Design Of Chebyshev Band-Pass Filter Of 3cm Wavelength By SIW

Filter is the selective device which can allow certain frequency to pass but attenuate the outside pass-band component. Filter is widely applied in the current handheld devices, base stations and wireless network equipments. It is indispensable components of system. The design of the filter is one of the important fields of microwave technology subject. It can be used to eliminate the clutter signals we don’t need in the system. With the rapid development of satellite and handheld wireless devices, microwave and millimeter wave filter performance of the system of the demand is higher and higher, such as high frequency selectivity, broadband networks, miniaturization, etc. Traditional filter include waveguide and microstrip structure, however, both of them have the contradiction of high power, low loss, and ease of integration. Each can only meet one or two of these advantages. Therefore, integrating the advantages become the difficulty of current research of filter and it is necessary to be solved.Substrate Integrated Waveguide(SIW) is put forward by Japanese scholars in the early 1990 s, and it is noticed by scholars in the subsequent years. It has a large capacity of power, low loss, ease of integration, easy processing, low cost, etc. It combines the advantages of microstrip and traditional metal waveguide. The SIW not only has the performance of rectangular waveguide, but also has the small size of microstrip. It can be used as a traditional cavity filter structure, in addition, it is widely used in the field of microwave and millimeter wave in recent years, and because of its unique advantage, SIW filter has been noticed by many people.In this paper, we first studied the transmission properties of SIW structure, and got the law through the data fitting which the size is changed in this structure, then we apply the theory of resonant cavity in the SIW, designed out the SIW resonator. Compared with microstrip resonators, SIW have the higher quality factors. We put the traditional method of cavity filter in the SIW cavity filter structure, and designed a good performance of bandpass filter. In order to reduce the volume of the device in the process of designing, we use the cavity laminated structure. Considering the system integration and the need of test, we analyze and design the transition structure between SIW transmission line and the microstrip at the input and output ports. Finally, the X-band laminated structure bandpass filter achieve the required index: Center frequency on 10 GHz, 0.77 GHz bandwidth of 1dB, return loss 22 dB, insert loss lower than 0.7dB, rectangular coefficient is 2.15, 30 dB attenuation outside the band at center frequency ±0.7GHz, and the size of device is only 40.8mm*16.4mm*4.3mm. We choose AutoCAD to complete the filter paper, and process the device, assembling, testing and commissioning. Within the allowed error range, the test results are consistent with the simulation. At this point, we completed the X-band bandpass filter which has a large capacity of power, low loss, small size, ease of integration and low cost.