用Cadence的pss分析环形压控振荡器的输出功率谱

何平

第二个竖线为所需要的振荡频率功率，振荡频率为280M，其他三根竖线是设置的三个谐波边带，为什么最左边的一个频率等于0的谐波边带的功率反而还大于第二个的功率呢？？？？？还是我本身就对这个图形理解错误呢？？？求高人解释，不胜感激！

hectorlzu

没进行隔直操作吧，0频处应该包含有直流电源提供的功率吧，我不清楚vco的结构

Accee

直流分量功率。

何平

回复 2# hectorlzu


    好的，谢谢你的建议。但是为什么振荡频率为280M，也就是第二个边带的功率到-20db这么小了，这个是我要的信号的功率啊，应该至少大于0才对啊，是不是我哪个地方没有设置好啊？？

elec_888

the circuit is ok and this is a usual result ..
simply your results in db means that ur voltage level is less than 1 ..
the DC component is determined by biasing .. ur DC component value is almost 0 db which means that ur oscillation happens around almost 1 V ..

now ur 1st harmonic ~ -21 db which means that ur oscillation is almost 89mv peak .. (20log(.089)=-21db) .. if u plot the magnitude instead of db u will find the values plotted in mv..

actually when designing VCOs u need gain just to make sure ur circuit is gonna oscillate .. ur gm*rp >2 is the condition .. so if u use inductors and caps with higher q factor u can get a better output , or if u increase ur diff pair width u can get higher gm .. u can also increase ur current ..
anyway the csystem u design ur VCO for is what determines the specs needed for output swing level ..

何平

回复 5# elec_888


    我又学到知识了！！太感谢你了！谢谢你这么细心回答！thank you!!!

a1054958688

回复 6# 何平
     “the DC component is determined by biasing .. ur DC component value is almost 0 db which means that ur oscillation happens around almost 1 V ..” 5楼说的这个什么意思呢？

为你到宁夏

你好我想问一下怎么样能够确定这个振荡器是否起振呢？或者怎样加输入让他起振呢？

罗伟淞

你好，之前查到说pss分析可以得到vco的中心频率，想请教你一下pss分析怎么设定仿真的对象和参数选取