Improving the Data Rates of
Organic Light Emitting Diodes
Andrew Burton, Yr 2
Supervisors
Dr. Hoa Le Minh
Prof. Z. Ghassemlooy
CEIS School Seminar 22/02/12
Light Emitting Diodes (LED)
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Organic Light Emitting Diodes
(OLED)
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Large Panel OLEDs used for Home
and Office Lighting
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Visible Light Communications
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What are Organic LEDs?
Cathode (-’ve)
Conductive Layer
(Organic Molecules
or Polymers)
Emissive Layer
(Organic Molecules
or Polymers)
Anode (+’ve)
Substrate (Glass, plastic)
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OLED Electrical Model
Rp = Contact resistance of electrodes
Rd = Diode resistance
C = Diode capacitance
Rp
Rd
C
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OLED testing and
Characterisation
Test 1: Illumination
Test 3: Bandwidth
System Bandwidth
Illuminance at 10 cm for OSRAM OLED
0
800
Normalised amplitude (dB)
Illuminance (Lux)
700
600
500
400
300
200
100
0
0
100
200
300
Bias Current (mA)
400
-4
-6
-8
-10 1
10
500
Test 2: Device Linearity
2
3
10
Frequency (kHz)
10
Test 4: Bit Error Rate
Vrec with Vtx for the OSRAM OLED
BER of OSRAM OLED
0
14
10
IDC=100mA
IDC=150mA
IDC=200mA
IDC=250mA
IDC=300mA
12
10
8
BER
Vrx (mV pk-pk)
-2
6
-1
10
4
2
0
0
-2
2
4
6
Vtx (V pk-pk)
8
10
10
100
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200
300
Rb (kbps)
400
500
Post Analogue RC Equalization
System Bandwidth
Normalised amplitude (dB)
0
-2
-4
-6
-8
-10 1
10
2
10
Frequency (kHz)
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3
10
RC Equalisation Results
BER of OSRAM OLED
0
10
Eq1
Eq2 30
Raw
300
350
35
250
30
250
200
200
-1
10
150
150
100
Power Penalty (dB)
Bandwidth (kHz)
BER
300
25
25
20
20
15
10
15
50
5
5
5
9
6.75
3.75
Capacitor, C
EQ
6.75
3.75
0
Resistor, REQ (kW)
Capacitor, C
EQ
(nF)
10
2.25
1.25
2.25
0
4.5
2.5
4.5
2.5
1.25
(nF)
100
9
0
0
Resistor, REQ (kW)
-2
10
100
200
300
Rb (kbps)
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400
500
?
BER of OSRAM OLED
0
10
BER
Eq1
Eq2
Raw
-1
10
-2
10
100
200
300
Rb (kbps)
400
500
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Decision Feedback Equalisation
(DFE)
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DFE Results
0
Bit Error Rate (BER):
131 Lux unequalized
254 Lux unequalized
440 Lux unequalized
131 Lux equalized
254 Lux equalized
440 Lux equalized
-log10(BER)
1
2
3
4
5
6
200
400
Bit rate (kb/s)
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600
800
Orthogonal Frequency Division
Multiplexing (OFDM)
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Experimental Setup
cos(2πfUt)
Map
QAM
S/P
⋮
IFFT
⋮
Add
CP
cos(2πfUt)
×
×
+
h(0)
×
×
-sin(2πfUt)
+
OFDM
only
Cut
CP,
Pilot
-sin(2πfUt)
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S/P
⋮
FFT
⋮
EQ
Demap
⋮ QAM
OFDM Results
Normalized Amplitude (dB)
0
-10
-20
Missing frequency components
-30
-40
-50
System Frequency Response
Smoothed DMT Spectrum
0
50
1.0
100
Frequency (kHz)
150
200
1.5
Received constellation
After EQ
0.5
Imaginary Signal
Imaginary Signal
1.0
0.0
-0.5
0.5
0.0
-0.5
-1.0
-1.0
-1.0
-0.5
0.0
0.5
Real Signal
1.0
-1.5
-1.0
0.0
Real Signal
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1.0
Conclusions
 RC analogue equalisation is not suitable for systems running at low data rates
With DFE equalization we can achieve error free communications up to 500 kbps
With OFDM we can achieve error free communications in excess of 3 Mbps
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Acknowledgements
Fellow author and researcher Paul Anthony Haigh
MATLAB Guru Dr. Sujan Rajbhandari
The financial support received from the school
of Computing, Engineering and Information
Sciences at the University of Northumbria
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Publications
Journal
1. H. Le Minh, Z. Ghassemlooy, A. Burton, P.A. Haigh, S.K. Liaw, “Experimental Study of
the equalisation for Organic Light Emitting Diodes in Visible Light Communications”,
2011.
Conferences
2. A. Burton, C. Amiot, H. Le Minh and Z. Ghassemlooy, “Design of an integrated optical
receiver for mobile visible light communications” 12th Annual Symposium on the
Convergence of Telecommunications, Networking and Broadcasting, Liverpool, 2011,
pp.286-289
3. H. Le Minh, Z. Ghassemlooy, A. Burton, and P. A. Haigh, "Equalization for organic
Light Emitting Diodes in Visible Light Communications," IEEE Global Communications
Conference 2011 (IEEE GLOBECOM 2011), Workshop on Optical Wireless
Communications in Houston, USA, 5-9 December, 2011.
Posters
4. A. Burton, “Smart White LED based Lighting and Communications”, Northumbria
Research forum, Newcastle upon Tyne, 2011
5. A. Burton, “Visible Light Communications using Organic Light Emitting Diodes”, EPRSC
Photonics Communications Workshop, Oxford, 2011
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Publications
(under review & writing)
Conferences
6. A. Burton, H. Le Minh , Z. Ghassemlooy, S. Rajbhandari ,P. A. Haig “Smart Receiver
for Visible Light Communications: Design and Analysis” CSNDSP 2012, Poland
7. A. Burton, H. Le Minh, Z. Ghassemlooy “Smart Visible Light Communications Receiver
” IEEC 2012, Vietnam
Journal
8. A. Burton, P.A. Haigh, H. Le Minh, Z. Ghassemlooy , S. Rajbhandari and S.K. Liaw,
“Increasing Data Rates in Organic Light Emitting Diodes for Visible Light
Communications” , IEEE Journal of Light wave Technology
9. A. Burton, H. Le Minh, Z. Ghassemlooy , S. Rajbhandari and S.K. Liaw, “The Full
Design and analysis of a Smart Receiver for Visible Light Communications”, IETCommunications
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Awards
1. Full Studentship from the School of Computing,
Engineering and information Sciences Northumbria
University to carry out my Ph.D.
2. Awarded best performing first year PhD student for the
School of Computing, Engineering and information
Sciences, May 2011
3. IEEE UK & RI Communications Chapter Tutorial grant
for “Protection Switching in Communication Networks”,
16th European Conference on Networks and Optical
Communications, 2011
4. IEEE Travel grant for Wavelet transform workshop,
Northumbria University, 2011
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Questions???
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