×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

PE Power Question - Bode Plots

PE Power Question - Bode Plots

PE Power Question - Bode Plots

(OP)

Hey everyone.
I'd like some tips on bode plots. Here is an issue i have,


I haven't seen an example of a scenario like this:
H(s) = [1+(s/0.5)] / [1+(s/0.3)]
or
H(s) = [1-(s/5)] / [1-(s/3)]
or
H(s) = [1-(s/0.5)] / [1-(s/0.3)]

the issue here is the denominators have decimals and the terms have negative signs
Again, none of the examples i've seen or worked out had a situation like these and i'd like to know how they would be plotted
thanks

RE: PE Power Question - Bode Plots

There's no problem with a decimal, it's just a decimal value where the pole or zero is located.

The negative sign in the numerator or denominator indicates the zero or pole is in the right half of the complex plane. There is no effect on the magnitude plot, i.e., the pole or zero has the same magnitude effect, but the phase angle plots go the opposite direction from left-half plane poles or zeros. While a left-half plane pole has a -45°/decade slope for the two decades surrounding it and contributes a total of 90° of phase lag, a right-half plane pole has a +45°/decade slope for the two decades surrounding it and contributes a total of 90° of phase lead. While a left-half plane zero has a +45°/decade slope for the two decades surrounding it and contributes a total of 90° of phase lead, a right-half plane zero has a -45°/decade slope for the two decades surrounding it and contributes a total of 90° of phase lag.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: PE Power Question - Bode Plots

(OP)

Quote (xnuke)

There's no problem with a decimal, it's just a decimal value where the pole or zero is located.

The negative sign in the numerator or denominator indicates the zero or pole is in the right half of the complex plane. There is no effect on the magnitude plot, i.e., the pole or zero has the same magnitude effect, but the phase angle plots go the opposite direction from left-half plane poles or zeros. While a left-half plane pole has a -45°/decade slope for the two decades surrounding it and contributes a total of 90° of phase lag, a right-half plane pole has a +45°/decade slope for the two decades surrounding it and contributes a total of 90° of phase lead. While a left-half plane zero has a +45°/decade slope for the two decades surrounding it and contributes a total of 90° of phase lead, a right-half plane zero has a -45°/decade slope for the two decades surrounding it and contributes a total of 90° of phase lag.


shoot, i'm gonna have to read this a few times with a plot in front of me. it's kinda hard to follow for me.
thanks for the reply

RE: PE Power Question - Bode Plots

I'll try to make it simpler:

Positive signs in the binomial terms, i.e., negative real parts, mean they lie in the Left-Half Plane (LHP):
LHP pole: magnitude slopes down at 20 dB/decade above pole frequency, phase slopes down at -45°/decade for the decade above and the decade below the pole frequency.
LHP zero: magnitude slopes up at 20 dB/decade above zero frequency, phase slopes up at +45°/decade for the decade above and the decade below the zero frequency.

Negative signs in the binomial terms, i.e., positive real parts, mean they lie in the Right-Half Plane (RHP):
RHP pole: magnitude slopes down at 20 dB/decade above pole frequency, phase slopes up at +45°/decade for the decade above and the decade below the pole frequency.
RHP zero: magnitude slopes up at 20 dB/decade above zero frequency, phase slopes down at -45°/decade for the decade above and the decade below the zero frequency.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources