【正文】 e air below the substrate as well as above! ? If ground plane is present, port should terminate at ground plane ? Port Width: ? Should contain 35g or 35s of the side grounds, whichever is larger ? Total about 10g or 10s ? Port outline must intersect side grounds, or they will ?float? and bee additional signal conductors along with the center strip. Larger of approx. 10g or 10s s h Larger of 4h or 4g g 273 CPW Wave Ports: Starting Remendations Wave Port Size The standard remendation for most CPW wave ports is a rectangular aperture Port width should be no less than 3 x the overall CPW width, or 3 x (2g + w) Port height should be no less than 4 x the dielectric height, or 4h Wave Port Location The wave port should be centered horizontally on the CPW trace If the port is on GCPW, the port bottom edge should lie on the substrate bottom ground plane If the port is on ungrounded CPW, the port height should be roughly centered on the CPW metal layer Wave Port Restrictions As with all wave ports, there must be only one surface normal exposed to the field volume Port should be on exterior model face, or capped by a perfect conductor block if internal The wave port outline must contact the side grounds (all CPWs) and bottom ground (GCPW) The wave port size should not exceed lambda/2 in any dimension, to avoid permitting a rectangular waveguide modal excitation 3 (2g + w) w h 4h minimum g Ungrounded CPW (Port height centered on trace) Grounded CPW (Port height begins at lower ground) 3 (2g + w) w h 4h minimum g 274 HFSS Ports: Sizing Handbook V。 Thickness/Type。 217 218 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 secondorder impedance calculation ? Boundary should be constructed correctly for proper absorption ? Distance: For strong radiators (. antennas) no closer than ?/4 to any structure. For weak radiators (. 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. 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: Resista