close all, clear all, clc
num = [1 1];
R = 1000;
C = 0.1E-6;
den = [1 0 2 3];
f = logspace(-1,6, 1024);
w = 2*pi*f;
H = freqs(num, den, w);
subplot(2,1,1)
semilogx(w/(2*pi), 20*log10(abs(H)))
xlabel('Hz'), ylabel('|H(j\omega)'), grid
subplot(2,1,2)
semilogx(w/(2*pi), angle(H))
xlabel('Hz'), ylabel('Phase'), grid