# lefti's profile - activity

2015-09-01 19:07:21 +0100 asked a question Trying to find phase and group delay of transfer functions

I have several functions I would like to get the phase and group delay. In python I did the following

from sympy import pi, Symbol, I , atan, im, re, simplify, collect, trigsimp, sign

fr = Symbol('fr', real=True) fo = Symbol('fo', real=True) fn = Symbol('fn', real=True) f = Symbol('f',real=True) q = Symbol('q', real=True) qn = Symbol('qn', real=True)

wr = 2pifr wo = 2pifo wn = 2pifn w = 2pif s = I*w

# Lp1 - s domain

H_lp1 = wr/(s+wr)

(re_part,im_part) = H_lp1.expand(complex=True).as_real_imag()

H_lp1_ph = atan(im_part/re_part)

Which returns the correct answer but when I try a more complicated function such as

H_lpn2 = ((s2+wn2)(wo/wn)2)/(s2+s(wo/q)+wo**2)

(re_part,im_part) = H_lpn2.expand(complex=True).as_real_imag()

H_lpn2_ph_expanded = atan(im_part/re_part)

H_lpn2_ph = simplify(H_lpn2_ph_expanded)

It does not return the complete solution. Any ideas?

2015-03-07 02:19:31 +0100 asked a question solve 2 equations in terms of other variables

Hi,

I have

RL,Rs,C,L,Q,wo=var('RL Rs C L Q wo')


then I say

eq1=wo==Q*(C*RL*Rs+L)/(C*L*RL)
eq2=wo==sqrt((RL+Rs)/(C*L*RL))
solve([eq1,eq2,C,L)


I would like to solve the above system in terms of C and L. How do I do this?

2015-03-06 20:47:56 +0100 answered a question Solve symbolically Vo/Vin

This seems to work

solve([(Vin-Vo)...=0],Vo)

2015-03-06 20:23:34 +0100 asked a question Solve symbolically Vo/Vin

Hi, My equation is

(Vin-Vo)/(Rs+sL)=Vo/RL+Vos*C

where Vo,Vin are variables, Rs,RL,C,L are constants s is the complex number s=i2pi*f

I would like to see Vo/Vin=

in a symbolic expression