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https://designers-guide.org/forum/YaBB.pl Design >> RF Design >> noise figure of passive circuit https://designers-guide.org/forum/YaBB.pl?num=1436941268 Message started by VNF on Jul 14th, 2015, 11:21pm |
Title: noise figure of passive circuit Post by VNF on Jul 14th, 2015, 11:21pm Hi, It is shown in multiple places that noise figure of a passive circuit equals to the power loss. My question is, theoretically (assuming no bandwidth issue), if the network is a simple capacitor divider, i.e. with voltage gain of 1/2, then the signal, along with the noise will scale by 1/2 altogether, therefore SNR_out should be the same as SNR_in, which leads to NF = 1. so what am I missing here? thanks, VNF |
Title: Re: noise figure of passive circuit Post by bellona on Jul 18th, 2015, 9:31pm The CAP divider is actually a impedance transformer, and ideally it introduces no power loss (Voltage halved with Current doubled), so the NF should be 0dB (F=1) |
Title: Re: noise figure of passive circuit Post by baohulu on Jul 23rd, 2015, 11:59pm I think you are right |
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