Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

[SOLVED] Noise figure in mixers

Status
Not open for further replies.

samaneh_mahmoudian

Newbie level 5
Joined
Feb 21, 2018
Messages
8
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
49
Hi dear friends...
one question...in my simulation for linearization an active mixer, The conversion gain is reduced but the noise figure dose not decrease,it is possible? what is the reason? could u help me?
 

Noise Figure is the added noise ratio from the device you are using.

Conversion gain is an actual loss in passive mixers due to(mostly) diode mixing the signals. When in an active mixer, you use an active device to eliminate the loss in the mixer and u get an actual gain instead of a say -7db conversion gain.

Noise figure on the other hand, is a result of the active pieces you are using in the mixer. Your transistor has a dc operating point, which consumes current; hence adds noise signal on top of your desired signal. Only way to decrease is to implement the mixer with a low-current low-noise transistor which may be specified for LNA. That way, you can decrease some, but it will always add some because of the active devices.
 

NF=10*lg(SNR.in/SNR.out)=10*lg((Pin/Pout)*(Sout/Sin)).
If the gain decreases the Pout decreases, but Sout decreases too so NF shouldn't change too much.
NF should increase by the added extra noise of the amplifier but not too much if the gain is still high enough.
 
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top