Research And Design Of High Performance Miniature Filter Based On LTCC

The development of 5G not only brings faster transmission rates and higher transmission quality,but also puts forward more demand and higher requirements for various devices in the communication system.As one of the key microwave passive devices,the filter has received wide attention in the industry.High performance and miniaturization become research hotspots of the filter.LTCC(Low Temperature co-fired Ceramic)technology is easy to embed components and multi-layer wiring,with high integration,good encapsulation,low loss,low cost and other characteristics,and it is very suitable for the research and development of high-performance micro passive filters.In this paper,based on LTCC technology,reflectless,stopband suppression and frequency selectivity of the filter are studied,and relevant micro filters are designed.The research results are as follows:(1)According to the principle of the symmetric network to achieve non-reflection performance and the design theory of lumped elements,a lumped single reflectionless bandpass filter and a lumped combined reflectionless bandpass filter are designed,and their sizes are respectively 6.8mm*3.6mm*1mm and 2.6mm*5mm*1mm.The combined reflectionless bandpass filter is realized by the cascade of a reflectionless lowpass filter and a reflectionless highpass filter.Both filters have certain ability to absorb reflected energy,and their LTCC lumped structures provide new solutions for the design of reflectionless filters.(2)According to the principle of the cross-coupling comb-like structure to achieve high-suppression performance,two six-order comb-like high-suppression bandpass filters with the same structure and different working frequencies are designed,and their size is3.2mm*1.6mm*0.94 mm.These two filters innovatively add cross-coupling Z-shaped structures to introduce transmission zeros for stopbands,which facilitates the realization of stopband high-suppression performance.In addition,they also have the characteristics of higher frequencies and wider passbands.One filter has been processed and its physical test curve is good,which proves the feasibility of the design scheme.(3)According to the principle of hybrid coupling and source-load coupling to achieve high-selectivity performance,a helical hybrid-coupling high-selectivity bandpass filter and a multi-layer source-load-coupling high-selectivity bandpass filter are designed,and their sizes are respectively 3mm*3mm*1.6mm and 2.3mm*2.3mm*0.8mm.Hybrid coupling respectively introduces a transmission zero on each side of the passband and at the high-frequency stopband.Source-load coupling and frequency-selective coupling are used innovatively in combination to respectively introduce a transmission zero on each side of the passband and at the high-frequency stopband.These two filters not only have steep transition bands and high frequency selectivity,but also prove the superiority of coupling structures in generating transmission zeros.