-contained omni-directional antenna, permits you to make test-chamber measurements with no surprises hidden at frequencies that you might not otherwise be able to generate using conventional sources or comb generators.

Powered by a rechargeable battery pack, it requires no power cables, which could distort emission fields. The continuous broadband output of the CNE6507 ensures observation of narrow resonance frequencies and other details that may well be missed using a comb generator.

The main housing containing the RF noise source and its amplifier, as well as a power-supply control board, also houses the system's omni-directional antenna. It's permanently attached, eliminating any possible errors that could be caused by connectors.

When you consider how critical lead lengths, lead placement, and mechanical connections are at these frequencies (especially at the source's high end of operation at 7 GHz), you don't want insidious errors from separable interconnects to enter into a test procedure. The same goes for the unit's lack of connecting cables. The fact that there aren't any will ensure a clean and repeatable radiated pattern.

If your requirements go below 1.5 GHz, Schaffner also has another battery-powered instrument that will take you down to VLF at 9 kHz. The company's CNE6500B, suggested for use in checking screen-room resonance, as well as for making tests in open-area test sites (OATS) and anechoic chambers, is a broadband noise source with output power extending from the very low 9 kHz end to 2 GHz. It uses an array of three monopole antennas.

Like the CNE6507, the broadband nature of the '6500B's output lets you make broadband tests that might otherwise be missed with a comb generator. This unit also avoids overloading other test gear on a range or in a screen room. Some impulse noise sources have been known to occasionally damage sensitive test receivers with sudden overloads. Not so, the 6507.

For more information on companies and products mentioned in this article, contact:

Aeroflex Inc., 35 So. Service Rd., Plainview, New York 11803. Phone: (516) 694-6700. Fax: (516) 694-4823.

Agilent Technologies, 395 Page Mill Rd., P.O. Box 10395, Palo Alto, Calif. 94303. Phone: (800) 452-4844. Fax: (888) 900-8921.

Analog Devices, One Technology Way, PO Box 9106, Norwood, Mass. 02062-9106. Phone: (781) 329-4700, or (800) 262-5643. Web site.

Anritsu Co., 1155 E. Collins Blvd., Richardson, Texas 75081. Phone: (800) ANRITSU. Fax: (972) 644-1877. Web site.

Geotest-Marvin Test Systems, Inc., 17570 Cartwright Rd., Irvine, Calif. 92614-5846. Phone: (888) TEST-BY-PXI, or (888) 837-8297, or (949) 263-2222. Fax: (949) 263-1203. E-mail: info@geotestinc.com. Web site.

Honeywell Aerospace Electronic Systems, One Technology Center, 23500 W. 105th Street, Olathe, Kansas 66061-1950. Phone: (602) 365-2055

National Instruments Corp., 11500 North Mopac Expwy., Austin, Texas 78759-3504. Phone: (512) 683-0100. Fax: (512) 683-8411. Web site.

Nova Engineering, Inc., 5 Circle Freeway Dr., Cincinnati, Ohio 45246. Phone: (513) 642-3000, or (800) 341-NOVA. Fax: (513) 642-3300. E-mail: info@nova-eng.com. Web site.

Schaffner-Chase EMC Limited, Broadwood Test Centre, Rusper Road Capel, Dorking, Surrey, RH5 5HF, United Kingdom. Phone: +44 1306 710205. Fax: +44 1306 713303.

Teradyne, Inc., 600 River Park Dr., North Reading, Mass. 01864. Phone: (978) 370-2700.

ZTEC Inc., 6610 Gulton Ct. NE, Albuquerque, New Mexico 87109. Phone: (505) 342-0132. FAX: (505) 342-0222. E-mail: sales@ztec-inc.com.