Siw Application And Simulation Study

Mircrostrip and waveguide are two important kinds of microwave transmission line which are widely used in microwave area. As a planar structure, microstrip fit for hybrid integrity, but their disadvantages also exist: the dissipation loss caused by conductor, radiation, and dielectric, therefore, they are not suitable to be used in millimeter wave applications and couldn't compose high Q passive components. On the other hand, waveguide could compose high quality components but hard to be integrated for their huge volume.Substrate Integrated Waveguide (SIW) is a new kind of microwave transmission line in these years which can be widely used in microwave and millimeter wave circuit. The substrate integrated waveguide borrow advantages of both of the rectangular waveguide and the microstrip, such as: high Q, low loss just like rectangular waveguide; small size, low profile, low cost, easy to be integrated like microstrip. The basic concept of SIW is that it use the top and bottom layers of metal together with two row of vias is very small compared with wavelength, the dissipation loss of radiation is very small. It acts like a rectangular waveguide filled with some dielectrics, so components which can be composed by rectangular waveguide can also composed by SIW such as antenna, filter, power divider, coupler, resonator.Two kinds of filters are presented: by transferring the conventional waveguide cavity filter to the SIW, a narrow bandstop filter is designed and simulated, get characteristic of narrow-band bandstop filtering. For example, relative bandwidth 1.2%, most attenuation of 48dB in band. Electromagnetic bandgap (EBG) structures present"forbidden band"characteristics, SIW features high-pass characteristics, so bandpass filters can be composed by combing EBG and SIW. We simulate other structures using the commercial software CST Microwave Studio, we get the tendency of the change, better filtering characteristics and we gain some useful conclusions.