Changes

[[File:RFSpice_Screen.png|thumb|400px|]]You can use [[RF.Spice A/D]] is an enhanced superset of EMAG Technologies' older [[B2.Spice A/D]] application with an extensive library of RF devices that include S-parameter-based [[Multiport Networks|multiport networks]] and a variety of generic and physical transmission line types. You can use [[RF.Spice]] to simulate or design distributed analog and mixed-mode circuits at high frequencies. RF circuit analysis, by nature, is an AC analysis that you typically run at high frequencies ranging from tens of Megahertz to tens of Gigahertz. At such high frequencies, the dimensions of your circuit may become comparable in order of magnitude to the wavelength, when wave retardation effects start to appear. In other words, your circuit starts to act like a distributed structure rather than a lumped circuit where signals propagate instantaneously. In the analysis of a low frequency circuit, two nodes that are connected to each other through a wire are assumed to have equal potentials or identical voltages. In RF circuits, however, parts and devices are connected to one another using transmission line segments, which introduce additional phase shifts depending on their electrical lengths and may also alter the voltages and currents at different points of the circuit due to impedance mismatch.

<table><tr><td> [[File:RFSpice_Screen.png|thumb|left|720px|RF circuit analysis, by nature, is an AC analysis that you typically run at high frequencies ranging from tens of Megahertz to tens of Gigahertz. At such high frequencies, the dimensions of your circuit may become comparable simulation in order of magnitude to the wavelength, when wave retardation effects start to appearRF. In other words, your circuit starts to act like a distributed structure rather than a lumped circuit where signals propagate instantaneously. In the analysis of a low frequency circuit, two nodes that are connected to each other through a wire are assumed to have equal potentials or identical voltages. In RF circuits, however, parts and devices are connected to one another using transmission line segments, which introduce additional phase shifts depending on their electrical lengths and may also alter the voltages and currents at different points of the circuit due to impedance mismatchSpice A/D. ]]</td></tr></table>

[[RF.Spice A/D]] uses the same Berkeley SPICE and XSPICE simulation engines of its forerunner [[B2.Spice A/D]]. In other words, the high frequency AC analysis is carried out by the same analog and mixed-mode SPICE simulation engines based on nodal admittance analysis, which have been enhanced with additional RF simulation capabilities. As a result, you can mix the RF devices in your circuits with all the other analog and mixed-mode devices of [[B2.Spice A/D]]. You can also mix transmission-line-type RF devices with digital parts and perform mixed-mode time domain simulations.

The concepts of [[Transmission Lines|transmission lines]] and [[Multiport Networks|multiport networks]] are integral to any RF simulation. From a simulation point of view, an RF circuit is made up of a collection of [[Multiport Networks|multiport networks]] that are interconnected via [[Transmission Lines|transmission lines]] segments or components. If the input of your circuit is connected to a source and its output is connected to a load, then you can compute all the voltages and currents at all various circuit nodes, some of which may serve as external or internal ports of your circuit. Or you can calculate the port characteristics of the overall network by designating input and output ports to your RF circuit.

All the RF devices of [[RF.Spice A/D]] can be divided into two groups: devices based on transmission line models, and devices based on multiple networks. [[RF.Spice]]'s transmission line models are enhanced versions of SPICE's standard LTRA model. The transmission-line-based devices typically utilize a combination of LTRA and passive RLC models. [[Multiport Networks|Multiport networks]] are characterized and modeled based on their frequency-domain scattering (S) [[parameters]]. The S-[[parameters]] are tabulated as a function of frequency, and their values are interpolated in between the frequency samples. [[RF.Spice A/D]] performs an AC analysis of these RF devices by converting their S-[[parameters]] to Y-[[parameters]] and using them in conjunction with SPICE’s nodal admittance matrix formalism. The S-parameter-based RF devices of [[RF.Spice A/D]] are primarily intended for use in two types of [[tests]]:

{{Note | S-parameter-based RF devices do not work with “Live Simulation” or Transient Test as their models typically contain S-[[parametersImage:Tutorial_icon.png|40px]] at high frequencies only'''[[RF.}}Spice_A/D#RF_Tutorial_Lessons| RF.Spice A/D RF Tutorial Lessons Gateway]]'''

{{Note | S-parameter-based RF devices do not work with “Live Simulation” or Transient Test as their models typically contain S-parameters at high frequencies only.}} == RF Circuit Simulation vs. Electromagnetic Simulation ==

As the frequency increases, more complex wave radiation and propagation effects start to appear and affect the performance of your circuit. At much higher frequencies and in the millimeter wave region of the spectrum, the coupling between adjacent [[Transmission Lines|transmission lines]] may no longer be neglected. In such cases, a full-wave electromagnetic analysis of portions of the circuit might become inevitable. This might be especially true for junction areas and vertical interconnects that join transmission line traces on two sides of a board and across different substrate layers. For accurate analysis of structures of this type you need a full-wave electromagnetic (EM) modeling tool. [[EM.Cube]] is a modular suite of EM simulation tools for this very purpose. Among its computational modules are time domain full-wave simulators like [[EM.Tempo]] based on the Finite Different Time Domain (FDTD) method as well as frequency domain full-wave simulators like [[EM.Picasso]] and [[EM.Libera]] based on different variations of the Method of Moments (MoM).

{{Note | You can analyze a complex passive multiport device in [[EM.Cube]] and import its simulated S-parameter data into [[RF.Spice A/D]] as a new custom devicein your parts database.}}

A multiport network is a frequency-domain “black-box” block that is modeled by its S-[[parameters]] as a function of frequency. [[RF.SpiceA/D]] currently offers the following models:

An N-port device is characterized by a complex-valued NxN scattering (S) matrix. A one-port has only one S-parameter, i.e. s11. A two-port has four S-[[parameters]]: s11, s21, s12 and s22. A Complex Impedance is a special type of one-port that is defined by its complex-valued z11 parameter rather than by s11. [[Multiport Networks|Multiport networks]] can be connected to one another through their ports. For example, you can cascade two two-ports as shown in the opposite figure. Note how the negative pins of the two devices have been grounded.

<table><tr><td>[[File:twoport1.png|thumb|left|480px| Cascading two two-port network devices.]]</td></tr></table> {{Note | Multipart Network devices do not work with “Live Simulation” or Transient Test as their models normally contain S-[[parameters]] at high frequencies only.}}

=== Defining S-Parameters ===

Each multiport network device has a property dialog where you can specify its S-[[parameters]] as a function of frequency. Each row of the S-parameter table in the property dialog represents a frequency sample. The complex-valued elements of the scattering matrix are listed column by column in each row of the table after the frequency value. For example, for a two-port, the format is as follows:

Among <table><tr><td>[[RFFile:twoport2.Spice]]'s png|thumb|left|550px| The property dialog of a multiport network device, the one-port, two-port, three-port and four-port are all defined based on their S-[[parameters.]]. All multiport network devices have a "Port Reference Impedance" parameter. The default value of the reference impedance is 50 Ohms for the one-port, two-port, three-port and four-port. For most RF circuits, you do not have to touch the 50&Omega; default value. </td></tr></table>

Besides entering the S-parameter values manually using in the parameter table, you can directly import these values from a text file with a ".TXT" file extension. For this purpose, click the button labeled "Load from File..." in the property dialog. This opens up the standard [[Windows]] Open dialog, with the file type set to text files. Browse your folders and select the text file to load the data from. The S-[[parameters]] you import to [[Among RF.Spice]] can come from manufacturer data sheets or they can be generated by electromagnetic simulation suites such as [[EM.Cube]]. For example, among [[EM.Cube]]'s computational modulesmultiport network device, the FDTDone-port, Planar MoMtwo-port, Wire MoM three-port and Surface MoM simulation engines four-port are all generate defined based on their S-parameters. All multiport network devices have a "Port Reference Impedance" parameter text files . The default value of the reference impedance is 50 Ohms for structures with the one-port, two-port, three-port and four-port definitions. These files can directly be loaded into [[For most RFcircuits, you do not have to touch the 50&Omega; default value.Spice]].

[[Besides entering the S-parameter values manually using in the parameter table, you can directly import these values from a text file with a ".TXT" file extension. For this purpose, click the button labeled "Load from File:twoport3.png|thumb|350px| The .." in the property dialog of . This opens up the standard Windows Open dialog, with the Complex Impedance devicefile type set to text files.Browse your folders and select the text file to load the data from. The S-parameters you import to [[RF.Spice A/D]]can come from manufacturer data sheets or they can be generated by electromagnetic simulation suites such as [[EM.Cube]]. For example, among [[EM.Cube]]'s computational modules, the FDTD, Planar MoM, Wire MoM and Surface MoM simulation engines all generate S-parameter text files for structures with port definitions. These files can directly be loaded into [[RF.Spice A/D]].

===The Complex Impedance Device===

Note that the default reference impedance of the Complex Impedance is zero and must always stay zero to function properly. In order to have a fixed impedance element, define the same Real(z11) and Imag(z11) values for the minimum and maximum frequencies of your circuit. Due to the interpolation between these two values, you will always get the same impedance value at all the frequencies in between those two limits.  <table><tr><td>[[File:twoport3.png|thumb|left|550px| The property dialog of the Complex Impedance device.]]</td></tr></table> == List of Standard Imported RF Devices == {| class="wikitable"|-! Device Type !! Symbol Name !! Model Type !! Schematic Symbol|-| RF Capacitor || capacitor || one-port || [[File:G6a.png]]|-| RF Inductor || inductor || one-port || [[File:G7a.png]]|-| RF Diode || diode || one-port || [[File:G9.png]]|-| RF BJT || bjt_npn_2port <br /> bjt_pnp_2port || two-port || [[File:G11A.png]]|-| RF JFET || jfet_n <br /> jfet_p || two-port || [[File:G12.png]]|-| RF MOSFET || mosfet_n <br /> mosfet_p || two-port || [[File:G13a.png]]|-| RF MESFET || mesfet_n <br /> mesfet_p || two-port || [[File:G14.png]]|-| One-Port|| one-port || one-port || [[File:G60.png]]|-| Two-Port|| two-port || two-port || [[File:G61.png]]|-| Three-Port|| three-port || three-port || [[File:G62.png]]|-| Four-Port|| four-port || four-port || [[File:G63.png]]|-| Open End || open_end || one-port || [[File:G64.png]]|-| Bend || bend_junction || two-port || [[File:G65.png]]|-| Step Junction || step_junction || two-port || [[File:G66.png]]|-| Tee Junction || tee_junction || three-port || [[File:G67.png]]|-| Cross Junction || cross_junction || four-port || [[File:G68.png]]|-|}

The standard SPICE provides two types of general-purpose transmission line models: lossless (TRA) and lossy (LTRA). These models are primarily intended for transient analysis. The lossless transmission line model is characterized by either its delay in seconds or by its normalized length at a given frequency. On the other hand, the lossy transmission line model is characterized by distributed RLCG [[parameters]]: resistance per unit length (R), inductance per unit length (L), capacitance per unit length (C), and conductance per unit length (G). Both [[B2.Spice A/D]] and [[RF.SpiceA/D]] offer the native SPICE transmission line models TRA and LTRA as passive devices.

However, [[RF.SpiceA/D]] also offers a number of other transmission line models specifically intended for use in RF circuit analysis. These include the generic T-Line, the generic coupled T-lines, and a variety of physical transmission line models.

=== The Generic T-Line ===

[[File:tline.png|thumb|250px| The schematic symbol of the Generic T-Line device.]] [[RF.SpiceA/D]] offers a passive device called Generic T-line with the keyboard shortcut “T”, which is a general purpose frequency-domain transmission line segment model. It is based on the native SPICE LTRA model, but with the following [[parameters]]:

The default [[parameters]] of the Generic T-Line are Z0 = 50 Ohms, eeff = 1, alpha = 0, and len = 10mm. A unit effective permittivity implies a TEM transmission line because &radic;&epsilon;_eff = &beta; / k₀, where &beta; is the propagation constant of the transmission line and k₀ = 2&pi;f/c is the free space propagation constant, with f being the frequency in Hertz and c = 3e8 m/s being the speed of light. A zero attenuation constant represents a lossless transmission line. The Generic T-Line device is indeed a two-port network with a 2&times;2 scattering matrix or four S-parameters: s11, s21, s12 and s22. Obviously, this is a reciprocal and symmetric network, i.e., s11 = s22, and s21 = s12.

Note that N-port networks in <table><tr><td> [[RFFile:tline.Spice]] have png|thumb|left|360px| The schematic symbols with 2N pins. Each pair symbol of pins represents a port. In a similar way, the generic Generic T-line has two ports and four pins. The pins are marked with plus and minus signs. For example, in the figure above, the pins P1+ and P1- together form Port 1. Normally, the negative pins are grounded, and the positive pins are connected to the other parts of the circuitLine device. ]]</td></tr></table>

{{Note | Proper grounding that N-port networks in [[RF.Spice A/D]] have schematic symbols with 2N pins. Each pair of pins represents a port. In a similar way, the transmission generic T-line devices is critical for a successful simulationhas two ports and four pins. The pins are marked with plus and minus signs. For example, in the figure above, the pins P1+ and P1- together form Port 1. Normally, the negative pins are grounded, and the positive pins are connected to the other parts of the circuit.}}

[[File:tline2.png|thumb|350px{{Note | The schematic symbols Proper grounding of the Generic Open Stub (left) and Generic Short Stub (right) transmission line devicesis critical for a successful simulation.]]}}

The Generic Open Stub and Generic Short Stub are two one-port devices based on the Generic T-Line device. They represent terminated generic transmission line segments. In the open stub case, the termination load is Z_L &rarr; &infin;, and in the short stub case, the termination load is Z_L = 0. The [[parameters]] of both open and short stub devices are the same as those of the generic T-line device.

[[File:tline3.png|thumb|250px| The schematic symbol of the Generic Coupled T-Lines device.]]<table><tr>=== Generic Coupled T-Lines === Many passive RF devices such as directional couplers, hybrids and some filter designs involve segments of parallel coupled [[Transmission Lines|transmission lines]]. According to the coupled mode theory, one can define even and odd mode impedances for such [[Transmission Lines|transmission lines]]. The resulting RF structure can be modeled as a four-port network device as shown in the opposite figure. Note that the four-port device has eight pins. Ports 1 and 2 correspond to the input and output of the first transmission line segment, while Ports 3 and 4 correspond to the input and output of the second (coupled) line segment. It is very important to connect and ground the negative pins at the input and output of the two transmission line segments.  The Generic Coupled T-Lines device has the following [[parameters]]: * Z0e: Even Mode Characteristic Impedance in Ohms * Z0o: Odd Mode Characteristic Impedance in Ohms * eeff: Effective Permittivity * len: Physical Length in meters  This model assumes lossless [[Transmission Lines|transmission lines]]. <td>[[File:tline4tline2.png|thumb|450pxleft|480px| The schematic symbols of the Generic T-Line Discontinuity devices: (a) Open End, Stub (bleft) Bend, (c) Step Junction, (d) Tee Junction and Generic Short Stub (eright) Cross Junctiondevices.]]</td></tr></table>

In real practical RF circuits, you often need to transition from one transmission line to another or connect two or more [[Transmission Lines|transmission lines]] together. These transitions can be modeled as [[Multiport Networks|multiport networks]]. [[RF.SpiceA/D]] currently offers five generic T-Line discontinuity devices as follows: 

The schematic symbols of these devices are shown in the opposite figure. Similar to other RF devices or [[Multiport Networks|multiport networks]], the negative pins of the ports must always be grounded. Unlike the T-line device described earlier which have models based on or derived from the standard SPICE LTRA, the generic T-line discontinuities have S-parameter-based models.

When you first place these discontinuity parts on your circuit, they have default S-parameter values. The default values have been chosen to be very general and may not necessarily represent the physics of your specific circuit. You must enter your own S-parameter values over the desired frequency range and replace the default values. These data can easily be generated in and imported from an electromagnetic simulation suite like [[EM.Cube]]. Unlike physical [[Transmission Lines|transmission lines]] like microstrip or coaxial line (to be discussed later) that have particular geometries and physical structures, the Generic T-Line device and Generic T-Line Discontinuities are very general by definition and do not have physical, material or dimensional [[parameters]]. You can model and simulate very complicated transmission line structures as well as open end, bend, step, tee or cross junctions based on those structures using [[EM.Cube]] and then import their S-parameter data into the corresponding discontinuity parts.

== Physical Transmission <table><tr><td>[[File:tline4.png|thumb|left|720px| The schematic symbols of the Generic T-Line Types ==Discontinuity devices: (a) Open End, (b) Bend, (c) Step Junction, (d) Tee Junction and (e) Cross Junction.]]</td></tr></table>

== Physical Transmission Lines == === The Variety of Physical Transmission Line Types === In addition to the Generic T-Line, [[RF.SpiceA/D]] also offers a large number of physical [[Transmission Lines|transmission lines]] as follows:

[[Image:Info_icon.png|40px]] Click here to see a '''[[List of === Physical Transmission Line Types]]'''.Calculators and Designers ===

[[File:tline5.png|thumb|450px| The schematic symbols of the some Physical Transmission Line Discontinuity devices. When you place a generic T-line part in your circuit, you have to specify its characteristic impedance (Top RowZ0) microstrip components: right-angled bend, mitered bend, tee effective permittivity (eeff) and cross junctions, attenuation constant (Bottom Rowalpha) . In the case of physical transmission line parts like mircostrip, coaxial line or CPW components: open end, short end, gap you specify the physical parameters of the line such as various dimensions and step junctionmaterial properties.[[RF.Spice A/D]]then automatically calculates the necessary transmission line parameters at the time of simulation based on your physical data.

=== Physical Transmission <table><tr><td> [[File:tline6.png|thumb|left|480px| Microstrip Line Discontinuities ===Calculator.]]</td></tr></table>

Besides the Generic T-Line Discontinuity devices described earlierFor every physical transmission line type listed above, the '''Device Manager''' of [[RF.SpiceA/D]] also offers provides a large number of physical transmission corresponding '''Line Calculator'''. The line discontinuity devices based on some calculators are accessible form the '''Tools Menu''' of the transmission Device Manager. The line calculators take the substrate properties and the physical dimensions of a line types listed aboveand calculate its characteristic impedance (Z0) and effective permittivity (eeff). Among theseThe Line Calculator dialog also has an "Operational Frequency" input with a default frequency of 1GHz, the microstrip components are more widely which is used and have more variety. Unlike to calculate the generic T-guide wavelength of the transmission line components which require at that you supply the S-parameter data, the physical components are parameterized based on their geometrical and material propertiesfrequency. As a resultIn many practical applications, you simply enter the physical dimensions and other [[parameters]] and their Sneed quarter-[[parameters]] are automatically calculated by [[RF.Spice]] during the circuit simulationwavelength line segments. In other wordsthat case, you must first calculate the property dialog guide wavelength of these components contains their physical [[parameters]] only and does not show the values of their S-[[parameters]] transmission line as a function of defined by &lambda;_g = &lambda;₀ / &radic;&epsilon;_eff, where &lambda;₀ = c/f is the free space wavelength at the operational frequency.

For more information about Some of physical transmission line discontinuity devicestypes such as microstrip, please refer to [[Glossary_of_Physical_Transmission_Lines_and_Components|Glossary of Physical Transmission Lines stripline, coaxial line, twin-lead line and Components]]twisted-pair line, have loss parameters: dielectric loss tangent and metal conductivity. For these lines, the line calculator calculates the conductor attenuation constant (&alpha;_c) and dielectric attenuation constant (&alpha;_d), both in Neper per meter (Np/m). Note that the total attenuation constant is the sum of these two: &alpha; = &alpha;_c + &alpha;_d. You can convert the value of attenuation constant from Np/m to dB/m using the relationship 1Np = 8.6859dB.

=== Physical <table><tr><td>[[File:tline10.png|thumb|left|480px| CPW Line Calculations and Design ===Calculator.]]</td></tr><tr><td>[[File:tline12.png|thumb|lrft|480px| Coaxial Line Calculator.]]</td></tr></table>

When you place a generic T-line part in your circuit, you have to specify its characteristic impedance (Z0), effective permittivity (eeff) and attenuation constant (alpha). Or you may accept the default values Z0 = 50, eeff = 1, and alpha = 0. In the case of physical transmission line parts like mircostrip, coaxial line or CPW, you specify the physical parameters of the line such as various dimensions and material properties. In that case, RF.Spice automatically calculates the necessary transmission line parameters based on your physical data at the time of simulation. Oftentimes, you may want You often need to design a 50&Omega; transmission line of a certain type, or calculate and compare the characteristics of several transmission line types. Another practical need in [[RF design is to quarter-wavelength line segments. In this case, you must calculate the guide wavelength of the Spice A/D]] provides ten physical transmission line as defined by &lambda;_g = &lambda;₀ / &radic;&epsilon;_eff, where &lambda;₀ = c/f is the free space wavelength at the operational frequency. design tools for:

=== Physical * Microstrip Line* Coupled Microstrips * Stripline* Coupled Striplines* Coplanar Waveguide (CPW) Line* Finite-Ground CPW Line* Conductor-Backed CPW Line* Coaxial Line* Twin-Lead Line* Twisted-Pair Line Calculators ===

The Device Editor of <table><tr><td> [[RFFile:tline7.png|thumb|left|480px| Microstrip Line Designer.Spice]] provides ten line calculators and ten designer tools for all the transmission line types listed in the above </td></tr></table. These tools are accessible form the RF Menu of the Device Editor. > The above line calculators take designers ignore the substrate properties conductor and dielectric losses and calculate the physical dimensions of the line for a line types and calculate its given value of the characteristic impedance (Z0) . For example, given a substrate with thickness h and effective relative permittivity (eeff). The Line Calculator dialog also has an &epsilon;_r, the "Operational FrequencyMicrostrip Designer" input with calculates the microstrip width in mm for a given value of Z0 (50 Ohms by default frequency of 1GHz, which is used to calculate the guide wavelength of the transmission line at that frequency). Some of the line types, microstrip, stripline, type like CPW and coaxial line, twin-lead line and twisted-pair line, have loss [[parameters]]: dielectric loss tangent and metal conductivitymore than one dimensional parameter that can be varied. For these linesexample, the line calculator calculates the conductor attenuation constant CPW has slot width (&alpha;_cw) and dielectric attenuation constant center strip width (&alpha;_ds), both in Neper per meter (Np/m)while coaxial line has inner and outer conductor radii. Note that In such cases, the total attenuation constant is the sum of these two: &alpha; = &alpha;_c + &alpha;_d. Also, you can convert these values from Np/m line designer dialog provides radio button options to dB/m using fix one parameter and vary the relationship: 1Np = 8.6859dBother.

[[File:tline6tline11.png|thumb|320pxleft| Microstrip 480px| CPW Line CalculatorDesigner.]]

[[File:tline10tline13.png|thumb|320pxleft| CPW 480px| Coaxial Line CalculatorDesigner.]]

[[File:tline12tline5.png|thumb|320pxleft| Coaxial 720px| The schematic symbols of the some Physical Transmission Line CalculatorDiscontinuity devices. (Top Row) microstrip components: right-angled bend, mitered bend, tee and cross junctions, (Bottom Row) CPW components: open end, short end, gap and step junction.]]

=== List of Physical Transmission Line Designers =Types ==

For every physical transmission {| class="wikitable"|-! Line Type !! Model Name !! Parameters !! Image !! Schematic Symbol|-| Microstrip Line || microstrip-line type, || len: line segment length in mm <br /> w: microstrip width in mm <br /> h: substrate thickness in mm <br /> er: substrate relative permittivity <br /> sigma: microstrip conductivity in S/m <br /> tand: substrate dielectric loss tangent <br /> t: metallization thickness in mm || [[RFFile:microstrip.Spicepng]] also provides a designer tool|| [[File:microstrip1. The designer ignores conductor and dielectric losses and calculates the physical dimensions of the png|120px]] |-| Coupled Microstrips || coupled-microstrips || len: line for a given value of the characteristic impedance Z0. For example, given a segment length in mm <br /> w: strip width in mm <br /> s: microstrip spacing in mm <br /> h: substrate with thickness h and in mm <br /> er: substrate relative permittivity &epsilon;|| [[File:coupled_microstrips.png]] || [[File:coupled_microstrips1.png|120px]] |-| Covered Microstrip Line || microstrip-covered || len: line segment length in mm <subbr />rw: microstrip width in mm <br /sub>, the "h: substrate thickness in mm <br /> er: substrate relative permittivity <br /> hc: cover height in mm || [[File:microstrip_cover.png]] || [[File:CoveredMS1.png|120px]] |-| Suspended Microstrip Designer" calculates the Line || microstrip-suspended || len: line segment length in mm <br /> w: microstrip width in mm for a given value <br /> h: substrate thickness in mm <br /> er: substrate relative permittivity <br /> b: height of Z0 substrate above ground in mm || [[File:SUSPMS.png]] || [[File:SuspMS1.png|120px]] |-| Inverted Microstrip Line || microstrip-inverted || len: line segment length in mm <br /> w: microstrip width in mm <br /> h: substrate thickness in mm <br /> er: substrate relative permittivity <br /> b: microstrip height above ground in mm || [[File:INVMS.png]] || [[File:InvMS1.png|120px]] |-| Coplanar Strips (50 Ohms by defaultCPS)Line || cps-line || len: line segment length in mm <br /> w: strip width in mm <br /> s: strip spacing in mm <br /> h: substrate thickness in mm <br /> er: substrate relative permittivity || [[File:CPS. Some png]] || [[File:CPS1.png|120px]] |-| Stripline || stripline || len: line type like segment length in mm <br /> w: strip width in mm <br /> b: parallel plate spacing in mm <br /> er: substrate relative permittivity <br /> sigma: strip conductivity in S/m <br /> tand: substrate dielectric loss tangent <br /> t: strip thickness in mm || [[File:stripline.png]] || [[File:stripline1.png|120px]] |-| Coupled Striplines || coupled-striplines || len: line segment length in mm <br /> w: strip width in mm <br /> s: strip spacing in mm <br /> b: parallel plate spacing in mm <br /> er: substrate relative permittivity || [[File:coupled_striplines.png]] || [[File:coupled_striplines1.png|120px]] |-| Off-Center Stripline || coupled-striplines || len: line segment length in mm <br /> w: strip width in mm <br /> s: offset from centerline in mm <br /> t: strip thickness in mm <br /> b: parallel plate spacing in mm <br /> er: substrate relative permittivity || [[File:OffCenter.png]] || [[File:OffStrp1.png|120px]] |-| Coplanar Waveguide Line || cpw-line || len: line segment length in mm <br /> w: slot width in mm <br /> s: center strip width in mm <br /> h: substrate thickness in mm <br /> er: substrate relative permittivity || [[File:cpw.png]] || [[File:cpw1.png|120px]] |-| Conductor-Backed CPW and coaxial Line || cbcpw-line have more than one dimensional parameter that can be varied|| len: line segment length in mm <br /> w: slot width in mm <br /> s: center strip width in mm <br /> h: substrate thickness in mm <br /> er: substrate relative permittivity || [[File:cbcpw. For example, png]] || [[File:cbcpw1.png|120px]] |-| Covered CPW has Line || cpw-covered || len: line segment length in mm <br /> w: slot width (in mm <br /> s: center strip width in mm <br /> h: substrate thickness in mm <br /> hc: cover height in mm <br /> er: substrate relative permittivity || [[File:cpw_cover.png]] || [[File:CovCPW1.png|120px]] |-| Covered Conductor-Backed CPW Line || cbcpw-covered || len: line segment length in mm <br /> w) and : slot width in mm <br /> s: center strip width (in mm <br /> h: substrate thickness in mm <br /> hc: cover height in mm <br /> er: substrate relative permittivity || [[File:cbcpw_cover.png]] || [[File:CovCBCPW1.png|120px]] |-| Finite-Ground CPW Line || fgcpw-line || len: line segment length in mm <br /> w: slot width in mm <br /> s), while : center strip width in mm <br /> g: ground strip width <br /> h: substrate thickness in mm <br /> er: substrate relative permittivity || [[File:fgcpw.png]] || [[File:fgcpw1.png|120px]] |-| CPW Line with a Superstrate || cpw-super || len: line segment length in mm <br /> w: slot width in mm <br /> s: center strip width in mm <br /> g: ground strip width in mm <br /> h: substrate thickness in mm <br /> er: substrate relative permittivity <br /> hs: superstrate height in mm <br /> ers: superstrate relative permittivity || [[File:SuperCPW.png]] || [[File:SuperCPW1.png|120px]] |-| Double-Layer CPW Line || cpw-doublelayer || len: line segment length in mm <br /> w: slot width in mm <br /> s: center strip width in mm <br /> h1: lower substrate layer thickness in mm <br /> er1: lower substrate layer relative permittivity <br /> h2: upper substrate layer thickness in mm <br /> er2: upper substrate layer relative permittivity || [[File:DoubleCPW.png]] || [[File:DoubleCPW1.png|120px]] |-| Coaxial Line || coaxial -line has || len: line segment length in mm <br /> r_in: inner and conductor radius in mm <br /> r_out: outer conductor radiiradius in mm <br /> er: dielectric core relative permittivity <br /> sigma: metal conductivity in S/m <br /> tand: dielectric core loss tangent || [[File:coax. In png]] || [[File:coax1.png|120px]] |-| Twin-Lead Line || twin-lead || len: line segment length in mm <br /> r: wire radius in mm <br /> s: wire spacing in mm <br /> er: dielectric medium relative permittivity <br /> sigma: wire conductivity in S/m <br /> tand: dielectric medium loss tangent || [[File:twin.png]] || [[File:twin1.png|120px]] |-| Twisted-Pair Line || twisted-pair || len: line segment length in mm <br /> r: wire radius in mm <br /> s: wire spacing in mm <br /> T: number of twists per length in 1/m <br /> erc: dielectric cover relative permittivity <br /> erm: dielectric medium relative permittivity <br /> sigma: wire conductivity in S/m <br /> tand: dielectric cover loss tangent || [[File:twisted.png]] || [[File:twisted1.png|120px]] |-|} == Working with Coupled Transmission Line Devices == Many passive RF devices such casesas directional couplers, the Line Designer dialog provides radio button options hybrids and some filter designs involve segments of parallel coupled transmission lines. According to fix the coupled mode theory, one parameter can define even and vary odd mode impedances (Z0e and Z0o) for such transmission lines. The resulting RF structure can be modeled as a four-port network device as shown in the otheropposite figure. Note that the four-port device has eight pins. Ports 1 and 2 correspond to the input and output of the first transmission line segment, while Ports 3 and 4 correspond to the input and output of the second (coupled) line segment. It is very important to connect and ground the negative pins at the input and output of the two transmission line segments.

[[File:tline7tline3.png|thumb|320pxleft| Microstrip Line Designer.]]</td><td>[[File:tline11.png|thumb|320px| CPW Line Designer.]]</td><td>[[File:tline13.png|thumb|320px300px| Coaxial Line DesignerThe schematic symbol of the Generic Coupled T-Lines device.]]

In [[RF.Spice A/D]] provides three coupled line devices, all of which assumes lossless transmission lines:  # Generic Coupled T-Lines # Coupled Microstrips# Coupled Striplines The Generic Coupled T-Lines device has the case of following parameters: * Z0e: Even Mode Characteristic Impedance in Ohms* Z0o: Odd Mode Characteristic Impedance in Ohms* eeff: Effective Permittivity* len: Physical Length in meters  The coupled microstrips and coupled striplinesstripline devices are characterized by their strip width, it is the even strip spacing and odd mode characteristic impedances (Z0e and Z0o) that really mattersubstrate properties. The Coupled Microstrips Calculator and Coupled Striplines Calculator find these two the even and odd mode impedances for the given strip width and strip spacing. They also calculate the even and odd mode effective permittivities, which are typically different. The system characteristic impedance of the coupled line is calculated from the formula: Z :<sub>0s</submath> Z_0 = &radic;( Z_{\sqrt{ Z_{0e} } . Z<sub>Z_{0o} } </submath> ).  To calculate the guide wavelength, the average of the two effective permittivities is used. In addition, the coupling coefficient of the coupled line is calculated in dB from the formula:  :<math> C = ( Z_{\frac{ Z_{0e} } - Z_{Z_{0o} ) / ( Z_{} }{ Z_{0e} } + Z<sub>Z_{0o} } </submath> ).

[[File:tline8.png|thumb|320pxleft|480px| Coupled Microstrips Calculator.]]

[[File:tline14tline9.png|thumb|320pxleft|480px| Coupled Striplines CalculatorMicrostrips Designer.]]

[[File:tline9tline14.png|thumb|320pxleft|480px| Coupled Microstrips DesignerStriplines Calculator.]]

[[File:tline15.png|thumb|320pxleft|480px| Coupled Striplines Designer.]]