RAKE receiver is a receiver which is planned to calculate the effects of multipath fading. The multipath channel plays the major part in the rake receiver because it consists of following parts like correlator, match filter, attenuator, adder, integrator etc.
Its multipath channels reminds the function of a garden rake where rake is a steel or wooden tool which consisting of a toothed bar fixed horizontally to a handle and used to collect leaves, grass, hay etc. in gardening, light weeding and levelling, removing dead grass from lawns.
They are common in a wide variety of radio devices such as mobile phones, wireless LAN equipment or apparatus etc.
In the cellular systems, if the multiple versions of a signal arrive more than one chip interval apart from each other, then the receiver can recover the signal by correlating the chip sequence with the superior incoming signal and the remaining signals are treated as noise. If the receiver attempts to recover the signals from multiple paths and combine them with suitable delays then we can be achieved the better presentation of the system. This principle is used in the RAKE receiver as shown below in fig:
Above figure illustrates the principle of the RAKE receiver. According to the above figure, firstly original binary signal or data to be encoded using code generator and then transmitted data is spread by the exclusive-OR (XOR) operation. The spread data is then modulated for transmission over the wireless channel using modulator.
Then modulated signal applied to the multipath channel. Because of multipath effects, the channel generates multiple copies of the signal where each signal with the different amount of time delay and the different attenuation factors as shown below in figure.