Design Of LTCC Microwave Bandpss Filter And Performance Research

With the wireless communication technology fast developing, the miniaturization technology of electronic equipments becomes necessary. The research and development of small size and high performance microwave filter becomes crucial.LTCC, Low Temperature Co-fired Ceramic, a remarkable new technology develops rapidly in recent years. It has become one of the main technologies in embedded integrated passive field. With this technology, filter is designed to stereoscopic structure instead of plane layout. The advantage of multi-layer filter is smaller size, lower cost and flexibility. In addition, multi-layer structure provides electromagnetic coupling which optimizes the filter to better performance, integration and reliability.The theory of microwave filter is briefly described in this paper. A 2.45GHz filter is taken as a research object, which is widely applied in wireless communication equipments. Based on practical usage, this paper realizes two kinds of LTCC microwave filters separately. The main works are as follows:1.LC configuration LTCC filter:In the process of designing LC configuration LTCC filter, implementing embedded passive device is one of the difficulties. This thesis gives the detailed and systematic design principles and methods of LTCC embedded passive device. With the electromagnetic simulation and circuit simulation, this thesis analyzed the factors impaired the performance of LTCC embedded passive devices. A novel architecture is proposed to implement on-chip spiral inductor. High Q can be gotten by change the ratio of trace widths and trace spacing each spiral under the condition that the sum of them are constant. Based on above works, LC configuration LTCC filter is designed for application in engineering, center frequency=2.45GHz, bandwidth=100MHz, size of 6.0×2.8×0.7mm32. Strip line configuration LTCC filter:This thesis researches the Stepped Impedance Resonator (SIR). The separation of the resonant frequency by the distance of coupling is indicated and explained. It uses the SIR structure and cross-coupling to lead 2 transmission-zeros into the low stop-band. Strip line configuration LTCC filter is designed for application in engineering successfully, center frequency=2.45GHz, bandwidth=100MHz, insertion loss<1.8dB, size of 2.2×1.8×0.9mm3, and the attenuation of stop-band also accords with the requirement. Finally, this thesis analyses the effect of resonators'area, taps location, resonators'spacing and so on and summarizes the law of change.