The micro strip transmission line illustrated below cannot s

The micro strip transmission line, illustrated below, cannot support a pure transverse elecrtomagnetic wave because the phase velocity of the field in air is 3 Times 10^8 m/s but the phase velocity of the field in the pressure in the substrate is 3 Times 10^8/epsilon_r^1/2 m/s which leads to an intermediate effective dielectric constant. True False Design a dielectric coating to provide total transmission of a 1550 nm optical communications signal from air into a glass substrate with an index of refraction n_g = 1.52. That is, determine the required index of refraction of the coating, n_c, and its minimum thickness. 1 (nm). n_c = 1.20, 1= 119.0 nm n_c = 1.23, 1 = 315.0 nm n_c = 1.52, 1 = 315.0 nm n_c = 377, 1 = 1550 nm

Solution

9.

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.