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Portable Test & Measurement Equipment Provides Benchtop Performance

Portable Test & Measurement Equipment Provides Benchtop Performance

Portable equipment for RF/microwave testing has advanced dramatically in recent years. RF researchers, engineers, and technicians could find the latest in these portable units anywhere from table tops to tower tops.

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Every year, RF technologies are integrated into more mission-critical systems for military, industrial, and commercial installations or products. As applications for RF equipment expand, the need for high-performing, portable test and measurement equipment also increases. Traditionally, testing complex RF systems in the field involved mobilizing rack-mount, laboratory-grade equipment. These testing operations incurred high monetary as well as opportunity costs. Valued laboratory test and measurement equipment also was unavailable at times, as it would be used by other departments. These factors pushed RF test and measurement equipment companies to offer scaled-down, portable solutions with specific or limited uses.

In recent years, the heightened integration of RF components has enabled substantial feature upgrades to RF portable test and measurement equipment (Fig. 1). These enhancements have led to correlations between laboratory-grade, rack-mount products and portable solutions. Additionally, the market is seeing new varieties of applications for these high-end instruments outside of the field. This is good news for engineers, researchers, or technicians looking for cost-effective and durable RF portable test and measurement equipment. When choosing one of these feature-dense devices, however, they now have a lot of factors to consider. The following types of RF portable test and measurement equipment are commonly bridging gaps between the lab and field: vector network analyzers (VNAs), spectrum analyzers, signal generators, and cable/antenna analyzers.

Portable Test & Measurement Equipment Provides Benchtop Performance, Fig. 1
1. This analyzer can be remotely controlled via modern tablets through a convenient Ethernet link.

Signal generators stimulate an RF medium, like a coaxial cable or waveguide, with an RF signal. This operation is commonly used to service/test RF installations and support development when a medium- to high-powered RF signal is needed. Some signal generators can produce modulated signals, mimicking telecommunications systems for advanced test. These instruments are defined by metrics like signal resolution, settling time, phase noise, power range/resolution, spectral purity, frequency range, and frequency switching speed. Many modern signal generators come with USB, GPIB, or Ethernet connectivity for automated control and integration with test environments. Hittite and AnaPico, for example, offer compact RF signal generators with internal battery options. They can serve as portable test and measurement equipment in optimal field conditions. Of course, there are more ruggedized, extreme-weather offerings for devices that are more likely to be used in servicing and troubleshooting situations, such as RF analyzers.

For their part, VNAs measure the magnitude and phase of the reflection and transmission of RF energy through a system. VNA measurements are used to characterize a device, component, or sub-assembly to determine if the unit is operating according to specification. The number of ports, frequency range/resolution, data points, measurement speed, error correction, and sensitivity/noise floor are usually the critical specifications for portable VNAs. Most portable VNAs have one or two test ports and come with a variety of upgradable options, such as the following: modules that enable time-domain analysis, remote control, rapid calibration, signal-analyzer features, USB power sensing, GPS localizing, DC voltage sourcing, power metering, pulse measurement, and distance domain measurement. Bird, Agilent, and Anritsu all offer ruggedized versions of portable VNAs with many optional upgrades (Fig. 2).

Portable Test & Measurement Equipment Provides Benchtop Performance, Fig. 2
2. These vector network analyzers sport a large screen with many configurable options.

Portable VNAs are similar to signal analyzers with a few key differences. Signal analyzers measure a device’s RF characteristics using communications specifications. Such specifications include amplitude, carrier level, phase noise, sidebands, bandwidth, and harmonics. These analyzers are most commonly used to measure unknown and uncharacterized signals for identification and classification. Demodulation and scalar measurement techniques aid in these measurements. According to Richard Duvall, Technical Marketing Manager for Tektronix,"Portable spectrum analyzers are best used in spectrum-management applications. Performing spectrum mapping and chasing down interference signal needs to be done quickly, and often involves drive tests where portability can be critical.”

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Seeking Signal Analyzers

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Where VNAs stimulate a system with RF energy, signal analyzers are predominantly sophisticated receivers. They have many of the same key specification as VNAs with the addition of amplitude accuracy, sweep time, tracking, and channel-measurement capacity. In addition to modules that are common in portable VNAs, signal analyzers may be equipped with: modulation-analysis software/hardware, channel scanner, security features, spectrum monitor with spectrogram analysis, tracking generator, and time-gated spectrum analysis. Bird, Agilent, Anritsu, Tektronix, Rhode & Schwarz, and BK Precision all offer portable signal analyzers.

In addition, many of these companies offer combination analyzers that allow for full VNA and signal-analyzer features. Some hybrid devices even mix and match these features, such as cable and antenna analyzers. Cable and antenna analyzers are specialized test products, which are designed to offer some features of both VNAs and signal analyzers for advanced antenna and cable testing/verification. These analyzers combine modules like distance-to-fault measurements, RF power metering, optical power metering, insertion/reflection measurements, modulation measurements, and RF sourcing. In doing so, they provide easy-to-understand cable, filter, and antenna analysis. JDSU, Anritsu, Rhode & Schwarz, and Bird all offer versions of cable and antenna analyzers (Fig. 3). These products show how increased RF integration is enabling a combination of advanced features to be embedded into portable test equipment.

Portable Test & Measurement Equipment Provides Benchtop Performance, Fig. 3
3. In addition to ruggedized, field-ready exteriors, these cable and antenna testers promise easy operation with user-configurable test sequences.

For the most advanced portable test and measurement equipment, software modules are largely enabling new features. The hardware, which is integrated for use throughout the device series, simply requires software activation. This is a common trend with state-of-the-art test and measurement equipment as RF hardware becomes more compact. Thanks to this integration, some high-end portable test and measurement equipment has emerged with data-correlation with its higher-performing, laboratory-grade counterparts.

Yet modern, portable test and measurement equipment is not yet able to match laboratory-grade test and measurement equipment in specifications like dynamic range, sensitivity, noise floor, speed of test, or repeatability. Though there are these tradeoffs when using portable rather than full-sized test and measurement products, portability, battery power, physical/environmental ruggedness, and reduced cost add versatility and cost benefit for certain users. Tom Hoppin, Product Manager for RF Handhelds for Agilent, shared, “We are seeing a lot more interest from the R&D sector than we thought. As our message about the data correlation between the handhelds and the big boxes gets out, we are selling more units to R&D houses.” Given all of the optional modules and the versatility of modern portable test and measurement equipment, weighing the attributes and deciding on the right product for the user has become quite extensive.

The purchasing of laboratory-grade test and measurement equipment, for example, is a high-price decision usually conducted at the department level with input from the engineers. Because portable test and measurement equipment is lower cost and often purchased for the requirements of a specific user, it may require more personal attention during selection. Among the key factors to consider are the environments where the equipment will be used, who will be using it, and what features best lend themselves to aiding in the test and measurement process without adding unnecessary complication.

Hoppin comments, “I would urge someone to demo it. You need to look at the ergonomics, the weight, balance, and the way it fits in your hand. As some users are in the field for over 8 hrs, if the ergonomics aren’t just right, it can make a big difference for a user.” Many PTME companies will allow potential clients to demo their units to see if they are a right fit for their application. As with any high-end electronics equipment, the standard length of the warranty offered for the device may be an indication of the quality. Additionally, some field environments require very specific ruggedness measures. The device companies label their devices with the tests that they have undergone and passed.

Today’s portable test and measurement equipment manufacturers design their devices to receive software upgrades, thereby enabling additional and enhanced features. This aspect could allow for future feature scaling, as the uses for the device may increase and translate into cost savings in the short term. Thus, portable test and measurement equipment is no longer just scaled-down and lower performing versions of laboratory equipment. Enabled by RF integration, it offers many advanced features in a compact and rugged package. In addition, data correlation with laboratory-grade instruments opens doors to new applications for these devices. The demand for flexibility in RF test and measurement is encouraging the development of these portable products. The RF test and measurement field should witness huge advancements in these devices as frequencies increase and testing environments become more feature dense.

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