function plotbode(freq,varargin);
% bodeplot for many TFs

tf=[varargin{:}];

subplot(2,1,1);
loglog(freq,abs(tf));
ylabel('Gain');
grid on;
subplot(2,1,2);
semilogx(freq,angle(tf)/pi*180);
xlabel('Frequency [Hz]');
ylabel('Phase [deg]');
grid on;
ylim([-180,180]);
set(gca,'YTick',linspace(-180,180,7));