The optimal antenna length of the tag is related to the case of the encapsulated or embedded non-conductive material (the dielectric constant of the non-conductor is generally greater than the dielectric constant in the air, resulting in the effective wavelength in the medium is shorter than the effective wavelength in the air). For the electronic tag embedded in the non-conductor, if the effective electrical length of the antenna is adjusted to the optimal length in the air (that is, the reading distance is the furthest when it is coordinated with the reader), when it is placed in the non-conductor or on the substrate, the electrical length of the tag antenna should be adjusted to the direction of reduction to achieve the optimal effect equal to that in the air. On the contrary, if the effective electrical length of the tag antenna is adjusted to the optimal electrical length in the non-conductive medium, the optimal electrical length in the air should be adjusted to the direction of increasing the electrical length.