Interview questions about LNA and Mixer ?
Mixer:
types?
advantages of each type?
gilbertcell mixer?
increasing linearity?
increasing gain?
noise figure?
noise cancellation?
sources of noise?
low voltage applications?
before LNA the noise
simple noise qustions ,
noise of the filter , equivalent noise band width
MOS transistors noise sources , the corner frequency of the flicker noise
LNA
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noise matching , impedance matching
increasing gain
which to use CG , CS ?
degeneration
many many more
khouly
Lets say you had a receiver front end, that consisted of a 30 dB LNA with a 2 dB noise figure, that fed a mixer with a 6 dB conversion loss. The desired operating frequency is 10 GHz, the LO frequency is 9 GHz, so the IF frequency is at 1 GHz.
You go out into the lab and make a noise figure measurement. You expect the system noise figure to be a little higher than 2 dB, but instead you are surprised to see the noise figure meter reading 5.3 dB. What is up? What do you have to do to get the system down to a 2.2 dB noise figure?
I guess you are asking about the SSB NF right? Adding a SAW filter (image rejection) before the mixer can lower down the NF by 3dB. Using mixer + polyphase filter also can reject the image.
Thanks.
