Research On Slow-Wave Substrate Integrated Waveguide Theory And Its Miniaturization Application

Substrate Integrated Waveguide(SIW)is a technical solution that inherits the advantages of the rectangular metal waveguide and traditional planar interconnect circuit,with the merit of self-sealing,low cost,high-quality factor,high power capacity,and easy integration,has become an important candidate for the planar interconnection of microwave and millimeter-wave circuit subsystems.However,the SIW still suffers the drawback of bulk physical size due to the limitation of the inherent cut-off frequency at lower frequency band,which restricts its application in the compact microwave system.Therefore,it is imperative to explore the theory and application of SIW miniaturization technology.Carrying out research on SIW miniaturization technology,especially opening up new directions for miniaturization technology,has very important theoretical significance and engineering application value.In retrospect of various SIW miniaturization technologies in recent years,detailed studies on the Slow-Wave Substrate Integrated Waveguide(SW-SIW)is carried out in this dissertation,by using the scientific research method incorporating theoretical analyses and experimental verifications.The essential causes of slow-wave effect and the key factors of regulation are analized from the perspective of both "circuit" and"field",respectively.The influences of guiding-wave mechanism under periodic and non-periodic loading situation are discussed.Two types of microwave devices(a slow-wave evanescent mode filter and a slow-wave power divider)with compact structure and good performance are realized by using periodic loading and non-periodic loading-type respectively.In the end,two new types of SW-SIW structures are proposed.Compared with all the reported SW-SIW structures,they achieved better miniaturization performance.The main research contents and contributions of this dissertation are as follows:1.An equivalent electromagnetic parameter extraction method for periodically loading SIW is proposed.This method is based on the scattering parameter retrieval theory and the dispersion analysis of the equivalent homogeneous media unit cell,which can effectively and accurately obtain the vertical effective permittivity and the horizontal anisotropic permeability parameter during the frequency band of interests.With this method,(a)extracted,verified,explained and compared various types of periodically loaded SIW schemes.Compared with the traditional qualitative interpretation,this method offers a quantitative explanation of the miniaturization performance of each unit cell for the first time,and can be used to evaluate and predict the miniaturization potential of the microwave device;(b)reveals the unprecedented changes in effective permeability while enhancing the permittivity,which provides a more accurate characterization of unit cell;(c)shows that the non-central symmetric periodic loading unit cell will bring anisotropy characteristics on the permeability;(d)Effectively offers some help on the design of a slow-wave evanescent mode filter,which would become more accurate compared with traditional methods,and a 60%reduction in plane size due to the introduction of slow-wave effects.2.The guided wave characteristics of an anisotropic artificial medium loaded SW-SIW are studied,and this type of anisotropic SW-SIW circuit is implemented using surface-mount inductor arrays.Compared with the previously proposed microstrip polyline network loading structure,(a)the scheme effectively avoids the problem of parasitic capacitance of the microstrip meander line and the mutual coupling between horizontal and vertical loading;(b)the introduction of lumped components greatly widens the adjustment range of phase velocity and cutoff frequency of SW-SIW;(c)more importantly,it can independently control the equivalent parameters of lateral and longitudinal directions to realize some unique features that cannot be achieved by the microstrip polyline scheme.3.The slow wave mechanism and guided wave characteristics of non-periodically loaded Type-I microstrip polyline network are studied.With the help of the transmission/reflection algorithm in TE10 mode,the variation of equivalent electromagnetic parameters under each topology is extracted.In addition,a broadband 3-dB Wilkinson power divider is designed.Under the condition that the isolation is better than 10 dB,the power divider obtains 91.4%relative bandwidth,the in-band amplitude imbalance is less than±0.5 dB,and the phase imbalance is less than±4°.Compared with the conventional HMSIW power divider,the plane size of the power splitter is reduced by 40%,and the relative bandwidth is increased by 50%.4.A multi-technology incorporation slow-wave effect enhancement method of SIW is proposed.It mainly includes:(a)The equivalent inductance/capacitance dual enhancement method.This method etched a microstrip polyline network on the upper surface of the SW-SIW loaded with a metalized blind hole array to further enhance the series inductance.Without increasing additional processing costs,its cut-off frequency was further reduced by 18.5%,and the guided wave phase velocity was significant reduced,slow wave miniaturization performance has been improved again.(b)The distributed ridged slow-wave substrate integrated waveguide(DR-SW-SIW)is proposed The technology is based on multiple longitudinally embedded metallized ridge lines and blind via-hole arrays.This structure achieves a 55.5%cut-off frequency reduction and an 80%plane size reduction compared with conventional SIW.The two new types of guided wave structures have stronger slow-wave performance and more flexible design freedom,which fully demonstrates their potential and advantages in miniaturization of SIW-based microwave millimeter wave devices.