1. Oct. 4, 2006 Assignment #2 Marked Lab #3 due today Electromagnetic Radiation and Health Systems

2. Non-ionizing Radiation Insufficient energy to cause ionization High energy non-ionizing radiation still won’t cause ionization –Ionizing energy: depends on frequency not amplitude –UV frequency: 750-800THz

3. Sources of Non-ionizing Radiation Mostly man-made sources Electronics and electrical devices –FCC/Industry Canada regulations High voltage power lines Mobile phones and base stations WLANs, bluetooth Microwave ovens Cordless phones Number is growing

4. Health Effects of Non-Ionizing Radiation Thermal – increase temperature of molecules –Microwave oven –Smaller scale effect in any RF field Non-thermal – uncertain as to any non-thermal effect –Potentially: damage to cells, DNA, chromosomes REFLEX study, Cemfec project, Interphone project, Perform-A project, and others

5. Measuring EM Exposure Specific Absorption Rate –Measures absorption of EM radiation by body –RF electronics have SAR ratings available to users –Less than 1.6watts/kg is max level allowed

6. Health Effects of Non-Ionizing Radiation Independent Expert Group on Mobile Phones “Weight of evidence does not suggest that there are adverse health effects from exposure to RF fields below guideline levels, but the published research…has limitations, and mobile phones [and WLANs] have only been in widespread use for a limited time. The possibilty therefore remains open that there could be health effects from exposure to RF fields below guideline levels; hence more research is needed.” “Weight of evidence does not suggest that there are adverse health effects from exposure to RF fields below guideline levels, but the published research…has limitations, and mobile phones [and WLANs] have only been in widespread use for a limited time. The possibilty therefore remains open that there could be health effects from exposure to RF fields below guideline levels; hence more research is needed.”

7. What then to do?

8. WHO suggests: –Take precautions to minimize exposure –Limit cellphone use –Limit WLAN use (how do we do that at OC) –Limit wireless use by children –Place high power antennas away from people –Microcell networks

9. EM and Health Review What is ionizing radiation? Name 2 natural sources of ionizing radiation. Name 2 man-made sources of ionizing radiation. Ionizing radiation is known to be harmful, why are there any man-made sources of ionizing radiation.

10. EM and Health Review (2) When is non-ionizing radiation harmful. What is potentially the most harmful source of non-ionizing radiation that you might encounter? Is there reason to be worried about the levels of non-ionizing radiation we are exposed to today? What about in the future? Which would you rather be subjected to, 60 watts of 2.4 yoctohertz EM waves, or 60 watts of 2.4 yottahertz EM waves?

11. Systems

12. Systems

13. Generic Communications Block Diagram This diagram generalizes previous one –Can be used to model entire thing or just a part of it Qualitatively: System will do something to input to give output Quantitatively: If you know any two of the three parts, you can figure out the third

14. System Types Gain/LossFiltering/Bandlimiting Adding Noise Changing signal type Modulating/Demodulating

15. Gain and Loss SigOut watts = SysGain absRatio x SigIn watts SigOut dBm = SysGain dB + SigIn dBm

16. Filtering/Bandlimiting System prevents certain frequencies from passing through Range allowed is between an upper cutoff and a lower cutoff –For low pass filters, the lower cutoff is 0 –For high pass filters, the upper cutoff is infinity

17. Adding Noise No signal can be free of noise No system can be free of noise Noise SigOut (watts) = Noise System (watts) + Noise SigIn (watts) Caveat: To do above calculation, noise must be in watts – you can’t add dBm together

18. Changing Signal Type Converts signal from one type to other –Continuous ↔ discrete –Analog ↔ digital –Periodic ↔ aperiodic –Deterministic ↔ random –Finite ↔ infinite Analog to Digital Converters (ADCs) Digital to Analog Converters (DACs)

19. Modulation/Demodulation Analog Modulation/Demodulation –AM: Vary signal amplitude to carry data –FM: Vary signal frequency to carry data Digital Modulation/Demodulation –FSK: Use frequencies to encode/decode data –PSK: Use phase to encode/decode data –ASK: Use amplitude to encode/decode data