oscillator can't work in transient simulation

[happsky]

The error message and schematic is as below. the schematic is using nport with a 16 ports s-parameter. I have using the same topology with 8 Ports nport ,it OK most time ,but this never work ,I have set the step time to 0.001n 0.0001n and so on( the vco is center frequency is about 30G). Thanks in advance^^



error information


the result

 

[BradtheRad]

Just in case this helps...
Simulators often want a capacitor to have a series resistance somewhere nearby, through which to calculate the RC time constant for charging or discharging.

 

[happsky]

I can't understand :?:

 

[palmeiras]

Hi happsky,

First of all.... have you tried to add an impulsive current source between the output nodes? You need it in order to start-up the oscillation. This current source adds an current pulse and after that, it is disconnect from the circuit.

 

[happsky]

Just in case this helps...
Simulators often want a capacitor to have a series resistance somewhere nearby, through which to calculate the RC time constant for charging or discharging.

Hi Bratherad, what can I do to improve the situation?

 

[happsky]

In my opinion , connect a very big resistor to the floating pin maybe ok,but it no a good method ,it seems that sometime it still have the problem.

 

[BradtheRad]

Hi Bratherad, what can I do to improve the situation?

I was thinking maybe a 1/100 ohm resistor, inline with any capacitor that doesn't already have some resistance between (a) it and a supply rail, or (b) it and another capacitor.