Mixer SSB and DSB conversion loss and NF - RF Cafe Forums
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Below are all of the forum threads, including all the responses to the original posts.
Post subject: Mixer SSB and DSB conversion loss and NF
Unread postPosted: Fri Dec 24, 2004 5:22 pm
I read in an application note that there is a difference of 3dB between SSB noise figure and conversion loss of a mixer to these paramaters in DSB (conversion loss of SSB is 3dB higher than DSB).
If you input DSB (Dual Side Band) signal with twice as power as SSB signal to a given mixer you will obtain twice as power at the output as well. And if you input the SSB signal to that mixer the ratio of power in the input and output should remain the same (only with 3dB less in the aboslute values at each port) - please correct me if I am wrong!
My question is why is this difference?
Post subject: Mixer Noise Figure
Unread postPosted: Mon Dec 27, 2004 2:36 pm
The double side band has twice the power level , therfore the signal to noise ratio at the output is 3dB higher. In a SSB mixer, half the power is at the output, but the same noise power. The signal to noise ratio is 3dB lower. Therefore, the noise figure is 3dB higher.
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