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STUDY ON SOFTWARE AND HARDWARE IMPLEMENTATION OF BPSK MODULA

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Ramratan Mahato

on 17 May 2014

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Transcript of STUDY ON SOFTWARE AND HARDWARE IMPLEMENTATION OF BPSK MODULA

STUDY ON SOFTWARE AND HARDWARE IMPLEMENTATION OF BPSK MODULATION & DEMODULATION
SUBMITTED BY
PAPIYA DAS
SUBHAMOY DAS
RAMRATAN MAHATA
SUPRATIM SADHUKHAN
UDAY BHANU SEN
DR. KABITA PURKAIT
Under the guidance of
Modulation
WHAT IS MODULATION ???
Modulation is defined as the process by which some charactristics of the carrier is varied in accordance with the modulating signal.

TYPES OF MODULATION:
Modulation Can be of two types..
1.Analog
2.Digital.

ANALOG MODULATION:
Analog modulation means the amplitude,frequency & phase of the carrier signal is switched according to the input analog signal
.

DIGITAL MODULATION:

Digital Modulation means the amplitude, frequency or phase of the carrier is switched depending on the input digital signal.(ASK,FSK,PSK).

TYPES OF DIGITAL MODULATION
ASK(AMPLITUDE SHIFT KEYING)
FSK(FREQUENCY SHIFT KEYING)
PSK(PHASE SHIFT KEYING)

BRIEF THEORY ABOUT BPSK
In BPSK phase of sinusoid is changed according to DATA bit

A bipolar NRZ signal is used as data in BPSK.

REPRESENTATION OF BPSK
In a BPSK the binary symbols 1 & 0 modulate the phase of the carrier.
Carrier
s(t)=Acos(2*pi*f*t)
The power dissipated can be expressed as,
P=1/2(A*A)
so,
s1(t)=√2P cos(2*pi*f*t) (for symbol 1)
s2(t)=√2P cos(2*pi*f*t+pi) (for symbol 0)
s2(t)= -√2P cos(2*pi*f*t)
In generalize,
s(t)=b(t) √2P cos(2*pi*f*t)
b(t)=+1 (when symbol 1 transmitted)
b(t)= -1 (when symbol 0 transmitted)


BPSK GENERATION




Diagram of Binary Sequence carrier & corresponding modulated signal.


BPSK WAVEFORM

An Op amp inverting amplifier with gain 1 is used to invert the phase of the input sine wave.
Sine wave can be obtained from a function generator or by using a RC phase shift oscillator.
Two switches inside the quad analog switch CD 4016 are used in the circuit.When the enable input of one gate is high, the input will appear at the output.
When the binary data is 1, sine wave is switched to output because the sine wave is connected to 1st switch and the binary data is applied to enable pin (13th pin) of 1st switch.

BPSK MODULATION PRINCIPLE IN OUR PROJECT

PRACTICAL APPROACH GENERATING BPSK

In hardware part of this project the following components has been used.
BPSK MODULATOR
IC-741 OPAMP for inversion of signal.
CD4016 quad switch for synchronizing carrier and modulating signal.
IC-7474 D flipflop for generating PN sequence
NE555 timer circuit for generating clock pulse used in PN sequence generation.
BPSK DEMODULATOR
IC-741 OPAMP for adding bpsk and synchronised carrier signal.
1N4001 Diode used inenvelop detection.
IC-741 OPAMP for comparison.


HARDWARE APPROACH

In hardware part of this project the following components has been used.
BPSK MODULATOR
IC-741 OPAMP for inversion of signal.
CD4016 quad switch for synchronizing carrier and modulating signal.
IC-7474 D flipflop for generating PN sequence
NE555 timer circuit for generating clock pulse used in PN sequence generation.
BPSK DEMODULATOR
IC-741 OPAMP for adding bpsk and synchronised carrier signal.
1N4001 Diode used inenvelop detection.
IC-741 OPAMP for comparison.


EQUIPMENTS FOR IMPLEMENTATION

IC-741 OP AMP SPECIFICATION

OUTPUT OF OPAMP AS AN INVERTING AMPLIFIER

In astable mode IC555 acts as an pulse or clock genertor.
The width of the pulse is determined by the RC time constant.Here R means comination of pot and 100 k and the value of capacitor .001 microfarad.


CLOCK GENERATOR

PIN OUT CONFIGURATION OF IC555

Output of clock generator is a clock pulse of frequency 1 khz.

OUTPUT OF CLOCK GENARATOR





Its a digital pulse train generator.
It simulates the data to be transmitted.
The more number of D latches used here,the longer the random sequence will be.


RANDOM SEQUENCE GENERATOR




Its a dual positive edge triggered D type flip flop.
Here SET & RESET are asynchronous active low inputs & operate independently of the clock input.
Clock triggering occurs at voltage level & is not directly related to transition time of positive edge pulse.


D FLIP FLOP IC SPECIFICATION
RANDOM SEQUENCE GENERATOR PRACTICAL CIRCUIT

Each with an active-high enable input (A) and two input/outputs (X and Y). When the enable input is asseted (high), the X and Y terminals are connected by a low impedance; this is the on condition. When the enable is low, there is a high impedance path between X and Y, and the switch is off.


OPERATING PRINCIPLE OF CD4016
It is a bilateral quad switch.
The binary signal should be applied at the terminals 5,6,12,13.
The carrier should be applied at terminals 1,3,9,11.
In this project two switches will be used.


CLOCK GENERATOR PRACTICAL CIRCUIT

BPSK PRACTICAL CIRCUIT

BPSK PRACTICAL CIRCUIT

PRACTICAL BPSK MODULATED WAVEFORM

In our project bpsk demodulaor circuit consists of adder and envelop detector.

Adder circuit adds the PSK output and carrier signal(same phase and frequency is used in transmitter section for syncronisation purpose).

An envelope detector is an electronic circuit that takes a high-frequency signal as input and provides an output which is the envelope of the original signal. 

BPSK DEMODULATOR CIRCUIT DIAGRAM

THEORITICAL OUTPUT OF BPSK DEMODULATED SIGNAL

BPSK MODULATOR

SOFTWARE APPROACH(SIMULINK)

BPSK MODULATED OUTPUT(SIMULINK)

RANDOM SEQUENCE GENERATOR(SIMULINK)

SEQUENCE OUTPUT(SIMULINK)

BPSK DEMODULATOR(SIMULINK)

In the modulation circuit using the IC CD4016, there is a disadvantage of using CD4016.From observation it is founded that as the frequency increases, it can’t fully block the ac signal when logic ‘0’ is given at the control input of the switch .It passes a certain amount of ac signal.

After some repeatition, the switch can’t work properly.

If a high frequency switch is used, then the above drawback can be removed.

As we set up the clock frequency for 1 khz, so a 10k resistance is used instead of pot.


CONCLUSION

DEMODULATOR OUTPUT(SIMULINK)

“Digital Communication” by S. Haykin,Wiley India.
“Digital Communication” by A. Bhattacharya.
“Design of a low cost BPSK modulator & Demodulator”- By Phllippe DONDON published in “Engineering Education,Agios Nicholaos”
www.circuitsgallery.com/2012/04/binary-phase-shift-keying-bpsk.html

REFERENCES

THANK YOU

RANDOM SEQUENCE GENERATOR PRACTICAL CIRCUIT

Practical Demodulator Circuit
DEMODULATOR OUTPUT(SIMULINK)
Full transcript