Multi-Layer Structure Filter Optimization And Integrated Design Of Filter-Antenna

With the rapid development of wireless communications and electronictechnology, electronic devices in the wireless communication system need amultifunction, miniaturization and integration. This requires a filter and antennaminiaturization and multi-band characteristics. Meanwhile filter and antenna areintegrated. This paper combines a variety of wireless communication systems need tofocus on the miniaturization of LTCC filter, miniaturized multi-frequency antenna,dual-band filter-antenna and filter-antenna synthesis design issues. The author’s workand creative results can be summarized as follows:1. Fuzzy algorithm simulates human thought to optimize the LTCC filter design.The expert information and a large number of coarse model design are used toestablish the fuzzy inference system to optimize a fine model. The combination of thefuzzy algorithm and HFSS simulation software seamlessly links. Using this method tooptimize a LTCC filter working in the4.15-4.85GHz, the calculation and experimentalresults show that this method has good practicability2. The two basic structures of the antenna design—the monopole and ring arecombined to achieve dual-band characteristics. Analyzed the monopole and loopantenna input impedance, the two kinds of antennas input reactance hascomplementary characteristics in lower than the resonant frequency. So loading thering structure at the top of the monopole to achieve the miniaturization of the antenna,the impedance bandwidth is not reduced and the gain and radiation efficiencyimproved slightly. Simulation and test results are in good agreement.3. The synthesis design of miniaturized dual-passband bandpass filter andminiaturized dual-frequency antenna is studied. A miniaturized dual-band filterantenna is designed. Optimizing the length and width of the microstrip line betweenthe filter and the antenna, the filter-antenna can be matched well within the two bands.4. Integrated design of the filter with flat printed monopole antenna is study. Aprinted monopole filter-antenna is designed using coupled band-pass filter synthesisapproach. Because the line spacing of the coupling line is too small to process, theDGS is introduced in the filter design to solve this problem. A printed monopolefilter-antenna is designed based on DGS. This filter-antenna is realized integration andminiaturization design. The antenna performs not only a radiator but also the last resonator of the bandpass filter. On the overall performance, the filter-antennareflection coefficient and gain curve are similar to the filter return loss and insertionloss curve.5. The microstrip filter-antenna integrated design is studied. Using one-quarterwavelength openings on circular patch, an open-circuit transmission line is insertedthrough the opening. Microstrip antennas and open transmission lines are linked torealized the second-order filter using this coupling structure of the admittanceconverter. The filter-antenna and2-pole bandpass filter have the same equivalentcircuit. When the filter-antenna is designed using the filter synthesis approach, thereare strict requirements in antenna design, which is brought difficulties to the design ofthe antenna. The study found that the impedance transformation line between themicrostrip antenna and the coupling line can make antenna design simpleness. Themcirostrip performs not only a radiator but also the last resonator of the bandpass filter.From the simulation and test results, the two filter-antennas reflection coefficient andthe gain curve is similar to the return loss and insertion loss of the filter.