[第六课]HFSS求解类型及激励说明

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Ansys官方Online Help中给出的求解类型说明如下： mI'&!@WG  
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Solution Types $i@I|y/  
Before creating the design, you must specify the type of solution that you want HFSS to calculate. The following solution types are available: >!Dp'6
 
1.DrivenModal nrg$V>pD  
2.DrivenTerminal eY[kUMo  
3.Transient "h-ZwL  
4.Eigen mode U^8S@#1Q  
5.Characterisic mode NG_7jZzXA9  
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Driven Solutions `BVXF#sb  

Modal

For calculating the mode-based S-parameters of passive, high-frequency structures such as microstrips, waveguides, and transmission lines which are "driven" by a source, and for computing incident plane wave scattering. Network Analysis is the default and functions as before.

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+U)4V}S)   Terminal

For calculating the terminal-based S-parameters of passive, high-frequency structures with multi-conductor transmission line ports which are "driven" by a source. 055C1RV%   This solution type results in a terminal-based description in terms of voltages and currents. Some modal data is also available. 0f#xyS 3   Network Analysis is the default and functions as before.

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+kN,OK~   Transient

For calculating problems in the time domain. It employs a time-domain ("transient") solver. For Transient your choice of Composite Excitation or Network Analysis affects the options for the setup. If you select Network Analysis the setup includes an Input Signal tab for the simulation. 'xL Xj>   Typical transient applications include, but are not limited to: Simulations with pulsed excitations, such as ultra-wideband antennas, lightning strikes, electro-static discharge; field visualization employing short-duration excitations; time-domain reflectometry.

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Eigenmode

For calculating the eigenmodes, or resonances, of a structure. The Eigenmode solver finds the resonant frequencies of the structure and the fields at those resonant frequencies. Eigenmode designs cannot contain design parameters that depend on frequency, for example a frequency-dependent impedance boundary condition.

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Characteristic Mode

This option is used for calculating the characteristic modes of a structure. The solution reports the Number of Modes, the characteristic angle and current (amp/meter), the modal significance and quality factor, and the voltage per port based in edit sources weighing. The Selecting Characteristic Modes changes the Solution Setup criteria and dialog. Xdf4%/Op   You specify the minimum modal significance (default 0.02). Convergence is based on Max E rather than Max S (default (0.02). YSrjg|k*   Only discrete sweeps are supported. Only the CMA solver is supported. Only lossless boundaries are allowed. Finite conductivity boundaries are allowed but are converted to lossless. The half-space boundary is not allowed.

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For open region problems (typically antennas), you can choose Auto-Open Region. The option is available for Driven modal, terminal and transient solution type. This automatically creates an open region and a predefined Analysis setup for the project. You can select whether the region is Radiation, FE-BI, or PML. This simplifies the design process. If you do not choose Auto-Open Region, you must create an airbox and then assign a radiation boundary, either manually, or using the Create Open Region command. (&Rql7](8  
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For most HFSS simulations, the Driven Modal solution type is used. For simulations that deal with signalintegrity, Driven Terminal solution type is preferred; such problems generally include transmission lines with single as well as multiple conductors. F^Bk @  
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Simulations that use the drivenmodal solution type yield S-matrix solutions that are expressed in terms of theincident and reflected powers of transmission line modes. The S-matrix that is produced by the driven terminal solution type, however, is expressed in termsof terminal voltages and currents. .yDGwLry  
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For example, if HFSS is used to model a pair of coplanar, parallel microstrip transmission lines, a driven modal solution yields results in terms of the even and odd modes that propagate on the structure whereas a driven terminal mode solution generates the common and differential mode results.The design below represents a driven terminal problem of a differential pair via model with a pair of lines that transition through the vias to a pair of striplines on a lower layer. The two microstrip lines and the striplines are each assigned a terminal in the coupled microstrip port. The conductors are copper and a radiation boundary is applied to the airbox. The design was solved at 4.38 GHz and the electric field plots on the surfaces of the wave ports with terminals are shown in the figure below. 1nw\?r2  

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                Driven Terminal Problem of a Differential Pair Via Model )|_L?q#w!'  
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The figure below represents a driven modal problem of a connector between a coaxial and microstrip line. XOLE=zdSp  

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                  Connector between coaxial and microstrip line 3-&~jm~"  
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The eigenmode solver provides results in terms of eigen modes or resonances of a given structure. This solver provides the frequencies of the resonances as well as the fields at a particular resonance. U>OAtiq JX  
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The Transient solution is used for calculating problems in the time domain. They are applicable for simul .. BeN]D  
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激励形式如下图： mhMTn*9  
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Excitations are sources of electromagnetic fields in the design. HFSS has various options to generate incident fields that interact with a structure to produce the total fields. |&MOus#v  
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1.Wave port x21XzGLY|}  
Represents the external surface through which a signalenters or exits the geometry. It is effectively a semi-infinite waveguide attached to the model. This waveguide has the same cross-section and material properties as the port. Wave ports are placed on this interface to provide ameans to link the model device to the external world. l>T]Y  
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2.Lumped port ,*sKr)9)  
Representsan internal surface through which a signal enters or exits the device. It is effectively a lumped element for exciting the device and measuring S-parameters. 6st^-L  

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3.Floquet port ub2B!6f a  
Floquet Ports are used exclusively with periodic structures defined by Master-Slave boundaries. They contain plane waves whose frequency, phasing, and the geometry of the periodic structure determine the propagation direction. Chief examples are planar phased arrays and frequency selective surfaces when these may be idealized as infinitely large and analyzed using a unit cell. ezA&cZ5  
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4.Terminal yb-4[C:i  
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Aterminal is defined by one or more conductors in contact with the port. HFSStreats microwave structures as a black box that may have one or more terminals,each of which has a voltage/current pair. Terminals are assignedautomatically. ~ %Ij5PD  
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5.Incident wave [M#(su0fv  
Representsa propagating wave impacting the geometry. fjMmlp  
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6.Linked wave braI MIQ`  
Represents a FarField Wave or NearField Wave or Cable Network. &srD7v9M8  
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7.Voltage Z?qc4Cg  
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Represents a constant electric field across feed points. 5'[yw:P-8  
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8.Current 3
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Represents a constant electric current across feed points. L+lX
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9.Magnetic bias As??_=>4  
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Used to define the net internal field that biases a saturated ferrite object. sfp.>bMj  
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Wave Ports EJ.oq*W!*J  
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The objective of this section is to provide a thorough description of wave ports. You must know what a wave port represents in HFSS to understand its capability. To illustrate we will use an HFSS model of a coaxial bend as an example where the wave port is assigned on the outer face. (8qMF{  
HFSS treats this wave port as though a waveguide or a transmission line of the exact same cross-section (in this case the cross-section of the coaxial bend) and material properties, comes from infinity and ends at the port as shown in the figure below. 7UejK r  

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The properties and the cross section of the waveguide or the transmission line determine the natural field patterns called modes that excite the model and the HFSS port solver determines the propagating modes that the waveguide or transmission line will carry. tlV>  
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Note: A wave port can be placed internal to a model as long as it is backed by a PEC object.  nk>  
By default, the interface between all 3D objects and the background is a perfect E boundary through which no energy may enter or exit. Wave ports are typically placed on this interface to provide a window that couples the model device to the external world. '+?AaR&p?  
HFSS assumes that each wave port you define is connected to a semi-infinitely long waveguide that has the same cross-section and material properties as the port. When solving for the S-parameters, HFSS assumes that the structure is excited by the natural field patterns (modes) associated with these cross-sections. The 2D field solutions generated for each wave port serve as boundary conditions at those ports forthe 3D problem. In addition to serving as a boundary condition, a wave portalso supplies port impedances and propagation constants that are useful indescribing waveguides or transmissi on lines. ,u#uk7V  
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A wave port is restricted to resideat an external boundary of a 3D problem. In some instances, it makes sense toget around this restriction by defining a wave port in the interior of a 3Ddomain by capping the wave port surface with a PEC object. In doing this, ineffect the wave port is viewed as residing at the external boundary of a 3Dproblem. However, in general lumpedports shouldbe used when defining ports in the interior of a 3D domain. hq6fDR
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Lumped Ports .lu:S;JSnS  
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Lumped ports support single mode excitations when S-parameters have to be extracted at internal locations of amodel. It can also be used to represent a terminal of a passive component to be subsequently optimized in a circuit simulator using S-matrix description of themodel. 2rHw5Wn]~  
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For lumped ports all edges that do not touch metal are treated as perfect H boundaries. From this definition the resulting field distribution on the lumped port geometry is solved with thewave port solver. For a rectangular lumped port this results in electric fields orientated parallel to these perfect H sides. See figures below. The physical geometry of the rectangular lumped port carries current with the corresponding H fields resulting in parasitic inductance. For these same rectangular lumped ports the parasitic inductance can be calibrated out of the s-parameter response with the deembedding option for lumped ports. Okk[}G)  
Note: When a lumped port is used as an internal port, the conducting cap required for a traditional wave port must be removed to prevent short-circuiting the source. KsYT3  

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Lumped ports resemble wave ports, but can be located internally and have a complex user-defined reference impedance. Lumped ports are restricted to single mode ports and the S-parameters are always based on the user defined reference impedance. This mainly because no transmission line is being modeled in the interior domain which suggests an interpretation of the lumped port as a measurement probebeing connected to the surface of the lumped port with the reference impedance specified by the user. G],+?E_,  
When a lumped port is used internal to a 3D problem, it makes sense to place the lumped port at a location where the field distribution would approximately be the same as the dominant mode ofthe port definition in the absence of the lumped port. A typical example of this is when a rectangular port is drawn between a conductor trace and a ground plane with the face oriented perpendicular to both conductors. The port mode resulting from this case is a parallel plate mode which will often closely resemble the field distribution at that location in the absence of the port. >V(>2eD'S  
A perhaps unsuspected result of using a complex reference impedance is that the S-parameters can be greater than one even for a passive device. Wm:3_C +j  
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Terminals 0@AK  
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HFSS can categorize microwave structures in terms of a black-box that relates voltages and currents flowing in and out of a given structure. The black-box has several terminals, each with an associated voltage/current pair. In HFSS, these terminals reside inside wave ports that enable post processing of a modal representation of the black-box into the terminal representation. ,}{E+e5jh7  
When a terminal project is solved using HFSS, the number of modes for a port is determined by the number of terminals touching the port. If N+1 distinct conductors touch the port, there are N terminals and one reference conductor usually referred to as ground. 2#+@bk>^{  
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Floquet Ports [wu%t8O2  
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The Floquet port in HFSS is used exclusively with planar-periodic structures. Chief examples are planar phased arrays and frequency selective surfaces when these may be idealized as infinitely large. The analysis of the infinite structure is then accomplished by analyzing a unit cell. Linked boundaries most often form the side walls of a unit cell, but in addition, at least one "open'' boundary condition representing the boundary to infinite space is needed. The Floquet port is a specialized boundary condition to handle this case. my} P\r.  
The Floquet port is closely related to a wave port in that a set of modes, here "Floquet modes", is used to represent the fields on the port boundary. Fundamentally, Floquet modes are plane waves with propagation direction set by the frequency and geometry of the periodic structure. Just like Wave modes, Floquet modes have propagation constants and experience cut-off at a sufficiently low frequency. .9ROa#7U;n  
When a Floquet port is present, HFSS performs a modal decomposition that gives additional information on the performance of the radiating structure. As in the case of a wave port, this information is cast in the form of an S-matrix interrelating the Floquet modes. In fact, if Floquet ports and wave ports are simultaneously present, the S-matrix will interrelate all wave modes and all Floquet modes in the model. Floquet ports can be combined with lumped ports, but not with terminal ports.

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Incident Waves X=hgLK^3<,  
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An incident field is the electromagnetic field in the absence of any scatterers. We suppose that the incident field is present everywhere and it comes from a source residing in some location. The source can even be another HFSS project or an SIwave project. ^Pf&C0xXv  
Incident waves can be of the following types: z>{KeX:  
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Hertzian-Dipole Wave W>~%6K>p  
Cylindrical Wave <d^7B9O?&w  
Gaussian Beam KH7]`CU  
Linear Antenna Wave GKSy|z  
For incident analytical waves (plane waves through linear antenna waves) HFSS supports two basic methods: scattered field formulation and total field formulation. +wSm6*j7=  
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The total field formulation is useful for viewing weak total fields while scattered field formulation is useful for viewing weak scattered fields. =gn}_sKNE  
For near field and far field waves we are merely specifying the fields on the radiation surfaces. So, we cannot view only the total fields. +,[3a%c)H  

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Far Field Wave 5L F/5`  
A far field wave originates at a distance several wavelengths from the computational domain. Far field values are defined on the surface of a unit sphere. YydA6IK4  
When you use a Far Field link, the origin of the global coordinate system of the source project should be in the phase center of the antenna. QIQfI05  
Near Field Wave $*k)|4
 
A Near Field wave source is close enough to the design for near field effects to occur, typically within one wave length. Objects in the near field wave source project should NOT be too close to the radiation surface where a Near Field Wave pings in. Near field waves tend to have both evanescent and propagating content. UVrQV$g!  
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A Cable Network is linked field excitation used as part an overall cable solution implemented as dynamic data links between HFSS, 2D Extractor, and Circuit. K}x_nW  
Each cable harness in HFSS is modeled as a single external field source based on quasi-static simulation of each cable cross section in 2D Extractor and an analysis of the cable network in Circuit. The magnitude and distribution of the fields along each cable section is determined by the voltages and currents at the ends of each section, and then transmission line model is applied to propagate these fields along the cable length. Y,C=@t@_  
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This HFSS design is a target of a new “Cable Field” coupled field datalink. The source of the datalink is the Circuit design that models the cable network. Each Cable Network will be treated as a single source and can be scaled at Edit Sources. +IrZ ;&oy  

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Voltage Sources *if`/N-q(m  
A voltage source in HFSS can be defined on surface located anywhere in the 3D problem space, but it typically makes sense to place the source on a surface between two conductors such that a user defined total voltage is maintained between the conductors. w0lT%CPx  
A voltage source is implemented in HFSS by forcing the electric field on the source surface to maintain a user-specified voltage drop along the voltage line. You can specify any surface as the source surface, but the prescribed field pattern is best suited for rectangular planar surfaces or non-planar surfaces obtained from the side wall surface of cylinders with uniform cross sections such as a circular cylinder. The enforced electric field pattern is obtained by projecting a static uniform field onto the source surface with the electric field in the direction of the user defined voltage line. <RXwM6G2  
A voltage source cannot be used to extract S-parameters. For S-parameter computations of an HFSS design involving a mixture of ports and voltage sources, all the voltage sources are shorted by treating the voltage source surface as a perfect electric conductor. 2g-` ]Vqb  

Current Sources F
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A current source in HFSS can be defined on a surface located anywhere in the 3D problem space, but it typically makes sense to place the source on a surface between two conductors such that it injects the user defined total current onto the conductors. x+8_4>,>Y7  
A current source cannot be used to extract S-parameters. For S-parameter computations of an HFSS design involving a mixture of ports and current sources, all the current sources are kept opened by treating the current source surface as a natural boundary condition where no special behavior of the electric field is explicitly enforced. .IBp\7W!?E