微波工程CAD-电子科技大学课件-05-边界与端口设置.ppt

边界与端口设置,电子科技大学 贾宝富,HFSS Boundary List,Perfect E and Perfect H/Natural Ideal Electrically or Magnetically Conducting Boundaries ‘Natural’ denotes Perfect E ‘cancellation’ behavior Finite Conductivity Lossy Electrically Conducting Boundary, with user-provided conductivity and permeability Impedance Used for simulating ‘thin film resistor’ materials, with user-provided resistance and reactance in /Square Layered Impedance Radiation An ‘absorbing boundary condition,’ used at the periphery of a project in which radiation is expected such as an antenna structure Symmetry A boundary which enables modeling of only a sub-section of a structure in which field symmetry behavior is assured. “Perfect E” and “Perfect H” subcategories Lumped RLC Master and Slave ‘Linked’ boundary conditions for unit-cell studies of infinitely replicating geometry (e.g. a slow wave circuit & an antenna array) PML (Perfect Match Layer),HFSS Boundary Descriptions: Perfect E and Perfect H/Natural,Parameters: None Perfect E is a perfect electrical conductor* Forces E-field perpendicular to the surface Represent metal surfaces, ground planes, ideal cavity walls, etc. Perfect H is a perfect magnetic conductor Forces H-field perpendicular to surface, E-field tangential Does not exist in the real world, but represents useful boundary constraint for modeling Natural denotes effect of Perfect H applied on top of some other (e.g. Perfect E) boundary ‘Deletes’ the Perfect E condition, permitting but not requiring tangential electrical fields. Opens a ‘hole’ in the Perfect E plane,Perfect E Boundary*,Perfect H Boundary,‘Natural’ Boundary,,,,,,,,,,,,,,,,,,,,,,,,,,*NOTE: When you define a solid object as a ‘perf_conductor’ in the Material Setup, a Perfect E boundary condition is applied to its exterior surfaces!!,Perfect H for 2D Aperture (I),Monopole Over a Ground plane,Perfect H Surface Interior to the Problem Space Behaves Like an Infinitely Thin 2D Aperture,,Perfect H,Perfect H for 2D Aperture (II),Small Hole Can be “Cut” in infinitely Thin Septum Between the Upper and Lower Guide Using a Perfect H Surface at the Hole,,,,Perfect H,HFSS Boundary Descriptions: Finite Conductivity,Parameters: Conductivity and Permeability 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,,,,,,,,,,,,,,,,HFSS Boundary Descriptions: Impedance,Parameters: Resistance and Reactance, ohms/square (/) Impedance boundary is a direct, user-defined surface impedance Use to represent thin film resistors Use to represent reactive loads Reactance will NOT vary with frequency, so does not represent a lumped ‘capacitor’ or ‘inductor’ over a frequency band. Calculate required impedance from desired lumped value, width, and length Length (in direction of current flow)  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.,HFSS Boundary Descriptions: Layered Impedance,Parameters: Surface Roughness; Layer; Thickness/Type; Materials 用于定义多层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HFSS Boundary Descriptions: 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.,HFSS Boundary Descriptions: 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),,,,,ETM,θ。