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E-Vest: WIRELESS NON-INVASIVE ECG MONITORING
Digital FM Serial transmitter
Faculty Advisor:
Dr. Kamesh Namuduri
Mohammed Alsadah
Alexander Wright
Department of Electrical Engineering
University of North Texas
Denton, Texas
Objectives
• Contemporary Issues
• Testing
• Introduction
• Difficulties
• Design Consideration
• Standards & Ethics
• Circuit Design
• Result /Conclusion
• Hardware/Software
• Team Work
Implementation
• Reception Information
• Further Exploration “Work”
• References
Contemporary Issues “ Motivations”
• On March 17th 2014,
Carmen, a 16 year old
Virginia girl dies moments as
soon as she completes the
half-marathon.
• This is our potential goal to
save lives and prevent
sudden Cardiac Arrest
Fall 2013 : Bluetooth
• The Bluetooth frequency range is at
2.4 to 2.485 GHz/
• The distance range is only 100 meters
or approximately 328 feet.
• Predefined Standard : FCC approved
• Low power and Low voltage (3.3V)
• Built in Antenna
• Encrypted Connection
Introduction
• In order to support remote monitoring of EKG signals we
need the ability to transmit digital information over long
distances in a cheap and efficient manner
– We decided to perform FM transmission of digital data through Binary
Frequency Shift Keying
– In order to minimize cost and complexity we made use of an LC circuit
instead of phase locked loop based oscillator
– This design will have less frequency stability and higher phase noise
than a PLL based system
– Goal is to be able to transmit a digital signal at least half mile (805
meters ).
BFSK
• Binary Frequency
Shift keying
• Uses two discrete
frequencies vs
entire continuous
variation range
used in FM
FM Circuit
Design
• Multiple BJT amplification stages some with feedback
• LC Hartley oscillator using hand wound inductors made of enameled
magnet wire.
• LM566 Voltage Controlled oscillator used to generate square waves for
bits through UART connected to an NMOS
Oscillator circuit
• Voltage divider of output
square wave
• NTE2932 NMOS used to switch
voltage on pin 5 based on 3.3V
TTL signal input
Circuit design
•
Circuit in the breadboard for
the original FM transmitter
•
Below, the circuit successfully
soldered
Hardware/Software Implementation
• Interface control documentation
Reception Information
Software Defined Radio using Realtek RTL2832U chip
•
http://sdr.osmocom.org/trac/wiki/rtl-sdr
SDR# Software
•
http://sdrsharp.com/
Testing
• Oscilloscope used to verify
TTL to square wave conversion
SDR# used to verify
transmission of square
waves
Reception
• WinFM software
created to decode data
images show 0’s
and 1’s being received
Difficulties
• Ordering components
– Lead times, hard to find components
• Soldering circuit
– Special thanks to Abraham Hasir for helping us
• Differences between theoretical values and what provided the
results we wanted
– likely due to breadboard capacitance/resistances
Standards & Ethics
• Standard for medical equipment from ISO/IEEE 11073
• IEEE 1284: UART Serial Communication
• UNT Institutional Review Board (IRB) Procedures
Federal Communications Commission
• The FCC limits unlicensed FM broadcasts to a maximum signal strength of
250uV/m (microvolts per meter), measured at a distance of 3m--about 10
feet
• limiting both the antennae gain and voltage level of the circuit we can
control the field strength of the transmitted signal
• we have both lowered the voltage and completely eliminated the
antennae in order to prevent exceeding these limits.
Result/Conclusion
• We have successfully transmitted serial TTL level data using
binary frequency shift keying over FM bands using available
electronics components.
• We believe this project will assist in the remote monitoring of
athletes as they compete toward reaching their goals while
remaining safe from abnormal heart conditions.
Further Exploration “ work”
• Jarvis Jones and I will be
Design flow diagram for the Antenna Design
Manufacture usable
silicone micro strip
antennae
Antenna Design
Requirements
designing the Antenna
(summer 2014).
Designing The Antenna using
the HyperLynx Software
• Transmits at a carrier
Finished Design and
requirements accomplishe
Simulation and
Parameter Review
frequency of 2.75 GHz
Prototype evaluation
using no more than 24
Mhz bandwidth.
No
Requirements
met?
Yes
References
• "Frequency-shift Keying." Wikipedia. Wikimedia Foundation, 15 Mar. 2014.
Web. 21 Mar. 2014. <http://en.wikipedia.org/wiki/Frequencyshift_keying>.
"Headlines." Home. N.p., n.d. Web. 21 Mar. 2014. <https://www.fcc.gov/>.
• Kim, Hyoung Soo, Venu Varanasi, Gayatri Mehta, Hualiang Zhang, Tae-Youl
Choi, Kamesh Namuduri, Jakob Vingren, Nandika Anne D'souza, and
Robert Kowal. "Circuits, Systems, and Technologies for Detecting the Onset
of Sudden Cardiac Death Through EKG Analysis." IEEE Circuits and Systems
Magazine 13.4 (2013): 10-25. Print.
• "Virginia Girl, 16, Dies Moments after Finishing Half Marathon ." NY Daily
News. Carol Kuruvilla, 17 Mar. 2014. Web. 18 Mar. 2014.
<http://www.nydailynews.com/news/national/virginia-teen-16-diesmoments-finishing-marathon-article-1.1725562>.
Questions