SUBMITTED BY:RAMRATAN MAHATOPAPIYA DASSUBHAMAY DASSUPRATIM SADHUKHANUDAY BHANU SEN

PPT ON DIGITAL SIGNAL(BPSK,QPSK)

GENERATION,TRANSMISSION & RECEPTION

INTRODUCTION

In satellite or telecommunication system, modulation is the process of conveying a

message signal over a medium. To extend the range of the analog signal or digital data,

we need to transmit it through a medium other than air. The process of converting

information so that it can be successfully transmitted through a medium is called

modulation. We are working with BPSK & QPSK modulation which is kind of a digital

modulation. Before going into the main focus we shall have a brief discussion on

modulation, different types of modulation and the analysis of it. This chapter gives a

brief and basic idea on modulation and different types of modulation techniques.

PURPOSE OF MODULATION

Ease of radiationSimultaneous transmission of several signals.

Reduction of Antenna Size.

Modulation

Modulation is defined as the process by which some charactristics of the carrier is varied in accordance with the modulating signal.

Modulation Can be of two types.. 1.Analog 2.Digital. Digital Modulation means the amplitude, frequency or

phase of the carrier is switched depending on the input digital signal.(ASK,FSK,PSK).

In BPSK according to the label change of the symbol(1-0 or 0-1) the phase of carrier is changed by 180 degree.

In QPSK, the successive bits are coupled generating four symbols.(10 00 01 11).the phase shift in carrier become 45, 135, 225, 315 degree respectively.

RANDOM SEQUENCE GENERATOR

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 CIRCUIT

BPSK GENERATION

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 PRACTICAL CIRCUIT

WORKING PRINCIPLE

BPSK WAVEFORM

Diagram of Binary Sequence & The corresponding Bipolar Signal.

IC-741 OP AMP SPECIFICATION

PIN CONFIGURATION 1,5=offset null 2=inverting input 3=non-inverting input 4=v- 6=output 7=v+ 8=nc Performance range=(0-70

degree) Overload protection on input

and output Supply voltage is 22v Differential input voltage 30v.

CD4016 IC specification

Wide range of supply voltage(3-15V)

Wide range of digital & analog switching.

ON resistance is 400 ohm. High degree of

linearity.Extremely low off switch voltage.

D FLIP FLOP IC SPECIFICATION

Its a dual positive edge triggerd 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

Its a 14 pin ic. Range of Vcc=5v(+10 -10%) 1D & 2D=Data inputs 1Ck &2ck=clock input. 1Q,2Q,1Q’ &2Q’=Data outputs CLR1 &CLR2=Reset inputs 1PR & 2PR=Preset inputs

CLOCK GENERATOR

The 555 has three operating modes: Monostable mode: In this mode, the 555

functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.

Astable (free-running) mode: The 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation and so on. The 555 can be used as a simple ADC, converting an analog value to a pulse length. E.g. selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor: the period of the output pulse is determined by the temperature. The use of a microprocessor based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means.

Bistable mode or Schmitt trigger: The 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce-free latched switches.

SUBSEQUENT PART & QPSK

QPSK

In QPSK two successive bits are combined together

This produce four different symbols .(10 00 01 11).

When the symbol is changed to next symbol,the phase of carrier is changed by 45 deg

CONCLUSION

We would like to express our gratitude to our respected mam Dr. Kabita Purkait for guidance and valuable suggestions and inspirations through out the process.

We give our admiration to our lab assistant Nimai ch. Pal.we are also thankful to HOD sir Dr.Achintya kr. Das along with all the faculty members of ECE department.