oct. 4, 2006 assignment #2 marked lab #3 due today electromagnetic radiation and health systems
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Oct. 4, 2006Oct. 4, 2006
Assignment #2 MarkedAssignment #2 Marked
Lab #3 due todayLab #3 due today
Electromagnetic Radiation and HealthElectromagnetic Radiation and Health
SystemsSystems
Non-ionizing RadiationNon-ionizing Radiation
Insufficient energy to cause ionizationInsufficient energy to cause ionization
High energy non-ionizing radiation still High energy non-ionizing radiation still won’t cause ionizationwon’t cause ionization– Ionizing energy: depends on frequency not Ionizing energy: depends on frequency not
amplitudeamplitude– UV frequency: 750-800THzUV frequency: 750-800THz
Sources of Non-ionizing RadiationSources of Non-ionizing Radiation
Mostly man-made sourcesMostly man-made sourcesElectronics and electrical devicesElectronics and electrical devices– FCC/Industry Canada regulationsFCC/Industry Canada regulations
High voltage power linesHigh voltage power linesMobile phones and base stationsMobile phones and base stationsWLANs, bluetoothWLANs, bluetoothMicrowave ovensMicrowave ovensCordless phonesCordless phonesNumber is growingNumber is growing
Health Effects of Non-Ionizing Health Effects of Non-Ionizing RadiationRadiation
Thermal – increase temperature of moleculesThermal – increase temperature of molecules– Microwave ovenMicrowave oven– Smaller scale effect in any RF fieldSmaller scale effect in any RF field
Non-thermal – uncertain as to any non-thermal Non-thermal – uncertain as to any non-thermal effecteffect– Potentially: damage to cells, DNA, chromosomesPotentially: damage to cells, DNA, chromosomes
REFLEX study, Cemfec project, Interphone REFLEX study, Cemfec project, Interphone project, Perform-A project, and othersproject, Perform-A project, and others
Measuring EM ExposureMeasuring EM Exposure
Specific Absorption RateSpecific Absorption Rate– Measures absorption of EM radiation by bodyMeasures absorption of EM radiation by body– RF electronics have SAR ratings available to RF electronics have SAR ratings available to
usersusers– Less than 1.6watts/kg is max level allowedLess than 1.6watts/kg is max level allowed
Health Effects of Non-Ionizing Health Effects of Non-Ionizing RadiationRadiation
Independent Expert Group on Mobile Independent Expert Group on Mobile PhonesPhones
“ “Weight of evidence does not suggest that there are Weight of evidence does not suggest that there are adverse health effects from exposure to RF fields below adverse health effects from exposure to RF fields below guideline levels, but the published research…has guideline levels, but the published research…has limitations, and mobile phones [and WLANs] have only limitations, and mobile phones [and WLANs] have only been in widespread use for a limited time. The possibilty been in widespread use for a limited time. The possibilty therefore remains open that there could be health effects therefore remains open that there could be health effects from exposure to RF fields below guideline levels; hence from exposure to RF fields below guideline levels; hence more research is needed.”more research is needed.”
What then to do?What then to do?
What then to do?What then to do?
WHO suggests: WHO suggests: – Take precautions to minimize exposureTake precautions to minimize exposure– Limit cellphone useLimit cellphone use– Limit WLAN use (how do we do that at OC)Limit WLAN use (how do we do that at OC)– Limit wireless use by childrenLimit wireless use by children– Place high power antennas away from peoplePlace high power antennas away from people– Microcell networksMicrocell networks
EM and Health ReviewEM and Health Review
What is ionizing radiation?What is ionizing radiation?
Name 2 natural sources of ionizing Name 2 natural sources of ionizing radiation.radiation.
Name 2 man-made sources of ionizing Name 2 man-made sources of ionizing radiation.radiation.
Ionizing radiation is known to be harmful, Ionizing radiation is known to be harmful, why are there any man-made sources of why are there any man-made sources of ionizing radiation.ionizing radiation.
EM and Health Review (2)EM and Health Review (2)
When is non-ionizing radiation harmful.When is non-ionizing radiation harmful.
What is potentially the most harmful source of What is potentially the most harmful source of non-ionizing radiation that you might encounter?non-ionizing radiation that you might encounter?
Is there reason to be worried about the levels of Is there reason to be worried about the levels of non-ionizing radiation we are exposed to today? non-ionizing radiation we are exposed to today? What about in the future?What about in the future?
Which would you rather be subjected to, 60 Which would you rather be subjected to, 60 watts of 2.4 watts of 2.4 yoctohertzyoctohertz EM waves, or 60 watts EM waves, or 60 watts of 2.4 of 2.4 yottahertzyottahertz EM waves? EM waves?
SystemsSystems
SystemsSystems
Generic Communications Block Generic Communications Block DiagramDiagram
This diagram generalizes previous oneThis diagram generalizes previous one– Can be used to model entire thing or just a part of itCan be used to model entire thing or just a part of it
Qualitatively: System will do something to input Qualitatively: System will do something to input to give outputto give outputQuantitatively: If you know any two of the three Quantitatively: If you know any two of the three parts, you can figure out the thirdparts, you can figure out the third
System TypesSystem Types
Gain/LossGain/Loss
Filtering/BandlimitingFiltering/Bandlimiting
Adding NoiseAdding Noise
Changing signal typeChanging signal type
Modulating/DemodulatingModulating/Demodulating
Gain and LossGain and Loss
SigOutSigOutwattswatts = SysGain = SysGainabsRatioabsRatio x SigIn x SigInwattswatts
SigOutSigOutdBmdBm = SysGain = SysGaindBdB + SigIn + SigIndBmdBm
Filtering/BandlimitingFiltering/Bandlimiting
System prevents certain frequencies from System prevents certain frequencies from passing throughpassing through
Range allowed is between an upper cutoff Range allowed is between an upper cutoff and a lower cutoffand a lower cutoff– For low pass filters, the lower cutoff is 0For low pass filters, the lower cutoff is 0– For high pass filters, the upper cutoff is infinityFor high pass filters, the upper cutoff is infinity
Adding NoiseAdding Noise
No signal can be free of noiseNo signal can be free of noise
No system can be free of noiseNo system can be free of noise
NoiseNoiseSigOutSigOut(watts) = Noise(watts) = NoiseSystemSystem(watts) + (watts) +
NoiseNoiseSigInSigIn(watts)(watts)
Caveat: To do above calculation, noise Caveat: To do above calculation, noise must be in watts – you can’t add dBm must be in watts – you can’t add dBm togethertogether
Changing Signal TypeChanging Signal Type
Converts signal from one type to otherConverts signal from one type to other– Continuous ↔ discreteContinuous ↔ discrete– Analog ↔ digitalAnalog ↔ digital– Periodic ↔ aperiodicPeriodic ↔ aperiodic– Deterministic ↔ randomDeterministic ↔ random– Finite ↔ infiniteFinite ↔ infinite
Analog to Digital Converters (ADCs)Analog to Digital Converters (ADCs)
Digital to Analog Converters (DACs) Digital to Analog Converters (DACs)
Modulation/DemodulationModulation/Demodulation
Analog Modulation/DemodulationAnalog Modulation/Demodulation– AM: Vary signal amplitude to carry dataAM: Vary signal amplitude to carry data– FM: Vary signal frequency to carry dataFM: Vary signal frequency to carry data
Digital Modulation/DemodulationDigital Modulation/Demodulation– FSK: Use frequencies to encode/decode dataFSK: Use frequencies to encode/decode data– PSK: Use phase to encode/decode dataPSK: Use phase to encode/decode data– ASK: Use amplitude to encode/decode dataASK: Use amplitude to encode/decode data