Bruce M. Green and Dr. Michael A. Jensen, Electrical and Computer Engineering
The presence of human tissue near the antenna of a portable cellular phone reduces its range of reception and transmission. This research investigates the feasibility of antenna diversity (more than one antenna on a handset) as a means of combating the loss of received signal power to a cellular phone antenna due to the biological tissues of the operator. The Finite Difference Time Domain (FDTD) method provides simulations of two antenna designs that accurately models both the antenna and tissue of the operator.
This research considers cellular phones whose receiver circuitry chooses to use the strongest signal available on either of two antennas on the handset. When the head and hand of the operator block radio waves traveling to one antenna, it is statistically unlikely that they will be blocking the signal to the other antenna. Thus the receiver has a more powerful signal available to it most of the time.
FDTD simulations of two antennas show that the operator’s tissue causes a 99% loss of signal power in the direction of the user’s ear. This work combines combinations of two single element antennas of different designs on a handset in order to achieve antenna diversity. The performance of diversity employing handsets compared with single element handsets shows a 4 to 6 dB (250% to 400%) increase in the minimum received signal power given the assumptions of a moving user and a single radio wave in the horizontal plane incident to the antenna. Prototypes of each antenna in the figures have been built and soon measurements will be taken that will test the accuracy of the simulations performed.
References
- M. A. Jensen and Y. Rahmat-Samii. Performance analysis of antennas for hand-held transceivers using FDTD. IEEE Trans. Antennas Propag., 42:1106-1113, Aug. 1994.
- W. C. Jakes, Jr. Microwave Mobile Communications. John Wiley & Sons, New York, 1974.
- This research was supported in part by Hughes Research Laboratories, Malibu, CA.
