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ECEN4523 Commo Theory
Lecture #29
26 October 2015
Dr. George Scheets
www.okstate.edu/elec-engr/scheets/ecen4533
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Read 7.5
Problems: 7.7-2, 4, & 5
Exam #2, 30 October (Live) [Chapter 4 – Chapter 7]
 Remote DL students < 6 November
Design Problem, due 6 November (Live)
 Remote DL students < 13 November
ECEN4523 Commo Theory
Lecture #30
28 October 2015
Dr. George Scheets
www.okstate.edu/elec-engr/scheets/ecen4533
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Read 7.7 & 7.8
Problems: 7.7-6 & 7.8-1 & 3
Exam #2, 30 October (Live) [Chapter 4 – Chapter 7]
 Remote DL students < 6 November
Design Problem, due 6 November (Live)
 Remote DL students < 13 November
Quiz 5 Results
 High = 10, Low = 1.0, Ave = 7.13, σ = 2.69
Binary ASK
1.5
1 MHz
0
-1.5
0
.00001
Two different Amplitudes are transmitted
10 cycles/.00001 seconds = 1 MHz (cycles/second)
5 cycles/symbol
200 K symbols/second = 200 K bits/second
Receiver Coherent Detection
X
Low Pass
Filter
Digital
Decision
cos(2πfct)
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Generate a frequency and phase locked sinusoid
Multiply by received signal
Filter out double frequency term
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Decide which symbol was probably transmitted
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Output is a noisy baseband symbol stream
Requires syncing to the symbol stream
Output a cleaned up version
Binary PSK
1.5
1 MHz
0
-1.5
0
.00001
Two different phases are transmitted
10 cycles/.00001 seconds = 1 MHz
5 cycles/symbol
200 K symbols/second = 200 K bits/second
Unfiltered 802.11b Spectrum
Binary FSK
1.5
0
-1.5
0
.00001
Two different frequencies are transmitted
Symbol #1) 5 cycles/.000005 seconds = 1 MHz
Symbol #2) 10 cycles/.000005 seconds = 2 MHz
1.5 MHz Average (center) Frequency
2 symbols in .00001 seconds =
200 K symbols/second = 200 K bits/second
PSK Signal Constellations
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Distance along I axis is cosine Vpeak
Distance along Q axis is sine Vpeak
Use negative voltage if sine or cosine inverted
Distance from origin is magnitude
 [Vcosine_peak2 + Vsine_peak2] 0.5
source: slideplayer.com
16 QAM Signal Constellations
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Distance along I axis is cosine Vpeak
Distance along Q axis is sine Vpeak
Use negative voltage if sine or cosine inverted
Distance from origin is magnitude
 [Vcosine_peak2 + Vsine_peak2]0.5
source: waltertech426.blogspot.com/2013/08/matlab-m-ary-quadrature-signal.html & Wikipedia