What is Radio ? Justin Champion Room C203, Beacon Building Tel 3292, [email protected]...

What is Radio ?What is Radio ?Justin ChampionJustin Champion

Room C203, Beacon BuildingRoom C203, Beacon BuildingTel 3292, Tel 3292,

[email protected]@staffs.ac.uk

ContentContent

IntroductionIntroduction– What is RadioWhat is Radio– Sine waveSine wave– ModulationModulation– InterferenceInterference

ConclusionConclusion

Radio FrequenciesRadio Frequencies

We use this technology everydayWe use this technology everyday– This course would be a lot shorter with out them!This course would be a lot shorter with out them!

They allow forThey allow for– Cellular DevicesCellular Devices– Wireless NetworksWireless Networks– TelevisionTelevision– Radio MicrophonesRadio Microphones– Satellite CommunicationsSatellite Communications– DECT TelephonesDECT Telephones– Personal RadiosPersonal Radios

– The full name is Radio Electromagnetic Spectrum, The full name is Radio Electromagnetic Spectrum, but we use the shortened term Radiobut we use the shortened term Radio


Radio is an electronic magnetic waveRadio is an electronic magnetic wave– Connect a wire to a battery and touch the Connect a wire to a battery and touch the

ends close to an AM radioends close to an AM radioYou should hear the sound which is producedYou should hear the sound which is produced

– The magnetic pulse which is transmitted The magnetic pulse which is transmitted will be picked up on a nearby wire as will be picked up on a nearby wire as electricity and converted to sound.electricity and converted to sound.By touching and letting go you can produce By touching and letting go you can produce

Morse code over the radio!Morse code over the radio!The distance this will be picked up by is related The distance this will be picked up by is related

to power in the sourceto power in the source

Radio FrequenciesRadio Frequencies To transfer information a carrier wave is To transfer information a carrier wave is

required.required.– On/Off carrier would look like thisOn/Off carrier would look like this

– More Common is the Sine waveMore Common is the Sine wave This changes its value continuouslyThis changes its value continuously

1 Cycle

Radio FrequenciesRadio Frequencies Sine WaveSine Wave

– As we know what the carrier wave should be As we know what the carrier wave should be showingshowing

It is easier now to check for changesIt is easier now to check for changes– These changes will be used to encode informationThese changes will be used to encode information

– Carrier wave will also allow for information to Carrier wave will also allow for information to be transferred over greater distancesbe transferred over greater distances

Without errorsWithout errors

1 Cycle

Amplitude


FrequencyFrequency– This refers to how often the Sine wave cycles up This refers to how often the Sine wave cycles up

and down per secondand down per second 1 cycle = Hertz (HZ)1 cycle = Hertz (HZ) 1,000 Cycles = Kilohertz (KHz)1,000 Cycles = Kilohertz (KHz) 1,000,000 cycles = 1 Megahertz (MHz)1,000,000 cycles = 1 Megahertz (MHz) 1,000,000,000 cycles = 1 Gigahertz (GHz)1,000,000,000 cycles = 1 Gigahertz (GHz)

Encoding DataEncoding Data– Adjustments to this Sine wave can then be used to Adjustments to this Sine wave can then be used to

encode 1’s and 0’s, voice or videoencode 1’s and 0’s, voice or video– These adjustments are referred to as ModulationThese adjustments are referred to as Modulation

Radio FrequenciesRadio Frequencies The following are all radio wavesThe following are all radio waves

– X-Ray, Light, Gamma RaysX-Ray, Light, Gamma Rays– For our normal interest of Radio we useFor our normal interest of Radio we use

Very Low Frequency (VLF)Very Low Frequency (VLF)– 3-30 KHz3-30 KHz

Low Frequency (LF)Low Frequency (LF)– 30 – 300 KHz30 – 300 KHz

Medium Frequency (MF)Medium Frequency (MF)– 300 – 3000 KHz300 – 3000 KHz

High Frequency (HF)High Frequency (HF)– 3 – 30 MHz3 – 30 MHz

Very High Frequency (VHF)Very High Frequency (VHF)– 30 – 300 MHz30 – 300 MHz

Ultra High Frequency (UHF)Ultra High Frequency (UHF)– 300 – 3000 MHz300 – 3000 MHz


http://lasp.colorado.edu/cassini/images/Electromagnetic%20Spectrum_noUVIS.jpg

Radio ModulationRadio Modulation

Modulation of the signalModulation of the signal– Changes which can be made to a carrier waveChanges which can be made to a carrier wave

Frequency Shift Keying (Frequency Modulation (FM))Frequency Shift Keying (Frequency Modulation (FM))– Increases / decreases the cycling rate of the sine waveIncreases / decreases the cycling rate of the sine wave

Amplitude Shift Keying (Amplitude Modulation (AM))Amplitude Shift Keying (Amplitude Modulation (AM))– Changes the power of the signalChanges the power of the signal

Phase Shift KeyingPhase Shift Keying– Changes the phase that the sine wave is inChanges the phase that the sine wave is in

Frequency Shift KeyingFrequency Shift Keying

(“Les modulations de base(“Les modulations de base ”, 2004, ”, 2004, http://deptinfo.cnam.fr/Enseignement/Memoires/LUSTEAU.Fhttp://deptinfo.cnam.fr/Enseignement/Memoires/LUSTEAU.Franck/Pages/Les_modulations_de_base.htm)ranck/Pages/Les_modulations_de_base.htm)

Amplitude Shift KeyingAmplitude Shift Keying


Phase Shift KeyingPhase Shift Keying



Bits EncodedBits Encoded– The previous methods allowed for the The previous methods allowed for the

encoding of 1 bit at a timeencoding of 1 bit at a time Multiple Bits EncodedMultiple Bits Encoded

– Quadrature Phase Shift Keying (QPSK)Quadrature Phase Shift Keying (QPSK)Allows for 2 bits to be encoded each modulation.Allows for 2 bits to be encoded each modulation.This technology is used in the IEEE 802.11x This technology is used in the IEEE 802.11x

standardsstandards


QPSK ModulationQPSK Modulation– Adjusting the phase puts the signal into one Adjusting the phase puts the signal into one

of the quartersof the quarters

1110

00 01


ModulationModulation– More than 2 bits can be encoded by encoding More than 2 bits can be encoded by encoding

phase and amplitude changesphase and amplitude changesThe more bits that are encoded the more The more bits that are encoded the more

susceptible to errors the signal will besusceptible to errors the signal will beQuadrature Amplitude modulation (QAM) Quadrature Amplitude modulation (QAM)

– 4 bits4 bits64 QAM64 QAM

– 6 bits6 bits

Antenna SizeAntenna Size

Optimum Antenna SizeOptimum Antenna Size– 4 phases of the carrier wave4 phases of the carrier wave– Speed of Light is Speed of Light is 299,792,458 meters per 299,792,458 meters per

secondsecond– At a frequency of 20Mhz (20,000,000 Hz)At a frequency of 20Mhz (20,000,000 Hz)

Each cycle takes (1/20,000,000)/4 = 0.0000000125Each cycle takes (1/20,000,000)/4 = 0.0000000125 Speed of light * each cycle = Speed of light * each cycle = Antenna size of 3.74 meters ! Antenna size of 3.74 meters !

Antenna SizeAntenna Size

Optimum Antenna SizeOptimum Antenna Size- Change this to 900 MHz- Change this to 900 MHz– 4 phases of the carrier wave4 phases of the carrier wave– Speed of Light is Speed of Light is 299,792,458 meters per 299,792,458 meters per

secondsecond– At a frequency of 900MHz (900,000,000 Hz)At a frequency of 900MHz (900,000,000 Hz)

Speed of light * each cycle gives Speed of light * each cycle gives Antenna size of 8 centimeters Antenna size of 8 centimeters

Radio Frequency - AuthorityRadio Frequency - Authority

Allocation of useAllocation of use– In the UK OFCOM is responsible for In the UK OFCOM is responsible for

allocating licenses for use of the radio allocating licenses for use of the radio spectrumspectrum

– They allocate all of the civilian uses of the They allocate all of the civilian uses of the spectrumspectrumwww.ofcom.org.ukwww.ofcom.org.uk

– List of recently awarded uses of the radio spectrumList of recently awarded uses of the radio spectrum http://www.ofcom.org.uk/radiocomms/http://www.ofcom.org.uk/radiocomms/

spectrumawards spectrumawards

– Military portion of the spectrum is Military portion of the spectrum is controlled by the Ministry of Defencecontrolled by the Ministry of Defence


Frequency spreadingFrequency spreading– Unfortunately no one country can control Unfortunately no one country can control

radio waves as they travel until they have radio waves as they travel until they have no powerno powerThe International Telecommunication Union The International Telecommunication Union

(ITU) based in Switzerland working the United (ITU) based in Switzerland working the United Nations holds regular meetings to agree across Nations holds regular meetings to agree across countries what frequencies to allocate to whatcountries what frequencies to allocate to what

Signal are difficult to contain within an areaSignal are difficult to contain within an area


Frequency spreadingFrequency spreading– Consider this when you are sending your Consider this when you are sending your

credit card detailscredit card detailsYou may be in a buildingYou may be in a buildingThe signal will travel outside of the buildingThe signal will travel outside of the building

– Unless the building has been specially built to deal with Unless the building has been specially built to deal with thisthis

Someone standing outside will receive these Someone standing outside will receive these signalssignals

– If they are not encrypted in some manner the If they are not encrypted in some manner the information is plainly availableinformation is plainly available

(www.computerweekly.com/Article110695.htm, (www.computerweekly.com/Article110695.htm, 2003)2003)

Radio Frequency - ModulationRadio Frequency - Modulation

Problems with Radio SignalsProblems with Radio Signals– InterferenceInterference

Any signal which is on the same frequency is Any signal which is on the same frequency is interferenceinterference

Even though to other people it may be a valid Even though to other people it may be a valid signal !signal !

– Bluetooth and 802.11b working in the same area is a Bluetooth and 802.11b working in the same area is a exampleexample

Radio Frequency - ModulationRadio Frequency - Modulation

InterferenceInterference– Unless something physical blocks the signals Unless something physical blocks the signals

will travel in all directions the same distancewill travel in all directions the same distance

Radio Frequency - ModulationRadio Frequency - Modulation InterferenceInterference

– ContinuedContinued It is difficult to predict who far a signal will travelIt is difficult to predict who far a signal will travel A lot of factors impact on the radio signalA lot of factors impact on the radio signal

– Frequency usedFrequency used In general the higher the frequency the shorter the distance In general the higher the frequency the shorter the distance

travelledtravelled The higher the frequency the more information you can encode The higher the frequency the more information you can encode

per secondper second The higher the frequency the more the signal resembles the The higher the frequency the more the signal resembles the

effects of light!effects of light!– WeatherWeather

Outdoor the weather can effect the signal, with heavy rain Outdoor the weather can effect the signal, with heavy rain increasing the attenuation on a signalincreasing the attenuation on a signal

– Physical AttributesPhysical Attributes Signals will have reduced power when passing through physical Signals will have reduced power when passing through physical

items, like walls, trees, safety windows being particularly bad !items, like walls, trees, safety windows being particularly bad !

Radio - AttenuationRadio - Attenuation

AttenuationAttenuation– The distance travelled by a signal is related The distance travelled by a signal is related

to the powerto the powerThere will still be a maximum effective distance There will still be a maximum effective distance

for the communicationsfor the communications– After this point more errors will be received than valid After this point more errors will be received than valid

data.data.

Time / Distance

StrengthPower

ConclusionConclusion

What we have discussedWhat we have discussed– What is radioWhat is radio– Radio FrequenciesRadio Frequencies– Sine WavesSine Waves– ModulationModulation– InterferenceInterference

What is Radio ? Justin Champion Room C203, Beacon Building Tel 3292, [email protected]...

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