SAR/Human body tissues/ Conductivity/HFSS

[vijaimvk]

Hi all,

Human body tissues are characterized mainly by three properties Permittivity, Conductivity and loss tangent..

1)Since the body tissues are dielectric, how it could have conductivity ?


For all materials in the material library of HFSS, we have mention these values..(Permittivity, conductivity,loss tangent etc..)

2)How could dielectrics like FR4 have conductivity values ?


3) Whether permittivity have imaginary part? or it have any relation with the loss accounted ?

plz reply for these questions..

 

[jiripolivka]

Hi all,

Human body tissues are characterized mainly by three properties Permittivity, Conductivity and loss tangent..

1)Since the body tissues are dielectric, how it could have conductivity ?


For all materials in the material library of HFSS, we have mention these values..(Permittivity, conductivity,loss tangent etc..)

2)How could dielectrics like FR4 have conductivity values ?


3) Whether permittivity have imaginary part? or it have any relation with the loss accounted ?

plz reply for these questions..

Please read first a textbook on basic electronics and materials. Any material has its impedance expresses as resistivity/conductivity, permittivity (complex). Loss tangent is only one way to exres the complex impedance.

 

[volker@muehlhaus]

1)Since the body tissues are dielectric, how it could have conductivity ?

You might think of "ideal conductors" and "ideal dielectrics", but the real world is more complicated. In your body example, there is a lot of water. Is water a conductor or a dieelectric? It is really both, and for simulation you need to set both properties: permittivy and conductivity.

How could dielectrics like FR4 have conductivity values ?

FR4 is an isolator at low frequency, but it has high frequency losses. There typical material description in the simulator is to set the loss tangent (tand delta), with DC conductivity = 0. You could get the same results with a frequency dependent conductivity, but that's just a different way to specify the frequency dependent losses.