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26th March 2020, 17:59 #1
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Interpreting NF Circle ang Gain circle for matching network
Hello,i have built a circuit shownbellow,from the Sparam simulation i got the Gain circle and NF circle
how to know from the circles to what input impedance network should i use and to what output impedance network should i use?
Thanks.
   Updated   
update:
Why the point we take on the smith chart in the Gamma_s and not the Gamma_L?
Thanks
Last edited by yefj; 26th March 2020 at 18:20.

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26th March 2020, 19:23 #2
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Re: Interpreting NF Circle ang Gain circle for matching network
NFmin is a single point and NF Circles are rounding this point by sacrificing NF value.So the best NF can be obtained at that point only, then first circle covers more points ( impedance values ) by cost of degradation of NF by xdB ( more flexibility but more NF ) so on..
Gain circles are also interpreted as such that way,,
Noise is a function of Source Impedance which is seen by active device so Gamma_S is used.Gamma_L has very little contribution onto this.

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26th March 2020, 19:52 #3
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Re: Interpreting NF Circle ang Gain circle for matching network
for whar kind of circle Gamma_L is used?
Thanks.

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27th March 2020, 01:26 #4

27th March 2020, 21:29 #5
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28th March 2020, 01:24 #6
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Re: Interpreting NF Circle ang Gain circle for matching network
Is it a joke ?? Everything is short circuited..
Read on simulation techniques much.There are millions app notes and papers about it.

28th March 2020, 13:42 #7
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Re: Interpreting NF Circle ang Gain circle for matching network
Hello , yes i had a little biasing problem where i put Vdc in port 0.8 and for some reason it biased 1.6V on the gate as shown bellow.
i Have succseeded building those circles and i picked a point in between the NF circle an GAIN circle and the GAMMA is GAMMA_S(as you said)
Next i calculate from GAMMA_S yo GAMMA_L extract the impedance using the following matlab code
My question is, what is the best tool you reccomend for building a matching network from 50 to the load impedance and source impedance we calculated?
gamma=0.548*exp(deg2rad(159.05)*i);
z=gamma2z(gamma,50)/50;
   Updated   
I have calculated the Zs and ZL as shown bellow so i need to do a matching network from 50 to Zs and ZL to 50 so i will get minimum S11 and minimum S22?
Updated matlab code:
gamma_s=75.8966*exp(deg2rad(280.88)*i);
z_s=gamma2z(gamma_s,50);
s11=0.998750.03202*i
s12=721.33*10^(6)+8.622*10^(3)*i
s21=188.37*10^(3)+30.611*10^(3)*i
s22=875.51*10^(3)100.72*10^(3)*i
gamma_L=conj((s22+(s12*s21*gamma_s)/(1s11*gamma_s)))
z_L=gamma2z(gamma_L,50)
   Updated   
Do i need to build the network to the conjugate value of Zs and ZL
?

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29th March 2020, 07:01 #8
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Re: Interpreting NF Circle ang Gain circle for matching network
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