RF Harmonics Measurement not following expected slope

[EltrnLearn]

Hi All

When measuring the Pin vs Pout (fundamental, 2nd & 3rd harmonics) of switch or transmission line, what can cause the 2nd and 3rd harmonics not to follow a slope of 2 and 3 respectively?

I have checked and my fundamental is still responding linearly with a loss of about 2dB at the power output.

 

[pancho_hideboo]

Is your issue EDA Tool Play or Actual Measurement ?

 

[FvM]

not to follow a slope of 2 and 3

Expected slope depends on assumptions, particularly a device nonlinearity model. If they aren't fulfilled, you get different curves.

 

[EltrnLearn]

@pancho_hideboo: they are from actual measurement.

@all: for the case of a 2mm Tline (which I am observing), what factors could contribute to the non-linearity?

 

[pancho_hideboo]

@pancho_hideboo: they are from actual measurement.

Show me actual measurement results.

When measuring the Pin vs Pout (fundamental, 2nd & 3rd harmonics) of switch or transmission line

Describe your situations in detail and correctly.

"transmission line" is linear. So it doses not give any Harmonics.
Don't you mean switch with transmission line ?

 

[biff44]

"expected slope"?? Never heard of it.

 

[FvM]

Theoretical slopes of distortion versus magnitude are e.g. used in the calculation of intercept points.

But I agree that the discussion would be much easier if the OP manages to report his observations clearly.

 

[EltrnLearn]

Hi

Attached is image of the fundamental and harmonics for a simple CPW (transmission line) on silicon.

It can be clearly seen that 2nd slope is about 1, while the slope for 3rd harmonics is about 2 at higher power input.

 

[BMR]

Are you seriously giving us those curves?

It has no information relevant to your question.

 

[EltrnLearn]

How about this plot

 

[pancho_hideboo]

Both H2d and H3d are less than -90dBc.
I think you can not measure them correctly.
How do you measure them.

Show me your setting of Spectrum Analyzer.

 

[BMR]

Your 2nd HD is -35 dBc which is acceptable, but I don't understand your 3 rd HD which is the same as that of 2nd HD. This is something very strange.

At 2nd HD you are losing 0.02% of power where as at 3rd HD you are losing the same power. Check your measurements again.

 

[FvM]

Are you sure that the harmonic distortion isn't already present in the input signal and simply attenuated with the fundamental?

 

[pancho_hideboo]

Your 2nd HD is -35 dBc which is acceptable

What do you see from his plot ?
I think you are misunderstanding his plot.

His DUT is CPW (transmission line) on silicon.
So both H2d and H3d are very small.

X-Axis(Power Input)=20dBm~35dBm

Fundamental=17.5dBm~32.5dBm

2nd Harmonics=-80dBm~-62.5dBm ; -97.5dBc~-95dBc

3rd Harmonics=-82.5dBm~-65dBm ; -100dBc~-97.5dBc


We need notch filter to suppress Fundamental to measure 2nd and 3rd Harmonics.

I suspect his spectrum analyzer settings.

 

[BMR]

What do you see from his plot ?

I was looking at the Peak output power of the fundamental ( When Pin=35 dBm, he has a Max Pout of ~32.5 dBm).

Anyways what does the values in Y-axis plot represents? May be my assumption is wrong.

Now I realize measuring CPW in silicon has a different bench set up.