course: digital communication and coding professor: dr. tareq alnafouri

A QPSK Modulator Using Microwave Couplers and Switches for Satellite Transmitter and Its

Performance Analysis

Course: Digital Communication and CodingProfessor: Dr. Tareq AlNafouri

Presented By: Farhan Abdul Ghaffar

QPSK MODULATION• INTRODUCTION

• WHY QPSK MODULATION?REMOTE SENSING PURPOSES

X BAND 8 GHz to 12 GHz

DESIGN OF THE MODULATOR

THEORY OF THE MODULATORCIRCUIT ELEMENTS

• MICROWAVE COUPLERS

POWER DIVISIONPHASE SHIFTS PARAMETERS

• HIGH SPEED MESFET SWITCHES

MICROWAVE COUPLERS

• WILKINSON DIVIDER

• THREE PORT ELEMENT

EQUAL POWER DIVISION

S21 = S31= -3dB

NO PHASE SHIFTS21= S31

• BRANCH LINE HYBRID COUPLER

• FOUR PORT ELEMENT

EQUAL POWER DIVISIONS21 = S31= -3dB

QUADRATURE PHASE SHIFTS31- S21 = 90

• RAT RACE COUPLER

• FOUR PORT ELEMENT

EQUAL POWER DIVISION

S23 = S13= -3dB

180 PHASE SHIFT

S23- S13 = 180

STRUCTURE and WORKING

TESTING AND MEASUREMENT

• DATA RATE = 160Mbps• PHASE IMBALANCE = 0.4• AMPLITUDE IMBALANCE < 1%• EVM = 0.75%

PERFORMANCE ANALYSIS• AMPLITUDE IMBALANCE

• PHASE IMBALANCE

• ERROR VECTOR MAGNITUDE

EVM OF MODULATOR WITH AMPLIFIERS

• EVM OF THE TRANSMITTER < 8%

EVM vs. BER

• To keep the value of EVM minimum we need S parameters to be as optimized as possible.

EVM and SNR

• Lesser EVM will give greater SNR and lesser Probability of Error

HARDWARE OF THE MODULATOR

Q & A Session