Dear all: In order to make the problem clear, I will explain the details: 1.All the model we use in simulation is measured by VNA. Our model is s-parameter. 2.I simulate in frequency domain by means of impedance curve of caps and beads. 3.I have simulate the impedance of decoupling circuit. There is only difference in low frequency domain. 4.There is one PLL in CDC2516. Is this the reason? I still did not understand why the difference in low frequency could affect the noise in high frequncy domain. Best Regards Zhangkun 2003.12.5 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu