A GROWING VARIETY OF BODY PARAMETERS are monitored by mobile, compact, intercommunicating sensors that make up wireless bodyarea networks (WBANs). To design efficient WBANs, engineers must know the radiation and propagation in close proximity of human bodies. Recently, the Finite Difference Time Domain (FDTD) technique was used to perform on-body radio channel modeling at 900 MHz by Hanae Terchoune, Azeddine Gati, Albert Cortel Carrasco, Man Fa Wong, and Joe Wiart from France's Orange Labs R&D together with David Lautru and Victor Fouad Hanna from the Universit Pierre et Marie Curie in Paris.
The researchers investigated the behavior of half-wave dipole antennas in a BAN scenario. They evaluated the associated channel parameters to determine how antenna parameters are affected by the presence of the body. The team also studied the influence of human morphology on the on-body radio channel. Six different body models were considered.
For the simulation, the dielectric properties of the tissues were made constant over the utilized frequency band. Antennas were placed either on the body or at a distance of 20 mm. The presence of the body detuned the antenna so that resonance appeared at a lower frequency. When antennas were affixed directly to the body, the frequency shifted by more than 200 MHz. Absorbed power was higher than 90 percent and radiated power was less than 10 percent. In addition, the presence of the body reduced gain performance by 8 dB. When the same dipoles were placed 20 mm from the body surface, the absorbed power was roughly 65 percent while 35 percent was radiated. See "On-Body Radio Channel Modeling for Different Human Body Models Using FDTD Techniques," Microwave And Optical Technology Letters, October 2009, p. 2498.