Fc = frequency;
a=0.7654
a0 = 4+Fc^2+2*a*Fc;
a1 = -8+2*Fc^2;
a2 = -2*a*Fc + 4 + Fc^2;
b0 = Fc^2;
b1 = 2*Fc^2;
b2 = Fc^2;

freqz([b0, b1, b2], [a0, a1, a2]);