Wireless Telephony

Overview
You have made it this far young one. Now prepare to do it without wires! Muahahaha!

Transduction

 * the conveyance or nrg from on e electron to another at the same time that the class of nrg changes
 * way of converting nrg between forms
 * size of antenna is inverse to freq of wave
 * links
 * use electromag spectrum
 * digital radio and tv broadcasting
 * national defense and EMS
 * avaition and maritime

Modulation of Wirelesss

 * Fourier theorum
 * alter char of a carrier signal to enable it to carry info
 * what chars can be modulated?
 * amplitude, freq, and phase
 * input:
 * take a base band signal
 * modualtion
 * the max amplitude
 * carrier wave is always higher freq than modulating wave's freq. done so that you can easily strip off carrier wave from baseband

Demodulation of Wireless

 * eliminate the negative part: ends up with only half of wave ( the positive part)
 * low pass filter:strips away high freq
 * 100% modulation, 50%, 25% etc. wave gets flat
 * 150% modulation: wave loses its valleys
 * spectrum of AM (amp mod) waves
 * Fc= carriers freq
 * Fm=modulating signals freq
 * located above and below carrier wave.
 * reason for odd numbers for each radio channel: to eliminate contamination between signals
 * FM (freq mod)
 * the freq of the carrier is modulated and hte amp of hte signal is modulated
 * DEMOD
 * limiter clips filters to remove unwanted amplitude variation
 * outoputs amplitude proportional to signal
 * discriminator
 * tuned cicuit that outputs and amp proportional to freq
 * actually converst fm to am
 * then AM demod process

Effect of Noise

 * noise:any signal that does not convey useful info
 * affected by addtive noise
 * AM:yes
 * FM:relativly resistant to additive noise
 * affected by impulse noise. eg: lighting
 * AM:very affected
 * FM:much less affected
 * signal to noise ratio(S/N)
 * the bigger the better
 * signal to noise ratio is 75 times better in FM than AM(formula 3* square of modulation index)
 * max freq of baseband signal

CONTINUE...

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