- freely available
Sensors 2010, 10(6), 5503-5529; doi:10.3390/s100605503
2. Mathematical Model
2.1. Wave Propagation through Biological Media
2.2. Scattering, Reflection, and Anti-Reflection
2.2.1. Scattering by a Single Interface
2.2.2. Single-Layer Case: Scattering
2.2.3. Single-Layer Case: Reflection and Transmission Coefficients
2.3. Filtering Property of the Layer
2.4. Path Loss in the Human Body (Near Field Far Field Consideration)
2.4.1. Power Absorbed in the Near Field
2.4.2. Power Absorbed in the Far Field
- PR in the Near Field: There is no general formula for the estimation of field strength in the near field zone . Only measurements can provide a simple means of field evaluation. However, reasonable calculations can be made for antennas like dipole or monopole. When the receiving antenna is in the near field region of the transmitting antenna, the power density does not necessarily depend on the distance from the antenna, but varies rapidly with distance, and may exhibit oscillatory behavior. The magnitude of on-axis (main beam) power density varies according to the location in the near field and its maximum value is approximated by  Pe = 16 δP / πL2, where L is the largest dimension of the antenna, P is PT − PNF, and δ is the aperture efficiency (typically 0.5–0.75) . It can be approximated as δ = Ae/A (Ae is the effective aperture and A is the physical area of the antenna). The power received by the receiving antenna in the near field can be approximated by:
- PR in the Far Field: On the other hand when the receiving antenna is in the far field region of the transmitting antenna, the power density is dependent on the distance d and is given by:
3. Numerical Results
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Right- and Left-Going Waves
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