calcs for bfq19 100mW amp

git-svn-id: https://svn.code.sf.net/p/freetel/code@2499 01035d8c-6547-0410-b346-abe4f91aad63

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+% bfq19ssa.m
+%
+% David Rowe Dec 2015
+%
+% Working for 100mW class A small signal amp using the BFQ19
+
+rfdesign;
+
+w = 2*pi*150E6;
+
+% BFQ19 Vce=10V Ic=50mA 100MHz
+
+S11 = 0.251*exp(j*(-142.7)*pi/180);
+S21 = 20.28*exp(j*(103.1)*pi/180);
+S12 = 0.030*exp(j*(72.9)*pi/180);
+S22 = 0.290*exp(j*(-61.9)*pi/180);
+
+% Lets check stability
+
+Ds = S11*S22-S12*S21;
+Knum = 1 + abs(Ds)^2 - abs(S11)^2 - abs(S22)^2;
+Kden = 2*abs(S21)*abs(S12);
+K = Knum/Kden
+figure(1);
+clf
+scCreate;
+
+if K < 1
+  C1 = S11 - Ds*conj(S22);
+  C2 = S22 - Ds*conj(S11);
+  rs1 = conj(C1)/(abs(S11)^2-abs(Ds)^2);           % centre of input stability circle
+  ps1 = abs(S12*S21/(abs(S11)^2-abs(Ds)^2));       % radius of input stability circle
+  rs2 = conj(C2)/(abs(S22)^2-abs(Ds)^2);           % centre of input stability circle
+  ps2 = abs(S12*S21/(abs(S22)^2-abs(Ds)^2));       % radius of input stability circle
+
+  s(1,1)=S11; s(1,2)=S12; s(2,1)=S21; s(2,2)=S22;
+  plotStabilityCircles(s)
+end
+
+% determine collector load Rl for our desired power output
+
+P = 0.1;
+Irms = 0.02;
+Rl = P/(Irms*Irms);
+
+% choose gammaL based on Rl
+
+zo = Rl/50;
+[magL,angleL] = ztog(zo);
+gammaL = magL*exp(j*angleL*pi/180);
+
+% calculate gammaS and Zi and plot
+
+gammaS = conj(S11 + ((S12*S21*gammaL)/(1 - (gammaL*S22))));
+[zi Zi] = gtoz(abs(gammaS), angle(gammaS)*180/pi,50);
+
+scAddPoint(zi);
+scAddPoint(zo);
+
+% Design ouput matching network
+
+Ro = 50;
+[Xs Xp] = z_match(Ro, Rl)
+Cos = 1/(w*Xs);
+Lop  = Xp/w;
+
+printf("Output Matching:\n");
+printf("  Rl = %3.1f  Ro = %3.1f\n", Rl, Ro);
+printf("  Xp = %3.1f Xs = %3.1f\n", Xp, Xs);
+printf("  Cos = %3.1f pF Lop = %3.1f nH\n", Cos*1E12, Lop*1E9);
+
+% design input matching network between 50 ohms source and 10 ohms at base
+
+Rb = real(Zi); Rs = 50;
+
+[Xs Xp] = z_match(Rb, Rs);
+
+Lip = Xp/w;
+Cis = 1/(w*Xs);
+
+printf("Input Matching:\n");
+printf("  Xs = %3.1f Xp = %3.1f\n", Xs, Xp);
+printf("  Lp = %3.1f nH Cs = %3.1f pF\n", Lip*1E9, Cis*1E12);