Hi all,
I have a question of how to measure the radius of the radiative/reactive near fields.
according to Balanis (Antenna theory and design) the outer radius of the radiative near field for example, is 2D^2/lambda.
where lambda is the wavelength, and D is the largest dimension of the antenna.
So my question is this - if my antenna is implanted inside materal, how then will I calculate it ?
do I need to use lambda of the material? and is D need then to be the electrical length, instead of the physical length ?
Let's say real example, where D=2cm (physcial length) and lambda = 400MHz (inside material 100MHZ). what is the correct math for this ?
please help.