Transmission Loss

The field strength E t _ of the transmitted wave is computed using the transmission factors and the field strength E i _ of the incident wave:

(1) E t E i = | T 12 _ | | T 21 _ | | T 2 _ |

| T 12 | and | T 21 _ | are caused by the transition from air to the material and the other way round, whereas | T 2 _ | is caused when the wave penetrates through the material. The values are shown in columns N, O and P in the table. Additionally, column Q shows the product | T 12 _ | | T 21 _ | , which is the contribution of the losses due to the transition into the material and the transition back to air.

The values are computed as follows1:

(2) | T 12 _ | = 2 1 + ε r ' 2 + ε r ' ' 2 + 2 ( ε r ' 2 + ε r ' ' 2 ) 1 4 cos ( 1 2 arctan ε r ' ε r ' ' )
(3) | T 21 _ | = 2 ( ε r ' 2 + ε r ' ' 2 ) 1 4 1 + ε r ' 2 + ε r ' ' 2 + 2 ( ε r ' 2 + ε r ' ' 2 ) 1 4 cos ( 1 2 arctan ε r ' ε r ' ' )
(4) | T 2 _ | = e 2 π f d μ 0 ε 0 ε r ' 2 ( 1 + ( ε r ' ' ε r ' ) 2 1 )

The transmission loss is then computed as follows:

(5) L T = 20 log ( | T 12 _ | | T 21 _ | | T 2 _ | )

1 O. Michler and M. Strey: DAB- Indoor- Versorgung im L- Band. Eine Studie im Auftrag der Sächsischen Landesanstalt für privaten Rundfunk und neue Medien (DAB Indoor Coverage in the L-Band). April 1998