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.
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.