Research On The Design And Integrated Printing Of Bandpass Filter

The requirement of frequency is becoming higher and higher in the field of communication,microwave and radar,accompanied by the rapid development of wireless communication technology.The filter is developing towards the direction of easy integration,miniaturization,low loss and high performance.Traditional technology can not adapt to the development of filter,because there are many limitations in design and processing.With its advantages of personalization,low cost and short cycle,3D printing has been applied more and more widely in the electronic field.In this paper,the design and integrated fabrication of LTCC parallel coupled microstrip bandpass filters based on multi-material 3D printing technology are discussed.The main work of this paper is as follows:(1)A LTCC parallel-coupled microstrip bandpass filter is designed by ADS software.Its center frequency is 9 GHz,bandwidth is 1 GHz,in-band loss is less than 3 dB,and out-band suppression is greater than 30 dB.The thickness of ceramic substrate is 200 micron,dielectric constant is 9.5,loss tangent value is 0.0015,and the thickness of nano-silver metal layer microstrip line is 25 micron.(2)The preparation and printing process of high dispersibility and stability LTCC ceramic slurry-borosilicate glass-ceramic slurry were studied.Powder ball milling time 12 hours,solid content 40%,dispersant 3%,binder 4%,printing effect is good.In order to solve the problems of microstrip line connection,uneven end of microstrip line and accumulation of end,step-by-step method,internal-out method and flat-spread method are adopted respectively.When the pressure is 220 kPa,the diameter of the nozzle is 0.41 mm,the wire spacing is 0.4 mm and the moving speed is 610 mm/min,the thickness of the prepared ceramic substrate is(240±5.5)um and the surface roughness is(0.94 ±0.06)um.(3)The co-firing process of LTCC ceramic substrates and microstrip lines was studied,and the shrinkage law of ceramic substrates and microstrip lines was analyzed.The results show that the sintering temperature is 850 C,the heating rate is 15 C/min,the holding time is 120 min,and the density is 2.85g/cm3.With the increase of ceramic substrate thickness,the shrinkage rate of ceramic substrate thickness first decreases and then increases.The shrinkage rate of microstrip line on the same ceramic substrate decreases with the increase of linewidth.(4)Using network analyzer to test the performance of bandpass filter.The test results show that the center frequency of the filter fabricated by printing is 8.8188 GHz,the in-band loss is 17.8 dB,the out-of-band suppression is more than 47.8 dB,and the bandwidth is about 800 MHz.Compared with the simulation results,the center frequency is offset by 2.0%,the insertion loss is increased by 15 dB,and the bandwidth is reduced by 20%.The difference between insertion loss and theoretical design is probably due to the inadequate accuracy of 3D printing equipment,which leads to the deviation of forming size.When the simulation model is revised according to the actual data,the simulation results are similar to the measurement results.In view of the problems arising in the manufacturing process,solutions are put forward.It provides a certain reference value for further research on LTCC microstrip line filter in the future.