The document discusses the Rake receiver, which is used to counter the effects of multipath fading in wireless communications. It works by using multiple "fingers" to collect different time-shifted versions of the original signal transmitted over multiple paths. Each finger correlates and extracts one of the multipath components. The outputs are then weighted and combined to provide a better estimate of the transmitted signal. This allows the Rake receiver to equalize the effects of multipath and improve the signal-to-noise ratio. While useful for CDMA, W-CDMA and other technologies, Rake receivers are also more complex and expensive than conventional receivers.

1. RAKE RECEIVER
PRESENTED BY-
DIVYA SHUKLA

2. Learning Objectives
 Multipath
 Rake- Introduction
 How does it works?
 Role of Rake Receiver
 Block diagram
 Use, Advantage, Disadvantage
 Conclusion

3. Multipath
 Multipath occurs when RF signal arrives at the destination via
different paths due to the reflected transmitted signal from moving or
fixed objects.
The RAKE receiver uses a multipath diversity principle.
– It rakes the energy from the multipath
propagated signal components.

4. What is Rake Receiver?
 A Rake Receiver is radio receiver designed to counter the
effects of multipath fading.
 Several “sub-receivers” called fingers are used.
 RAKE receiver attempts to collect the time-shifted versions of
the original signal by providing a separate correlation receiver
for each of the multipath signals.

5. BLOCK DIAGRAM OF RAKE RECEIVER

6. M- Branch Rake Receiver

7. How Does It Works?
The outputs of each correlator are weighted to provide better
estimate of the transmitted signal than provided by a single
component.
Demodulation is then based on the weighted outputs of the M-
correlators.

8. Role of rake receiver
 Equalize the effects of multipath.
 Spread out the individual echo signals of the multipath
 Each signal is then delayed according to peaks found in the
receiver signal.

9. USES OF RAKE RECEIVER
 CDMA & W-CDMA radio devices – Mobile Phones & Wireless LAN.
 Radio astronomy
ADVATAGES OF RAKE RECEIVER
 Improved SNR
 Improved performance
DISADVANTAGES OF RAKE RECEIVER
Cost
Size
Complexity

10. Conclusion
 Rake receiver is used in CDMA and W-CDMA as an
efficient way of multipath signal reception, where several
receptors are able to reconstruct the signal with different
time-codes, amplitude and phase.

11. THANKYOU
for your patience listning..!!