What is the significance of bandwidth?

[tansah]

hey..hows everybody doing out there?..well my question is that we have this quantity called "bandwidth" when we discuss RLC circuits or resonant circuits..now i know that bandwidth is something equals to resosnat frequency divided by q-factor..what i actually want to ask is that what is the "significance" of this quantity?..what does it actually represents in real life when we dicuss resosnat circuits?..why is it always taken at R.M.S value of resonant frequency?..why not anywhere else?..and what are its applications?...and please do tell me what does "sidebands" means as well?..i hope this is not a burden on your precious time!!..thank you ..awiaitng your feedback..regards..tansah

 

[fcfusion]

Re: Help plz..urgent!!!

I'm gonna explain it with little theory.

A circuit's bandwidth is a interval of frequencies where the ouput signal has the same amplitude (or almost the same) has the input signal. This means the signal passes through tat RLC circuit without beign changed or attenuated. This allows you to create filters.

Imagine a filter with bandwith of 1kHz [from 0 Hz to 1 KHz].

For signals with frequency between 0 Hz and 1 kHz: Vout = Vin
For signals with frequency over 1 kHz: Vout < Vin

A ressonant filter has the same behaviour, with a little exception. At the ressonant frequency the circuit HAS SOME GAIN without using an amplifier, which is odd but good . It also allows to make "better" filters with the same number of components.

Ressonant circuits are used to filter signals like, for example, in a radio. The filter allows the signal of the radio station you want to hear, to pass while all the other radio stations are rejected. The better the quality factor, the better your radio filter will reject unwanted stations.

Sidebands is something that appears due to amplitude modulation. But thats harder to explain but also very important in radio communication. Wen you transmit voice over radio you have to change your voice signal frequency to radio frequency, for example 1 MHz. The result is a signal centered at 1 MHz (carrier) with your voice signal around it, spread between 0.980MHz and 1,020 MHz. Those spread frequencies make up your sideband.

Hope it helped

 

[LvW]

Re: Help plz..urgent!!!

Hi Tansah,

the above answer contains a lot of errors and simplifications - too much to correct everything and to give you a detailed answer.
My recommendation: Read an introductory chapter of a relevant textbook and/or search on the web (keywords: bandwidth, filter, filter basics,...).
As an example, I enclose such a paper on filter basics.