why the input sinewave got a THD

[[email protected]]

When I do my silulation in Cadence spectre,
I input a sinewave into the filter block and test the THD of the output

I also tested the input and find that the input sinewave still got a
THD of 100m. Why does the input also has such a high THD? Wouldn't it
be ideal?
Confusing~~~~~~

 

[Jim Thompson]

When I do my silulation in Cadence spectre,
I input a sinewave into the filter block and test the THD of the output

I also tested the input and find that the input sinewave still got a
THD of 100m. Why does the input also has such a high THD? Wouldn't it
be ideal?
Confusing~~~~~~

Length of simulation?

Time step?

Data range limit?

Education test: What is the spectrum of a sine wave that starts at
t=0 ?

...Jim Thompson

 

[Roger Bourne]

When I do my silulation in Cadence spectre,
I input a sinewave into the filter block and test the THD of the output

I also tested the input and find that the input sinewave still got a
THD of 100m. Why does the input also has such a high THD? Wouldn't it
be ideal?
Confusing~~~~~~

Long time ago I seem to recall a similar problem (or maybe the same
problem) using the THD fct in spectre. I think what I did was:
1.subtract the DC component from the sine wave (or input wave)
2. run THD


I just want to mention that the above stems from a long ago
recollection. I may be completly off base ;-)/

-Roger

 

[[email protected]]

I input a 1V sinewave of 5KHz.
I select from 5ms to 7.6ms(that is 13cycle)
and the sample number is 5000.
then I run the THD.

the spectrum of a 1V sinewave of 5K is only one spectrum of 1V at 5K

is that right?
Looking forward to reply!
Thank you

 

[[email protected]]

I have got no DC component.
Maybe there is something wrong with the way I test.

 

[Rene Tschaggelar]

I input a 1V sinewave of 5KHz.
I select from 5ms to 7.6ms(that is 13cycle)
and the sample number is 5000.
then I run the THD.

the spectrum of a 1V sinewave of 5K is only one spectrum of 1V at 5K

But only if it lasts infinitely long.
... a minimum of theory is required ..
... lookup : me and the fourier transform ..

Rene