The biomedical monitoring and imaging system requires data and power transmission through short-range communication, and the interference between large antennas placed within near-field region becomes the important consideration in designing an entire system. For the short-range communication, the electromagnetic computation becomes more complex, which requires huge computational resources. The efficient numerical methods that can be used in short-range communication are (1) Friis formula with correction term and (2) integral coupling formula. Both formulas are similar in an aspect that far-field gain pattern is used to calculate the link budget in a short range. The range of the communication link between two antennas can be defined as reactive near-field, radiating near-field including Fresnel region, a far-field region in the order of nearest distance. Friis formula with correction term can be useful for the simple on-axis antenna displacement in Fresnel region. The integral coupling formula is flexible to compute the mutual coupling of diverse antenna geometries within an entire radiating near-field and a far-field region. Those two methods are evaluated using several examples of short-range communication and interference, and indoor measurement evaluates the validity of the calculated results.
Part of the book: Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing