Current Research Projects

Handheld Radios and the Human Head and Hand

This project studies the interaction between a handheld radio such as a cellular telephone, and the human head and hand. The far field is of interest to evaluate the pattern coverage of the radio. The far fields are determined by the design of the handset itself. And they are strongly influenced by the head and hand of the operator, and as the operator holds the radio at various angles and various distances to the head. The near field is of interest to evaluate the field strengths around the head and inside the head.

The human head and body behave electrically as high-permittivity, lossy dielectrics. The head and body have a complex internal structure consisting of many different tissue types, each with its own permittivity and conductivity. Further, the electrical parameters of human tissue vary with frequency. The finite-difference time-domain method is used to compute the field strengths inside and around the head as a function of time, due to a sinusoidal generator that gradually turns on.

This project includes the validation of the computational model against measurements of the near field and the far fields of a portable radio operating near a model of the human head. The initial validation studies use a box or a sphere filled with liquid with the electrical parameters of brain tissue at the frequency of interest. Current work uses a realistic three-dimensional model of the head called a "phantom". The head phantom includes brain, bone, muscle, eye and skin tissue with the electrical parameters of real biological materials.

This research is funded by the Communications Research Centre of the Industry Canada and by the National Sciences and Engineering Research Council of Canada.

Related Publications

  1. C.W. Trueman, S.J. Kubina, J.E. Roy and W.R. Lauber, “Radiation Patterns of a Portable Handset with Simple Head Models”, to be published in the Canadian Journal of Electrical and Computer Engineering.
  2. C.W. Trueman, S.J. Kubina, D. Cule, and W. Lauber, “Near Fields of a Portable Radio in Front of and on the Far Side of a Model of the Head,” Symposium on Antenna Technology and Applied Electromagnetics (ANTEM), pp. 65-70, Winnipeg, Manitoba, July 30-August 2, 2000.
  3. C.W. Trueman, S.J. Kubina, D. Cule and W.R. Lauber, "Validation of the FDTD Near Fields of a Portable Radio Handset and a Simple Head", Conference Proceedings, 15th Annual Review of Progress of the Applied Computational Electromagnetics Society, pp. 660-667, Monterey, California, March 16-28, 1999.
  4. C.W. Trueman, S.J. Kubina, J.E. Roy and W.R. Lauber, "Validation of FDTD Handset and Head Patterns by Measurement", 1998 IEEE APS Conference on Antennas and Propagation for Wireless Communications, Watham, Mass., Nov. 1-4, 1998.
  5. C.W. Trueman, S.J. Kubina, J.E. Roy and W.R. Lauber, "Portable Radio Handset Patterns in the Presence of a Model of the Head", Symposium on Antenna Technology and Applied Electromagnetics, Ottawa, August 9-12, 1998.
  6. C.W. Trueman, S.J. Kubina, J.E. Roy, W.R. Lauber, and M. Vall-llossera, "Validation of FDTD-Computed Handset Patterns by Measurement", Conference Proceedings, 14th Annual Review of Progress of the Applied Computational Electromagnetics Society, pp. 93-98, Monterey, California, March 16-20, 1998.
  7. C.W. Trueman, D. Rensburg, S.J. Kubina, M. Danesh, and S.R. Mishra, "Validation of Computed Portable Radio Handset Near Fields by Measurement", Symposium on Antenna Technology and Applied Electromagnetics(ANTEM '96), August 6-9, 1996, Montreal.

 

Antenna Performance and EMC on Aircraft

Aircraft carry many antennas for communication and other purposes. Each antenna must be certified to have suitable pattern coverage over the frequency bandwidth of the associated system, to ensure the integrity of that system. Aircraft antennas interact strongly with the aircraft itself and with one another. In this project both computer modeling and scale-model measurement are used to investigate the radiation patterns of various antennas on aircraft and helicopters.

Antenna-to-antenna coupling poses a severe problem in electromagnetic compatibility on a typical aircraft. Each system radiates both the desired frequency and harmonics of that frequency. The antenna can couple into other antennas on the aircraft and cause electromagnetic interference. Each system is sensitive to the signals and harmonics of the signals radiated by other systems and can thus be a victim of electromagnetic interference. The full evaluation of source and victim pairs is thus a complex problem that must be addressed systematically to ensure the electromagnetic compatibility of the full complement of avionics systems carried by a typical search and rescue aircraft. An EMC test plan identifies critical source and victim pairs to be tested to ensure the proper operation of all systems.

This project is funded by the National Sciences and Engineering Research Council of Canada.

Related Publications

  1. Stanley J. Kubina, Christopher W. Trueman, and David Gaudine, “Modeling the Characteristics of a CH-149 Helicopter Hybrid HF Antenna,” 17th Annual Review of Progress in Applied Computational Electromagnetics, March 19 to 23, 2001, Monterey, California.
  2. D.R. Munn, C.W. Trueman, and Y.M.M.  Antar, “Gaining Insight Into HF Resonance Features Using Model Morphing,” Symposium on Antenna Technology and Applied Electromagnetics (ANTEM), pp. 195-199, Winnipeg, Manitoba, July 30-August 2, 2000.
  3. D.R. Munn, C.W. Trueman, and Y. Antar, “Novel Method of Improving Model Confidence Through Metamorphosis,” Millennium Conference on Antennas and Propagation, AP2000, European Space Agency, Davos, Switzerland, April 9-14, 2000.
  4. D.R. Munn and C.W. Trueman, “Improving Model Confidence through Metamorphosis,” ACES 16th Annual Review of Progress in Applied Computational Electromagnetics, pp. 373-380, Monterey, California, March 20-24, 2000.
  5. D.R. Munn and C.W. Trueman, “Model Morphing for Insight into the HF Assessment Parameters,” ACES 16th Annual Review of Progress in Applied Computational Electromagnetics, pp. 381-386, Monterey, California, March 20-24, 2000.
  6. Stanley J. Kubina, Christopher W. Trueman, and David Gaudine, “A Virtual Radiation Pattern Range and Its Uses – C-130/Hercules HF Notch Antenna,” ACES 16th Annual Review of Progress in Applied Computational Electromagnetics, pp. 356-364, Monterey, California, March 20-24, 2000.
  7. S.J. Kubina and C.W. Trueman, "Computer Simulations of an Aircraft HF Notch Antenna, IEEE Conference on Electromagnetic Computations, Tuscon, Arizona, June 1-3, 1998.
  8. S.J. Kubina, C.W. Trueman, and D. Gaudine, "Experiments with NEC3 and NEC4 - Simulation of Helicopter Antennas, 13th Annual Review of Progress of the Applied Computational Electromagnetics Society, Monterey, California, March 17-21, 1997.
  9. C.W. Trueman and S.J. Kubina, "Fields of Complex Surfaces Using Wire Grid Modelling," IEEE Trans. on Magnetics, Vol. 27, No. 5, pp. 4262-4267, Sept. 1991.
  10. C.W. Trueman and S.J. Kubina, "Verifying Wire-Grid Model Integity with Program CHECK", Applied Computational Electromagnetics Society Journal, Vol. 5, No. 2, pp. 17-42, Winter 1990.

 

Helix Antennas for Spacecraft Applications

A helix antenna is an efficient radiator of a circularly-polarized field in a narrow beam, over a wide bandwidth. Multi-section helices can be used to increase the bandwidth. Helices are often flown on spacecraft, where the desired performance must be achieved with an antenna of the lightest possible weight and most compact design. In research funded by the Canadian Space Agency in 1995 and 1996, computer modeling was used to study a very general class of helix antennas, with a view to optimizing the design for spacecraft applications. Measurements of the radiation patterns of various helices over a wide frequency range were used to validate the calculations for cylindrical helices, two-section cylindrical helices and tapered helices.

In the current project, software is being created to design a cylindrical helix antenna to meet a performance specification including the minimum gain, the maximum axial ratio, the beamwidth, and the desired bandwidth. The software package identifies combinations of helix pitch angle and length that with meet the performance specification. It may be that no helix of this design can achieve the required performance, in which case a more complex design will be required. The software package permits the engineer to systematically explore the performance of cylindrical helices to determine what is possible from this relatively simple design.

This research is funded by the National Sciences and Engineering Research Council of Canada.

Related Publications

  1. M. Slater and C.W. Trueman, “Design Software for Cylindrical Helix Antennas,” ACES 16th Annual Review of Progress in Applied Computational Electromagnetics, pp. 281-285, Monterey, California, March 20-24, 2000.
  2. C.W. Trueman, S.J. Kubina and M. Slater, "Modelling Helix Antennas with NEC4", 1997 Digest, IEEE Antennas and Propagation Society International Symposium 1997, pp. 1584-1487, Montreal, July 13-18, 1997.
  3. N. Sultan, T. Pellerin, C.W. Trueman, and S.J. Kubina, "Design and Validation of Uniform Helical Antennas, with Varying Diameters, Using NEC", "Progress in Electromagnetics Research Symposium"(PIERS), Hong Kong, January 6-9, 1997.
  4. N. Sultan, T. Pellerin, C.W. Trueman, and S.J. Kubina, "Stepped Helical Antenna Modelling Using NEC and Validation by Measurements", Symposium on Antenna Technology and Applied Electromagnetics(ANTEM '96), August 6-9, 1996, Montreal.
  5. C.W. Trueman, N. Sultan, S.J. Kubina, and T. Pellerin, "Software for Modelling Helix Antennas with NEC and Validation by Measurement", 12th Annual Review of Progress of the Applied Computational Electromagnetics Society, Monterey, California, March 21-26, 1996.

 

The Fields of Portable Radios in an Indoor Environment

Portable radios such as cellular telephones or the walkie-talkies used by security guards radiate electromagnetic fields for communication with their base station. In an indoor environment, cell phone fields travel along corridors and into the rooms of the building, and then through the windows to the outdoors to reach the base station antenna atop a nearby building. Other electronic equipment is exposed to these fields, with may interfere with the operation of that equipment. Such interference can be of great importance in a hospital environment.

In this project ray-optical methods are being used to map the fields of a cellular telephone in the corridors and rooms of a hospital. Three dimensional maps of all three field components are created and studied to determine the regions where the radiated field strength is strong enough that interference may be a concern. The objective of the project is to identify locations where a cellular telephone may be used safely, and conversely, areas where cellular phones should never be used. Computations are being verified against measurements being done at McGill University.

This project is funded under a contract with the Jewish General Hospital of Montreal.

Related Publications

1.      C.W. Trueman, D. Davis, and B. Segal, “Ray Optical Simulation of Indoor Corridor Propagation at 850 and 1900 MHz,” IEEE AP-S Conference on Antennas and Propagation for Wireless Communication, pp. 81-84, Waltham, Massachusetts, November 6-8, 2000.

2.      D. Davis, B. Segal, C.W. Trueman, R. Calzadilla, and T. Pavlasek, “Measurement of Indoor Propagation at 850 MHz and 1.9 GHz in Hospital Corridors,” IEEE AP-S Conference on Antennas and Propagation for Wireless Communication, pp. 77-80, Waltham, Massachusetts, November 6-8, 2000.

3.      Don Davis, Bernard Segal, David Chu, Christopher Trueman, and Tomas Pavlasek, “Effect of Spatial-Sampling Resolution on Electromagnetic Path-Loss and Interference-Potential Estimates in Hospital Corridors,” The Canadian Medical Biological Engineering Society, pp. 46-47, Halifax, Nova Scotia, October 26-28, 2000.

4.      C.W. Trueman, D. Davis, and B. Segal,  “Specifying Zones for Cellular Telephone Operation in Hospital Hallways,” Symposium on Antenna Technology and Applied Electromagnetics (ANTEM), pp. 381-386, Winnipeg, Manitoba, July 30-August 2, 2000.

5.      C.W. Trueman, R. Paknys, J. Zhao, D. Davis, and B. Segal, “Ray Tracing Algorithm for Indoor Propagation,” ACES 16th Annual Review of Progress in Applied Computational Electromagnetics, pp. 493-500, Monterey, California, March 20-24, 2000.

Validation of Various Modeling Codes in Computational Electromagnetics

Code validation is the comparison of computed data such as antenna radiation patterns, antenna near fields, or radar cross-section with measured data to verify that the computational method is correct, and to assess the accuracy of the computational method. Code validation serves to identify the limitations of a computational method, such as the frequency bandwidth over which the computer model obtains useful results. Code validation is carried out in conjunction with all the projects carried out at the EMC Laboratory.

Related Publications

  1. C.W. Trueman and S.R. Mishra, "Numerical Computation and Measurement: Building an Experience Base for Code Validation", invited paper, Latsis Symposium 1995 on Computational Electromagnetics, Zurich, Switzerland, Sept. 19-21, 1995.
  2. S.J. Kubina and C.W. Trueman, "The Validation of EM Modeling Codes - A User Viewpoint", The Applied Computational Electromagnetics Society Journal, Special Issue on Electromagnetics Computer Code Validation, 1989.
  3. C.W. Trueman, S.R. Mishra, C.L. Larose and R.K. Mongia, "Resonant Frequencies and Q Factors of Dielectric Parallelepipeds by Measurement and by FDTD", IEEE Trans. on Instrumentation, Vol. 44, No. 2, pp. 322-325, April 1995.

 

Code Validation Data Base

In this collaboration between the David Florida Laboratory of the Canadian Space Agency and Concordia's EMC Laboratory, a "data base" of radar cross-section measurements and computations was built up over a period of about five years. The RCS measurements and computations are available to the community for the purpose of validating existing and new computer modeling codes in computational electromagnetics. At DFL, the radar cross-section of various simple and complex targets has been measured using state-of-the-art instrumentation and facilities. Computations are done at Concordia using modeling techniques such as wire-grid modeling, surface-patch modeling, and the finite-difference time-domain method, to demonstrate the agreement currently possible. Targets include simple and complex objects of metal, and cubes and rods of low and high-permittivity dielectric.

Related Publications

  1. C.L Larose, S.R. Mishra, and C.W. Trueman, "Measured RCS Polar Contour Maps for Code Validation", Applied Computational Electromagnetics Society Journal, Vol. 11, No. 3, pp. 25-43, November, 1996.
  2. C.W. Trueman and S.R. Mishra, "A WWW-Based Data Base for Code Validation", 12th Annual Review of Progress of the Applied Computational Electromagnetics Society, Monterey, California, March 21-26, 1996.
  3. S.R. Mishra, C.L. Larose and C.W. Trueman, "Precision Radar Cross-Section Measurements for Computer Code Validation", IEEE Trans. on Instrumentation and Measurement, Vol. 42, No. 2, pp. 179-185, April 1993.
  4. C.W. Trueman, S.J. Kubina, S.R. Mishra and C. Larose, "RCS of Scatterers with Attached Wires," IEEE Trans. on Antennas and Propagation, Vol. 41, No. 3, pp. 351-355, March 1993.
  5. C.W. Trueman, S.J. Kubina, S.R. Mishra and C. Larose, "RCS of Four Fuselage-Like Scatterers at HF Frequencies", IEEE Trans. on Antennas and Propagation, Vol. AP-40, No. 2, pp. 236-240, Feb. 1992.

 

Development of Computer Graphics for Computational Electromagnetics

Computer graphics is used extensively in electromagnetics. In developing a computer model of a complex object such as an aircraft, computer graphics is used to input geometry data from drawings, to convert the aircraft surface into elements suitable for input into computational code, and to verify that the resulting computer model is the best possible representation of the aircraft within the limitations imposed by the associated computer code.

Computer graphics is used to study the results obtained from solving a complex structure such as an aircraft or a portable radio handset and head model. Graphics can display the magnitude and phase of the currents flowing on an antenna, and over the surface of an object such as an aircraft. Graphics shows the near fields, both electric and magnetic, associated with an antenna. Graphics displays the far field in terms of individual radiation patterns, and representations of the components of the electric field over the whole radiation sphere. Graphics depicts the frequency variation of these quantities. In time-domain problems computer graphics can show the fields as they develop as a function of time in response to a time-dependent generator.

The development of computer graphics for electromagnetics is an ongoing project at Concordia's EMC Laboratory, and is funded by the National Sciences and Engineering Research Council of Canada.

Related Publications

  1. S.J. Kubina, C.W. Trueman, D. Gaudine and A. Ramos, "Creation, Visualization and Analysis - The Dynamics of Complex Models", 9th Annual Review of Progress of the Applied Computational Electromagnetics Society, Monterey, California, March 22-26, 1993.

 

Broadcast Antennas and Steel-Tower Power Lines

To ensure that commercial radio stations in the AM band in a given area can be enjoyed by the public without interference from other stations in nearby cities, each broadcaster must build and maintain a directional antenna. The antenna must provide good signal strength in the station's service area, but at the same time protect other stations in nearby cities by radiating very little signal toward those cities. Unfortunately, large metallic structures near the station's antenna, such a tower carrying other antennas, or a steel-tower power line, can effectively scatter the station's signal toward cities the station must protect, and give rise to interference. This project uses computational electromagnetics to assess the degree to which structures such as another antenna tower or a steel-tower power line scatters a station's signal. Computer modeling is used to design "detuners" which are installed on the towers to suppress the scattered signal. Computer modeling can greatly reduce the cost of modifying any power line to reduce scattering sufficiently that no significant interference can be measured.

Related Publications

  1. C.W. Trueman, S.J. Kubina, J. Provost, P. Labarre and G. Lussier, "Quick and Effective Adjustment of Stub Detuners by a Two-Loops Method", IEEE Trans. on Broadcasting, Vol. 40, No. 3, pp. 141-176, Sept. 1994.
  2. C.W. Trueman and S.J. Kubina, "Scattering from Power Lines with the Skywire Insulated from the Towers", IEEE Trans. on Broadcasting, Vol. 40, No. 2, pp. 53-62, June 1994.
  3. C.W. Trueman and S.J. Kubina, "Power Line Tower Models Above 1000 kHz in the Standard Broadcast Band", IEEE Trans. on Broadcasting, Vol. 36, No. 3, pp. 207-218, Sept. 1990.
  4. C.W. Trueman, T.M. Roobroeck, and S.J. Kubina, "Stub Detuners for Free-Standing Towers", IEEE Trans. on Broadcasting, Vol. 35, No. 4, pp. 325-338, Dec. 1989.
  5. C.W. Trueman, "Modelling a Standard Broadcast Directional Array with the Numerical Electromagnetics Code", IEEE Trans. on Broadcasting, vol. 34, No. 1, pp. 39-49, March, 1988.
  6. C.W. Trueman and S.J. Kubina, "Ground Loss Effects in Power Line Reradiation at Standard Broadcast Frequencies", IEEE Trans. on Broadcasting, vol. 34, No. 1, pp. 24-38, March, 1988.
  7. C.W. Trueman and S.J. Kubina, "Detuning Power Lines by Isolating Towers for the Suppression of Resonances", IEEE Trans. on Broadcasting, Vol. BC-32, No. 3, pp. 44-55, Sept., 1986.
  8. C.W. Trueman and S.J. Kubina, "Initial Assessment of Reradiation from Power Lines", IEEE Trans. on Broadcasting, Vol. BC-31, No. 3, pp. 51-65, Sept.,1985.
  9. C.W. Trueman, S.J. Kubina, R.C. Madge and D.E. Jones, "Comparison of Computed RF Current Flow on a Power Line with Full Scale Measurements," IEEE Trans. on Broadcasting, Vol. BC-30, No. 3, pp. 97-107, Sept., 1984.
  10. C.W. Trueman, S.J. Kubina and J.S. Belrose, "Corrective Measures for Minimizing the Interaction of Power Lines with MF Broadcast Arrays," IEEE Trans. on Electromagnetic Compatibility, Vol. EMC-25, No. 3, pp. 329-339, Aug. 1983.
  11. C.W. Trueman and S.J. Kubina, "Numerical Computation of the Reradiation From Power Lines at MF Frequencies," IEEE Trans. on Broadcasting, Vol. BC-27, No. 2, pp. 39-45, June, 1981.

Teaching Electromagnetics

Students in electromagnetics courses often have problems visualizing the propagation of pulses on transmission line circuits. To aid in teaching transients on transmission lines I have written a program called BOUNCE which uses computer animation to bring propagation problems to life. BOUNCE can show a pulse starting at a generator, propagating at a finite speed along a transmission line, being partially reflected from various discontinuities, and finally reaching a load. This is a very effective classroom demonstration. BOUNCE provides a "laboratory" in which students can test their pencil-and-paper solutions to homework problems. Also, BOUNCE is useful in the classroom for showing, graphically, the change from "transient" to "sinusoidal steady state" when the generator is sinusoidal. The program shows the build up of the steady state response as the superposition of many reflections of ever-smaller amplitude, and prepares the students for studying transmission lines in the sinusoidal steady state.

To aid in teaching transmission lines in the sinusoidal steady state, I wrote a program called "TRLINE" standing for "Transmission LINE". The program solves various transmission line circuits in the sinusoidal steady state and illustrates the use of the Smith Chart. Like BOUNCE, the TRLINE program can be used at home by students as a "laboratory" for verifying their homework assignments. TRLINE permits me to illustrate advanced concepts such as microwave filters in the classroom, and so prepare students for the elective "Microwave Circuits" course.

Related Publications

  1. C.W. Trueman, “Interactive Transmission Line Computer Program for Undergraduate Teaching,” IEEE Trans. on Education, Vol. 43, No. 1, pp. 1-14, February 2000. 
  2. C.W. Trueman, "Teaching Transmission Line Transients Using Computer Animation", Frontiers in Education Conference, Puerto Rico, Nov. 10-13, 1999.

 

Department of ECE

People of ECE

Faculty of ECE

Christopher W. Trueman

Last Modified on Tuesday, 28-Sept-99 08:00:00 EST