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What is Radio ? Justin Champion Room C203, Beacon Building Tel 3292,

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Presentation on theme: "What is Radio ? Justin Champion Room C203, Beacon Building Tel 3292,"— Presentation transcript:

1 What is Radio ? Justin Champion Room C203, Beacon Building Tel 3292,

2 Content  Introduction –What is Radio –Sine wave –Modulation –Interference  Conclusion

3 Radio Frequencies  We use this technology everyday –This course would be a lot shorter with out them!  They allow for –Cellular Devices –Wireless Networks –Television –Radio Microphones –Satellite Communications –DECT Telephones –Personal Radios –The full name is Radio Electromagnetic Spectrum, but we use the shortened term Radio

4 Radio Frequencies  Radio is an electronic magnetic wave –Connect a wire to a battery and touch the ends close to an AM radio  You should hear the sound which is produced –The magnetic pulse which is transmitted will be picked up on a nearby wire as electricity and converted to sound.  By touching and letting go you can produce Morse code over the radio!  The distance this will be picked up by is related to power in the source

5 Radio Frequencies  To transfer information a carrier wave is required. –On/Off carrier would look like this –More Common is the Sine wave  This changes its value continuously 1 Cycle

6 Radio Frequencies  Sine Wave –As we know what the carrier wave should be showing  It is easier now to check for changes –These changes will be used to encode information –Carrier wave will also allow for information to be transferred over greater distances  Without errors 1 Cycle Amplitude

7 Radio Frequencies  Frequency –This refers to how often the Sine wave cycles up and down per second  1 cycle = Hertz (HZ)  1,000 Cycles = Kilohertz (KHz)  1,000,000 cycles = 1 Megahertz (MHz)  1,000,000,000 cycles = 1 Gigahertz (GHz)  Encoding Data –Adjustments to this Sine wave can then be used to encode 1’s and 0’s, voice or video –These adjustments are referred to as Modulation

8 Radio Frequencies  The following are all radio waves –X-Ray, Light, Gamma Rays –For our normal interest of Radio we use  Very Low Frequency (VLF) –3-30 KHz  Low Frequency (LF) –30 – 300 KHz  Medium Frequency (MF) –300 – 3000 KHz  High Frequency (HF) –3 – 30 MHz  Very High Frequency (VHF) –30 – 300 MHz  Ultra High Frequency (UHF) –300 – 3000 MHz

9 Radio Frequencies

10 Radio Modulation  Modulation of the signal –Changes which can be made to a carrier wave  Frequency Shift Keying (Frequency Modulation (FM)) –Increases / decreases the cycling rate of the sine wave  Amplitude Shift Keying (Amplitude Modulation (AM)) –Changes the power of the signal  Phase Shift Keying –Changes the phase that the sine wave is in

11 Frequency Shift Keying (“Les modulations de base”, 2004, Franck/Pages/Les_modulations_de_base.htm) (“Les modulations de base ”, 2004, Franck/Pages/Les_modulations_de_base.htm) Franck/Pages/Les_modulations_de_base.htm Franck/Pages/Les_modulations_de_base.htm

12 Amplitude Shift Keying (“Les modulations de base”, 2004, Franck/Pages/Les_modulations_de_base.htm) (“Les modulations de base ”, 2004, Franck/Pages/Les_modulations_de_base.htm) Franck/Pages/Les_modulations_de_base.htm Franck/Pages/Les_modulations_de_base.htm

13 Phase Shift Keying (“Les modulations de base”, 2004, Franck/Pages/Les_modulations_de_base.htm) (“Les modulations de base ”, 2004, Franck/Pages/Les_modulations_de_base.htm) Franck/Pages/Les_modulations_de_base.htm Franck/Pages/Les_modulations_de_base.htm

14 Radio Modulation  Bits Encoded –The previous methods allowed for the encoding of 1 bit at a time  Multiple Bits Encoded –Quadrature Phase Shift Keying (QPSK)  Allows for 2 bits to be encoded each modulation.  This technology is used in the IEEE x standards

15 Radio Modulation  QPSK Modulation –Adjusting the phase puts the signal into one of the quarters

16 Radio Modulation  Modulation –More than 2 bits can be encoded by encoding phase and amplitude changes  The more bits that are encoded the more susceptible to errors the signal will be  Quadrature Amplitude modulation (QAM) –4 bits  64 QAM –6 bits

17 Antenna Size  Optimum Antenna Size –4 phases of the carrier wave –Speed of Light is 299,792,458 meters per second –At a frequency of 20Mhz (20,000,000 Hz)  Each cycle takes (1/20,000,000)/4 =  Speed of light * each cycle =  Antenna size of 3.74 meters !

18 Antenna Size  Optimum Antenna Size - Change this to 900 MHz –4 phases of the carrier wave –Speed of Light is 299,792,458 meters per second –At a frequency of 900MHz (900,000,000 Hz)  Speed of light * each cycle gives  Antenna size of 8 centimeters

19 Radio Frequency - Authority  Allocation of use –In the UK OFCOM is responsible for allocating licenses for use of the radio spectrum –They allocate all of the civilian uses of the spectrum  –List of recently awarded uses of the radio spectrum  wards wards wards –Military portion of the spectrum is controlled by the Ministry of Defence

20 Radio Frequency - Authority  Frequency spreading –Unfortunately no one country can control radio waves as they travel until they have no power  The International Telecommunication Union (ITU) based in Switzerland working the United Nations holds regular meetings to agree across countries what frequencies to allocate to what  Signal are difficult to contain within an area

21 Radio Frequency - Authority  Frequency spreading –Consider this when you are sending your credit card details  You may be in a building  The signal will travel outside of the building –Unless the building has been specially built to deal with this  Someone standing outside will receive these signals –If they are not encrypted in some manner the information is plainly available  (www.computerweekly.com/Article htm, 2003)

22 Radio Frequency - Modulation  Problems with Radio Signals –Interference  Any signal which is on the same frequency is interference  Even though to other people it may be a valid signal ! –Bluetooth and b working in the same area is a example

23 Radio Frequency - Modulation  Interference –Unless something physical blocks the signals will travel in all directions the same distance

24 Radio Frequency - Modulation  Interference –Continued  It is difficult to predict who far a signal will travel  A lot of factors impact on the radio signal –Frequency used  In general the higher the frequency the shorter the distance travelled  The higher the frequency the more information you can encode per second  The higher the frequency the more the signal resembles the effects of light! –Weather  Outdoor the weather can effect the signal, with heavy rain increasing the attenuation on a signal –Physical Attributes  Signals will have reduced power when passing through physical items, like walls, trees, safety windows being particularly bad !

25 Radio - Attenuation  Attenuation –The distance travelled by a signal is related to the power  There will still be a maximum effective distance for the communications –After this point more errors will be received than valid data. Time / Distance Strength Power

26 Conclusion  What we have discussed –What is radio –Radio Frequencies –Sine Waves –Modulation –Interference


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