April
2006, Issue 189
Low-Cost
2.4-GHz Spectrum Analyzer
RESULTS
I
made the charts in Figure 2 in Excel after exporting
the spectrum data from the Windows software application.
Hopefully, you can appreciate how useful scans like
these can be when you are trying to make your microwave
radios work properly in the presence of other signals
in a crowded spectrum.
|
(Click
here to enlarge)
|
Figure
2a—Even at a distance of 30', the sensitive receiver
can detect a signal leaking from a microwave. Such
signals can disrupt Wi-Fi communications in the
area. b—The spectrum of a 802.11b access point operates
on channel 9. The 22-MHz transmission centered at
2,452 MHz is visible, as are some side lobes. c—Take
a look at the spectrum of a Bluetooth-enabled PDA
searching for nearby devices (a so-called “inquiry
sequence”). During an inquiry, a subset of the 79
possible Bluetooth channels are used. The channels
are visible as peaks in the spectrum. |
As
I explained, my circuit is designed for 2.4 GHz. However,
Chipcon recently released a pin-compatible RF transceiver
(C1100) that operates from 300 to 900 MHz. You can adapt
my circuit to perform spectum analysis for the UHF ISM
bands using the CC1100.
