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47Ghz VCO,transient simulation success, HB simulation failed

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mingpangzi

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This is a around 47 Ghz LC oscillator. I used a Capacitor instead of tuning Capacitor.
I can observe oscillation when I do th transient simulation.
But I can't observe any harmonic when I do the HB simulation.
Is anybody who had the similar experience?
Thanks!
 

HB doesn't like floating nodes or unconnected components because they make it nervous..
There are two capacitors connected in series, put a 1GOhm resistor between ground and floating point of the capacitors.
And then put the same resistor besides to current source in parallel.
And play some HB parameters like solver method, robustness etc.
 

Re: 47Ghz VCO,transient simulation success, HB simulation fa

BigBoss said:
HB doesn't like floating nodes or unconnected components because they make it nervous..
There are two capacitors connected in series, put a 1GOhm resistor between ground and floating point of the capacitors.
And then put the same resistor besides to current source in parallel.
And play some HB parameters like solver method, robustness etc.
Click to expand...

Hi, thanks very much for your suggestion! modified the circuit to a equivalent circuit with only one capacitor, and the resistor is in parallel.

But I get the warning that "the loop gain is larger than 1, but we need extra phase shift".
And the result is still not right, minus -∞. I guess something is wrong with my LC tank. But I haven't figure why, because this tank model is the typical model for LC VCO.
 

But on your circuit, the gates are short circuited by OSC Port..Therefore your loop gain is infinite.
 

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