微波无源电路仿真技术(04)资料.pptx

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,#,边界与端口设置,HFSS,中的边界条件,Perfect E,Perfect H,Finite Conductivity,Impedance,Layered Impedance,Radiation,Symmetry,Master&Slave,Lumped RLC,Screen Impedance,PML(Perfect Matched Layer),边界条件定义的覆盖,如果边界被多次定义，则后定义的边界条件覆盖前面定义的边界条件,几种例外情况：,端口不被覆盖,如果用,Perfect H,覆盖,Perfect E,边界条件，则覆盖区域的边界条件实际为,Natural,，即自然边界条件,Perfect E and Perfect H/Natural,Perfect E,是理想电导体,*,E-,场垂直于边界表面；,可以表示金属表面、地平面、理想腔体表面等；,无限大地平面选项：用于模拟,I,无限大地平面；,Perfect H,是理想磁导体,H-,场垂直于边界表面，,E-,场平行于边界表面；,现实世界不存在这种边界，但对模拟模型边界非常有用；,Natural,是指理想磁边界施加到其它边界,(,如,.Perfect E),删除,理想电边界，但允许存在切向电场。,其作用为在理想导电平面开了一个,孔,。,Boundary/Excitations-Overview,Perfect E,应用实例,不考虑损耗的金属平面,地平面,腔体表面,微带线导带,Perfect H,应用实例,对,Outer,定义,Perfect H,相当于理想开路,在内部定义，用,Perfect H,覆盖,Perfect E,，用以在地平面上开孔,=,首先定义,Perfect E,将其中的局部定义为,Perfect H,PerfectH,定义的区域实际为自然边界条件，相当于在零厚度的金属平面上开孔,趋肤深度,趋肤深度,趋肤深度,f=1 GHz,铜的趋肤深度,=2.088,m,钛的趋肤深度,=10.97,m,趋肤深度正比于,1/f,趋肤深度正比于,to f,d=,趋肤深度,直流区域,:,d 3,趋肤深度,d,Finite Conductivity,参数,:,电导率和磁导率,Finite Conductivity is a lossy electrical conductor,E-field forced perpendicular,as with,Perfect E,However,surface impedance takes into account resistive and reactive surface losses,User inputs conductivity(in siemens/meter)and relative permeability(unitless),Used for non-ideal conductor analysis*,Finite Conductivity Boundary,Impedance,参数,:,电阻和电抗,ohms/square,Impedance,边界使用户定义的表面阻抗；,用于表示薄膜电阻,（,thin film resistors,）,用于表示电抗性负载,（,reactive loads,）,电抗不随频率变化，所以他不能表示一个频段内的“电容”或“电感”。,由需要的薄膜电阻值、宽度和长度计算设定的薄膜阻抗。,Length(,电流方向,),Width,=number of squares,Impedance per square=Desired Lumped Impedance,number of squares,EXAMPLE:Resistor in Wilkenson Power Divider,Resistor is 3.5 mils long(in direction of flow)and,4 mils wide.Desired lumped value is 35 ohms.,Layered Impedance,参数,:,:Surface Roughness,Layer,Thickness/Type and material,用于模拟由多个薄层构成的阻抗表面。它的作用与阻抗边界相同。均匀材料组成的边界。如在某种涂敷吸波材料散射特性的计算中，可以使用这种边界。,Radiation,Parameters:None,A,Radiation,boundary is an,absorbing boundary condition,used to mimic continued propagation beyond the boundary plane,Absorption is achieved via a,second-order impedance calculation,Boundary should be constructed correctly for proper absorption,Distance,:For strong radiators(e.g.antennas)no closer than,/4,to any structure.For weak radiators(e.g.a bent circuit trace)no closer than,/10,to any structure,Orientation,:The radiation boundary absorbs best when incident energy flow is,normal,to its surface,Shape,:The boundary must be,concave,to all incident fields from within the modeled space,Note boundary does not follow break at tail end of horn.Doing so would result in a convex surface to interior radiation.,Boundary is,/4 away from horn aperture in all directions.,Radiation,cont.,Radiation boundary absorption profile vs.incidence angle is shown at left,Note that absorption falls off significantly as incidence exceeds 40 degrees from normal,Any incident energy not absorbed is reflected back into the model,altering the resulting field solution!,Implication,:,For steered-beam arrays,the standard radiation boundary may be insufficient for proper analysis.,Solution,:,Use a,Perfectly Matched Layer(PML),construction instead.,Incorporation of PMLs is covered in the Advanced HFSS training course.Details available upon request.,Reflection of Radiation Boundary in dB,vs.Angle of Incidence relative to boundary normal(i.e.for normal incidence,=0),E,TM,Radiation,Symmetry,Parameters:Type(Perfect E or Perfect H),Symmetry,boundaries permit modeling of only a fraction of the entire structure under analysis,Two Symmetry Options:,Perfect E,:,E-fields are perpendicular to the symmetry surface,Perfect H,:,E-fields are tangential to the symmetry surface,Symmetry boundaries also have further implications to the Boundary Manager and Fields Post Processing,Existence of a Symmetry Boundary will prompt,Port Impedance Multiplier,verification,Existence of a symmetry boundary allows for near-and far-field calculation of the,entire,structure,Conductive edges,4 sides,This rectangular waveguide contains a symmetric propagating mode,which could be modeled using half the volume vertically.,Perfect E Symmetry(top),.or horizontally.,Perfect H Symmetry(left side),Symmetry,cont.,Geometric symmetry does not necessarily imply field symmetry for higher-order modes,Symmetry boundaries can act as,mode filters,As shown at left,the next higher propagating waveguide mode is,not,symmetric about the vertical center plane of the waveguide,Therefore,one,symmetry case is valid,while the other is not!,Implication:,Use caution when using symmetry to assure that real behavior in the device is not filtered out by your boundary conditions!,Perfect E Symmetry(top),Perfect H Symmetry(right side),TE20 Mode in WR90,Properly represented with Perfect E Symmetry,Mode can,not,occur properly with Perfect H Symmetry,Impedance Multiplier,Symmetry,Lumped RLC,Lumped RLC,参数,:Resistance,Inductance,和,Capacitance,；,输入的是并联电阻、电容或电感的实际值。,这个边界条件支持快速（,Fast,）扫频。,Master/Slave,Parameters:Coordinate system,master/slave pairing,and phasing,Master,and,Slave,boundaries are used to model a unit cell of a repeating structure,Also referred to as,linked boundaries,Master and Slave boundaries are always,paired,:one master to one slave,The fields on the slave surface are constrained to be identical to those on the master surface,with a phase shift.,Constraints,:,The master and slave surfaces must be of identical shapes and sizes,A,coordinate system,must be identified on the master and slave boundary to identify point-to-point correspondence,Unit Cell Model of End-Fire Waveguide Array,WG Port(bottom),Ground Plane,Perfectly Matched Layer,(top),Slave Boundary,Master Boundary,Origin,V-axis,U-axis,Screen Impedance,Screen Impedance,Screen Impedance,Perfect Matched Layer,（,PML,）,Parameters:Resistance,Uniform Thickness,Frequencies and Minimum Radiation Distance.,理想匹配层,(PML),boundary is fictitious material that fully absorb the electromagnetic fields impinging upon them.There are two types of PML applications:,PML Objects Accept Free Radiation if the PMLs terminate in free space.,PML Objects Continue Guided Waves if the PMLs terminate in a transmission line.,Guidelines for assigning PML boundaries,HFSS treats PMLs uniformly with regard to,thickness.If the PMLs in your design vary in thickness,create a separate PML group for each thickness.,You should manually create a PML when,The base object is curved.,The material of the corresponding base object touching the PML is not homogenous.,HFSS,中的缺省边界条件,与背景的交接面自动定义为,Outer,，即,Perfect E,良导体的表面自动定义为,Perfect E,或,Finite Conductivity,不同介质之间的交接面自动定义为自然边界条件,Natural,默认边界条件,HFSS,中的激励源,HFSS,中的端口,端口（,Ports,）,端口是一种特殊类型的边界条件。它允许能量通过端口进入或流出仿真模型。端口定义在一个,2,维平面上。解算器首先计算该平面的本征模式。平面的背面等效为一个界面相同的半无限长的波导。,激励类型,波端口,-,外部,端口背后是外表面或良导体。,波端口支持多模（例如，耦合线）和端口偏移；,计算通常的,S-Parameters,；,端口阻抗与频率有关，但在任何一个频率端口都是匹配的。,集中端口,内部,建议端口处于几何模型内部；,Recommended only for surfaces internal to geometric model,集中端口仅支持单模,(TEM),并且端口不能偏移；,端口阻抗,Zo,可以归一化到一个常数值。,HFSS,中的端口（续）,模式、反射和传播,一个特定信号的可以激励起,3,维场；,包含由高频结构不连续性产生的高次模反射,如果这些高次模被反射到激励端口或其它端口，与这些模式相关的,S,参数需要计算。,如果这些高次模在到达任何端口前由于衰减或不传输的凋落模衰落了，端口不计算这些模式的,S,参数。,波端口需要一段一定长度均匀横截面波导。,端口延伸和高次模问题,高次模传输问题,波端口中的简并模,Degenerate,modes have identical impedance,propagation constants,Port solver will arbitrarily pick one of them to be,mode(n),and the other to be,mode(n+1),Thus,mode-to-mode S-parameters may be referenced incorrectly,To enforce numbering,use a,polarize,the first mode to the line,OR,introduce a dielectric change to slightly perturb the mode solution and separate the degenerate modes,Example,:A dielectric bar only slightly higher in permittivity than the surrounding medium will concentrate the E-fields between parallel wires,forcing the differential mode to be dominant,If dielectric change is very small(approx.0.001 or less),impedance impact of perturbation is negligible,For parallel lines,a,virtual object,between them aids mode ordering.Note virtual object need not extend entire length of line to help at port.,In circular or square waveguide,use the calibration line to force(polarize)the mode numbering of the two degenerate TE11 modes.This is also useful because without a polarization orientation,the two modes may be rotated to an arbitrary angle inside circular WG.,端口阻抗定义,HFSS provides port characteristic impedances calculated using the,power-current,definition(Z,pi,),Incident power is known excitation quantity,Port solver integrates H-field around port boundary to calculate current flow,For many transmission line types,the,power-voltage,or,voltage-current,definition is preferred,Slot line,CPW:Z,pv,preferred,TEM lines:Z,vi,preferred,HFSS can provide these characteristic impedance values,as long as an,impedance line,is identified,The,impedance line,defines the line along which the E-field is integrated to obtain a voltage,For a Coax,the,impedance line,extends radially from the center to outer conductor(or vice versa).Integrating the E-field along the radius of the coaxial dielectric provides the voltage difference.,In many instances,the,impedance,and,calibration,lines are the same!,X-,波段波导中的传输模式,阻抗线和极化线,Impedance line and polarization line are optional in port setup.,They are located in the port and have a starting point and an end point.,Port=cross section,of waveguide,I and/or P Line,Integration Line,（积分线）,集中端口（,Lumped Port,）,Parameters:Mode Count,Calibration,Impedance,Polarization,A,port,is an aperture through which guided electromagnetic field energy is injected into a 3D HFSS model.,Lumped,Ports:Approximated field excitation is placed on the gap source port surface,Characteristic impedance is provided by the user during setup,入射波（,Incident Wave,）,入射波（,Incident Wave,）,Parameters:Poynting Vector,E-field Magnitude and Vector,Used for radar cross section(RCS)scattering problems.,Defined by Poynting Vector(direction of propagation)and E-field magnitude and orientation,Poynting and E-field vectors must be orthogonal.,Multiple plane waves can be created for the same project.,If no ports are present in the model,S-parameter output is not provided,Analysis data obtained by post-processing on the Fields using the Field Calculator,or by generating RCS Patterns,In the above example,a plane incident wave is directed at a solid made from dielectrics,to view the resultant scattering fields.,电压源和电流源,Example Voltage Drop(between trace and ground),Example Current Source(along trace or across gap),Parameters:Direction and Magnitude,A,voltage drop,would be used to excite a voltage between two metal structures(e.g.a trace and a ground),A,current source,would be used to excite a current along a trace,or across a gap(e.g.across a slot antenna),Both are ideal source excitations,without impedance definitions,No S-Parameter Output,User applies condition to a 2D or 3D object created in the geometry,Vector identifying the direction of the voltage drop or the direction of the current flow is also required,本征模的边界与源,An,Eigenmode,solution is a direct solution of the resonant modes of a closed structure,As a result,some of the sources and boundaries discussed so far are,not,available for an Eigenmode project.These are:,All Excitation Sources:,Wave Ports and Lumped Ports,Voltage Drop and Current Sources,Magnetic Bias,Incident Waves,The only unavailable boundary type is:,Radiation Boundary,A,Perfectly Matched Layer,construction is possible as a replacement,磁偏置,Parameters:Magnitude and Direction,or,Externally Provided,The,magnetic bias,source is used only to provide internal biasing H-field values for models containing nonreciprocal(ferrite)materials.,Bias may be uniform field(enter parameters directly in HFSS).,Parameters are direction and magnitude of the field,.or bias may be non-uniform(imported from external Magnetostatic solution package),Ansofts,3D EM Field Simulator,provides this analysis and output,Apply source to selected 3D solid object(e.g.ferrite puck),波端口与集中参数端口的选择,什么时候你选择,Lumped,Port,而不是,Wave Port,呢,?,当模型中导线之间的间隙太小时；,当使用,Wave port,很难确定一个端口的参考定位时；,当你希望使用电压降，而不是,S,参数作为输出时。,Lumped Ports(blue),端口尺寸,A port is an,aperture,through which a guided-wave,mode,of some kind propagates,For transmission line structures entirely enclosed in metal,port size is merely the waveguide interior carrying the guided fields,Rectangular,Circular,Elliptical,Ridged,Double-Ridged Waveguide,Coaxial cable,coaxial waveguide,squareax,Enclosed microstrip or suspended stripline,For unbalanced or non-enclosed lines,however,field propagation in the air around the structure must also be included,Parallel Wires or Strips,Stripline,Microstrip,Suspended Stripline,Slotline,Coplanar Waveguide,etc.,A Coaxial Port Assignment,A Microstrip Port Assignment(includes air above substrate),微带线,Microstrip Port Sizing Guidelines,Assume width of microstrip trace is,w,Assume height of substrate dielectric is,h,Port Height Guidelines,Between 6,h,and 10,h,Tend towards upper limit as dielectric constant drops and more fields exist in air rather than substrate,Bottom edge of port coplanar with the upper face of ground plane,(If real structure is enclosed lower than this guideline,model the real structure!),Port Width Guidelines,10,w,for microstrip profiles with,w,h,5,w,or on the order of 3,h,to 4,h,for microstrip profiles with,w h,w,h,6h to 10h,10w,w,h,or,5w(3h to 4h),w h,Note:Port sizing guidelines are,not,inviolable rules true in all cases.For example,if meeting the height and width requirements outlined result in a rectangular aperture bigger than,/2 on one dimension,the substrate and trace may be ignored in favor of a waveguide mode.,When in doubt,build a simple ports-only model and test.,带状线,Stripline Port Sizing Guidelines,Assume width of stripline trace is,w,Assume height of substrate dielectric is,h,Port Height Guidelines,Extend from upper to lower groundplane,h,Port Width Guidelines,8,w,for microstrip profiles with,w,h,5,w,or on the order of 3,h,to 4,h,for microstrip profiles with,w h,Boundary Note:Can also make side walls of port,Perfect H,boundaries,w,h,8w,w,h,or,5w(3h to 4h),w h,槽线,Slotline Port Guidelines,Assume slot width is,g,Assume dielectric height is,h,Port Height:,Should be at least 4,h,or 4,g,(larger),Remember to include air below the substrate as well as above!,If ground plane is present,port should terminate at ground plane,Port Width:,Should contain at least 3,g,to either side of slot,or 7,g,total minimum,Port boundary,must,intersect both side ground planes,or they will float and become signal conductors relative to outline ground,g,Approx 7g minimum,h,Larger of 4h or 4g,共面线,CPW Port Guidelines,Assume slot width is,g,Assume dielectric height is,h,Assume center strip width is,s,Port Height:,Should be at least 4,h,or 4,g,(larger),Remember to include air below the substrate as well as above!,If ground plane is present,port should terminate at ground plane,Port Width:,Should contain 3-5,g,or,3-5,s,of the side grounds,whichever is larger,Total about 10,g or,10,s,Port outline,must,intersect side grounds,or they will float and become additional signal conductors along with the center st