Rake demodulator

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RAKE DEMODULATOR

IT HAS BEEN COINED FOR THIS DEMODULATOR STRUCTURE BY

PRICE AND GREEN (1958 )


Published in: Devices & Hardware
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  • THE NAME HAS BEEN INTRODUCED B
  • Rake demodulator

    1. 1. RAKE DEMODULATOR BY AJAL.A.J
    2. 2. NOMENCLATURE • RAKE DEMODULATOR IT HAS BEEN COINED FOR THIS DEMODULATOR STRUCTURE BY PRICE AND GREEN (1958 )
    3. 3. RAKE DEMODULATOR OPTIMUM DEMODULATOR REALIZATION ALTERNATE DEMODULATOR REALIZATION
    4. 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. 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. 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. 7. CONSIDER …………… • CONSIDER BINARY SIGNALLING OVER THE CHANNEL . • WE HAVE 2 EQUAL ENERGY SIGNALS , WHICH ARE EITHER ANTIPODAL OR ORTHOGONAL ASSUMPTION
    8. 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. 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

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