[moved] lumped circuit or distributed

Hi everyone,

I know if maximum length of a circuit be smaller than wavelength of the RF signal enough, then it considered a lumped circuit.

But i have a problem...

What's meaning of "maximum length"? for example consider a microstrip line from input port to a resistor and from the resistor to an inductor, now the length of each part of microstrip line between elements should be considered for maximum length or overall length of microstrip line?

Thanks.

hi salehr,
the maximum length is referring to length of the 50ohm line before the lumped components. interconnection between components are not counted here.



microstrip line from input port to a resistor will fall under this rule. if resistor to an inductor is just an interconnect (short trace), this rule wont apply here.

Thanks pragash,

You said maximum length is referring to length of the 50ohm line before the lumped components.
Even if interconnection be long?
I have a series resistor-inductor feedback trace from output to input. If i count interconnections between output and resistor, and between resistor and inductor and ... these traces are small enough. But if i count overall length of microstrip line from output to input then maybe it's very long proportional to highest frequency of circuit.

Now is my circuit lumped or not?

hi salehr,
interconnects usually short/small. as long as your 50ohm trace does not exit wavelength, you are good. i think you are good. dont need to worried.

For reasonable accuracy, a good rule of thumb is that one usually wants to start examining the effects of phase when the electrical length of the object exceeds a tenth of a wavelength.