PHYS-P 150 Lecture Notes - Lecture 22: Carrier Wave, James Clerk Maxwell, Simple Harmonic Motion
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James clerk maxwell discovered electromagnetic waves by equations: confirmed electromagnetic waves and confirmed that they would travel at a particular speed. Strength of signal at the receiver is directly related to the intensity of a particular wave: a measurement of power/area. As the wave travels an increasing distance, the waves spread out of a greater area than the initial wave: area of wave-front grows with the square of the distance, area = 4pi (radius)^2. So intensity also weakens proportional to inverse of square of distance from transmitter. Transmitted waves are polarized: this means oscillation occurs parallel to transmitter antenna. Carrier wave: a wave at a constant frequency and amplitude. Indicates that no information is being transmitted through the channel: different channels have carrier waves with different frequencies. There are three ways to change properties of carrier waves: changing amplitude amplitude modulation or am, changing frequency frequency modulation or fm, changing phase shifting the wave left or right (phase modulation or.
