Bandwidth definition

Today you will enjoy to learn something new about bandwidth, You will learn in this post actual meaning of bandwidth, What is bandwidth ? examples of bandwidth, types of bandwidth, how bandwidth is measured ? What is bandwidth limit ? What is device bandwidth ? What is difference between bandwidth and speed ? You will learn all about bandwidth in easy way, so that you will never forget bandwidth, lets start.

What is bandwidth ?

In communication when you  are sending signals, So first you should understand what are signals ? The signals are variation of voltage, but made of what ? you can think from where this variation comes ?.
The answer is simple, it is message signal created  by the source,like if you are sending your voice and  communicating  it. Now your voice is made by vibration of your vocal cords, which start the wave, this wave is again converted into electrical signal in the form of voltage.



This frequency is a constant and remains constant, whether it is converted into electrical form which is voltage.What types of frequency generated by your vocal cords ? there is a particular value of frequency generated by your vocal cords.


It is not an unique and single value of frequency generated by your vocal cords, It is a combination of frequencies generated by vocal cords.

So there are so many frequencies which are generated at a time, because there are so many particle of vocal cords and all are vibrating with different frequency , but there is a mean frequency all of them.



Hence there are two things one is all frequencies and other is a mean frequency, all there frequencies are around the mean frequency.  

Suppose you are speaking and the mean frequency is 300 Hz, May be there are certain lyrics in your voice, which are at 250 Hz and 350 Hz, See there is a range of frequencies in your voice which is  250, 300, 350 Hz. This range is called bandwidth of your voice see below picture.


bandwidth definition,bandwidth examples,what is bandwidth


As seen from the picture the bandwidth will be more if this range is high, So total range of frequency associated with signal, device and channel.
So you will learn about bandwidth with reference to signal, device and channel, the signal which is produce by the source of information, like sound you produce, there may be a video, there may be a picture, there may be audio voice, these all are signals.



There may be mobile, TV, Camera, microphone, and many more are example of devices.

A cable which is carrying signal to your house, AM wave, FM wave, radio wave electromagnetic wave, which are coming from the space all are example of channel.



Hence all of these three signals, devices and channel, so all are having  their own bandwidth. you can refer link for communication fundamental concepts

Signals bandwidth 

Suppose your speech having frequency 300 to 3100 Hz, there are few people which are making loud sound. there may be 500, 600 and 700 Hz.generally male voice having frequency 300 to 400 Hz and female voice having frequency 500 to 700 Hz.
Now with this frequency, there are harmonic attach with this.
If your frequency is 300 Hz then there is mixture of 600 Hz frequency also, there is a mixture of 900 Hz frequency also and these are called harmonic frequencies , So that makes a complete group of 300 to 900 Hz, infect you are listening 300 Hz, but 600 and 900 Hz are harmonic so actually you are listening a combination of  frequencies . Means to say in this combination some percentage of 600 Hz and some percentage of 900 Hz very low but always a combination of frequencies.
This combination make your voice signature, due to this voice signature if in a dark hall many people are sitting, you are not seeing them face but somebody shout your name and you recognize that is your mother.
How this happen because you are listening a combination of frequencies, which is their voice signature, 

which is a combination of frequencies belongs to them. So every body has their own speech frequency. Hence for your speech frequency 300 to 3100 Hz, Bandwidth will be (3100-300) = 2800 Hz .



Now if you want to talk on telephone, the telephone is used for human voice, Therefore you have to keep your device and channel, which is fit for 2800 Hz bandwidth, If it is not fit for 2800 Hz bandwidth then your original voice will not be produce to listener.


Suppose device has only bandwidth of 1500 Hz, then it will allow to pass 300 Hz , 1800 Hz but it will not allow to pass 2000 Hz, 2500 Hz and 3000 Hz, whereas you have greater bandwidth of 2800 Hz contains so many frequencies. 


Hence if you want to hear real voice, the bandwidth of your device should be larger than your message signal bandwidth.You know that human hear range of frequency is 20 to 20 KHz, beyond and below this frequency human can’t hear any voice or music.

So music bandwidth is 20 KHz.



Similarly for video signal 4.2 MHz frequency required and for safe guard it is take as 6 MHz for a TV channel, which will transmit video and audio signal together required 6 MHz bandwidth. 


So range of frequencies is called a bandwidth, that indicate all the frequencies in the range will be handle during the communication.This is called a bandwidth of a signal.So larger bandwidth is better to accommodate complete information of wave. 

I hope you have got bandwidth concept clear now.

Bandwidth characteristics 

You should remember bandwidth is not use only for a signal, every things has its own bandwidth, likes
1 bandwidth of signal ( Audio signal, video signal,speech signal)
2 bandwidth of device ( mobile, TV, microphone, transmitter, receiver, headphone etc )
3 bandwidth of Channel ( AM wave, FM wave, Electromagnetic wave, radio wave, cable )



All above three having their own bandwidth, for example when you speak directly to somebody, your voice is different than when you talk on phone. This is because of fault of phone bandwidth. The phone bandwidth does not pass all the frequencies band of your voice because it is design for mean frequency only.


So some harmonic frequency of your voice is not pass though the phone bandwidth, that is the reason your voice is different from direct listen.  

Bandwidth speed 

Increasing the bandwidth you can increase the speed of the data transfer rate but its range will decrease see the picture below.



bandwidth definition,bandwidth speed
Bandwidth speed



Types of bandwidth

There are two types of bandwidth see below.
1 Base Band
2 Broad Band

Base Band is used for Ethernet, only one way signal, whereas Broad band used for TV, Radio and electromagnetic wave, travel in both way .


bandwidth definition,bandwidth types
Bandwidth types


Base band allow you to either send or receive the signal one at a time only but in broad band you can send and receive the signal at a time.
Base band use low frequency wave, So it is used for local area network like Ethernet, it can’t used for long distance communication.



Broad band used very high frequency wave, such frequency wave can travel low distance easily, hence a broad band is used for long distance communication system.

Like TV and radio wave communication system.



I hope you have enjoyed learning  bandwidth definition, I will continue in next post with more concepts, I want your feedback, comments and share. Learn and grow, thanks for sharing .


Date 30th Dec 2018.                 



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