【正文】 drop would be used to excite a voltage between two metal structures (. a trace and a ground) ? A current source would be used to excite a current along a trace, or across a gap (. across a slot antenna) ? Both are ?ideal? source excitations, without impedance definitions ? No SParameter 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 263 Sources/Boundaries and Eigenmode Solutions ? 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 ? Magic Bias ? Incident Waves ? The only unavailable boundary type is: ? Radiation Boundary ? A Perfectly Matched Layer construction is possible as a replacement 264 HFSS Source Descriptions: Magic Bias ? Parameters: Magnitude and Direction or Externally Provided ? The magic bias source is used only to provide internal biasing Hfield 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 nonuniform (imported from external Magostatic solution package) ? Ansoft?s 3D EM Field Simulator provides this analysis and output ? Apply source to selected 3D solid object (. ferrite puck) 265 HFSS Ports: A Detailed Look ? The Port Solution provides the excitation for the 3D FEM Analysis. Therefore, knowing how to properly define and create a port is paramount to obtaining an accurate analysis. ? Incorrect Port Assignments can cause errors due to... ? ...Excitation of the wrong mode structure ? ...Bisection by conductive boundary ? ...Unconsidered additional propagating modes ? ...Improper Port Impedance ? ...Improper Propagation Constants ? ...Differing phase references at multiple ports ? ...Insufficient spacing for attenuation of modes in cutoff ? ...Inability to converge scattering behavior because too many modes are requested ? Since Port Assignment is so important, the following slides will go into further detail regarding their creation. 266 HFSS Port Selection: Wave Port or Lumped Port? ? 什么時候你選擇 Lumped Port 而不是 Wave Port呢 ? ? 當模型中導線之間的間隙太小時； ? 當使用 Wave port很難確定一個端口的參考定位時； ? 當你希望使用電壓降，而不是 S參數(shù)作為輸出時。 Layer。 Inductance。 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 。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。 Materials ? 用于定義多層均勻材料組成的邊界。 Lumped Ports ? Lumped ports behave differently from Wave Ports ? Any port edge not in contact with metal structure or another port assumed to be a Perfect H conductor ? Lumped Port Sizing (microstrip example): ? “Striplike”: [RECOMMENDED] No larger than necessary to connect the trace width to the ground ? “Wavelike”: No larger than 4 times the strip width and 3 times the substrate height ? The Perfect H walls allow size to be smaller than a standard port would be ? However, in most cases the striplike application should be as or more accurate ? Further details regarding Lumped Port sizing available as a separate presentation Perfect H Perfect H Perfect E Perfect E Perfect H Perfect H Perfect E Perfect H 275 HFSS Port Selection Example: Parallel Traces Spaced by 8 or more times Trace Width Inputs sufficiently isolated that no coupling behavior should occur Sufficient room for Wave port apertures around each trace Use Wave Ports as shown Spaced by 4 – 8 times Trace Width Inputs still fairly isolated, little to no coupling behavior should occur Insufficient room for Wave port apertures around each trace without clipping fringing fields Use Lumped Ports as shown Spaced by less than 4 times Trace Width Traces close enough to exhibit coupling Even and Odd modes possible。 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 Scree