RAKE DEMODULATOR IT HAS BEEN COINED FOR THIS DEMODULATOR STRUCTURE BY PRICE AND GREEN (1958 )

1. RAKE DEMODULATOR
BY
AJAL.A.J

2. NOMENCLATURE
• RAKE DEMODULATOR
IT HAS BEEN COINED FOR THIS DEMODULATOR STRUCTURE BY
PRICE AND GREEN (1958 )

3. RAKE DEMODULATOR
OPTIMUM
DEMODULATOR
REALIZATION
ALTERNATE
DEMODULATOR
REALIZATION

4. ANOTHER NAME
• TAPPED DELAY LINE DEMODULATOR
• TAPPED DELAY LINE DEMODULATOR ATTEMPTS TO COLLECT THE SIGNAL ENERGY FROM ALL THE RECEIVED
SIGNAL PATHS THAT FALL WITHIN THE SPAN OF THE DELAY LINE AND CARRY THE SAME INFORMATION
• IN ITS ACTION IS SOME WHAT ANALOGU8S TO AN ORDINARY
GARDEN RAKE .

5. WE CALL THIS AS AN OPTIMUM
DEMODULATOR ALSO WHY
BECAUSE …………
• CAN ALTERNATIVE REALIZATION OF THE
OPTIMUM DEMODULATOR EMPLOYS A
SINGLE DELAY LINE THROUGH WHICH IS
PASSED THE RECEIVED SIGNAL R (t)

6. TAP WEIGHTS ……
• TAP WEIGHTS PROVIDES US WITH
L REPLICAS OF SAME TRANSMITTED
SIGNAL AT THE RECEIVER
HENCE IN A RECEIVER THAT PROCESS THE RECEIVED SIGNAL IN AN
OPTIMUM MANNER WILL ACHIEVE THE PERFORMANCE OF AN
EQUILAENT LTH
ORDER DIVERSITY COMMUNICATION SYSTEM

7. CONSIDER ……………
• CONSIDER BINARY SIGNALLING OVER
THE CHANNEL .
• WE HAVE 2 EQUAL ENERGY SIGNALS ,
WHICH ARE
EITHER
ANTIPODAL OR ORTHOGONAL
ASSUMPTION

8. WHAT IS TO BE NEGLECTED ?
• NEGLECT ISI DUE TO THE MULTIPATH
NOTE
ISI IS INTER SYMBOL INTERFERENCE
SINCE
BAND WIDTH OF THE SIGNAL EXCEEDS THE COHERENT BAND WIDTH
OF THE CHANNEL

9. • ASSUME THAT THE CHANNEL TAP
WEIGHTS ARE KNOWN
• HERE THE 2 FILTERS ARE MATCHED
TO V1 (t) & V2 (t)
• Also
The samples are passed toa decision
circuit that selects the signal
corresponding to largest output
ASSUMPTION