ECE 3300 LAB 0 (Pre-Lab)
Writing Lab
Overview:
This pre-lab will prepare you to complete the Lab 0 procedures during your lab session. The intent of this lab is to introduce you to the remaining labs and their objectives.
Purpose of the Labs:
As students progress through a traditional ECE program, they often learn a great deal about individual components and tools: resistors, transmission lines, antennas, etc. In a traditional lab, they build and test these individual units. However, students are often not exposed to the applications and relevance of what they are learning, do not see how it fits into a system, and are not aware of how they will ever use it.
Instead, in the labs for this course, you will be challenged to build a simple but complete system, using many of the concepts from class. Piece by piece, the components will be designed and tested, and they will all be integrated into a single system for a specific application. You will even predict how the design of each component of the system will affect the overall performance of the system.
The application of interest in this course is a communication system for a cardiac pacemaker. A transmitter will be positioned inside the body (tissue simulant material) and the receiver will be located immediately outside or near the outside of the body. The information that could be communicated with such a system includes: battery life, electrocardiogram (EKG) data, for example, etc. The communication system for a cardiac pacemaker of interest in this course relates to a growing trend in healthcare to provide more wireless monitoring, reporting, and feedback to improve patient health and quality of life.
Pre-Lab Objectives:
¨ Read the required background information to complete the Lab 0 procedures.
Pre-Lab Deliverables:
¨ Completed Lab 0 pre-lab document (this document) and any supporting documents uploaded to Canvas before the start of your Lab 0 session
Pre-Lab:
1. Read through Appendix A at the end of this document.
2. Read through Appendix B at the end of this document.
3. What information / data would be useful to communicate between a pacemaker inside of a body and a portable device or something similar outside of the body (aside from battery life and EKG data)? List two ideas here (directly edit this document).
4. Read the following article:
J. Smith, “Wireless Health Care: Wireless technologies are about to transform health care, and not a moment too soon,” IEEE Spectrum, Sept. 26, 2011.
List below three things you found interesting in the article. (If you aren’t already, become a student member of IEEE and receive IEEE Spectrum as part of your membership dues!)
5. Upload your completed pre-lab (this document) to Canvas before the start of your lab session for full credit.
Appendix A
Communication System for a Cardiac Pacemaker:
A cardiac pacemaker is a device to help control irregular heartbeats. Traditionally, a pacemaker might include a battery pack implanted in the shoulder with a long electrical wire going to the heart (see Fig. 1). The wire would be attached to the heart and provided a shock (from the battery pack) in order to pace or defibrillate the heart. The pacemaker also would communicate with a device outside of the body to report on battery life, etc.
Figure 1: Sketch of a traditional cardiac pacemaker (From Medtronic)
Figure 2 below presents a sketch of the basic components of a simple pacemaker communication system. Below is a list some of the primary components, including which lab they will be studied in this course.
- Tissue simulant material (Lab 1)
- Transmission line (Labs 2 & 4)
- Monopole antenna with stub-match system (Labs 3 & 5)
- Folded dipole antenna (Lab 6)
Figure 2: A block diagram of the communication system for medical implants. [C. Furse et al. IEEE Antenn. Propagat. Mag., 47:2, April 2005]. Frequency shift keying (FSK) is option that could be used to communicate information between the transmitter and receiver. The tissue-simulate material represents the body. The left-hand side monopole antenna is outside of the body.
Pacemaker technology continues to be improved by engineers. For example, developed pacemakers are now:
¨ Miniaturized (as of 2016, about the size of a large pill: ~1” long).
¨ Can be implanted without requiring surgery by placing it directly in the heart through a blood vessel in the groin and up to the right side of the heart (see “Wireless pacemaker from Medtronic is first to win OK from FDA,” Modern Healthcare, April 7, 2016).
Appendix B
Lab Summaries
Below is an overview of each of the ECE 3300 labs you will be completing. Each lab is focused on a different component or aspect of the communication system for a cardiac pacemaker.
Lab 1: Dielectric Properties
In this lab, you will learn about the dielectric properties of materials and how these properties affect electric fields (loss, skin depth, velocity of propagation, etc.). You will use a dielectric measurement probe to measure the properties of muscle, fat, a sugary substance, and then a mixture of water and salt that when combined has the same average electrical properties as the average composition of the body (quite literally, rats were blended up, their average electrical properties were measured, and the resulting values became a national standard). You will also measure power attenuation on a signal propagating through the average body composition mixture.
Relation to the pacemaker communication system: The pacemaker is embedded within the body. The muscular tissue in the body effects the electric fields in the signal being transmitted wirelessly from inside the body to a receiver outside of the body (or visa versa). We must study the effects the body will have on the propagating signal.
Lab 2: Transmission Lines and Time-Domain Reflectometry (TDR)
You will learn about different types of transmission lines, including coaxial cables and two wire lines. You will calculate and measure the characteristic impedance, and compute and understand R’, L’, G’, and C’ transmission line parameters. You will use a time-domain reflectometer to determine loads, learn about transient voltages, and better understand the concept of impedance.
Relation to the pacemaker communication system: Transmission lines are needed to connect the electronics to the antennas of a pacemaker communication system. We must understand any effects the environment and terminations will have on the performance of the transmission line, and also be aware of any faults along the transmission lines.
Lab 3: Matching Antenna and Single Stub Matching Network
In this lab, you will learn about antennas, their input impedance, radiation patterns, and how to match the antenna to a source using a single-stub matching network. Specifically, you will create a matched equivalent half-wave dipole antenna to a 50-ohm microstripline in Rogers R04350 Laminate.
Relation to the pacemaker communication system: It is important that the antenna for the pacemaker wireless communication system be matched to the transmission line so that the majority of the signal is radiated rather than reflected by the antenna back to the source. We also want to understand how the antenna will radiate (we ideally want the majority of the signal to radiate in the direction of the receiver and not into other parts of the body). When tested on a real person, we would also be required to make sure the radiation from the antenna is below any safety threshold imposed by the FDA on implantable devices.
Lab 4: Telegrapher’s Equations Solution using the Finite-Difference Time-Domain (FDTD) Modeling Approach
You will learn how to simulate voltage and current waves traveling down a transmission line characterized by R’, L’, G’, and C’ parameters. Specifically, you will solve the Telegrapher’s (transmission line) equations in one-dimension (along the length of the transmission line). The solution will be based on the finite-difference time-domain (FDTD) modeling approach (a very common approach to solving Maxwell’s equations). You will simulate both open and shorted lines, as well as line that has a fault (problem) somewhere along it, and observe the reflections that result from the terminations of the lines / fault. If you find this lab interesting, you may consider taking ECE 5340 / 6340 (Numerical Techniques in Electromagnetics).
Relation to the pacemaker communication system: Computer modeling is a very important step when designing biomedical (and other) devices. Testing devices in the lab is often expensive and can take a significant amount of time. Computer simulations (ranging from simple to large-scale complex solutions) can help engineers and researchers test designs and understand the physics of a problem quickly and inexpensively (relative to physical experiments). Subsequently, only the best design(s) optimized via computer simulations might be physically tested in the lab.
Lab 5: Magnetic Field Calculations using the Biot-Savart Law
You will use the Biot-Savart Law with trapezoidal integration to solve for magnetic field variation around an antenna. Specifically, you will consider a thin wire antenna oriented along the z-axis from zs = - L to L. The current distribution on the wire will be given as that for a dipole / monopole antenna over a groundplane. The goal of this lab is to find the magnetic field at any point (xp,yp,zp).
Relation to the pacemaker communication system: The antennas used to communicate between the cardiac pacemaker and the device outside of the person’s body will transmit and receive electromagnetic energy in a specific way. In order to design an effective communication system, it is important to understand how the magnetic field changes with angle and distance from the radiating antenna (i.e. the radiation pattern), and where the receiving antenna should be optimally positioned.
Lab 6: Link Budget Calculation
You will determine a link budget for a simplex (one-way) communication system for the cardiac pacemaker designed throughout the semester. The link budget predicts how much power is received from a known transmitter. The directivity and gain of the antenna, the propagation loss in the tissue simulation material, etc. will all be considered. You will also verify the link budget by testing the system in the lab.
Relation to the pacemaker communication system: Putting all the components together, we want to make sure they will successfully communicate with each other (that the received signal is not too weak)! We normally would also want to make sure our design satisfies safety and efficacy requirements set by the U.S. Food and Drug Administration (FDA), etc.
Additional Notes:
· Additional labs can be completed using your knowledge from ECE 3500. See SS Lab 1, and SS Lab 2 in Reference [1].
References:
[1] C. Furse, L. Griffiths, B. Farhang, and G. Pasrija, “Integration of signals/systems and electromagnetics courses through the design of a communication system for a cardiac pacemaker,” IEEE Antennas and Propagation Magazine, vol. 47, no. 2, April 2005.
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