How Do You Factor Transfer Functions in S-Plane Analysis?

  • Thread starter Thread starter FrankJ777
  • Start date Start date
  • Tags Tags
    Factoring
AI Thread Summary
The discussion centers on the confusion surrounding the factoring of transfer functions in S-plane analysis, specifically the example H(s) = (2s + 1)/(s^2 + 5s + 6). The user is struggling to understand the transition from H(s) to its factored form, questioning why the numerator is divided by 2 while the denominator is multiplied by 2. A participant confirms that the user's interpretation is correct and suggests that the original source may have made an error. This highlights the importance of verifying sources when studying complex mathematical concepts. The conversation underscores the challenges of relearning material after a significant break.
FrankJ777
Messages
140
Reaction score
6
Hi all. I'm trying to relearn S-plane analysis and filter transfer functions. What I'm having problems with is simple algebra i think, because it's been a while. Right now I've been reading http://www.ee.up.ac.za/main/_media/en/undergrad/subjects/eli220/polezero.pdf. What I'm confused about, among other things, is factoring the transfer function H(s).
In their example:

H(s) = \frac{2s + 1}{(s^2 + 5S + 6)}

factored

H(s) = \frac{1}{2} \frac{s+1/2}{(s+3)(s+2)}

I don't understand how they get that. The way I see it, because:
2s+1 = 2(s+1/2)
and
s^{2}+5s+6 = (s+3)(s+2)
so

H(s) = \frac{2s + 1}{(s^2 + 5S + 6)} = \frac{2}{1} \frac{s+1/2}{(s+3)(s+2)}

Also It seems that:

\frac{2s + 1}{(s^2 + 5S + 6)} ≠ \frac{1}{2} \frac{s+1/2}{(s+3)(s+2)}

So I guess what I don't understand is why it seems that instead of factoring out 2 from the numerator, we are dividing the numerator by 2 and multiplying the denominator by 2.

Can someone please set me straight. I know I did this a few years ago and it seemed to make more sense then, than it does now.

Thanks a lot.
 
Engineering news on Phys.org
Hi FrankJ777. The explanation is quite simple: you are right and they are wrong. :smile:
 
Really? I hope that's the case. Too bad I wasted several study hours trying to get it.

Thanks
 
Thread 'Weird near-field phenomenon I get in my EM simulation'
I recently made a basic simulation of wire antennas and I am not sure if the near field in my simulation is modeled correctly. One of the things that worry me is the fact that sometimes I see in my simulation "movements" in the near field that seems to be faster than the speed of wave propagation I defined (the speed of light in the simulation). Specifically I see "nodes" of low amplitude in the E field that are quickly "emitted" from the antenna and then slow down as they approach the far...
Hello dear reader, a brief introduction: Some 4 years ago someone started developing health related issues, apparently due to exposure to RF & ELF related frequencies and/or fields (Magnetic). This is currently becoming known as EHS. (Electromagnetic hypersensitivity is a claimed sensitivity to electromagnetic fields, to which adverse symptoms are attributed.) She experiences a deep burning sensation throughout her entire body, leaving her in pain and exhausted after a pulse has occurred...
Back
Top