Digital Modulation Technique Presented By: Amit Degada. Teaching Assistant, SV NIT, Surat.

Goal of Today’s Lecture Differential Phase Shift keying Quadrature Phase Shift Keying Minimum Phase Shift Keying Introduction To Information Theory Information Measure

Differential Phase Shift Keying (DPSK) Why We Require? To Have Non-coherent Detection That Makes Receiver Design How can we do? 0 may be used represent transition 1 indicate No Transition

DPSK Transmitter What Should We Do to make Encoder?

DPSK Transmitter…………Modified

Differentially Encoded Sequence Binary Data 0 0 1 0 0 1 0 0 1 1 Differentially Encoded Data 1 0 1 1 0 1 1 0 1 1 1 Phase of DPSK 0 π 0 0 π 0 0 π 0 0 0 Shifted Differentially encoded Data dk-1 1 0 1 1 0 1 1 0 1 1 Phase of shifted Data 0 π 0 0 π 0 0 π 0 0 Phase Comparision Output - - + - - + - - + + Detected Binary Seq. 0 0 1 0 0 1 0 0 1 1

DPSK Receiver

Goal of Today’s Lecture Differential Phase Shift keying Quadrature Phase Shift Keying Minimum Phase Shift Keying Introduction To Information Theory Information Measure

Quadrature Phase Shift Keying (QPSK) Extension of Binary-PSK Spectrum Efficient Technique In M-ary Transmission it is Possible to Transmit M Possible Signal M = 2n where, n= no of Bits that we Combine signaling Interval T= nTb In QPSK n=2 === > So M =4 and signaling Interval T= 2Tb

Quadrature Phase Shift Keying (QPSK) M=4 so we have possible signal are 00,01,10,11 Or In Natural Coded Form 00,10,11,01 -135 -45 45 135 Binary Dibit 00 Binary Dibit 10 Binary Dibit 11 Binary Dibit 01

QPSK Waveform 00 11 00 11 10 10

QPSK Signal Phase

Constellation Diagram

Quadrature Phase Shift Keying (QPSK) The QPSK Formula ………………(1) Where, ϕ(t)=135,45,-45,-135 Simplifying Equation 1 This Gives the Idea about Transmitter design

QPSK Transmitter

QPSK Receiver

Synchronization Circuit

Goal of Today’s Lecture Differential Phase Shift keying Quadrature Phase Shift Keying Minimum Phase Shift Keying Introduction To Information Theory Information Measure

Minimum Shift Keying (MSK) In Binary FSK the Phase Continuity is maintained at the transition Point. This type of Modulated wave is referred as Continuous Phase Frequency Shift Keying (CPFSK) In MSK there is phase change equals to one half Bit Rate when the bit Changes 0 to 1 and 1 to 0.

Minimum Shift Keying (MSK) Let’s take fc1 and fc2 represents binary 1 and 0 Respectively Similarly Where

Minimum Shift Keying (MSK) The MSK Equation where For Symbol 0 For Symbol 1

Carrier Phase Coding For dibit 00

Carrier Phase Coding For dibit 10

Carrier Phase Coding For dibit 11

Carrier Phase Coding For dibit 01

Goal of Today’s Lecture Differential Phase Shift keying Quadrature Phase Shift Keying Minimum Phase Shift Keying Introduction To Information Theory Information Measure

Information Theory It is a study of Communication Engineering plus Maths A Communication Engineer has to Fight with Limited Power Inevitable Background Noise Limited Bandwidth

Information Theory deals with The Measure of Source Information The Information Capacity of the channel Coding If The rate of Information from a source does not exceed the capacity of the Channel, then there exist a Coding Scheme such that Information can be transmitted over the Communication Channel with arbitrary small amount of errors despite the presence of Noise

Goal of Today’s Lecture Differential Phase Shift keying Quadrature Phase Shift Keying Minimum Phase Shift Keying Introduction To Information Theory Information Measure

Information Measure This is utilized to determine the information rate of discrete Sources Consider Two Messages A Dog bites a man A man bites a dog

Thank You