AM, CW effect on Sensor (EMC)

[harry456]

I read a paper in that is was mentioned that an CW with a peak of p=xdBm has the same effect on a ic than a modulated signal with peaks (all peaks have the same power as the cw signal). Is is possible? (the power of modulated signal would be much larger than that of the cw signal).
Would be nice if someone could post a source that proves this "thesis".

 

[hamidrezakarami]

In EMC standards continues wave (CW) with 80% amplitude modulation (AM) is used. the average power of CW is zeros, so I think the AM is necessary.

 

[chuckey]

If the sensor exhibits non linearity to RF, testing with CW, the result would be a shift in DC in the sensor, which may not effect subsequent amplifiers. if you use AM, then there will be the demodulated component as well as the DC shift, this would be a more stringent test.
Frank

 

[dick_freebird]

"Same" I would say not. Reads the same on a peak level
meter or such, probably. Varying amplitude is going to
test response to low and high level, there may be more
to see than simple worst case input will expose.

 

[harry456]

What with FM modulation? How would FM modulation effect testing? (Is there a reason way it's not used? A FM spectrum is much broader than the spectrum of an AM - signal. Would I use a fm spectrum ( with more power than an AM-Signal so that all peaks in the spektrum are nearly of the same magnitude as the AM peaks could I not test the device faster than with an AM -Signal?)

 

[chuckey]

The spectrum of a FM signal is relatively small compared with the potential frequencies that may interfer with the device. i.e. the spectrum of RF is 50 KHZ to 25 GHZ. the spectrum of a FM signal is typical limited to Fc +- 200KHZ.
Frank

 

[harry456]

Yes, it is. But you could use a fm signal with a bandwith of MHz and use it instead of an AM or CW Signal for the verification. Or is there a reason why it is not used? (it's not in the iso, but why not- wouldn't much faster?)

 

[chuckey]

FM has a constant amplitude. If you want the effect of its modulation to interfere with the sensor, then it must have a non-linear frequency (flank detection) response as well as amplitude non linearity.
Frank

 

[harry456]

What is if i would like to replace the cw-test? A FM with a large modulation index looks similar to a rectangle (in the frequency-domain) could i not used it to test a sensor faster? (only for test purpouses not for emc-verification)