【正文】 rbs 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. 219 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 steeredbeam 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. 1 0 0 8 0 6 0 4 0 2 0020Reflection Coefficient (dB)0 10 20 30 40 50 60t h e t a ( d e g )R e f l e c t i o n C o e f f i c i e n t ( d B )70 80 90Reflection of Radiation Boundary in dB, vs. Angle of Incidence relative to boundary normal (. for normal incidence, ? = 0) ETM θ 220 Radiation 221 HFSS Boundary Descriptions: 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 : Efields are perpendicular to the symmetry surface ? Perfect H : Efields 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 farfield 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) 222 HFSS Boundary Descriptions: Symmetry, cont. ? Geometric symmetry does not necessarily imply field symmetry for higherorder 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 223 Impedance Multiplier 224 Symmetry 225 Symmetry 226 Lumped RLC 227 HFSS Boundary Descriptions: Lumped RLC ? Parameters: Resistance。 Inductance。 Capacitance 228 229 HFSS Boundary Descriptions: Master/Slave Boundaries ? 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 pointtopoint correspondence Unit Cell Model of EndFire Waveguide Array WG Port (bottom) Ground Plane Perfectly Matched Layer (top) Slave Boundary Master Boundary Origin Vaxis Uaxis 230 Screen Impedance 231 Screen Impedance 232 Screen Impedance 233 HFSS Boundary Descriptions: PML 由物體表面創(chuàng)建PML層 234 HFSS Boundary Descriptions: PML 235 HFSS Boundary Descriptions: PML 由三維物體創(chuàng)建PML層 236 HFSS Boundary Descriptions: PML 237 HFSS中的缺省邊界條件 238 默認(rèn)邊界條件 239 HFSS Source List（ HFSS中的激勵(lì)源類型） 240 HFSS中的端口類型 241 Wave Port 表面 242 243 Wave Ports 位置 244 端口延伸和高次模問題 245 高次模傳輸問題 246 HFSS Ports: Spacing from Discontinuities ? Structure interior to the modeled volume may create and reflect nonpropagating modes ? These modes attenuate rapidly as they travel along the transmission line ? If the port is spaced too close to a discontinuity causing this effect, the improper solution will be obtained ? A port is a ?matched load? as seen from the model, but only for the modes it has been designed to handle ? Therefore, unsolved modes incident upon it are reflected back into the model, altering the field solution ? Remedy: Space your port far enough from discontinuities to prevent nonpropagating mode incidence ? Spacing should be on order of port size, not wavelength dependent Port Extension 247 HFSS Ports: SingleDirection Propagation ? Wave ports must be defined so that only one