B INARY P HASE S HIFT K EYING (BPSK) & Q UADRI P HASE S HIFT K EYING (QPSK)
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Binary Phase Shift Keying (BPSK) & Quadri Phase Shift Keying (QPSK)
Binary Phase Shift Keying (BPSK)&Quadri Phase Shift Keying (QPSK)Binary Phase Shift Keying (BPSK)The BPSK signal is generated as:
The transmitted signals are:
Illustration of BPSK
Note: Bits 1 and 0 have the same amplitude and frequency but they differ in phase.Frequency Spectrum of BPSK SignalNote : The spectrum of the binary BSK resemblesthat of double sideband suppressed carrier modulation.
BPSK DemodulatorThe detection of BPSK is achieved by:
Low pass filter ( LPF)
Quadri - Phase Shift Keying (QPSK)In QPSK, the phase of the carrier takes on one of four equally spaced values such as /4, 3/4, 5/4, 7/4 or 0,/2, , 3/4.
The transmitted signal is:
Generation of QPSK SignalsSignal space representation
- si(t) can be expressed as:
Illustration of QPSKQuadri means 4 messages are to be transmitted. Hence, 2 bits are needed to present each message
Detection of QPSKOptimum Receiver:
Examples on M-ary Constellation Diagrams
M-ary PSK Versus BPSKM-ary PSK requires more complexity in thedecision-making process.
M-ary PSK requires more transmitted power.