【正文】 ed 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 subsection 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 unitcell studies of infinitely replicating geometry (. a slow wave circuit an antenna array) ? PML (Perfect Match Layer) 26 邊界條件定義的覆蓋 27 HFSS Boundary Descriptions: Perfect E and Perfect H/Natural ? Parameters: None ? Perfect E is a perfect electrical conductor* ? Forces Efield perpendicular to the surface ? Represent metal surfaces, ground planes, ideal cavity walls, etc. ? Perfect H is a perfect magic conductor ? Forces Hfield perpendicular to surface, Efield 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 (. 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 larperpendicuE? continuousE? parallelE?*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!! 28 Perfect E應用實例 29 Perfect H應用實例 210 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 211 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 212 Finite Conductivity ? 趨膚深度 1=f? ? ? ?213 DC versus AC 214 HFSS Boundary Descriptions: Finite Conductivity ? Parameters: Conductivity and Permeability ? Finite Conductivity is a lossy electrical conductor ? Efield 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 nonideal conductor analysis* Finite Conductivity Boundary gattenuatinlarperpendicuE ,?215 HFSS Boundary Descriptions: Impedance ? Parameters: Resistance and Reactance, ohms/square (??/ ) ? Impedance boundary is a direct, userdefined 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 mils long (in direction of flow) and 4 mils wide. Desired lumped value is 35 ohms. squar eNRRNlu m p eds h eet /40875.35 ??????216 HFSS Boundary Descriptions: Layered Impedance ? Parameters: Surface Roughness。如在某種涂敷吸波材料散射特性的計算中，可以使用這種邊界。 Back side covered with Solid Cap 248 HFSS Ports: Mode Count ? Ports should solve for all propagating modes ? Ignoring a mode which does propagate will result in incorrect Sparameters, by neglecting modetomode conversion which could occur at discontinuities ? However, requesting too many modes in the full solution also negatively impacts analysis ? Modes in cutoff are more difficult to calculate。 N modes total for N conductors and one ground reference [odd mode shown at right] Lumped Ports from trace to ground neglect coupling behavior and are no longer appropriate Use multimode Wave Port Terminal line assignments can permit extraction of Sparameters referenced to each ‘trace’ 276 Phase Calibration 277 Impedance Definitions 。 Lumped Ports (blue) 267 HFSS Ports: Sizing ? A port is an aperture through which a guidedwave 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, DoubleRidged Waveguide ? Coaxial cable, coaxial waveguide, squareax, Enclosed microstrip or suspended stripline ? For unbalanced or nonenclosed 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) 268 HFSS Ports: Sizing, cont. ? The port solver only understands conductive boundaries on its borders ? Electric conductors may be finite or perfect (including Perfect E symmetry) ? Perfect H symmetry also understood ? Radiation boundaries around the periphery of the port do not alter the port edge termination!! ? Result: Moving the port edges too close to the circuitry for open waveguide structures