In telecommunications and electrical engineering, electrical length is the length of a transmission medium or antenna element expressed as the number of wavelengths of the signal propagating in the medium.
Electromagnetic waves propagate more slowly in a medium than in free space, so a wave in a medium will have a larger number of waves than a wave of the same frequency propagating over the same distance in free space. Alternatively put, the distance covered in free space by the same number of waves as are in the transmission medium will be greater, hence the transmission medium is said to have an electrical length greater than its physical length. The electrical length is most commonly expressed in units of the wavelength, λ, which is related to the velocity of propagation, v, and frequency, f, by
A length may be stated as 2λ or 3λ or 0.5λ etc. It is also sometimes expressed in radians or degrees. A length of ν λ can be converted to θ radians by
In conducting cables, distributed resistances, capacitances and inductances impede the propagation of the signal. In an optical fiber interaction of the light wave with the materials of which the fiber is made (and fiber geometry) affect the velocity of signal propagation. In both coaxial cables and optical fibers, the velocity of wave propagation is approximately two-thirds that of free space. Consequently, the wavelength will be approximately two-thirds that in free space, and the electrical length approximately 1.5 times the physical length.
Read more about Electrical Length: Antennas, Lengthening Antennas
Famous quotes containing the words electrical and/or length:
“Few speeches which have produced an electrical effect on an audience can bear the colourless photography of a printed record.”
—Archibald Philip Primrose, 5th Earl Rosebery (18471929)
“And my spirit is grown to a lordly great compass within,
That the length and the breadth and the sweep of the marshes of
Glynn
Will work me no fear like the fear they have wrought me of yore
When length was failure, and when breadth was but bitterness sore,
And when terror and shrinking and dreary unnamable pain
Drew over me out of the merciless miles of the plain,
Oh, now, unafraid, I am fain to face
The vast sweet visage of space.”
—Sidney Lanier (18421881)