Portable RF/microwave testing at remote locations once implied a battery-powered voltmeter. But handheld, portable RF/microwave test equipment has come a long way in the last decade, with the majority of benchtop measurement functions (such as signal generation and analysis) now available from portable packages. These miniature measurement powerhouses can be used manually, and many also include advanced test software programs and the latest computer interfaces for programmable and automatic testing at a remote site.

When specifying a portable RF/microwave measurement instrument, many of the test requirements may remain the same from what might have been sought from a benchtop instrument, such as certain output power level and output-power flatness over a required frequency range for a signal generator. Whereas a benchtop and a portable signal generator may be specified for a particular output-power flatness level, such as ±1 dB across a given frequency range, the benchtop instrument is typically operating in the controlled (temperature) environment of a laboratory or production facility. The portable signal generator, on the other hand, may need to provide its specified output-power flatness versus a wider range of operating temperatures than the benchtop unit, requiring a closer look at those performance specifications that might be affected by its operating environments.

What constitutes a truly portable RF/microwave test instrument? A large number of compact instrumentation modules have been introduced in recent years, such as modules for PXI and PXI-Express (PXIe) systems. Modular instruments are particularly useful for applications, such as in production and manufacturing, where a large number of test functions are needed from a small equipment housing. By sliding a number of different-function modular PXI/PXIe instrument functions into a rack-mount mainframe, what is essentially a full measurement system can be created within the space formerly held by a single function, such as a signal generator. But modular instruments are not necessarily portable, although they provide a great deal of measurement functionality from a small volume. 

Some modular test instruments may lend portability by merit of a Universal-Serial-Bus (USB) interface that allows these instruments to be controlled by a portable laptop computer with the appropriate software. When considering such instruments for portable test applications, however, it is recommended that the instruments are also powered by means of the USB bus; this will simplify setup and measurements made in a remote site, especially when relying on a portable computer’s power supply.

Because of the importance of signal analysis, one of the more popular of portable RF/microwave instruments is the spectrum analyzer. One of the earliest of portable RF/microwave spectrum analyzers is the model 492 from Tektronix. Not only did the 492 became legendary for its mobility and outstanding measurement capability, but its popularity played a key role in building the success of the company over the span of several decades. These portable spectrum analyzers were so well designed and constructed that units in excellent working condition can still be found on used-test-equipment websites.

Portable instruments such as the 492 spectrum analyzer established expectations for portable RF/microwave test instruments in terms of key parameters, such as measurement accuracy, frequency range, amplitude range, reliability, and even operating time on a battery charge. While newer portable spectrum analyzers may be considerably smaller and lighter than the robust 492, many can build upon the standards set by it for performance in a portable instrument.