What is in this article?:
- Portable RF/Microwave Testers Take To The Field
- Don't Forget Longevity
Portable RF testers have made significant strides over the past decade, both in terms of performance and variety.
Don't Forget Longevity
Portability in modern RF/microwave test instruments calls for small size and light weight, but also long operating times on a battery charge. As an example, model N9340B is a handheld RF spectrum analyzer from Agilent Technologies with a frequency range of 100 kHz to 3 GHz (Fig. 1). It shows measurements on a 6.5-in. thin-film-transistor (TFT) color liquid-crystal-display (LCD) screen. It can also operate for as long as four hours on a battery charge. For ease of use in the field, it features a number of one-button measurements, including channel power, adjacent-channel power ratio (ACPR), and occupied bandwidth (OBW). The compact spectrum analyzer includes Ethernet local-area-network (LAN) and USB ports for connection to a personal computer (PC). For even higher-frequency measurements, the firm’s model N9918A FieldFox analyzer combines spectrum analyzer, cable-and-antenna-test (CAT) analyzer, vector voltmeter, and power meter with measurement capability through 26.5 GHz—all in a handheld package capable of running for 3.5 hours on a single battery charge.
Some USB instruments, such as the LSG series of Lab Brick signal generators from Vaunix Technology, can also operate under battery power or a remote power supply for truly portable applications (Fig. 2). Available in models from 20 MHz to 6 GHz, these compact test signal sources measure only 4.90 x 3.14 x 1.59 in. (124 x 80 x 40 mm) and weigh less than 1 lb. (0.45 kg). Although requirements for portable instruments used in military environments versus commercial settings may differ, most portable RF/microwave test instruments should be designed to provide full performance levels under harsh working conditions. Some military specifications, such as MIL-PRF-28800F Class-2 requirements, provide limits to define worst-case environments for portable electronic equipment. Parameters for this include temperature and humidity, altitude, vibration, shock, and even water moisture, with the specification that gasket seals can protect an instrument from moisture damage. In addition, requirements as outlined in the MIL-STD-810G standards even set recommendations for portable test equipment when operating in environments subject to sparks and explosions.
When considering test equipment for portable applications, many additional parameters may factor in. For a portable frequency synthesizer or signal generator, for example, a useful feature is the inclusion of an internal frequency reference source—such as an oven-controlled crystal oscillator (OCXO)—in contrast to reliance upon an external reference source. A portable signal generator should also provide similar amplitude flatness with frequency and frequency accuracy and stability when operating under battery power as when running on a USB connection or from an AC power adapter. Considerations for portable analyzers include many of the features of the portable signal generators, along with suitable display capability with an on-board screen, as well as an interface to connect to an external display screen (if needed).
A current trend in portable RF/microwave measurement equipment is increased integration, so as to provide more functions from a single portable package, such as spectrum analyzers with built-in power meters or even test signal sources. As the military standards for portable equipment detail, highly integrated portable measurement solutions can be extremely useful for applications in which the test instruments must be carried to the test site, or even held in place while the measurements are being made. Under such conditions, the additional connection to a USB port on a PC is not feasible. Nonetheless, having the greatest number of measurement functions included within a single portable, light-weight package can make measurements at a remote site both possible and practical.