AM TRANSMITTER

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AM TRANSMITTER In an  AM  ( amplitude modulation )  transmitter  the amplitude (strength) of the carrier wave is varied in proportion to the modulation signal. In an FM (frequency modulation)  transmitter  the frequency of the carrier is varied by the modulation signal. There are two basic configuration for transmitters. High level modulation low level modulation  High level modulation In high power modulation signal,the carrier voltage is modulated at highest power level.the require power level is obtained by class c power amplifier.The block diagram of high level modulation as shown in fig(a). low level modulation In the low level modulation system, the carrier is modulated at low power level and the carrier power is subsequently raised to the desire level in the class B amplifier . transmitters using high power level are widely use at present .The block diagram of high level modulation as shown in fig(b). advantage AM sign
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Psk modulation block diagram .

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Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave) any digital modulation scheme uses a finite number of distinct signals to represent digital data. PSK uses a finite number of phases, each assigned a unique pattern of binary digits. Usually, each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase.

BLOCK DIAGRAM 
  


                                                                                                                                                           FIG.1
                   
 APPLICATION
  1. It is use in bluetooth communications
  2. It is widely  use in wirless LANs.
  3. it us use in bio-metric system.


ADVANTAGE
  1. It is more power efficient modulation techniques.
  2. high data transmission.
  3. psk is less susceptible to error than ASK,while it requires/occupies same bandwidth of ASK.
DISADVANTAGE
  1. It is low bandwidth efficiency.
  2. It produce more incorrect demodulation .
  3. It is non-coherent reference signal.
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