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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

http://techtonicsa.blogspot.com/2015/04/what-is-semiconductor.html

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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