环形VCO振荡器在ADEXL中PSS仿真时，如何让它起振呀？

liuqingfeng2011

仿真条件：振荡器是个四级环形VCO，电源（vdc）1.8V，期望输出频率是480MHz，“Beat frequency”=480M, tstab=1.5u, sweep (Vctr=(0.4~1.8V).

结果出来一个错：

Error:The user-provided period (frequency) estimate appears to be too short (high).This condition can arise because the estimate was wrong, because the oscillatorwas never properly started, or because numerical damping significantly reducedsignal amplitudes during the initial transient integration. In the latter caseswitching to method=traponly might be preferable.

做过这样的尝试：

1、延长tstab 还错。

2、将电源vdc改为vpulse，此时报电源错。

3、按照error提示，将method=traponly，错误：Vout istoo small to reliably detect the period of the oscillator. Perhaps nodes withinsignificant signal levels were chosen, or perhaps the oscillator was neverproperly started.

请路过的大侠不吝赐教，谢谢！

liuqingfeng2011

单独跑tran, 也不起振。因此我估计，可能是起振条件有问题。

但是我只要一尝试着改电源（将电源改为vpwl、vpulse或者加一个ipulse），就会报：netl err。

唉，头都大了，大侠请指点呀

fj198462

学习一下

appleyuchi2

回复 1# liuqingfeng2011


    电路截图放上来一下，您这样说不清楚

zhangwei198806

回复 3# fj198462


    跑tain的时候要在电路里加噪声vco才会震荡，你加一个和vco无关的小电路应该就会震荡了。

danglang

试试在tran里面设置下最大的仿真时间步长。默认的我不知道是多少，我设置的是50ps。然后就起振了。不设置的时候也是不起振。

88王道

请问你最终是怎样解决的？我也遇到了这样的问题，谢谢。

daodai

tran-- option -- method 选trap   maxstep填写成1/50/f      
加ipwl

88王道

回复 8# daodai


    是仿真PSS时当VCO电压增加到一定数值（比如1.4V时，AVD=1.8V）提示错误：

Error:The user-provided period (frequency) estimate appears to be too short (high).This condition can arise because the estimate was wrong, because the oscillatorwas never properly started, or because numerical damping significantly reducedsignal amplitudes during the initial transient integration. In the latter caseswitching to method=traponly might be preferable.

单独tran仿真VCO=1.4V时,是振荡的。

daodai

回复 9# 88王道

     单跑pss vctrl =1.4v时   会出现这个问题是吗？