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diff --git a/339/CH9/EX9.15/ex9_15.sce b/339/CH9/EX9.15/ex9_15.sce
new file mode 100755
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+global Z0;
+Z0=50;
+
+//define the S-parameters of the transistor
+s11=0.3*exp(%i*(+30)/180*%pi);
+s12=0.2*exp(%i*(-60)/180*%pi);
+s21=2.5*exp(%i*(-80)/180*%pi);
+s22=0.2*exp(%i*(-15)/180*%pi);
+
+//noise parameters of the transistor
+Fmin_dB=1.5
+Fmin=10^(Fmin_dB/10);
+Rn=4;
+Gopt=0.5*exp(%i*45/180*%pi);
+
+
+//compute a noise circle
+Fk_dB=1.6;//desired noise performance
+Fk=10^(Fk_dB/10);
+
+Qk=abs(1+Gopt)^2*(Fk-Fmin)/(4*Rn/Z0); //noise circle parameter
+dfk=Gopt/(1+Qk); //circle center location
+rfk=sqrt((1-abs(Gopt)^2)*Qk+Qk^2)/(1+Qk); //circle radius
+
+
+//plot a noise circle
+a=[0:360]/180*%pi;
+set(gca(),"auto_clear","off");
+plot(real(dfk)+rfk*cos(a),imag(dfk)+rfk*sin(a),'b','linewidth',2);
+
+//specify the goal gain
+G_goal_dB=8;
+G_goal=10^(G_goal_dB/10);
+
+
+//find constant operating power gain circles
+go=G_goal/abs(s21)^2;  //normalized gain
+dgo=go*conj(s22-delta*conj(s11))/(1+go*(abs(s22)^2)); //center
+
+rgo=sqrt(1-2*K*go*abs(s12*s21)+go^2*abs(s12*s21)^2);
+rgo=rgo/abs(1+go*(abs(s22)^2)); //radius
+
+//map a constant gain circle into the Gs plane
+rgs=rgo*abs(s12*s21/(abs(1-s22*dgo)^2-rgo^2*abs(s22)^2));
+dgs=((1-s22*dgo)*conj(s11-delta*dgo)-rgo^2*s22)/(abs(1-s22*dgo)^2-rgo^2*abs(s22)^2);
+
+//plot constant gain circle in the Smith Chart
+set(gca(),"auto_clear","off");
+plot(real(dgs)+rgs*cos(a),imag(dgs)+rgs*sin(a),'r','linewidth',2);
+
+
+//choose a source reflection coefficient Gs
+Gs=dgs+%i*rgs;
+
+//find the corresponding GL
+GL=(s11-conj(Gs))/(delta-s22*conj(Gs));
+
+//find the actual noise figure
+F=Fmin+4*Rn/Z0*abs(Gs-Gopt)^2/(1-abs(Gs)^2)/abs(1+Gopt)^2;
+
+//% print out the actual noise figure
+Actual_F_dB=10*log10(F)
+
+//find the input and output reflection coefficients
+Gin=s11+s12*s21*GL/(1-s22*GL);
+Gout=s22+s12*s21*Gs/(1-s11*Gs);
+
+
+//find the VSWRin and VSWRout
+Gimn=abs((Gin-conj(Gs))/(1-Gin*Gs));
+Gomn=abs((Gout-conj(GL))/(1-Gout*GL));
+
+VSWRin=(1+Gimn)/(1-Gimn); //VSWRin should be unity since we used the constant operating gain approach
+VSWRout=(1+Gomn)/(1-Gomn);
+
+//specify the desired VSWRin
+VSWRin=1.5;
+
+//find parameters for constant VSWR circle
+Gimn=(1-VSWRin)/(1+VSWRin)
+dvimn=(1-Gimn^2)*conj(Gin)/(1-abs(Gimn*Gin)^2); //circle center
+rvimn=(1-abs(Gin)^2)*abs(Gimn)/(1-abs(Gimn*Gin)^2); //circle radius
+
+//plot VSWRin=1.5 circle in the Smith Chart
+plot(real(dvimn)+rvimn*cos(a),imag(dvimn)+rvimn*sin(a),'g','linewidth',2);
+
+
+//plot a graph of the output VSWR as a function of the Gs position on the constant VSWRin circle  
+Gs=dvimn+rvimn*exp(%i*a); 
+Gout=s22+s12*s21*Gs./(1-s11*Gs);
+
+//find the reflection coefficients at the input and output matching networks
+Gimn=abs((Gin-conj(Gs))./(1-Gin*Gs));
+Gomn=abs((Gout-conj(GL))./(1-Gout*GL));
+
+//and find the corresponding VSWRs
+VSWRin=(1+Gimn)./(1-Gimn);
+VSWRout=(1+Gomn)./(1-Gomn);
+
+figure; //open new figure for the VSWR plot
+plot(a/%pi*180,VSWRout,'r',a/%pi*180,VSWRin,'b','linewidth',2);
+legend('VSWR_{out}','VSWR_{in}');
+title('Input and output VSWR as a function of \Gamma_S position');
+xlabel('Angle \alpha, deg.');
+ylabel('Input and output VSWRs');
+mtlb_axis([0 360 1.3 2.3])
+
+
+//choose a new source reflection coefficient
+Gs=dvimn+rvimn*exp(%i*85/180*%pi);
+
+//find the corresponding output reflection coefficient
+Gout=s22+s12*s21*Gs./(1-s11*Gs);
+
+//compute the transducer gain in this case
+GT=(1-abs(GL)^2)*abs(s21)^2.*(1-abs(Gs).^2)./abs(1-GL*Gout).^2./abs(1-Gs*s11).^2;
+GT_dB=10*log10(GT)
+
+//find the input and output matching network reflection coefficients
+Gimn=abs((Gin-conj(Gs))./(1-Gin*Gs));
+Gomn=abs((Gout-conj(GL))./(1-Gout*GL));
+
+//and find the corresponding VSWRs
+VSWRin=(1+Gimn)./(1-Gimn)
+VSWRout=(1+Gomn)./(1-Gomn)
+
+//also compute the obtained noise figure
+F=Fmin+4*Rn/Z0*abs(Gs-Gopt)^2/(1-abs(Gs)^2)/abs(1+Gopt)^2;
+F_dB=10*log10(F)
+\ No newline at end of file