--- /dev/null
+% rfdesign.m
+%
+% David Rowe Nov 2015
+%
+% Helper functions for RF Design
+
+1;
+
+
+% convert a parallel R/X to a series R/X
+
+function Zs = zp_to_zs(Zp)
+ Xp = j*imag(Zp); Rp = real(Zp);
+ Zs = Xp*Rp/(Xp+Rp);
+endfunction
+
+
+% convert a series R/X to a parallel R/X
+
+function Zp = zs_to_zp(Zs)
+ Xs = imag(Zs); Rs = real(Zs);
+ Q = Xs/Rs;
+ Rp = (Q*Q+1)*Rs;
+ Xp = Rp/Q;
+ Zp = Rp + j*Xp;
+endfunction
+
+
+% Design a Z match network with a parallel and series reactance
+% to match between a low and high resistance. Note Xp and Xs
+% must be implemented as opposite sign, ie one a inductor, one
+% a capacitor (your choice).
+%
+% /--Xs--+---\
+% | | |
+% Rlow Xp Rhigh
+% | | |
+% \------+---/
+%
+
+function [Xs Xp] = z_match(Rlow, Rhigh)
+ assert(Rlow < Rhigh, "Rlow must be < Rhigh");
+ Q = sqrt(Rhigh/Rlow -1);
+ Xs = Q*Rlow;
+ Xp = Rhigh/Q;
+endfunction
+
+
+% Design an air core inductor, Example 1-5 "RF Circuit Design"
+
+function Nturns = design_inductor(L_uH, diameter_mm)
+ Nturns = sqrt(29*L_uH/(0.394*(diameter_mm*0.1/2)));
+endfunction
+
+
+% Work out series resistance Rl of series resonant inductor. Connect
+% tracking generator to spec-an input, the series LC to ground. V is
+% the ref TG level (e.g. with perfect 50 ohm term) in volts, Vmin is the
+% minumum at series res freq.
+%
+% /-50-+---+
+% | | |
+% TG C 50 spec-an
+% | | |
+% | L |
+% | | |
+% | Rl |
+% | | |
+% \----+---/
+
+function Rl = find_rl(V,Vmin)
+ % at series resonance effect of C and L goes away and we are left with
+ % parallel combination of Ls and spec-an 50 ohm input impedance
+
+ Rp = Vmin*50/(2*V*(1-Vmin/(2*V)));
+ Rl = 1/(1/Rp - 1/50)
+endfunction
%
% David Rowe Nov 2015
%
-% RF small signal amplifier design, using equations from "RF Cicruit
-% Design" by Chris Bowick
+% Working for small signal VHF amplifier design using
+% S-param techniques from "RF Circuit Design" by Chris Bowick
-1;
-
-% Helper functions -------------------------------------------------
-
-% convert a parallel R/X to a series R/X
-
-function Zs = zp_to_zs(Zp)
- Xp = j*imag(Zp); Rp = real(Zp);
- Zs = Xp*Rp/(Xp+Rp);
-endfunction
-
-
-% convert a series R/X to a parallel R/X
-
-function Zp = zs_to_zp(Zs)
- Xs = imag(Zs); Rs = real(Zs);
- Q = Xs/Rs;
- Rp = (Q*Q+1)*Rs;
- Xp = Rp/Q;
- Zp = Rp + j*Xp;
-endfunction
-
-
-% Design a Z match network with a parallel and series reactance
-% to match between a low and high resistance. Note Xp and Xs
-% must be implemented as opposite sign, ie one a inductor, one
-% a capacitor (your choice).
-%
-% /--Xs--+---\
-% | | |
-% Rlow Xp Rhigh
-% | | |
-% \------+---/
-%
-
-function [Xs Xp] = z_match(Rlow, Rhigh)
- assert(Rlow < Rhigh, "Rlow must be < Rhigh");
- Q = sqrt(Rhigh/Rlow -1);
- Xs = Q*Rlow;
- Xp = Rhigh/Q;
-endfunction
-
-
-% Design an air core inductor, Example 1-5 "RF Circuit Design"
-
-function Nturns = design_inductor(L_uH, diameter_mm)
- Nturns = sqrt(29*L_uH/(0.394*(diameter_mm*0.1/2)));
-endfunction
+rfdesign; % library of helped functions
more off;
--- /dev/null
+% vhf_pa.m
+%
+% David Rowe Dec 2015
+%
+% Working for 0.5W VHF PA
+
+rfdesign;
+
+% BFQ19 Vce=5V Ic=50mA. These are small signal S-params,
+% which (according to "RF Cicruit Design") are not valid.
+% However I need to start somewhere.
+
+S11 = 0.324*exp(j*(-158.1)*pi/180);
+S12 = 0.031*exp(j*(75.9)*pi/180);
+S21 = 19.693*exp(j*(102.7)*pi/180);
+S22 = 0.274*exp(j*(-74.6)*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
+
+if 0
+P = 0.5;
+Vcc = 5;
+w = 2*pi*150E6;
+
+Rl = Vcc*Vcc/(2*P);
+end
+Rl = 10;
+
+% 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 Pi network for matching Rl to Ro, where Ro > Rl
+%
+% /---+-Xs1-Xs2-+---\
+% | | | |
+% Rl Xp1 Xp2 Ro
+% | | | |
+% \---+---------+---/
+%
+% highest impedance used to define Q of pi network and determine R,
+% the "virtual" impedance at the centre of the network, whuch is smaller
+% than Rl and Ro
+
+Ro = 50;
+Q = 3;
+R = Ro/(Q*Q+1);
+
+Xp2 = Ro/Q;
+Xs2 = Q*R;
+
+Q1 = sqrt(Rl/R - 1);
+Xp1 = Rl/Q1;
+Xs1 = Q1*R;
+
+Cp1 = 1/(w*Xp1);
+Cp2 = 1/(w*Xp2);
+Ls = (Xs1+Xs2)/w;
+
+printf("Output Matching:\n");
+printf(" Rl = %3.1f Ro = %3.1f\n", Rl, Ro);
+printf(" Q = %3.1f virtual R = %3.1f\n", Q, R);
+printf(" Xp1 = %3.1f Xs1 = %3.1f Xs2 = %3.1f Xp2 = %3.1f\n", Xp1, Xs1, Xs2, Xp2);
+printf(" Cp1 = %3.1f pF Ls = %3.1f nH Cp2 = %3.1f pF\n", Cp1*1E12, Ls*1E9, Cp2*1E12);
+
+% design input matching network between 50 ohms source and 10 ohms at base
+
+Rb = 10; Rs = 50;
+
+[Xs Xp] = z_match(Rb, Rs);
+
+Lp = Xp/w;
+Cs = 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", Lp*1E9, Cs*1E12);
+
projects / freetel-svn-tracking.git / commitdiff