Fundamental signal VS harmonics

Hi all,

Just want to know the relationship between fundamental signal and harmonics.
Let say i reduce my fundamental signal for 1 dB, what are the theoretical power level reduction at the 2nd ,3rd,4th , harmonics.
Is there any trend or formula for this?

thanks.

arr_baobao said:

Let say i reduce my fundamental signal for 1 dB,
what are the theoretical power level reduction at the 2nd ,3rd,4th , harmonics.

Click to expand...

2dB,3dB,4dB,.....

It depends on what is creating the harmonics. A Class C amplifier has harmonics that are non-linear, so sometimes they go up and sometimes they go down.

pancho_hideboo said:

2dB,3dB,4dB,.....

Click to expand...

is there a formula for this? =)
thanks

arr_baobao said:

is there a formula for this? =)

Click to expand...

Simply, Vin, Vin**2, Vin**3, Vin**4, ....

Here I assume following.
1st : Dominant by a1
2nd : Dominant by a2
3rd : Dominant by a3
4th : Dominant by a4

Hi,

I don't think there is a common formula.

Overtones are mainly caused by distortions:
Let's look at two cases:
1) audio amplifier, pure sine input, close to clipping:
The overtones are very low in amplitude, maybe -80dB
Now if you increase the input signal (fundamental) amplitude by 6dB..
Then the overtones will increase rapidly, maybe up to -24dB (referenced to the fundamental amplitude. not calculated) for the first overtone

2) audio amplifier, distorted sine input, not close to clipping:
The overtones do exist
Now if you increase the input signal (fundamental) amplitude by 6dB..
Then the overtones will increase by close to 0dB (referenced to the fundamental amplitude)

In case 1 the distortion increases with amplitude, whereas in case 2 the distortion does not increase with amplitude, and there will be all other sytems inbetween.

Klaus

Harmonics in semiconductors are hard to be accurate predicted.
I've seen semiconductors from the same wafer that have different non-linear response to the same input signal.