Miniature Ltcc Balance Filter

Recently, as wireless communication technology and personal wireless electronic products become popular, excellent performance, small size, low cost and high reliability electronic products have attracted people's attention and pursuit. RF passive components are an important part of RF front-end modules, Advanced LTCC (Low Temperature Co-fired Ceramic) technology using three-dimensional multi-layer integration technology, makes it possible to realize RF passive components small size, high performance and low cost. Microwave balance filter is a very important device in modern wireless communication systems. In many communication applications, e.g. wireless LAN, Bluetooth, WiMAX and LNB (low-noise down converter), etc, balanced circuit has been widely used in the RF front-end. This article introduces the research about micro balance filters.Microwave filters or baluns implemented by LTCC technology have been discussed and researched individually on many papers. However, the problem of integrating the two components to achieve miniature balance filter has not been given adequate attention. It is mainly because the complication of microwave passive device integration and the high circuit density characteristics of LTCC components, which is the enormous challenges and difficulties this study faced.The study and exploration use LTCC process technology to achieve balun and filter firstly. Then, we integrate LTCC balun and filter as a whole in a single module to achieve the microwave micro-balance filter by the vertical through-hole Interconnect process technology.Combing with LTCC process conditions, we have successfully designed two micro-balance filters, with operation frequency, (1) 1.65GHz～2.15 GHz, (2) 0.95 GHz～1.45 GHz. respectively. We proposed a new design method of balance filter with impedance conversion function(50 Ohm/75 Ohm conversion). The circuit module size is only 2.0mm×1.5 mm×1.38 mm. The operating bandwidth of the two microwave balance filters are 26.3% and 41.7% respectively. To our knowledge, we have not seen such a small size of microwave broadband balance filters at the corresponding bands. The components have been simulated and optimized by a full-wave three-dimension simulation software named HFSS (High Frequency Structures Simulator), provided by Ansoft corporation. Compared with the project requirements, the simulation results are better and the designed components have been scheduled to be produced. Considering the difficulties micro-balance filters have to solve:broadband, small size and impedance conversion, we have explored and solved the issues of filter with the impedance transformation function, the broadband balun and the overall design of the micro balance filter. This study achieved a new multiple coupled lines broadband balun with relative bandwidth of 91% and two high-pass and low-pass micro-balance filters with impedance transformation function. It is not only meanful to LTCC balance filters implementation, but also worth to be used as a reference in other RF passive components integrated designs.