Recent wireless terminals are equipped with multiple wireless communication systems, and multi-functionalization is progressing as represented by the smart phone. Since the frequency bands used in each of the wireless communication systems differ, it is necessary to prepare separate antennas for each system. In order to install multiple antennas in the limited space of mobile devices, miniaturization is required. The antenna is designed according to the wave length of the frequency to be used, therefore as the frequency becomes lower the wave length becomes longer, and the antenna also becomes larger.
Particularly, since UHF bands (470-800MHz) are used in antennas for MDTV(ISDB-T/CMMB/DVB-H) , it is difficult to miniaturize the antenna. As a method of miniaturization, adjustment of the resonance frequency by the inductor can be mentioned; however, it is necessary to select components taking into consideration the deterioration of the antenna characteristics. Antennas which cover the 700 MHz band or multiple bands have also been required by LTE which has already been started. Particularly, as a technology that is attracting attention, there is a switching method to adjust the frequency using a switch to change 1 antenna element. Even with this switching method, there are cases where a lumped constant (inductor and capacitor) is used to adjust the frequency along with the switch.
This paper introduces examples of selecting inductors for frequency variable chip dielectric antennas for MDTV. The frequency variable chip dielectric antenna covers the bands of 470-800MHz over 50% of the fractional bandwidth, by adjusting the resonance frequency of the antenna. Capacity variable diodes are used for the variable frequency, to change the frequency for each channel. This antenna was built into a mobile device using the LQW series to realize the miniaturization.