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Reconfigurable Communication System Design. Anthony Gaught Advisors: Dr. In Soo Ahn and Dr. Yufeng Lu Department of Electrical and Computer Engineering Bradley University Peoria, Illinois November 13, 2012. Outline. Motivation Brief Theory of QPSK Project Overview Project Description

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Reconfigurable communication system design

Reconfigurable Communication System Design

Anthony Gaught

Advisors:

Dr. In Soo Ahn and Dr. Yufeng Lu

Department of Electrical and Computer Engineering

Bradley University Peoria, Illinois

November 13, 2012


Outline
Outline

  • Motivation

  • Brief Theory of QPSK

  • Project Overview

  • Project Description

  • Project Milestones

  • Simulation

  • Project Status

  • Conclusions

  • References


Motivation
Motivation

  • Software defined radio (SDR) has advantages over traditional communication systems.

  • Design a reconfigurable digital communication system using FPGA.

  • QPSK system is studied for the project.


Brief theory of qpsk
Brief Theory of QPSK

  • Binary phase shift keying (BPSK) is a modulation scheme which transmits one bit of data per symbol.

  • Quadrature phase shift keying (QPSK) cuts the bandwidth necessary to transmit data in half when compared to BPSK.

  • QPSK’s bit error performance is the same as that of BPSK due to orthogonality of the I and Q carriers used in QPSK.

  • QPSK is used in many applications such as cell phones, satellite communication, cable modems, and others.


Brief theory of qpsk1
Brief Theory of QPSK

  • s(t) = I(t)*cos(2πfot) – Q(t)*sin(2πfot)

  • Each symbol represents two bits of data.

  • I and Q bits are determined based on the phase of the received symbol.


Project overview
Project Overview

  • This project implements a QPSK communication system consisting of both a transmitter and a receiver.

  • The system is designed using VHDL and is implemented on Xilinx Spartan 3E FPGAs.

  • Allows for flexible transmission data rates.


Project description at the transmitter
Project Descriptionat the transmitter

  • Two-bit random data is generated.

  • The data is split into In-phase (I) and quadrature-phase (Q) components.

  • The data is shaped using raised cosine filters.

  • The data is over sampled.

  • The data is modulated by cosine and sine carriers.

  • The modulated signals are combined for transmission.


Project description at the receiver
Project Descriptionat the receiver

  • The received signal is demodulated by local cosine and sine carriers.

  • The data passes through a matched filter.

  • The data is down sampled.

  • The data is fed into a threshold device.

  • The output is displayed on an oscilloscope.


Milestone one
Milestone One

  • The receiver and transmitter will be implemented on a single FPGA.

  • The transmitter is connected directly to the receiver.

  • A digital to analog converter (DAC) will be used to display data.


Milestone one block diagram
Milestone One Block Diagram

I = transmitter side in-phase Q = transmitter side quadrature phase

I_r = receiver side in-phase Q_r = receiver side quadrature phase

S(n) = internal signal from transmitter to receiver


Milestone two
Milestone Two

  • The receiver and transmitter will be implemented on different FPGA boards.

  • Data will pass through an (ADC) and a DAC in this milestone.

  • A carrier recovery circuit and phase locked loop will be implemented in the receiver.

  • Adverse affects caused by channel imperfections will be explored.


Milestone two three block diagram
Milestone Two & Three Block Diagram

I = transmitter side in-phase Q = transmitter side quadrature phase

I_r = receiver side in-phase Q_r = receiver side quadrature phase

S(t) = signal from transmitter to receiver


Milestone three
Milestone Three

  • High speed ADC and DAC modules will be used to connect the transmitter and receiver for assessing overall system operations.

  • Bit error rate of the system will be used to evaluate the overall system performance.


Simulation results
Simulation Results

  • I and Q data at the transmitter


Simulation results1
Simulation Results

  • The I and Q data are shaped using a set of raised cosine filters for controlling intersymbol interference.

Impulse Response of Raised Cosine Filter


Simulation results2
Simulation Results

  • The recovered I and Q after being filtered are identical to theoretical results from MATLAB simulations.


Simulation results3
Simulation Results

  • The demodulated I and Q data match up with their theoretical results.


Simulation results4
Simulation Results

  • The demodulated I and Q data are then resized to bring the amplitude into a usable range for the Spartan 3E.


Simulation results5
Simulation Results

  • Received I and Q data appear as a constellation of 4 groups of points which matches the theoretical results well.


Simulation results6
Simulation Results

  • Transmitted and received I and Q data.


Simulation results7
Simulation Results

  • The transmitted and received I and Q data after being cleaned up by using a threshold device.


Project status
Project Status

  • Milestone one has been completed.

  • Preliminary work for Milestone two has begun.

  • One of the biggest obstacles will be the implementation of the phase locked loop.


Schedule
Schedule

  • 1/24 - 2/07 phase locked loop and carrier recovery implementation

  • 2/14 - 2/21 system optimization and evaluation

  • 2/28 - 3/07 high speed ADC and DAC implementation

  • 3/14 - 3/28 system evaluation

  • 4/04 – 5/02 TBA note: the Bradley expo and project presentation will occur during this period.


Conclusions
Conclusions

  • FPGA design is flexible to build digital communication systems. The methods used for modulation can be reconfigurable.

  • The system has a fast design turn-around time compared to conventional design using specialized hardware or DSP processors.

  • SDR capabilities are to be investigated and demonstrated in the project.


References
References

  • Anton Rodriguez, and Michael Mensinger Jr., “Software-defined Radio using Xilinx”, Senior Project Report, Department of Electrical and Computer Engineering, Bradley University, Peoria Illinois, May 2011.

  • Anthony Gaught, “Software-defined Radio Symbol Generator”, Junior Project Report, Department of Electrical and Computer Engineering, Bradley University, Peoria Illinois, May 2012.

  • Anthony Gaught, Alexander Norton, and Christopher Brady., “FPGA-based 16 QAM communication system”, EE 568 Report, Department of Electrical and Computer Engineering, Bradley University, Peoria Illinois, April 2012.

  • Leon Couch, “Digital and analog communication systems”, 8th ed., Boston: Pearson, 2013.

  • Charles Roth Jr., and Lizy John, “Digital systems design using VHDL”, 2nd ed., United States: Thomson, 2008.

  • Spartan-3E Data Manual, Xilinx, San Jose, CA,2009.



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