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The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl Simulators >> RF Simulators >> How to simulate the NF of a circuit with high input impedance?? https://designers-guide.org/forum/YaBB.pl?num=1214890959 Message started by zhangjerome on Jun 30th, 2008, 10:42pm |
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Title: How to simulate the NF of a circuit with high input impedance?? Post by zhangjerome on Jun 30th, 2008, 10:42pm A 50-ohms port is used as the input noise source. Somebody told me to place a extra 50 ohms resistor in parallel with this port to simulate the NF of the circuit. Is it right?? Same questions arises in the IIp3 simulation for the same circuit. Is it right to place a resistor in parallel with the port? Thank you. |
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Title: Re: How to simulate the NF of a circuit with high input impedance?? Post by aaron_do on Jul 1st, 2008, 12:34am Hi, you could simulate the Input Referred Noise instead (V2/Hz). Same goes with IIP3. You can simulate the input referred IIP3 in terms of voltage. Remember NF is defined as total Nout ------------- Nout due to source cheers, Aaron |
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Title: Re: How to simulate the NF of a circuit with high input impedance?? Post by pancho_hideboo on Jul 1st, 2008, 1:30am zhangjerome wrote on Jun 30th, 2008, 10:42pm:
Generally it is not correct. See the follwing. http://www.designers-guide.org/Forum/YaBB.pl?num=1194006190 zhangjerome wrote on Jun 30th, 2008, 10:42pm:
As far as lumped component level simulation, such shunt 50ohm is not needed. In this case, you don't have to use port. You might use vsource depending on your application and purpose. But if you use actual signal generator of relative high frequency, such shunt 50ohm might be needed since signal is fed through 50ohm line. See http://www.designers-guide.org/Forum/YaBB.pl?num=1207009725 |
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