Modulation and demodulation definition
Today Our topic is Modulation and demodulation very interesting and important for telecommunication in real life we use and listen if you are found of radio program then you commonly listen 93.5FM, 92.7FM,90.4FM, what are these ? in this topic you will get all answer and the important hidden concept of modulation and demodulation and what is modulation ? why modulation is needed all questions and doubt will be clear very easily only need read complete post first of all we will define what is modulation ?
|Modulation and Demodulation best concepts|
What is modulation: Modulation is a mode of communication lets understand it by practical example suppose you want to go to your friend home 500m distance what travelling communication you will use probably by walking or by cycle if your friend home is 30km what travelling communication you will use probably by bike or car if you friend home is 500km probably by car, bus or train if you friend home is 2000km probably by train or flight if you friend home is 25000km by flight only from these examples what we observe as the distance increases mode of travelling is changing in similar fashion modulation is mode of communication data sent in efficient time without error here your mode of travel like cycle, bike, car, bus, train and Aeroplane is carrier frequency/ carrier signal and you are original data/modulating signal now you are going to your friend home means modulating signal you will be welcome in your friend room your carrier signal will be not be allowed to enter in room it will be discarded but without carrier signal you will not reach your friend home i hope you have got the point what i mean to say.
now come to human body audible frequency range is 20hz to 20khz below and above this frequency range human body can’t listen when we normally talk then our frequency is 3.4khz, when we listen music frequency is about 14khz but when you listen FM frequency is 98.3Mhz here frequency is in megahertz about 4000 times above our maximum range then how you are listening music on FM clear here 98.3Mhz is carrier signal which is carrying original song/modulating signal now as much of high frequency you are using means you are using fast mode of travel like if 98.3Mhz is train then 900Mhz is like Aeroplane so that your signal can reach timely and efficiently as i have already mentioned at destination carrier signal will be discarded only modulating signal will be receive carrier signal is only use for carrying modulating signal or modulating signal is superimpose upon carrier signal now i hope you have understand concept of modulation further we will see why is need of modulation.
Why modulation is needed ? as we have seen in previous topic you can refer Telecommunication fundamental see below diagram
when we talk on microphone our voice is converted into electrical signal and this electrical signal comes into the modulator in modulator high carrier signal is mixed with original voice electrical signal/modulating signal by some technique called AM (Amplitude modulation ) or FM (Frequency modulation ) made signal wave high frequency and this resultant wave is amplify means bust high power and then transmitted through transmitting antenna in form of electromagnetic wave in space now other side receiving antenna detect or receive this electromagnetic wave and send to demodulator where mixed signal carrier signal is removed then original electric signal becomes weak again it amplify bust this electric signal reaches to loudspeaker and converted into voice signal in audible frequency range this is the basic process of modulation and demodulation now this is important to know why modulation and demodulation is needed hence we will see reason of modulation see picture below.
when we transmit electromagnetic wave if its frequency is very low means its has very large wavelength then it has very low energy if transmit high frequency wave then its wavelength will be short and it has very high energy and its directional quality will improve if we transmit very large wavelength wave signal then its energy will be distract and at receiving antenna energy will reach very low which will not be detected with receiving antenna so this is one reason that we mixed high frequency carrier signal so that at receiving antenna reach maximum transmit energy and can detect receiving antenna and it has some directional quality this is one reason second reason is very important there are mainly two type of antenna which we use for transmit wave signal there are many type of antenna but mostly we use for transmit purpose only two one is dipole antenna and other is mono pole antenna as we know that dipole antenna has two pole this dipole antenna will transmit or receive electromagnetic wave its depends upon the length of antenna means the electromagnetic wave wavelength must be half of the length of antenna.
Antenna length ≤ (electromagnetic wavelength)/2 ≤ 𝛌 /2
for mono pole
Antenna length ≤ (electromagnetic wavelength)/4 ≤ 𝛌 /4
now take an example when we talk then our voice frequency is around 300- 3100 hz now suppose we speak and a sound frequency at 3000hz a sound wave is generated the same frequency electrical signal will be generated by microphone and we want to transmit this electrical signal without modulation as electromagnetic wave now we will calculate wavelength of this electromagnetic wave hence we know that speed of light means electromagnetic wave c = 𝛖𝛌
here 𝛖 = frequency = 3000 and c = 300000000 put in above equation 𝛌 = c/𝛖 = 300000000/3000 = 100000 = 100km
𝛌 = 100km now to detect this wavelength signal we need to made Antenna length = 𝛌/2 = 100km/2 = 50km for mono pole 25km which is physically and economically not feasible and sufficient
but when we modulate signal then its frequency will increase and its wavelength will be very short then we need to made antenna short length which is practically feasible and economical this is second very important reason why we need modulation we will continue this topic in other post please wait now i hope you have enjoyed learning Modulation and demodulation definition thanks for reading.
dated 8th Sep 2018