A chip antenna in via-free LTCC with symmetric structure for Bluetooth applications

Abstract

A chip antenna for Bluetooth applications is proposed. This antenna has three symmetric metallic layers implemented by low-temperature co-fired ceramic (LTCC) technique. Because of the symmetric structure, there is no need to mark the polarity of the antenna. No vias are required in the antenna, which leads to significant simplification of fabrication process. This is achieved by connecting the metallic layers using electrodes at two ends. The antenna behaves as a quarter-wave monopole loaded with inductors and the radiating area is the whole straight metallic strip in the middle layer, so the radiation pattern is omni-directional. The size of the antenna is only 9 × 2 × 1 mm³ at 2.45 GHz. The proposed antenna design is assessed by comparing the related simulated and measured results. The measured results show that the bandwidth of the antenna is 100 MHz (corresponding to 6 dB return loss) and the gain is 1.3 dBi. Measured results validate the novel design of the proposed antenna. In addition, the parametric study and frequency adjustment method are conducted to facilitate the design and optimization processes for engineers.