AirMagnet Spectrum Analyzer

| Wireless Driver & Software

What it is

ASA is essentially a repacked / rebranded version of Cognio’s ISMS Mobile 1.0 product, which provides the core technology. The family jewels come in the form of a CardBus card (AirMagnet calls it the Spectrum PC card) that contains the hardware guts of a miniature spectrum analyzer that covers the 2.4 and 5GHz 802.11a/b/g spectra, as well as the 4.94 – 4.99 GHz U.S. Public Safety Band.

Figure 1: The little wonder itself

Here’s what’s inside the card (from the ASA User Guide):

• Radio – The radio transceiver detects the RF spectrum and feeds this data to Spectrum Analysis Engine, SAgE
• SAgE – Spectrum Analysis Engine performs a Fast Fourier Transform (FFT) of the RF spectrum, and provides the feed of low-level data concerning the behavior of the RF spectrum. Low-level data includes basic information on the power vs. frequency in the spectrum at a given instant, and information on individual pulses in the RF spectrum. SAgE also performs on-board statistical analysis of the spectrum, and statistical analysis of RF pulses (which relieves CPUs of this processor intensive task)
• MCU – A programmable MicroController Unit (MCU), running proprietary software, provides low-level analysis of the data stream. The analysis engines include:
  • Measurement Engine – Aggregates SAgE data, and normalizes it into meaningful units.
  • Classification Engine – Identifies specific types of interferers (Bluetooth devices, microwave ovens, cordless phones and headsets, radar, etc.).

The card represents some pretty impressive engineering, especially considering that the ASA’s closest competitor – Berkeley Varitronics Systems (BVS) Bumblebee – requires a PocketPC-sized “sled” to hold its RF circuitry. Specs (Figure 2)are pretty impressive too, most notably a noise level of only -124dBm and amplitude accuracy of +/- 2.5dBm.

Figure 2: Spectrum Analyzer Specs

The card can be used with any laptop or tablet PC running Windows XP SP1 or SP2 that has a Type II CardBus slot. Note that the card cannot function as an 802.11a/b/g WLAN card, so can neither be used to connect to a wireless LAN nor run any of the other AirMagnet products. Note also that if the laptop or tablet that you run the ASA on has built-in Wi-Fi, you’ll need to turn it off – for obvious reasons!

The card has an MMCX style connector – same as used on the old ORiNOCO and many current Buffalo Technology WLAN cards – for external antenna attachment. AirMagnet also includes a simple 2dBi dipole with short cable and clip for mounting the antenna on a laptop display.