Question about receiver budget

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xjbocx

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I simulated a simple receiver using ADS budget,which has a amp,mixer and another amp.I find the noise figure is always 3dB more than that of non-image noise.But I read the "pratical rf system design".in page 69,it says,if the gain of first amp is low such as 5 dB,the difference between the noise and non-image noise is 1dB.
what's wrong?
 

what is the noise figure is it SSB , or DSB
it sure will affect the total noise figure of the system

Khouly
 


hi,

what do you mean with non-image noise? is your receiver zero-if or heterodyne? the contribution of the image noise to the noise figure depends on your receiver topology: homodyne or heterodyne for example...
 

it should be 3 dB difference between DSB and SSB.But in "pratical rf system design",it is not!
 

3dB degradation is the worst case due to the thermal noise at the image frequency.

I would recommend the book “RF Design Guide – Peter Vizmuller” (pag 16)
 

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