Beginners: Radio Frequency, Band and Spectrum

welcome to another tutorial 3G 4G tutorial this time we are looking at radio frequency band hand spectrum before we begin I should actually for warn you that this video provides a very simplistic explanation for a really complex topic I am going to omit some details to keep it high level and it's also a bit boring in the beginning but hopefully it will become interesting later on so what exactly spectrum a spectrum which is singular or plural is spectra or spectrums is used to classify something on a scale between two extreme points so for example in our daily life we referred to as the political spectrum which consists of left-wing parties extremists left-wing parties and extreme right-wing parties and a lot of different political parties in between we also have the socio-economic spectrum which indicate comprises of working class the middle class and the upper class in this video we will look at radio spectrum which is the part of a electromagnetic spectrum a very simple chart which I have found from Google search of course chart from surah and this chart shows electromagnetic spectrum the whole of electromagnetic spectrum now there are quite a few different charts if you just search electromagnetic spectrum on Google you can find quite a few charts which explains this very complex topic in different ways I recommend that you actually do this search and see which one suits you best so what exactly is an electromagnetic wave electromagnetic waves that compose electromagnetic radiation can be imagined as self-propagating transverse oscillating wave of electric and magnetic fields so in this picture you can see the less field is the vertical one which is blue and magnetic field is the horizontal one which is red and what exactly is frequency radio frequency is an electromagnetic wave using alternating current frequencies something that happens over and over again and again it's very frequent consistent and repetitive so frequency is a number of times as specified even occurs within a specified time interval a standard measure measure of frequency is Hertz which is the number of cycles per second if you look at this picture you can see a wave and an alternating current wave which goes from 0 all the way up comes back to 0 goes down and then comes back to 0 so this this wave goes up and down which completes one wave in a second so it's got a frequency of 1 Hertz this wave which it does this 5 it happens 5 types the cycle happens five times in a second so it's got a frequency of five Hertz the electromagnetic spectrum is a collective term which is used to refer to the entire range and scope of frequencies of electromagnetic radiation from 3 Hertz to 300 EXA hertz so exerts is a very very big number I put a lot of zeroes to show how big eggs are Hertz is and depending on what source you read it from some start rather than starting from 3 Hertz they start from 30 Hertz or 300 Hertz right and some of them only go to around 100 EXA Hertz so this is sometimes these things are different depending on different sources but let's not worry too much about it so we saw hurt thousand Hertz make a kilohertz thousand kilo Hertz make a mega Hertz thousand mega Hertz make a Giga Hertz some people pronounce it as but the Koran correct pronunciation his Giga and thousand gigahertz make a terahertz now thousand Giga Hertz is a very large number for this presentation so generally we will look at megahertz and may gigahertz in this presentation so looking back at this electromagnetic spectrum chart the radio spectrum is a part of spectrum from three Hertz to three terahertz right now in this particular picture it's shown from three Hertz to around one terahertz right but or less than one that hurts but generally it's up to three terahertz again as I said depending on the source you can have different information and different values so what is a frequency band or a spectrum band bands are group of frequencies defined to make it easier to remember and bandwidth is the difference between maximum and minimum of any defined or undefined band so let's say if we had a band which goes from 700 megahertz to 800 megahertz the bandwidth of that band would be hundred megahertz large bandwidth means more data flow so the way you can imagine his you can imagine the bandwidth as like pipes carrying water so the more bandwidth means the fatter pipe and the more water can flow through it wavelength wavelength generally referred written as the Greek letter lambda is the distance between similar points on the back-to-back wave on two back-to-back waves it is calculated as C divided by F where C is the speed of light so for one megahertz the wavelength would be roughly 300 meters and for one gigahertz is roughly 30 centimeter now wavelength is something very important which we need to remember because we will use wavelength when we want to calculate the length of an antenna so looking back at this electromagnetic spectrum chart you can see for one Giga Hertz the the wavelength is 1 feet so the frequency the wavelength is the first horizontal measurement and then you have frequency is the fourth one so for 1 Giga Hertz it's roughly 30 centimeter or 1 feet and if you go up so when you go to something like 100 Giga Hertz the wavelength becomes really small like 1 millimeter and please remember this we will use this when we are looking at 5g phase is the same frequency same cycle same wavelength but two or more both wave forms when they are not exactly aligned together so phase can be measured in distance times or degrees so if you look at this there are two waves here but the second wave starts is 90 degrees offset from the first one so basically we will say it's 90 degrees out of phase from the first one similarly in this one the two phases are 180 degrees out of phase from each other and it is important to see what effects the waves have now why would waves get earth have different phases so when something is transmitted right you can have a direct line of sight but you can also have a line a wave which is going through different paths so it's get reflected from a building or from some kind of a car or something and it arrives out of phase of course the waves would be slightly different in amplitudes but let's not worry about amplitude right now we will look at it in probably next couple of slides or something when the phases arrive when two waves are out arrives at different phases as you can see the pink wave in here is the result of two being out of phase so you can see sometimes it basically the two waves cancel each other and the phase B the resultant face wave becomes zero whereas sometimes the two waves are in the same phase and they add together so you have the resultant wave is even bigger than the original so you have to remember these things and the mobile phones they have to be designed in such a way that when you have this multiple waves coming out of phase they do not cancel each other but they add to each other so this is again another complex topic which we are not going to look in this particular video so what exactly is amplitude amplitude is the height force of power or power of the wave so the greater the power the more than platoon so when I am speaking if I speak loudly it means it has more amplitude if I speak slowly as without much amplitude then you can hardly hear me so amplitude is you can think of as the power of the wave and I often see people asking like oh how is amplitude related to frequency or wavelength or phase but so there is absolutely no relationship between frequency wavelength and phase as with amplitude so amplitude is completely different thing as compared to frequency wavelength or phase and I mentioned earlier that antennas are related to wavelength so generality said that container should be half wavelength or lambda by two for perfect reception but they can be as low as lambda by ten so to give a comparison the car on the left-hand side so these are both the same cause the same brand of cars the car on the left-hand side has got an antenna for FM radio only which is 88 208 megahertz whereas the car on the right it not only caters for FM radio but also caters for the digital DAB radio we is 175 to to 30 megahertz now again this is very simplistic explanation because in reality the car on the right has an active antenna but this is completely advanced topic so we won't look at it now for TV some of you may remember using rabbit ears antennae the one on the Left which is optimized for receiving VHF signals from 30 to 300 megahertz and again it should be with a very good quality high amplitude signal whereas the one on the right is it can catch a lot more frequencies not just the VHF but also works on a higher frequency and it can also work with poor quality signal the way it's designed is it works as a magnifying glass so when the different frequencies arrive it basically amplifies them and it makes them more easy to be received on a TV so a question which I often ask and which often gets asked in different fora is whether low frequencies important or high frequency is important and this question is more from mobile technology point of view so whether the mobile technology particular technology should use a low frequency or high frequency so if you have higher frequency higher frequency decays faster so if let's say if you have the same and same place from which you have two different antennas one for low frequency one for high frequency and you are transmitting at the same power the low frequency will go much further than the high frequency right here I am showing example of 900 megahertz and 2.1 gigahertz so the 2.1 gigahertz decays much faster than the 900 makers at the same time you have to remember is a cell has a certain capacity so the more users are there in the cell that means the so the lower the frequency that means the more number of users and it means everyone is getting lower data rates right if the cell size is smaller that means there are less users and that means everyone is getting higher data rates so again in this particular case you can think like okay you know what higher frequency means I can get higher data rates higher frequency gets reflected from walls and has poor penetration whereas lower frequency gets attenuated but it still penetrates that's why some of you may remember that the original GSM frequency was GSN 900 900 megahertz it performed much better than the other frequency which was 1800 megahertz right because 1800 got it decades much faster right and it had poor penetration capability so this is slightly older chart but it basically shows the cellular spectrum which is used in different parts of the world as you can see the 900 megahertz is mostly used for GSM right initially 900 and 1800 were used mostly for GSM the one in the blue but then most of these KT 100 megahertz frequency has been reformed that means people have started reusing it for 4G so this chart doesn't show that but most of the 4G frequencies throughout the world is 1800 megahertz band which is also known as band 3 similarly you can see most of the world has 3d on 2100 megahertz which is the one in green color of course you have some some of the other other frequencies being used for 3G but the most common frequency for 3G is 2100 megahertz that's why 3G was sort of quite poor in penetrating indoors so when you were indoors you might receive GSM but you might not receive 3G because of the frequency works are actually very high so just to give a continue with our example of antenna so this is an old gsm-900 feature phone and you can see then initially the antennas used to be sticking out of it because for 900 megahertz you still have slightly larger antennas to get better reception and for Wi-Fi so most of the Wi-Fi frequency in the world used to be 2.4 gigahertz so Wi-Fi was sort of a universally same bands of frequency being used throughout the world which was 2.4 gigahertz but now you also have the 5 gigahertz band which is being used and but the 5g 5 gigahertz is not completely aligned in different part of world so there are some overlaps and then there is some unique frequencies in different parts there is also a 60 gigahertz Wi-Fi frequency but you won't find them in your laptops or or your phones because of such high frequency it attenuates very very fast it's known as YG so if you see Y gig anywhere it's basically the 60 gigahertz Wi-Fi and this is just an example of iPhone 4 because our smartphones have to handle a lot of different kind of technologies radio technologies so it has to have antennas and it should be in such a way that you know it doesn't stick out so the iPhone 4 the one on the left is the one which was used in most part of the world but in u.s. you also had the 3gpp - CDMA standard or EVDO so you had the one in the red as you can see the antenna on the red on the right-hand side so this is just to give an idea and you can see the Bluetooth the Wi-Fi and the GPS antenna just very small this is from the one Samsung Galaxy s8 I am not sure if it's been released at this time or just about to be released but just to show an example of how different kind of antennas are in this particular smartphone for 5g now because we are sort of running out of spectrum in the lower frequency bands for 5g there has been a lot of discussion on what kind of a frequency should be used for five days because you want to have very large bandwidth to be able to deliver really really high data rates and some of these innovative services for which 5g is being touted so to have this really high bandwidth you have to go at higher frequencies and generally the frequencies about 30 gigahertz is known as the millimeter wave because the wavelength goes in millimeters so there are a lot of proposals so different regions had different proposals for frequencies and you can see the one at the bottom are the bands being studied by ITU for 5g but then there are also some bands which are not actually listed here for example in America in the u.s. they are using 28 gigahertz band to test the feasibility of 5g so but for 5g we are going to go and use much higher frequency in addition to the lower frequencies the way I show it is I say that there are going to be three different layers which will be used for five days so the one which is less than 1 gigahertz or in some cases it would be less than to gig earth which would be the coverage layer right because we saw that the lower frequency means it goes much further so it would be the coverage layer then you would have the capacity layer between 1 and 6 gigahertz right and in this capacity layer which is the same like LT frequency's nowadays mostly so you can give like higher throughputs whereas in the coverage layer because you won't have enough bandwidth you won't be able to give higher data rates so in the capacity layer you can get higher data rate and then you would have high throughput layers which is between 6 gigahertz and hundred gigahertz generally people refer to them as millimeter wave but millimeter wave generally means frequency about 30 key codes so below 30 giggles you can call it centimeter wave but generally you would see people refer to the whole 6 gigahertz 200 gigahertz band as millimeter wave so this high throughput layers would generally be quite small and it they it can be like you can get a really really high data rates in this high throughput layer so the expectation is like you can get easily 1 Gbps when on an average each user should get 1 Gbps or maybe at least 150 200 Mbps but you can get 152 Mbps with technologies called geeks with the technology called gigabit healthy which is either available today or will be available soon so because of high frequencies you can put the antenna size remember higher the frequency the lower the wavelength so the lambda by 2 goes very very small so this is a an example from a Samsung presentation and it shows that you can have 32 antenna elements like because each antenna element is so small so this is in 28 gigahertz frequency band you can have like a 16 element array on the top of this phone and 60ml has 16 element array at the bottom now remember this would be in addition to the already existing antenna switch because your phone will still have to support 3g 2g 4G Wi-Fi Bluetooth GPS right so you would still have existing antennas plus you have this new antenna array so this is one of the advantages of millimeter-wave because you can have more antenna elements and you can actually get better reception plus you can do something called beamforming so which is from the base station so the base station will again have a lot of antenna elements this is just one of the pictures from a high Tripoli magazine I think and it shows that there are knots of antenna elements at this particular base station and what this antenna elements allow you to do is they allows you to create a beam so each of these colors you can see is a beam and when you create a beam that means you can focus all this energy into one particular ue so h ue will sort of get its own beam and it can get like high data rates and very reliable coverage so there are a lot of different possibilities with 5g and millimeter wave so that's about it what I wanted to cover in this particular presentation hope you liked it and please leave your feedback in the comment section thank you

Channel: 3G4G

Views: 183,445

Keywords: Radio, Spectrum, Frequency, RF, Antennas, 4G, 5G, Smartphone, Bandwidth, Wavelength, Amplitude, Phase, Device Antenna, 28GHz, Massive MIMO, Beamforming

Id: nJe2a4EauUY

Length: 23min 27sec (1407 seconds)

Published: Tue Jul 25 2017