% Envelope transfer function of resonant inverters % Assumptions: frequency modulation, voltage driven resonant tank % See ECEN5817 course notes % DM Spring 2012 % global H; % Resonant-tank transfer function v/vs1 global fs; % Swithcing frequency [Hz] % % input voltage Vg = 100; Vs1 = 4*Vg/pi; % amplitude of the fundamental voltage at the input of the resonant tank % VCO gain [Hz/V] Km = 1e3; % scale = Vs1*Km*2*pi; % multiplicative scale factor in Genv(s) % % fs = 110e3; % steady-state switching frequency fs0 % % define resonant tank transfer function, series resonant example % change definition of H(s) to get Genv for other resonant tanks % s = tf('s'); fo = 100e3; % resonant tank center frequency Q = 10; % resonant tank Q factor wo = 2*pi*fo; H = ((1/Q)*(s/wo))/(1 + (1/Q)*(s/wo) + (s/wo)^2); % series resonant inverter % % plot tank H(s) magnitude and responses % figure(1); P = bodeoptions; P.FreqUnits = 'Hz'; bode(H,P,'b'); h = findobj(gcf,'type','line'); set(h,'LineWidth',2); grid on; title('Magnitude and phase responses of the resonant tank transfer function H(s)'); % % compute Genv % f=logspace(2,5,100); G=f; for fm=1:length(f) G(fm)=scale*Genv(f(fm)); end % % plot magnitude and phase of Genv % figure(2) subplot(2,1,1); semilogx(f,20*log10(abs(G)),'r','LineWidth',2); grid on; hold on; title('Magnitude and phase responses of the envelope transfer function Genv(s)'); subplot(2,1,2); semilogx(f,180*angle(G)/pi,'r','LineWidth',2); grid on; hold on;