other one 3mm.. It is important to note that both structures have been retuned to 2100 MHzto compare them. As it was already mentioned, the radiation efficiency is useful to comparedifferent systems. Figure 5.4 provides the radiation efficiency of the structure without dielectric,and with 2mm. and 3mm. wide dielectrics.When the dielectric is wider than 3mm the shift to low frequencies is bigger and is not possibleto retune to high frequencies without losing bandwidth. In this cases, it is impossible tocover all the band.Based on the results, this dielectric walls do not improve the total efficiency of the system.Although with dielectrics lower values of S21 are achieved, also the input impedance matchingS11 is worse, thereby, as