Research And Design Of Three - Dimensional Integrated Micro - High - Pass Filter

Due to the rapid development of wireless communication technology, electronic system trends to be in higher frequency, smaller size, with higher integration, greater performance and lower cost. As an essential element in a communication system, high-pass filter is with no exception. Researchers have given higher expectations on their work performance and researches on them become more and more popular. Miniature high-pass filters in high frequency can be widely used in transceiver components, wireless mobile terminals and other military and civilian equipment, and the researches on them will be of great significance and market value. This paper adopts the advanced LTCC technology to complete a series of researches on miniature high-pass filter.In this paper, combined the theoretical analysis and the multilayer LTCC technology, a series of novel high-performance high-pass filters have been successfully designed. Finally the other characteristics have also been improved and explored. The main work is as follows: (1) The high-pass filters with cutoff frequency of 760MHz and 650MHz are designed based on the component replacement method and multilayer LTCC technology, so that the volume is greatly reduced, and ultimately realizes the miniature size of 1.6mm×3.2mm×0.94mm.The bandwidth of the filter with cutoff frequency of 760MHz is about 2.06GHz, pass-band attenuation is less than 1.65dB, VSWR is less than 1.75, pass-band ripple is about 1.4dB, the stop-band rejection from 300MHz to 500MHz is greater than 30dB. The design of the filter with cutoff frequency of 650MHz has sharpened the rejection through three controllable transmission zeros. Whether impedance matching or stop-band rejection both meet the targets, and leave some redundancy for fabrication.(2) Based on the short transmission line approximately equivalent circuit theory, this paper has successfully designed 4 high-frequency high-pass filters, whose cutoff frequencies are respectively 3100MHz,3800MHz,4400MHz and 6300MHz. They are all at size of 1.6mm×3.2mm×1.2mm. This paper also puts emphasis on the impact of component values on the cutoff frequency, the length and width of short-circuit stubs on the bandwidth and the shield layer on the match. Finally, the conclusions are as follows:Firstly, to achieve a wider bandwidth, the parasitic stop band is the farther the better, the length of short-circuit stubs are required about a quarter of the wavelength in the parasitic frequency. Secondly, to pursue sharp stop-band rejection, the short-circuit stub should be wider, but this will lead to the reduction of bandwidth. To pursue large bandwidth, the short-circuit stubs should be narrower, but the steepness of the transition zone and stop-band rejection will be worse. In summary, researchers should reach a compromise in the design for real need. For filter with cutoff frequency of 3100MHz, the widest bandwidth can achieve about 11.7GHz, which broadens 18.4% compared the one with the sharpest stop-band rejection. Obviously, its steepness is not as good as the latter. The rules above can give some guidance in the future filter design.Based on the three-dimensional integrated LTCC technology, miniature high-pass filter designed in this paper can meet the project requirements with its small size, great band rejection, low insertion loss, high reliability and so on. Several productions have good test performance. This paper also discussed and summarized some rules and experience, which can be applied to other bands and bandwidths with a broad application prospects and reference value.