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Sam ParrotteJoshua Young

Jason Hernandez

November 19th 2013

Digital Modulation and Data Transfer

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1. What is Digital Modulation?2. Why use it?3. How is it related to Embedded

Systems?4. Sample Forms of Digital

Modulation5. Ethernet

Overview

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Process of using an analog carrier signal to contain discrete information Digital-to-analog modulation of data Analog-to-digital demodulation of carrier

Analog Modulation vs. Digital Modulation Similar: Manipulates a carrier wave to transmit data Different: Digital has a finite number of states the carrier will be in

=> often known as keying

What is Digital Modulation

http://www.mathworks.com/matlabcentral/fx_files/30580/1/ASK.jpg

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http://upload.wikimedia.org/wikipedia/commons/a/a4/Amfm3-en-de.gif

http://electronicdesign.com/communications/understanding-modern-digital-modulation-techniques

Analog and Digital Representations

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Why Modulate Digital Information?

http://www.ghielectronics.com/img/www/products/381-0_small.jpg

• Demodulation techniques offer beneficial recovery abilities

• Multiple parties share mediums to communicate information

Commonly shared mediums:o Cableo Air

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http://www.founten.com/wp-content/uploads/2012/06/WifiSpectrumComparisonFounten.png

http://pharos.ece.utexas.edu/wiki/images/thumb/4/40/XBee-pro-series1.jpg/300px-XBee-pro-series1.jpg

Xbee Spectrum

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http://www.siemon.com/us/white_papers/images/05-02-17_wifi_why_for_us-freq-allocations-chart_big.jpg

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Router Access Send information to a server Interact with Wifi devices

Direct communicationbetween devices When sending high data rates When multiple devices share

a medium

Commercial RF Product Can’t use predesigned boards Must understand individual

components

Why is this important for Embedded Systems?

http://www.atmel.com/Images/Atmel-42097-WIRELESS-AT02876-REB212BSMA-Hardware-User-Manual_Application-Note.pdf

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Types of Modulation

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FSK - Frequency Shift Keying

http://www.mathworks.com/matlabcentral/fx_files/30581/1/FSK.jpg

Uses:• Caller ID• 3G• Dial up Modem

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ASK - Amplitude Shift Keying

http://www.mathworks.com/matlabcentral/fx_files/30580/1/ASK.jpg

Uses:• Optical Fiber• Laser Communication• Short distance RF

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PSK - Phase Shift Keying

f(t) = cos(ωt + φ)

http://www.hill2dot0.com/wiki/images/thumb/3/30/MLG0013-binary-phase-shift-keying.jpg/300px-MLG0013-binary-phase-shift-keying.jpg

http://www.mathworks.com/matlabcentral/fx_files/30582/1/PSK.jpg

Uses:• Cable Modem• RFID• Digital Video

Broadcasting

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QPSK - Quadrature Phase Shift Keying

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/RadCom/part19/fig6.gif

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QAM - Quadrature Amplitude Modulation

● 16 States

● 4 Bits/Period (4^2 = 16)

● Utilizes both Amplitude and phasehttp://en.wikipedia.org/wiki/File:16QAM_Gray_Coded.svg

http://www.answers.com/topic/qam-television

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PAM - Pulse Amplitude Modulation

Transmission:PAM Signal = Carrier Waveform x Digital pulses

Reception:Digital Data (in pulses) =

PAM Signal / Carrier Waveform

http://vsagar.com/wp-content/uploads/2011/12/image63.png

Uses:• Ethernet

Ethernet in Digital Modulation

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Contains twisted pairs to limit amount of induced noise

Various Ethernet types, speeds from 10 Mbit/s up to 100 Gbit/s

Ethernet

http://randythetechprofessor.com/do-you-have-cable-confusion

http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi/0650/bks/SGI_Admin/books/IA_NetwkMail/sgi_html/ch01.html

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4 sets of twisted pair connections

Transmit/Receive pairs

Data sent in “packets” also called “Ethernet Frames”

Overview of Ethernet

http://www.iprobot.net/uncategorized/network-cables/

http://www.doc.ic.ac.uk/~nd/surprise_97/journal/vol4/mhl/giga.html

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Most common Ethernet interfaces use PAM-5(10BASE-T, 100BASE-TX)

5 voltage levels for modulation[-2, -1, 0 , 1 , 2]

10GBASE-T uses PAM-16 (DSQ128) for modulation

PAM in Ethernet

http://ecee.colorado.edu/~ecen4242/ethernet/ethernet.html

http://www.rwmonline.org/Metrotek/SC/s2p9_frameset.htm

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Digital Modulation is the process of modulating a discrete signal in an analog one

Carrier signals are useful where a bus may not be practical or possible

Digital modulation is widely used in many forms of electromagnetic communication

In Conclusion…

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http://www.doc.ic.ac.uk/~nd/surprise_97/journal/vol4/mhl/giga.html

http://en.wikipedia.org/wiki/Ethernet#Varieties_of_Ethernet

http://ecee.colorado.edu/~ecen4242/ethernet/ethernet.html

http://www.siemon.com/us/white_papers/images/05-02-17_wifi_why_for_us-freq-allocations-chart_big.jpg

http://www.atmel.com/Images/Atmel-42097-WIRELESS-AT02876-REB212BSMA-Hardware-User-Manual_Application-Note.pdf

References