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The ionosphere is a layer of partially ionized gases high above the majority of the Earth's atmosphere; these gases are ionized by cosmic rays originating on the sun. When radio waves travel into this zone, which commences about 80 kilometers above the earth, they experience diffraction in a manner similar to the visible light phenomenon described above. [1]
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]
Radio waves were first predicted by the theory of electromagnetism that was proposed in 1867 by Scottish mathematical physicist James Clerk Maxwell. [6] His mathematical theory, now called Maxwell's equations, predicted that a coupled electric and magnetic field could travel through space as an "electromagnetic wave".
Diffraction: When a radio wave encounters an obstacle, it can be diffracted, or bent around the edge of the obstacle. This can cause additional signal loss, especially in urban environments with many buildings. [3] Absorption: Certain atmospheric gases and obstacles like buildings and foliage can absorb radio waves, reducing their strength. [4]
diffraction through windows, and attenuated passage through walls, into the building reflection, diffraction, and attenuated passage through internal walls, floors and ceilings within the building The combination of all these effects makes the mobile phone propagation environment highly complex, with multipath effects and extensive Rayleigh ...
Diffraction is the same physical effect as interference, but interference is typically applied to superposition of a few waves and the term diffraction is used when many waves are superposed. [1]: 433 Italian scientist Francesco Maria Grimaldi coined the word diffraction and was the first to record accurate observations of the phenomenon in 1660.
Multipath interference is a common cause of "ghosting" in analog television broadcasts and of fading of radio waves. A diagram of the ideal situation for TV signals moving through space: The signal leaves the transmitter (TX) and travels through one path to the receiver (the TV set, which is labeled RX) In this illustration, an object (in this ...
Refraction of radio waves by the ionosphere rather than the atmosphere can therefore allow NLOS links of much greater distance for just one refraction path or 'hop' via one of the layers. Under certain conditions radio waves that have undergone one hop may reflect off the Earth's surface and experience more hops, so increasing the range.