exp function bode plot

I have a question about matlab bodeplot. I want to draw bodeplot this function .

(1-s/fref) / s * exp (-s/fref);

I made script as follow .

syms s;

fref = 1e6;

num = sym2poly(1-s/fref);

den = sym2poly(s);

ACC1 = tf(num,den);

num = sym2poly(exp(-s/fref));

den = sym2poly(s);

ACC2 = tf(num,den);

ACC3 = ACC1*ACC2;

bode(ACC3,{0.00001,10e13});

but, script have a error. matlap indicate this sentence as a error. ( ??? Error using ==> sym.sym2poly at 31 Not a polynomial. )

In this way, how i should solve the error?

Answer 1

[David Sanchez]

I forgot to add the solution to your question. Here it is:

% G(s) = (1-s/fref) / s*exp (-s/fref);

G = tf( [-1/fref 1],[1 0],'InputDelay', 1/fref);
bode(G,{0.00001,10e13});

or just

bode(G)

for a more general plot

[Wook Hong]

thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks

Answer 2

[David Sanchez]

exp(-s/fref)

is not a polynomial, you can not use sym2pol in that case

num = sym2poly(exp(-s/fref)); % -> not valid

[Wook Hong]

how to make transfer function of exp(-s/fref). impossible?