The microstrip transmission line illustrated below cannot su

The microstrip transmission line, illustrated below, cannot support a pure transverse electromagnetic wave because the phase velocity of the field in air ie 3 times 10^8 m/s but the phase velocity of the field in the substrate is 3 times 10^8/epsilon_r^1/2 m/s which leads to an intermediate effective dielectric constant.

Solution

It is a True statement

The microstrip has some (usually most) of its field lines in the dielectric region, concentrated between the strip conductor and the ground plane, and some fraction in the air region above the substrate. For this reason the microstrip line cannot support a pure TEM wave, since the phase velocity of TEM fields in the dielectric region would be c/_r, but the phase velocity of TEM fields in the air region would be c. Thus , a phase mismatch occurs at the dielectric- air interface.