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taz
Joined: 29 Aug 2004
Posts: 4
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 29 Aug 2004 17:41 Lumped vs Distributed Systems |
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hello,
What is the difference between Lumped and Distributed Systems, why distributed is more common in RF .
Thanks,
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Mazz
Joined: 03 Nov 2001
Posts: 523
Helped: 60
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| 29 Aug 2004 18:13 Re: Lumped vs Distributed Systems |
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It regards the relationship between maximum signal frequency (or wavelength) and phisical circuit dimentions.
All circuits could be considered distributed, but the lumped approximation is valid until the wavelength of the signal is comparable with phisical dimentions. Being for example lambda=30 cm @ 1 GHz, thats why RF is distributed.
Hope it's clear.
Mazz
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sergio mariotti
Joined: 22 Dec 2003
Posts: 454
Helped: 38
Location: Italy
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| 29 Aug 2004 18:17 Lumped vs Distributed Systems |
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Every electronic component has it's electrical lenght (read: delay). It's mainly related to it's geometrical lenght. For example a wire wound coil may contain many meters of copper wire.
Of course the lumped elements like capacitors and inductors have it's characteristic parameters be frequency invariant only if their lenght is much smaller than lambda (much smaller tha 1/4 lambda).
So at higher freq. , because they are long i compared to lambda, cannot be used.
Distributed elements work well both at high freq and low freq. But at low freq it's dimension rise until they became unuseful.
Note that, for reactive components, the range of possible reactance available from distributed element is limitate.
Note also that at high freq., generally the Q factor for distributed elemets is higher than lumped.
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