VISVESVARAYA TECHNOLOGICAL UNIVERSITYBELGAVI - 590018

KARNATAKA

A Mini-Project Report on

DIFFERENTIAL PHASE SHIFT KEYING (DPSK)

Submitted by

SUMUKH C. ATHREY 1DS13EC035BHARAT R. HEGDE 1DS13EC037BASAVARAJ MOOLI 1DS13EC036

2015-2016

Department of Electronics and CommunicationDayananda Sagar College of Engineering

Bengaluru – 560 078

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1. INTRODUCTION

2. DESCRIPTION – Equations, Mathematical Calculations, applications.

3. THE ALGORITHM OR FLOWCHART

4. PROGRAM

5. RESULTS AND DISCUSSION

6. REFERENCES

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INTRODUCTION

Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing (modulating) the phase of a reference signal (the carrier wave).The signal is impressed into the magnetic field x, y area by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs, RFID and Bluetooth communication.

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. The demodulator, which is designed specifically for the symbol-set used by the modulator, determines the phase of the received signal and maps it back to the symbol it represents, thus recovering the original data. 

Differential phase shift keying (DPSK) is a common form of phase modulation that conveys data by changing the phase of the carrier wave.

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DESCRIPTION

Differential phase shift keying (DPSK) is a common form of phase modulation that conveys data by changing the phase of the carrier wave. DPSP is similar to BPSK with the only addition of differential encoder, i.e., in differentially encoded BPSK a binary '1' may be transmitted by adding 180° to the current phase and a binary '0' by adding 0° to the current phase.

DPSK Transmitter :-

The block diagram of DPSK transmitter is as shown above. The first section of a DPSK transmitter is a PARALLEL-to-SERIAL converter. The circuit below shows the 8 –Bit parallel to serial converter.

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The logic network and the delay circuit together form the differential encoder and can be realized using a X-NOR gate and D-F/F to generate a delay as shown below.

The main transmitting section is realized as follows using two carriers with 180 degree phase shift which are then multiplexed by the following circuit such that the carrier sine wave with 180 degree phase shift is passed on ‘1’ and carrier sine wave with 0 degree phase shift is passed on ‘0’.

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DPSK Receiver

The receiver block diagram is as shown above. The band pass filter is used to remove noise from the received signal. It is followed by a comparator, decision device, i.e. , Schmitt Trigger and finally a differential decoder.

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PROGRAM

DPSK transmitter

nS=1000;nSym=2000; %Number of samplesM=2;Tb=1e-6; %Bit ratefc=1e6; %Carrier frequency

s=randi([0 M-1],nSym,1); %Information signal

s_mod=pskmod(s,M,pi); %NRZ Polar encoders_mod=rectpulse(s_mod,nS);

h1=scatterplot(s_mod); t=0:(Tb/nS):nSym*Tb-(Tb/nS); %Time domaint=transpose(t); figure(2);plot(t,s_mod)axis([0 (10*Tb-(Tb/(nS))) -1.2 1.2]); %plot only first 10 bitstitle('Input bit stream after NRZ Encoder');xlabel('Time(seconds)');ylabel('amplitude'); s_tx_nn=s_mod.*cos(2*pi*fc*t)

Channel with AWGN Noise

%Additive Channel Noiseatt=1;SNR=1;s_tx_noise=awgn(s_tx_nn,SNR,'measured');h2=scatterplot(s_tx_noise,nS,nS/2);

%Additive Channel attenuation(10dB)s_tx_noise_att=s_tx_noise/att;

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DPSK Receiver

s_tx=s_tx_noise_att;s_rx=s_tx.*cos(2*pi*fc*t); figure;plot(t,s_rx);axis([0 (10*Tb-(Tb/(nS))) -2/att 2/att]);title('Recieved Signal Before Integration')xlabel('Time(Seconds)')ylabel('Amplitude')

figure;stem(0:nS*nSym-1, s_mod(1 :nS*nSym))plot(t,s_tx_noise_att,'g')hold onplot(t,s_tx_nn/att,'LineWidth',1); %DPSK madulated signal+Noiseaxis([0 (10*Tb-(Tb/(nS))) -2/att 2/att]);title('Tx vs. Rx (Normalized)')xlabel('Time (Seconds) ')ylabel('Amplitude')

h3=scatterplot(s_rx,nS,nS/2);%Scatter Plot in presence of Noisey=intdump(s_rx,nS);y_mod=rectpulse(y,nS);h4=scatterplot(y_mod, nS, nS/2);%Scatter Plot when Noise is removedr_mod=pskdemod(y_mod,M,pi);%DPSK Demodulationfigure; plot(t,r_mod)axis([0 (10*Tb-(Tb/(nS))) -0.2 1.2]);title('Demodulated output')xlabel('Time (seconds) ')ylabel('Amplitude')

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