Research Of Multi-band And Low Profile LTCC Antenna For Mobile Handsets

Firstly, the radiation theory of antennas and the electrical parameters such as the impedance, directivity, bandwidth, and polarization have been introduced. The most important part of this paper is the design of multi-band LTCC antenna using meander line structure. The first meander line LTCC antenna has two radiation elements, the bottom meander patch was designed for GSM band, the top meander patch which was tuned to DCS band was connected to the bottom meander patch using a via. The coupling between the two meander patches is used to obtain the DAB band. The simulated results by HFSS indicated that the radiation patterns were omni-directional, and with the 2.5:1 VSWR bandwidth definition, the bandwidths were 120, 180 and 150 MHz for GSM/DAB/DCS respectively.The second meander line LTCC antenna was designed with two radiation elements, the surface-current length of the top layer was about 0.25λ@900 MHz and 0.5λ@1800 MHz, and the surface-current of the lower layer was about 0.25λ@2.1 GHz. The two layers were connected not with via but using the coupling effect between them. The simulated results showed that the radiation patterns were omni-directional, the bandwidths were 40, 120, and 110 MHz, and the gains were -0.77, 1.45, and 1.14 dB for GSM/DCS/UMTS respectively. Secondly, a helix structure LTCC antenna was simulated by HFSS, and the result indicated that the bandwidth was 240 MHz for DCS band. Then the helix structure and rectangular loop were added into the design of LTCC antenna, the simulated result showed that the bandwidth was 610 MHz (1.73-2.34 GHz), which was wide enough to cover DCS/PCS/UMTS/WiBro.One of the antennas was manufactured with LTCC process. Twenty-one layers of Dupont 951C2 (ε_r= 7.8±0.2, tanδ= 0.014) green tapes were laminated, and the electrode in the 9th layer was for the UMTS band, the electrode in the 21st layer was designed for the GSM and DCS bands. The measuring board was made by the FR4 material (ε_r= 4.4, tanδ= 0.02). The manufactured LTCC antenna was measured by the network analyzer. It can be seen from the results that the return loss was 11.5, 16.9, and 10.6 dB with the operating frequency 0.84, 1.49, and 2.23 GHz, respectively.