Precision is not a term often associated with in-field measurements. But the latest additions to the FieldFox family of handheld RF/microwave analyzers from Agilent Technologies may change all that.
Built with military-grade toughness and measurement accuracy to rival benchtop and rack-mount laboratory-grade instruments, 14 FieldFox portable microwave analyzers are available as cable-and-antenna analyzers, spectrum analyzers, vector network analyzers, or all-in-one combination analyzers. Frequency ranges start as low as 5 kHz and extend to 4.0, 6.5, 9.0, 14.0, 18.0, and 25.6 GHz.
Ideal for commercial and military in-field testing of communications, radar, and electronic-warfare systems and their components, these powerful test tools weigh only 6.6 lb (3.0 kg), making it easier to bring the test lab to the device under test (DUT), rather than the other way around.
The analyzers can be considered the result of “planned portability,” rather than simply efforts at trying to pack as many measurement functions as possible into a compact, lightweight carrying case (Fig. 1). True, some FieldFox analyzers could replace many standalone instruments, integrating a cable and antenna analyzer, spectrum analyzer, microwave vector network analyzer (VNA), vector voltmeter, power meter, variable dc source and current meter, frequency counter, interference analyzer, independent signal generator, and even a Global Positioning System (GPS) receiver to precisely determine the test’s location.
But these are not just “general-purpose” measurement functions bundled into lightweight portable housings. Many of the test capabilities draw from some of the company’s top benchtop instruments, adapted for more compact, portable use.
The microwave VNAs borrow from the PNA-X series of benchtop VNAs, while the microwave spectrum analyzers are based on Agilent’s PSA family of microwave spectrum analyzers. The performance levels of these portable instruments may lead many engineers to think they are looking at specifications for a benchtop instrument.
The VNAs provide full two-port S-parameter measurements with low trace noise of ±0.004 dB and dynamic range of 94 dB (to 18 GHz). Tuned by a local oscillator (LO) with phase noise of –111 dBc/Hz offset 10 kHz from a 1-GHz carrier, the spectrum analyzers deliver measurement amplitude accuracy of ±0.5 dB immediately upon power-up, with no warmup period required. The spectrum analyzer functions have a typical spurious-free dynamic range (SFDR) of 105 dB.
These are truly test instruments for applications in land, sea, and air. Much thought also went into the protective housings. Each instrument is contained within a completely sealed enclosure compliant with MIL-PRF-28800F Class 2 requirements. The instruments and their housings are type tested to meet MIL-STD-810G, Method 511.5 Procedure 1 requirements for operation in explosive environments.
In addition, a specially designed connector bay protects its connectors from damage due to drops or mishandling. The dust-free instrument housing is designed without vents or fans and can withstand high levels of shock and vibration.
The portable instruments are based on a vertical or “portrait” orientation, showing results on a low-reflectivity, 6.5-in. thin-film-transistor (TFT) display that’s visible in both full daylight and at night. The FieldFox instruments are only 7.4 in. (188 mm) wide and easy to hold, but also feature an easy-to-navigate control panel with large keys that can be controlled in the field even when wearing gloves (Fig. 2). They consume about 15 W typical power and run for about 3.5 hours per charge of the internal lithium-ion battery. They also weigh just 6.6 lb (3.0 kg) and are designed for a wide operating temperature range of –10°C to 55°C.
Admittedly, selecting a final FieldFox instrument configuration involves reviewing numerous options. For the spectrum analyzer, these include a built-in power meter, an interference analyzer with spectrogram, a full-band preamplifier, and a full-band tracking generator. For the VNA, these include a vector voltmeter, full two-port S-parameter measurement capability (transmission and reflection measurements), time-domain capability, and several calibration functions.
With the installed CalReady function, each FieldFox is calibrated at power on or for preset conditions and is ready for accurate, calibrated testing without additional calibration steps required. The QuickCal option for the VNA provides a means of performing a fast two-port calibration without a calibration kit of physical standards—a particularly useful feature for in-field measurements. This function automatically corrects for the phase shifts and insertion losses of coaxial cables and adapters and electrically shifts the calibration plane of the VNA to the end of these interconnect components and to the ports of the DUT.
In addition to the sophisticated calibration approaches for the VNA, the FieldFox spectrum analyzers benefit from automatic internal correction techniques such as InstAlign, an internal amplitude alignment process that automatically checks and corrects (without user intervention) amplitude accuracy as environmental conditions such as temperature change. InstAlign is one of the key contributors to the outstanding ±0.5-dB amplitude accuracy of the FieldFox spectrum analyzers, even at power-on.
The FieldFox portable instruments also leverage Agilent’s PowerSuite automatic measurement functions from the firm’s benchtop instruments. These functions allow users to make quick power measurements of communications channels simply by pressing one button.
In their “fully loaded” configurations, the FieldFox analyzers can include a cable and antenna analyzer with a frequency range of 30 kHz to 26.5 GHz, a full two-port microwave VNA with a frequency range of 30 kHz to 26.5 GHz, or a spectrum analyzer with a full-band, independently controlled signal (tracking) generator with a range from 5 kHz to 26.5 GHz. The VNA can include a vector voltmeter while the spectrum analyzer can add a full-range preamplifier, power meter, or interference analyzer.
Any of the configurations can add a GPS receiver or variable dc source and current monitor. A base configuration might include the cable and antenna analyzer, which can also be configured for the spectrum analyzer and VNA. Of course, since these FieldFox portable testers can be upgraded at any time, users can always add functionality later.
The FieldFox analyzers include local-area-network (LAN) and USB ports for transferring data and an SD card slot for data storage. A three-year warranty is standard for all FieldFox analyzers. Prices start at about $10,200 for the base 4-GHz cable and antenna analyzer model through about $45,000 for a fully equipped FieldFox.