Post on 25-Jul-2015
transcript
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Binary Phase Shift Keying
Presented By
Arkaprabha Pal and Avijit Mistry
ECE,3rd year
KGEC
2Contents What is BPSK?
Generation of BPSK
Reception of BPSK
Spectrum of BPSK
Features & Drawbacks of BPSK
BER & Possibility of Overlapping
Reference
3What is BPSK ?
Binary phase shift keying is digital modulation scheme that conveys data by changing or modulating two different phases of a reference signal.
Expression for BPSK signal: We can define
BPSK signal as
S(t)=b(t)√(2P) cos(2fct)
Where b(t)= +1 ,when 1 is to be transmitted
= -1 ,when 0 is to be transmitted
4Generation of BPSK
Bipolar NRZLevel
Encoder
ProductModulato
r orBalancedModulato
r
Carrier Signal
Bipolar NRZ signal b(t)Binary
data sequence
Carrier Signal Generator
BPSK Signal
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5Generation of BPSK contd.
1 1 0 1 0 1 Data
Carrier
Carrier+ p
BPSK waveform
6Reception of BPSK
Square Law Device
Band passFilter
FrequencyDivider by
two
Synchronous demodulator
Bit Synchronizer
BPSK Signal
Cos2(2fct+Ө) Cos2(2fct+Ө)
Cos2(2fct+Ө)
Reference Signal
b(t)√(2p)Cos2(2fct+Ө)
b(t)√(2p)Cos2(2fct+Ө)
IntegratorC
S1
S2
7Spectrum of BPSK
8Features of BPSK:
Less bandwidthMinimum error rateGood noise immunity
Drawbacks of BPSK:
To regenerate the carrier in the receiver, we start by squaring b(t)√2Pcos(2fct +Ө). If received signal is –b(t)√2Pcos(2fct +Ө),then the squared signal remains same as before.Hence ,the recovered carrier is unchanged even if the input signal has changed its sign.
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9Bit Error Rate(BER):
The expression for probability of error, Pe, of a BPSK system is given by
Pe=½erfc[√E/No]
Possibility of Overlapping:
If we try to multiplex signals using BPSK ,using different carrier frequencies, then due to the nature of frequencies spectrum of BPSK signal there will be an overlap. This overlapping is unwanted and called as interchannel interference. To reduce this interference NRZ signal b(t) is passed trough LPF before applying it to a modulator. Due to such spectrum suppression , the modulating signal is distorted and there is a partial overlap of a bit (symbol). This overlap is called intersymbol interference. It can be reduced by using equalizers at the receiver.
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Reference www.Powershow.Com
www.sloka.in
whatis.techtarget.com
Text book Sanjay Sharma
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