Editing Front-to-back ratio

[[File:Sidelobes en.svg|thumb|Radiation pattern of an antenna with main lobe (right) in red, and back lobe in blue]]
In telecommunication, the term '''front-to-back ratio''' (''also known as front-to-rear ratio'') can mean:
#The ratio of power gain between the front and rear of a [[directional antenna]]. 
#Ratio of [[signal strength]] transmitted in a forward direction to that transmitted in a backward direction. For receiving antennas, the ratio of received-signal strength when the antenna is rotated 180°.<ref>Radio Shack 1974-75 unabridged Dictionary of Electronics edited by Rudolf F. Graf, cat. no. 68-1030</ref>

The ratio compares the [[antenna gain]] in a specified direction, ''i.e.'', [[azimuth]], usually that of maximum gain, to the gain in a direction 180° from the specified azimuth. A front-to-back ratio is usually expressed in [[decibel]]s (dB).  

In [[Fixed wireless|point-to-point]] microwave antennas, a "high performance" antenna usually has a higher front to back ratio than other antennas.  For example, an unshrouded 38 GHz microwave dish may have a front to back ratio of 64 dB, while the same size reflector equipped with a shroud would have a front to back ratio of 70 dB.  Other factors affecting the front to back ratio of a parabolic microwave antenna include the material of the dish and the precision with which the reflector itself was formed.

In other electrical engineering the '''front to back ratio''' is a [[ratio]] of parameters used to characterize [[rectifier]]s or other devices, in which [[electric current]], signal strength, [[Electrical resistance|resistance]], or other parameters, in one direction is compared with that in the opposite direction.

== References ==
{{Reflist}}

{{FS1037C MS188}}

[[Category:Antennas]]
[[Category:Engineering ratios]]

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