Can't calculate magnitude and phase of a transfer function

Question

Connie Dubh 2020-11-10

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回答： Mathieu NOE 2020-11-13

I know of the commands abs() and angle(), but for some reason they're not working.

This is what I'm working with:

clear all
syms Req R_6 L C w
num1 = -Req*w^2/(Req+R_6)
den1= (-w^2 + 1/(L*C)) + 1i*(w/(C*(Req+R_6)))
func = num1/den1
abs(func)
angle(func)

However, it doesn't solve anything, it just says that the complex magnitude is |func| and that the phase is angle(func). How do I get the proper expressions?

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VBBV 2020-11-11

Which version of matlab are you using ?

VBBV 2020-11-11

You require some inputs values for symbilic variables in your func

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Answer 1

Mathieu NOE 2020-11-13

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hi

ok , I am using any symbolic stuff here

numerically speaking , everything works fine (as soon as there are dots when needed)

  Req = 1
  R_6 = 1
  L = 1
  C = 1
  w = logspace(0,3,10)
  
num1 = -Req*w.^2./(Req+R_6);
den1= (-w.^2 + 1/(L*C)) + 1i*(w/(C*(Req+R_6)));
func = num1./den1;
abs(func)
angle(func)