Gain and phase margin + phase and gain crossover frequeny results

I used this code to find phase and gain margin. Also to find phase and gain crossover frequeny

syms s
G = tf([7 14],[1 10 24])
[Gm,Pm,Wcg,Wcp]=margin(G)
grid on 

but I got this result. can any one explain to me why Gm and Pm = Inf and Wcg and Wcp= NaN?

and what is maning of Inf and Nan?

G =

7 s + 14

---------------

s^2 + 10 s + 24

Continuous-time transfer function.

Gm =

Inf

Pm =

Inf

Wcg =

NaN

Wcp =

NaN

Answer 1

[Keerthana Chiruvolu]

Hi,

Firstly, NaN means Not A Number and inf is infinite.

From the bode plot of the transfer function, we can observe that the Magnitude plot doesn’t cross 0. And the phase is not 180° at any frequency.

Wcp - 0-dB gain crossing frequency.

Wcg -180° phase crossing frequency

To calculate the gain and phase margins we require the crossover frequencies. Hence, the result for Wcp , Wcg is NaN and Gm, Pm are inf.

.For more information, please refer the following functions :margin(), bode()

[Gollapapani]

how to deal with complex coefficients as margin doesn't work on it

Answer 2

[Kingsley Osubor]

How can we explain a bode diagram with Gm with Infinity, Pm with infinity, Wcg with infinity and Wcg with not a number value.