1. A QPSK Modulator Using Microwave Couplers and Switches for Satellite Transmitter and Its Performance Analysis
Course: Digital Communication and Coding
Professor: Dr. Tareq AlNafouri
Presented By: Farhan Abdul Ghaffar

2. QPSK MODULATION INTRODUCTION WHY QPSK MODULATION?
REMOTE SENSING PURPOSES
X BAND 8 GHz to 12 GHz

3. DESIGN OF THE MODULATOR

4. THEORY OF THE MODULATOR CIRCUIT ELEMENTS
MICROWAVE COUPLERS
POWER DIVISION
PHASE SHIFT
S PARAMETERS
HIGH SPEED MESFET SWITCHES

5. MICROWAVE COUPLERS WILKINSON DIVIDER EQUAL POWER DIVISION
THREE PORT ELEMENT
EQUAL POWER DIVISION
S21 = S31= -3dB
NO PHASE SHIFT
S21= S31

6. BRANCH LINE HYBRID COUPLER
FOUR PORT ELEMENT
EQUAL POWER DIVISION
S21 = S31= -3dB
QUADRATURE PHASE SHIFT
S31- S21 = 90

7. EQUAL POWER DIVISION RAT RACE COUPLER S23 = S13= -3dB 180 PHASE SHIFT
FOUR PORT ELEMENT
EQUAL POWER DIVISION
S23 = S13= -3dB
180 PHASE SHIFT
S23- S13 = 180

8. STRUCTURE and WORKING

9. TESTING AND MEASUREMENT
DATA RATE = 160Mbps
PHASE IMBALANCE = 0.4
AMPLITUDE IMBALANCE < 1%
EVM = 0.75%

11. PERFORMANCE ANALYSIS AMPLITUDE IMBALANCE PHASE IMBALANCE
ERROR VECTOR MAGNITUDE

12. EVM OF MODULATOR WITH AMPLIFIERS
EVM OF THE TRANSMITTER < 8%

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

14. EVM and SNR
Lesser EVM will give greater SNR and lesser Probability of Error

15. HARDWARE OF THE MODULATOR

16. Q & A Session