Fabricate Modified Dual-Band Parallel-Coupled Microstrip Filters on the Al2O3 Ceramic Substrate

In the past, micro-strip line is a basic and useful method to design microwave devices, such as antennas and filters, because its structure is very simple, low cost, and easy to fabricate in the print circuit. Therefore, in this paper, the parallel-coupled micro-strip line structure is adopted to design a dual-band filter bandpass filters and the purpose of this research is to improve the microwave characteristics of designed filters. The design concept of the filters is based on the coupling theory of the parallel-coupled micro-strip line structure, and the methods of enhancing the second pass band response are proposed. All examples in the thesis were performed in real filters and the measured data are compared with the related simulation results. In this paper, Al₂O₃ is used as the substrates of the filters, and the optimum insertion loss of simulated filters is -1.75 dB at 2.41 GHz, and -2.537 dB at 5.08 GHz. However, the optimal insertion loss of fabricated filters is -3.538 dB at 2.45 GHz, and -2.619 dB at 5.2 GHz, respectively.