Editing Rake receiver (section)

{{Short description|Radio receiver}}
{{Use dmy dates|date=January 2022}}
A '''rake receiver''' is a radio [[receiver (radio)|receiver]] designed to counter the effects of [[multipath fading]]. It does this by using several "sub-receivers" called ''fingers'', that is, several correlators each assigned to a different [[Multipath propagation|multipath]] component. Each finger independently decodes a single multipath component; at a later stage the contribution of all fingers are combined in order to make the most use of the different [[Transmission (telecommunications)|transmission]] characteristics of each transmission path. This could very well result in higher [[signal-to-noise ratio]] (or [[Eb/N0|E<sub>b</sub>/N<sub>0</sub>]]) in a multipath environment than in a "clean" environment.

The multipath channel through which a radio wave transmits can be viewed as transmitting the original ([[Line-of-sight propagation|line of sight]]) wave pulse through a number of multipath components. Multipath components are delayed copies of the original transmitted wave traveling through a different echo path, each with a different magnitude and time-of-arrival at the receiver. Since each component contains the original information, if the magnitude and time-of-arrival (phase) of each component is computed at the receiver (through a process called channel estimation), then all the components can be added coherently to improve the information reliability.<ref name="ref 1">{{cite book| title=Principles of Spread-Spectrum Communication Systems, 4th ed.| year=2018|last1=Torrieri|first1=Don}}</ref><ref name="ref 2">{{cite book| title=Principles of Mobile Communication, 4th ed.| year=2017|last1=Stuber|first1=Gordon L.}}</ref><ref name="ref 3">{{cite book| title=Digital Communications, 5th ed.| year=2008|last1=Proakis|first1=John G.|last2=Salehi|first2=Masoud}}</ref>