Re: Measuring SpreadSpectrum Tx Power

On Nov 26, 2:47 am, "Joe G \(Home\)" <jo...@xxxxxxxxxxxxxxx> wrote:
I need to measure the power or power spectral density of some zigbee
modules....in the range -10dBm to 30dBm...

Any pointers were to understand power measurements with spreadspectrum would
be appreciated.

Regards
Joe

For total power in that range, you can perhaps find a thermal
converter--one that dissipates the input power in a load resistance,
and monitors the temperature rise. It's typical to do it in a bridge
circuit, where an identical converter is driven by DC to match
temperature rises. The DC input power then matches the RF input
power, and is easy to measure. You can also use an attenuator to
reduce the power to a level where one of the broadband RF detectors
from Analog Devices or Linear Technology or similar can be used
directly--they generally operate in the -60dBm to 0dBm range, more or
less.

For power spectral density, you'll want to be using a spectrum
analyzer. There are advantages to using a spectrum analyzer that
digitizes a relatively wide swath of spectrum all at once, but you can
also use a swept analyzer. Modern spectrum analyzers should have
power spectral density displays that you can read directly; or you can
convert from the indicated power to density if you know the resolution
bandwidth of the analyzer.

I don't know for sure what you'll find, but try looking on the Agilent
Technologies website for "white papers" and ap notes on spectral
measurements. Seems like there should be some good general articles
there, and maybe something very specific to what you want to do. Web
sites of some other spectrum analyzer suppliers may also turn up
useful resources: Rohde & Schwarz and Anritsu come immediately to
mind, but there are others too.

Cheers,
Tom
.

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