LQ1 - Digital Communication - Transmission Medium

Transmission medium

Refers to anything that convey signals for electronic communications

physical, medium, logical

The term transmission medium is reserved for ____ ___ and differentiated from the ____ channel

Unguided media

Type of signals that are essentially unconstrained by any physical structure

Guided media

Type of signals that are constrained a physical structure

crosstalk

Cables with two conductors twisted relative to each other is to prevent ____

crosstalk

unwanted signals produced by electromagnetic coupling between signals in different wires

Coaxial cables

Are copper cables where conductors are arranged in a concentric manner

outer, conductor, inner, conductor, shield

In a coaxial cable, the ___ ____ encloses the ___ ___, acting as a ___ from unwanted signals

Coaxial cable

Can carry higher frequency signals than a twisted pair

coaxial, cable, attenuation, higher, frequencies

____ ____ can have lower ____ at ___ ____ than twisted pair cables

Coaxial cables

Are needed by coaxial cables because of their particular construction

Fiber-optic cables

Cables made of optical fiber made of silica glass to allow light to travel through internal reflection

lasers, optical detectors

Fiber optic cables use ___ for transmission and ___ ____ for reception

Single mode wireless communication

Use highly focused or concentrated light that coalesce into one to reduce dispersion

wireless communication

are currently mostly implemented using radio wave propagation

polarization

radio waves exhibit ___

1/frequency

wavelength

3 radio wave propagation modes

1. Ground propagation

2. Sky propagation

3. Line-of-sight propagation

Groundwave propagation

the propagation mode where radio waves are reflected or refracted off the ionosphere

Antennas

Are devices central to wireless communications. They can convert electrical signals into EM waves and vice-versa

Antenna Radiation Pattern

Describes directionality with the antennas ability to transmit and receive EM waves

Repeaters

Extend the range of communications

Infrared

Uses light that have frequencies lower than red