Design Of Compact S-Band LTCC Bandpass Filter

In recent years,with the development of modern communication technology,especially in the mobile communication field,electronic device need more portable,therefore the market paid more attention to compact,lightweight and have high performance microwave devices.LTCC technology has advantages of high frequency characteristics,high integration and low cost,can be used to design small volume,low insertion loss and high performance of filters,plays more and more important role in the communication industry.This paper introduces the principle of LTCC technology and microwave filter.On this basis,the design of filter products is designed based on the simulation software of ADS and HFSS.1.With normalized chebyshev low-pass filter as the prototype,according to the performance index of filter to establish filter series,then take frequency conversion and impedance transformation,through the J/K conversion to simplify circuit,change hybrid resonant circuit into parallel resonant circuit,makes the design of the circuit can be achieved by coupling stripline.The design circuit is simulated with ADS software to verify the correctness of the design circuit2.In order to suppress the neighboring frequency signals and out-of-band interference,through transmission zeros formation principle,introduces transmission zeros on both sides respectively,and the transition zone of the filter to improve the steep stop-band attenuation,improving the frequency selective characteristics of the filter.3.Use HFSS simulation software to simulate the designed circuit,analysis the influence of the resonant length with center frequency,tap input position with the insertion loss in passband and resonator spacing with the bandwidth,the three parameters are optimized simulation.The final adjustment of the filter is 2.5mm×2.0mm×0.9mm,the center frequency is 2.45GHz,the bandwidth is 100MHz,the internal interpolation loss is less than 2.5 dB,and the VSWR is less than 2.0.Outside the zone has four transmission zeros,improve the stopband characteristic of the filter,the whole structure of the simulation results meet the demand of filter feature,realize the miniaturization of an s-band LTCC band pass filter.