COMMUNICATIONS Flashcards
sound waves
mechanical wave that propagates through a medium (typically air)
loudness
depends on the amplitude of the wave
pitch
depends on the frequency of the wave
microphone
- audio into electrical
- pressure of sound waves on the diaphragm moves the coil, generating a current
- different vibrations of the sound waves produce different currents that can be converted back into sound
speakers
- electromagetic into sound
- electric current in the coil produces motion causing the diaphragm to vibrate creating sound waves
- a microphone can be connected to a loudspeaker by copper wires
radio
- electromagnetic waves into sound
- consists of an electronic circuit to transform electric power from a battery into a radio frequency alternating current
- high frequencies allow the energy to radiate off a conductor (antenna) as electromagnetic waves that travel through air
amplitude modulation
- radio station generates a high frequency carrier wave
- the audio signal modulates the amplitude of the carrier wave
- the modulated carrier is transmitted, received, and demodulated to extract the original audio
- it travels using the ionosphere to reach grater distances
frequency modulation
- radio station generates a high frequency carrier wave
- the audio signal modulates the frequency of the carrier wave
- the modulated carrier is transmitted, received, and demodulated to extract the original audio
am
- can travel further
- cheaper/simpler equipment
- narrower bandwidth
- prone to interference
fm
- better sound quality
- less prone to interference
- wider bandwidth
- physical barrier
- more complex/expensive equipment
binary system
each piece data is converted into a series of binary digits (0,1) based on an encoding scheme
boolean logic
- mathematical approach to logical reasoning (and, or, not)
- variables take up binary variables
transistors
electronic switches that transform logic operations into electrical signals
optic fiber
- transmits information form one place to another by sending pulses of light through a glass pipe
- light is reflected back and forth through the pipe without getting lost
reflection
light travels through the pipe, and is reflected off the glass surface at the same angle
refraction
due to the lower reflective value of the outer level, the light doesn’t get refracted out
repeaters
object placed where there is a weakened signal, which transforms it into binary and back into light to continue down
amplifiers
doped with chemicals that amplify the light when the weakened signal hits them, to re emit the stronger signal
satellite
- machine launched into space that orbits around earth
- ground based stations send signals to satellites which process them, amplify them and retransmit it to earth
satellite role
- collect more data quicker and more effectively than instruments on ground
- better than telescopes on earths surface and have higher resolution (no weather interferences)
launch
- they are launched atop rockets, because the force of it must be grater than the force of gravity
- they are released into the orbit with the momentum they gained
- to stay in orbit they rely on a perfect balance between momentum and gravity, and also tangential velocity
polar satellites
- orbit north-south at a low orbit
- higher resolution
- global coverage
- no continuous viewing
- large scale mapping and global weather
geostationary satellite
- launched in a further orbit so they sync up to earths rotation, allowing for a fixed position
- clear signal
- signal may have delay because of distance
- tv, weather, gps
