Transcript Flawless audio

Optical SmartLink
EE513 Communication Electronics
Zheng Wang
Xin Li
Jialock Wong
Introduction
 To provide an all-in-one solution in a box through
fiber
To implement fiber optic audio, intercom and data
multiplexer
Source: http://www.tccomm.com/TC8000.htm
Goals
To study more about communication
electronics such as fiber communication,
DSP technology and multiplexing methods
To create a group oriented project
To create a fiber audio communication
system with programmable DSP
Benefits
Flawless audio
• No electromagnetic interference
• No crosstalk between channels
• No radiation of signals
Savings
• Fiber cable is only 5% as expensive as
multipair
• Installation savings: light weight, small
diameter
• Personal safety: fiber do not spark or
shock,
• Repair and replacement savings: less
prone to damage and corrosion
Implementations
Integrate audio and data streaming over
fiber optics cable in analog format
Support multiple channels
Implement FM multiplexing
Implement DSP programmable analysis
such as spectrum analysis and signal
conditioning at the receiver module
Procedures and timeline
Design and Simulate in Multisim
(Workbench):2/1
Build and analyze circuit:2/15
Code DSP program using TI C6211:3/15
Test Overall circuit :3/24
Lab Demo:4/7
Block Diagram






Multiplexer
Transmitter
Optical Fiber
Receiver
Demultiplexer
DSP TI C6211
Schematics (Redesigned Circuit)
Transmitter
Receiver
Multisim Simulation Results
 Frequency Response
Multisim Results: Waveforms
Receiver
Transmitter
Pictures of Built Circuits
Laboratory Analysis
To analyze frequency response
To analyze supported inputs
To measure output performances
Instruments used: Agilent digital function
generator, HP oscilloscope and Labview
Laboratory Results
 Frequency responses
Frequency response of FO transmitter
60
Gain (V/V)
50
Overall Gain vs Frequency
40
30
20
0
45
40
35
30
25
20
15
10
5
0
1
10
100
1000
10000
100000
1000000
Frequency (Hz)
Frequency Response of FO Receiver
1
10
100
1000
Frequency (Hz)
10000
100000
Gain (V/V)
Gain (V/V/)
10
160
140
120
100
80
60
40
20
0
1
10
100
1000
Frequency (Hz)
10000
100000
Laboratory Results
0.6
0.4
Voltage (V)
 Waveforms
 Sinusoidal wave input
Sinusoidal Input
0.2
0
-0.2
0
500000
1000000
1500000
2000000
2500000
2000000
2500000
-0.4
-0.6
time (ms)
Sinusoidal Output at 1kHz
Noise presents
2.5
2
Voltage (V)
1.5
1
0.5
0
-0.5 0
500000
1000000
1500000
-1
-1.5
time (ms)
Laboratory Results
 Square wave input
Voltage (V)
Square Wave Input
0.1
0.08
0.06
0.04
0.02
0
-0.02 0
-0.04
-0.06
-0.08
-0.1
500000
1000000
1500000
2000000
2500000
time (ms)
Output with Square Wave Input
10
Voltage (V)
8
6
4
2
0
0
500000
1000000
1500000
time (ms)
2000000
2500000
Laboratory Results
Real-time Music playback (DEMO)
Original Music (Input)
Recorded Music at Receiver (Output)
Result Analysis and Summary
Limited Bandwidth – 3kHz
Small SNR – loss is very significant
Incompatible with pulse signal input
Summary
Video and data cannot be supported
Bandwidth limits number of channels
New Implementations
Due to the hardware limitations, we will
implement DSP for signal conditioning and
signal analysis
scale down usable channels to 2 channels
use digital filters or crystal filters to
demultiplex FM signal
DSP Implementation:
Matlab Embedded Target for TIC6211
Example - MATLAB link for CCS Studio
Development Tools
 Top: Original Signal
 Center: Filtered signal
with slight delay
 Bottom: Spectrum
calculated by Matlab
 This method will be
used to cancel
environmental noise
and analyzing signal
quality
Functionality of DSP
Due to bandwidth limitation, we need a
high quality filter to demultiplex frequency
modulated signals at both 1kHz and 3kHz.
2 choices: Crystal filter or DSP digital filter
Noise canceling
cancel environmental noise
Signal Analysis
Spectrum analyzer and SNR indicator
Summary
Designed circuit has narrow bandwidth
We decided not to redesign the circuit, but
to challenge ourselves by squeezing more
information over limited bandwidth
information