Dear Shatrudhan Palsaniya ,

I would advise you to return to the exact definition of the quantities.

Let us assume that the reflection coefficient of the material = pr/Pi

If one evaluate the part penetrated inside the screen then it will be the transmitted part Pt= Pi - Pr, dividing by Pi then

Pt/Pi= 1- Pr/Pi , this will be a a positive fraction in this way.

In case of screening by absorption

Pt= Pi- Pa,

It turns out that

Pt/Pi= 1 - pa/Pi

which is also a fraction smaller than one.

Purposely the the part of power passing inside the screen will be always smaller than the incident or the environmental power Pi

If Pt/Pi is negative in case of reflection then it has an other definition than I brought here.

It may for example be defined as (Pr-Pi)/Pi.

Best wishes

Abdelhalim abdelnaby Zekry Thank you sir for a kind explanation.

Dear Mr. Zekry,

a negative shielding effect is a damping effect. If a shielding effect is a positive value, so we have a amplification of the field with a shieling material .

And this is wrong.

So we speak ( with the shielding logarithmic equation ) from a shielding valua : negative.

Sincerely Yours

F. Gräbner

Frank Gräbner thank you for your response. If it is a damping effect then ultimately restricting signal's reflectance. It could raise power dissipation in terms of signal loss.

I might be wrong, is it possible?.

Kulkarni, G., Kandesar, P., Velhal, N., Phadtare, V., Jatratkar, A., Shinde, S. K., ... & Puri, V. (2019). Exceptional electromagnetic interference shielding and microwave absorption properties of room temperature synthesized polythiophene thin films with double negative characteristics (DNG) in the Ku-band region. Chemical Engineering Journal, 355, 196-207.