Need help with OSC results please

[E-design]

Hi

When looking at a simple Colpitts OSC, we get completely different results on the calculated output level when using Genesys and Serenade 8.5 on the same circuit.

Can someone explain this? Our hardware prototype's measured results tend to agree with the Serenade graphs. Are we overlooking something when using Genesys?

I attach both project files

Thanks E

***As a follow up.. We did a simulation on MWO also and the output level results on all the harmonics are within 1dB from Serenade. Genesys reports a level 40dBm lower??

 

[BigBoss]

It's very normal.
Because each simulator uses different non-linear model. Namely the models are same but their parameters may be slightly different.

In additional to , HB (Harmonic Balance ) approximations and accuracies might be different.

You do an oscillator simulation..

I have done a very very simple amplifier simulation within 4 different simulator and I have found 4 different result that are close by 1 dB ..

The best is measurement.

 

[E-design]

I agree that you can expect differences by a few dB, but why does Genesys give a fundamental level of -50dBm and Serenade and MWO gives around -11dBm which agrees with our measurement. I feel a 40dB error is too much.

 

[BigBoss]

Could you post your circuit diagram here ?
I can simulate it in ADS if you don't have.
But in my opinion and regarding to my past exprience , Serenade has better HB simulator than other mid cost simulators. But ADS is better..

You're right , it can not be 40dB difference. You're absolutely right..

 

[nandopg]

Dear friend,
If you declare explicitly the impedance of the output port as 50Ohms overriding the default (that it is also 50 Ohms) the simulated output level of the oscillator will be -16dBm. This should be a bug in the program and happens only in the HB analysis.
I agree with BigBoss, you should expect no more that 1dB difference between simulations performed using different programs.

NandoPG

 

[E-design]

Here is the cct

 

[BigBoss]

Here is the ADS result ( it may be different than yours )**broken link removed**

 

[E-design]

I can live with the @DS result. So it looks like Genesys have a problem or the setup is not correct. Any Genesys guru's to comment?

 

[BigBoss]

I can live with the @DS result. So it looks like Genesys have a problem or the setup is not correct. Any Genesys guru's to comment?

What is your measurement result?

 

[E-design]

I can live with the @DS result. So it looks like Genesys have a problem or the setup is not correct. Any Genesys guru's to comment?

What is your measurement result?

H1 -12dBm
H2 -18dBm
H3 -21dBm

Follow up... Found Genesys OSC_PORT tool harmonics was set to 0 by default. Changed it to 5. Result now for H1 is -20dBm (still low for me, but a lot closer)

 

[BigBoss]

Here is Ansoft designer Result with real components from Murata and AVX.. almost near to measurement..

**broken link removed**