The Design And Optim Of Ltcc Filter Based On Implicit Space Mapping

With the development of science and technology, mobile devices have become more and more miniaturized. Therefore, filter-an indispensable component of mobile devices-wins a growing concern in the mean time. Small Low Temperature Co-fired Ceramic (LTCC) filter have been invented in the trend of the miniaturization. This paper describes the design of band-pass filter based on LTCC technology. Moreover, it also provides the implicit space mapping algorithm to solve issues of the time-consuming and the optimization direction during the design process.First of all, the approach to design band-pass filter lumped circuit to achieve the respective parallel circuit and the size of three-dimensional EM model is introduced. In this part, Chebyshev low-pass filter is taken as prototype. After frequency conversion and components transform, the J/K inverted converter transforms the band-pass filter circuit to a parallel circuit which is easier to implement. Size of the three-dimensional EM model is calculated based on the value of each element in the lumped circuit.Secondly, in the modeling process, the folding wire SIR resonator is used as the resonator of the lumped circuit. Additionally, the tap type "Z"-type structure is used in input and output terminator. The coupling between the resonant cavity and this structure produces a transmission zeros in the stopband of the filter, which strengthens characteristics of the stopband.Last but not the least, the calculated size by the empirical formula does not make the designed filter meet the specifications, optimization must be essential. This paper offers the implicit space mapping algorithm for iterative optimization. The coarse model which is matched the HFSS fine model is established by the application of multilayer elements in ADS software. Compared with the parameter sweep, implicit space mapping algorithm achieves overall optimization of the designed parameters. Moreover, it also reduces the number of simulation in the fine model. Therefore, it enhances the efficiency and solves the issue of the optimizing direction. The following parameters are established in the finally designed LTCC multilayer bandpass filter:size is2.5mm×2.0mm×0.9mm, center frequency is2.5GHz, bandwidth is200MHz, transmission zero is at3.4GHz and the pass band loss is less than-3.5dB. The designed filter meet the specifications and can be applied to Bluetooth and wireless local area network (WLAN).The correctness and validity of optimization theory about space mapping algorithm have been validated by the electromagnetic simulation responses of LTCC multilayer structure.