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iPAQ-hosted handheld works as RF spectrum analyzer

Posted: 14 Feb 2005 ?? ?Print Version ?Bookmark and Share

Keywords:windows? ipaq? pda? spirent communications? pocketdm?

One of the first pieces of handheld test gear to use a Windows CE-based iPAQ PDA was Spirent Communications' PocketDM cellphone tester. It was for is-95 and IS-2000 CDMA signal checking.

Shortly after the PocketDM was introduced a few years ago, another connubial union of PDA and RF instrumentation appeared, this time the Berkeley Varitronics Systems (BVS) Yellowjacket test receiver. Quite a few other handheld RF sniffers have made their way out of BVS's labs and other's, since then.

RF history

Going all the way back 1995, BVS has a history of producing unique pieces of wireless test equipment. This latest BumbleBee product continues the nomadic RF test trend, once again leveraging the power of a PDA, this time running the Pocket PC 2003 OS.

Like its Yellowjacket predecessor, the new BumbleBee is small, but nonetheless a precision touchscreen-equipped instrument. It's slated for ISM (industrial, scientific, medical) and U-NII (Unlicensed National Information Infrastructure) allocations, which is where 802.11a systems operate.

And it is indeed a precision unit; its reference oscillator stability, for example, is rated to within 2.5ppm, and the unit sports a very low noise-floor (more on that in a moment).

JPEG image files

One of the (many) things that make the BumbleBee attractive is that it can substitute for any number of other instruments, many of which are likely a lot larger and bulkierand perhaps more expensive, to boot (the BumbleBee costs about $2,500 sans an iPAQ, but you may already have one of those).

Once you feed RF into its 50-ohm input-impedance SMA connector, it will even let you save JPEG image files of captured signals.

As a calibrated spectrum analyzer, it will let you capture, display, and record RF signals in each of its four bands. It can then display multiple traces in three colors, with trace settings for peak-hold hold and screen averaging. Screen averaging can accommodate from one to 100 averages.

As you'd expect in a spectrum analyzer, the BumbleBee has a raft of marker functions. These include peak-search markers, center frequency markers, and left, right, and delta markers.

The unit also supports automatic or manual triggering modes, too. Its Packet/Interference Trigger, mentioned in the press release (on the left) triggers the BumbleBee if input power meets or exceeds a pre-set threshold across a 20MHz span. Not mentioned is that the trigger threshold is settable in dBm units, and there's a trigger delay that you can set in milliseconds.

Speaking of span, you can set it anywhere from 50kHz to 800MHz, and enjoy an RBW (resolution bandwidth) of 50kHz to 1MHz, adjustable in steps at 50kHz, 100kHz, 300kHz, 0.5MHz, and 1MHz). If you're using it to examine spectra in the 802.11 band, it has an automatic pre-set for bandwidth. Sweep time is 800ms (for a 20MHz span with 50kHz RBW).

Amplitude specs

On the vertical axis, the BumbleBee has a low average noise-floor. With no input, it's less than -100dBm (the reference level is -70dBm). The amplitude input has a dynamic range greater than 40dB, and exhibits a level accuracy within 1.5dB, too (rated at 25C).

In the field, you'll get about three hours of continuous run-time from a BumbleBee, thanks to BVS's use of a Ni-MH internal battery pack (four AA cells). In the lab you can run the unit from the ac mains.

Mentioned in BVS's release is the fact that the unit can be optionally equipped with a 2.4GHz-band directional antenna or a 900MHz-band Yagi beam antenna.

The corner reflector antennas can help you zero-in on interfering RF sources with a 9dB boost over an isotropic radiator (dBi). The unit ships with a 900MHz antenna, a 2.4GHz antenna, and a 5GHz antenna (a 5GHz directional antenna is an option). Other options include a 12V automobile power adapter.

- Alex Mendelsohn


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