## Implementation of QPSK – modulator

#### The block diagram of a QPSK modulator and detector is shown here and is simply two BPSK systems using quadrature carriers summed in parallel. The source data is first split into two data streams (often by allocating alternate bits to the upper and lower modulator), with each data stream running at half the rate of the input data stream. Conventional root raised cosine filtering would be used to shape the data pulses in each channel prior to modulation. The constellation diagram for the composite transmitted symbol set shows that the phase states observed in the channel would be 45o phase rotated with respect to the individual BPSK sources. |

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