PHASE SHIFT KEYING (PSK)

ARMY PUBLIC COLLEGE OF MANAGEMENT AND SCIENCES

WAQAS NASEEM ( S-3--- )

FARHAN HAKIM ( S-3--- )

MALIK ASIM IJAZ ( S-3--- )

SHAKIR KHAWAJA ( S-3--- )

GROUP MEMBERS

SUPERVISED BY: SIR. SAJJAD

Introduction

Contents

PSK (phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram (4 ,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

Introduction

Contents

PSK (phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram (4,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

DIGITAL MODULATION TECHNIQUES

There are basically two types of transmission of digital signals

1. Baseband data transmission :The digital data is transmitted over the channel directly. There is no carrier or any modulation. This is suitable for transmission over short distances

2. Passband data transmission: The digital data modulates high frequency sinusoidal carrier. It is suitable for transmission over long distances.

TYPES OF PASS BAND MODULATION:

The digital data can modulate can phase frequency , or amplitude of carrier. This gives

rise to three basic techniques• Phase shift keying (PSK)• Frequency shift keying (FSK)• Amplitude shift keying (ASK)

Introduction

Introduction

Contents

PSK ( phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram(4,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

PSK (PHASE SHIFT KEYING)

Phase Shift Keying (PSK)• Phase of carrier is varied to represent 1 or 0• Peak amplitude and frequency remain constant• Phase remains constant during each bit duration

Forms of phase shift keying

PSK - Phase Shift Keying

1. BPSK - Binary ( 2 point ) Phase Shift Keying

2. QPSK – Quadrature (4 point ) Phase Shift Keying

3. 8 PSK - 8 Point Phase Shift Keying

4. 16 PSK - 16 Point Phase Shift Keying

5. 32 PSK - 32 Point Phase Shift Keying

6. 64 PSK - 64 Point Phase Shift Keying

These are just some of the major forms of phase shift keying, PSK,

In general the higher order forms of modulation allow higher data rates to be carried within a given bandwidth.

Introduction

Contents

PSK (phase shift keying)

Binary Phase Shift Keying (BPSK)

( QPSK )

( 8-PSK )

Constellation diagram(4,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

Binary phase-shift keying (BPSK)

• BPSK is the simplest form of phase shift keying (PSK). It uses two phases which are separated by 180° and so can also be termed 2-PSK. It does not particularly matter exactly where the constellation points are positioned, and in this figure they are shown on the real axis, at 0° and 180°.

AdvantagesThe distance between the signal point is great, then the error rate of BPSK is less

BPSK Generation Scheme

• A sinusoidal waveform is multiplied by the input bit stream.

• Each time the bit stream changes sign (by crossing zero level), the phase of the PSK signal also changes.

BPSK ( 2 - PSK)

2-PSK: only 2 phase values are used, each for 1 or 0

Only phase is varied to represent 1 or 0

Introduction

Contents

PSK (phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram(4,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

Quadrature phase-shift keying

(QPSK) • 4-PSKQPSK can encode two bits per symbol. Analysis shows that

this may be used either to double the data rate compared to a BPSK system while maintaining the bandwidth of the signal or to maintain the data-rate of BPSK but halve the bandwidth needed.– May utilize four variations of phase shift by 90 degrees– Each phase shift represents 2 bits ;technique is

referred to as 4-PSK– Allows data transmission two times as fast as 2-PSK

4 -PSK

QPSK versus BPSK

• BPSK modulation results in 1 symbol/Hz, where QPSK modulation results in 2 symbols/Hz).

• As a result, the spectrum of QPSK is narrower than that of BPSK.

• The main lobe of QPSK is half the width of the BPSK spectrum mainlobe.

• The probabilities of bit error for BPSK and QPSK are equal, but QPSK can support twice the data rate that BPSK can.

• Higher orders of PSK can be designed (8-PSK, 16-PSK, etc.), but there is a tradeoff (higher required power or higher BER).

BPSK VS QPSK

Introduction

Contents

PSK (phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram (4,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

8-PSK

In this we Vary signal by shifts of 45 degrees; each shift may then represent three bits (tri-bit) and send data three times as fast

Introduction

Contents

PSK (phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram (4 and 8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

Constellation (or Phase-State) Diagram

Comparison b/w 4-psk and 8-psk

Introduction

Contents

PSK (phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram (4,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

M-PSK (Circular Constellations)

16-PSK

an

bn 4-PSK

M-PSK ( 16 - PSK) constellations

Tradeoffs – Higher-order modulations (M large) are more spectrally efficient but less power efficient (i.e. BER higher). – M-QAM is more spectrally efficient than M-PSK but also more sensitive to system nonlinearities.

BER and Eb/No

• The rate at which bits are corrupted beyond the capacity to reconstruct them �is called the BER (Bit Error Rate).

• A BER of less than 1 in 100,000 bits is generally desired for an average satellite communications channel (also referred to as a BER of 10-5).

• For some types of data, an even smaller BER is desired (10-7).

• The BER is directly dependent on the Eb/No, which is the Bit Energy-to-�Noise Density ratio.

• Since the noise density present on the channel is difficult to control, this basically means that BER can be reduced through using a higher powered signal, or by controlling other parameters to increase the energy transmitted per bit.

• As the following chart shows, the BER will decrease (i.e., fewer errors)

if the Eb/No increases.

Higher Eb/No Reduces the BER

Bandwidth vs. Power Efficiency

Bandwidth vs. Power Efficiency

MPSK:

Bandwidth of M-PSK

Introduction

Contents

PSK (phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram (4,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

Advantages and Disadvantages

Advantages1. BPSK produce less errors as compared to ASK2. More efficient use of bandwidth means higher data rate is possible

Disadvantages More complex detection process than ASK and FSK Rapid amplituded change between symbols due to phase discontinutyQPSK AND BPSK::::1. In QPSK higher data rate as compared to BPSK2. For the same bit error rate the band width required by QPSK is reduced to

half than BPSK

Introduction

Contents

PSK (phase shift keying)

(BPSK) generation scheme

( QPSK )

( 8-PSK )

Constellation diagram (4,8 PSK)

(16-PSK OR M-PSK)

Advantage and Disadvantage

applications

APPLICATIONS

•IN SATELLITE COMMUNICATION

• wireless LAN

•biometric passports

• Bluetooth

•CDMA system

•DVB-S

•Cable modems

•Vidio confferencing

•Cellular phone system and other forms of digital communication system over an RF

THANK YOU 4 ATTENTION!