If your structure has two microstrip feed lines, you can extract even and odd modes by creating weak coupling between main resonator and feed lines. Spurious Free Dynamic Range Calculator. This calculator determines the impedance of a symmetric differential stripline pair. 5. At the receiver, the signal is recovered by taking the difference between the signal levels on. There are many demands placed on PCB stackup design. A transmission line always features a differential microstrip impedance. • As shown in Figure 1, traces should be 100-Ω(±5%) differential impedance of differential microstrip or differential stripline. 6 ohms and Z even = 110 ohms for your geometry, very close to your result. Measurements of S-parameters. Speedstack is the stackup design tool of choice for professional PCB Designers fabricators and brokers who have a requirement to document and design stackups drill plans and material requirements complete with high. Impedance Calculators used by Mantaro engineers and provided here for your use freely. Impedance calculationWhen looking through the various transmission line impedance values, characteristic impedance and differential impedance generally stand out as the two important values as these are typically specified in signaling standards. 2 Stripline Impedance A circuit trace routed on an inside layer of the PCB with two low-voltage refere nce planes (such as, power and / or GND) constitutes a stripline layout. Equation 2. Here we assume that the board thickness is 1. In the special situation for which there is no coupling to ground, Differential impedance equals the Characteristic. When looking through the various transmission line impedance values, characteristic impedance and differential impedance generally stand out as the two important values as these are typically specified in signaling standards. With the expressions for VO± from before and some algebra, an equation to calculate the output impedance of the circuitTo change the low-pass filter into a band-pass filter, add two shunt inductors: L7 in parallel with C9 and L8 in parallel with C11. These parameters include: Characteristic impedance (Z 0): The online calculator can compute the characteristic impedance of a transmission line, which is the ratio of voltage to current in a. The plots show the magnitude and phase of the input impedance. 9. Still, as you correctly analyzed it is much better to think of the individual lines in a differential pair as two length-matched single-ended lines, both with the half impedance. Notes: 1) Calculation assumes traces are centered vertically. From here, we can see that there are specific stack-ups where a CPW and a microstrip/stripline will have 50 Ohm impedance and the same trace width, even though the ground clearance is quite close clearance to the trace in the CPW. Support for Coplanar Transmission Line Structures. Overview. A classic example of an impedance mismatched circuitA two part calculator which gives ideal and preferred value resistors, showing most formulas used and a link to the others. When dealing with differential pairs, thi. They are related by the following equations: ZD = 2*ZO. The user only needs to enter the attenuation in decibels (dB) and the given characteristic impedance of the transmission lines to. Odd-mode and differential-mode impedance formulas. Stable line source impedance 2. *The structure may propagate in 3 modes: coplanar waveguide, coupled slot lines and microstrip. 6mm 4 layer PCB, 1oz outer copper, 0. Board thickness (h) = 50 micron. Your relay is single line with characteristic impedance of 50 Ohms. You can see. One row entry in the Mode and Impedance dialog represents all constrains imposed to the mode selected in the first column. In some cases, we can also use 75-ohm differential. As we’ve seen above, the S-parameters and input impedance of a transmission line are the correct tools for describing signal reflection at the load end of a transmission line. The top surface and the sides of the traces are exposed to air and are referenced to a power or ground plane. 347 e -2. These calculators ALL use wrong naming for "differential impedance". Click the button corresponding to the unknown parameter to calculate its value ( w/ (h-t) <0. The JLCPCB Impedance Calculator computes track width values and recommended stack-ups from user-input values of board layer, thickness, copper weight, target impedance, trace spacing (for edge-coupled pairs), and impedance trace to copper gap (coplanar waveguides). The figure-1 above depicts differential microstrip line. You can define all aspects of the differential pair—including copper roughness—in your manufacturing process, directly in the Properties panel. If your design has controlled impedance traces, you can use our built-in impedance calculator. d = Trace Separation. This filter provides differential and common mode filtering. Because charging current enters the line from each end and escapes through the distributed capacitance, it appears as standing differential current to a line current differential (87L) scheme protecting the line. The original idea of USB physical drivers was a 18-mA current source into a transmission line terminated with 45Ω on both ends. (Not reasonable in general, but sometimes used for test and measurement purposes). This calculator is designed to calculate the characteristic impedance of a broadside couple stripline (see diagram below). You only need to know the resistance, the inductance, and the capacitance values connected in series or parallel. If the impedance of the load matches that of the source, impedance matching is not required, and the balun has a 1 : 1 impedance ratio. Z diff = 2* Zo (1 - 0. 0 and (t/h) less than 0. Or the odd mode impedance is half of the differential impedance. A PCB impedance calculation generally refers to the task of calculating trace impedance, or transmission line impedance, based on the stackup and material configuration used in your design. EEWeb offers a free online twisted pair impedance (transmission line) calculator. pair impedance with predifined traces’ gap. Multiply the result by the square root of the ratio of (1 + (2 * h / w)) to (1 – (2 * h / w)). 03556mm. The required inputs are the Dk value for the dielectric constant of the PCB substrate, and the. Here, we want to create a differential-pair impedance profile set to 90 Ohms differential impedance with 15% tolerance. At low frequencies near 0 GHz, the input impedance is inductive since. It is only equal to double the characteristic impedance in certain cases. This transmission line calculator. 150 inches (3. High speed PCBs and signaling standards almost entirely use differential pairs with precise impedance. Relative Dielectric Constant ( εr ): Track Width. Two conductors can create a transmission line. The reflection coefficient is only part of the story. Equation 3, which was developed by Martin Marietta in the mid 1980s, is a method for predicting the impedance of buried microstrip transmission lines. For an embedded (internal) microstrip, the formulas provided in paragraph 4. A quarter-wave line will present an input impedance of $frac{Z_{char}^2}{Z_{load}}$The impedance of the structure is the ratio of the voltage between, and the current in, the conductors. Build a model from experimental data of impedance vs. 1 to 2. Where the distance from trace to planes is not the same distance above and below. 5 to 4. We care about maintaining the same differential impedance for the. Zd (Differential Impedance, Ohms) = Zo (Single Ended Impedance, Ohms) = Calculate w from ZdThe Microstrip Differential Impedance Calculator simplifies the process of determining the differential impedance of a microstrip transmission line. Figure 2 illustrates the difference. For example, if you wish to input "25000000", just type "25M" instead. 5mm, T=0. Commonly fabricated with printed circuit board (PCB) technology, a microstrip antenna calculator tool is an electrical transmission line that is. Distance between tracks (s) = 254 micron. Saturn PCB - Toolkit for Impedance Calculation. R3 and R4 are two load resistors put at the input of AD6641 to be the load of filter. Differential Microstrip Impedance Calculator. The single-ended impedance requires 60 Ohm, and the differential impedance requires 100 Ohm. There are four different types of impedance used in characterizing differential trace impedances. 5. 1 where k is the solution of: Eq. Microstrip line is a widely used transmission line and for the appropriate transmission its characteristic impedance has to be calculated while using it in RF design & circuits. Here lies the challenge: impedance calculators must balance speed and accuracy. The difference between the total length of the data lines should be no more than 0. For this calculation, the units of d and h can be ignored as long as they have the same unit. 7: Characteristic Impedance. The characteristic impedance (Z 0) of a transmission line is the resistance it would exhibit if it were infinite in length. 9. An online transmission line calculator is a web-based tool that allows users to calculate various parameters associated with transmission lines. Distance elements enhance selectivity further by being both directional and having a defined reach in terms of impedance. It is a transmission line most commonly found in a pcb. I am routing differential pairs in Altium 20 and using controlled impedance profiles. Thus a "differential pair" any long distance apart will have an impedance of 98 ohms, without any coupling between the lines, i. One should always check carefully whether a calculator implements these equations under the appropriate approximations. However, during a handover of bus access from one node to another, or during a transmission pause, the bus idles. Also, be aware, 90 ohms is the differential impedance, the characteristic or single ended impedance will be more than half (ie. The top surface and the sides of the traces are exposed to air and are referenced to a power or ground plane. Choose the type of op-amp, e. Notes:. Where: Z is the characteristic impedance of the stripline (in ohms). Here, Z11 is the characteristic impedance looking into port 1 for one of the transmission lines. What is the characteristic impedance of twisted pair cables? 100 ohms. The differential impedance depends upon the D/H ratio. Notice the increased amplitude at the receiving end. 4. This PDF document provides a comprehensive guide on how to calculate the impedance of various PCB structures, such as microstrip, stripline, and differential pairs. Single ended impedance is the trace impedance with reference to ground. e. 6. Calculating the Differential impedance is a two-step process, first Calculate the single ended impedance Zo and then use this value to calculate the differential impedance. In some cases, users require a custom impedance value. has two length-matched 45 Ohm lines. For example, if u = 1 and ε r = 10, then from the figure, Z 0 ε e = 126 Ω and ε e / ε r = 0. Dielectric Thickness: mm. Unfortunately, TxLine doesn't do coplanar waveguide for differential traces. The Pi match circuit is so named because the circuit topology can resemble a pi symbol. ; H is the height of the dielectric layer (in meters). e. This calculator finds both odd and even transmission line impedance. Most RF Coaxial Cables have an impedance of 50 ohms or 75 ohms. Driver output impedance: If too high, this limits drive capability. If the traces are coupled, keeping the 100 ohm differential impedance, the common mode impedance. This calculator finds both odd and even transmission line impedance. If Z = 0 Z and ZL = ZG (for real GZ) we have a matched load, maximum available power goes into the load i. Multiply the result by the square root of the ratio of (1 + (2 * h / w)) to (1 – (2 * h / w)). Enter the relative permitivity, width of the trace, the ground plane spacing, and the substrate thickness to calculate the characteristic impedance. The stripline impedance calculator provided below is useful for gaining an initial estimate of trace impedance for striplines. The characteristic impedance and load impedance are used to calculate the input impedance of the terminated line at a particular frequency. Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. It mentions formula or equations used in this differential Microstrip Impedance Calculator. It has a common mode impedance of 25 ohm and and a differential impedance of 100 ohm. For example the impedance of a line with 1,5 mm width, conductor hight of 0,73 mm and. Figure 3. com Edge Coupled Stripline Impedance Calculator A calculator for computing the impedance of an edge coupled stripline. The Microstrip Differential Impedance Calculator simplifies the process of determining the differential impedance of a microstrip transmission line. In the special situation for which there is no coupling to ground, Differential impedance equals the Characteristic. The input impedance, RIN, is equal to 2RG1 for a balanced differential drive. I checked out TNT, but couldn't seem to be able to do the same with that either. For a printed circuit board (PCB) this is a pair of traces, also known as a differential pair. Broadside Coupled Stripline Transmission Line Models. Single Ended Impedance Ω. Edge Coupled Microstrip Impedance Calculator This tool helps calculate the impedance of an edge-coupled microstrip. Z 0 = ( Z 0o * Z 0e )^0. net Forum comes closest to the proper track width. The questions are mostly on the inner layer differential impedance item [4] below. Hi, I am working on my board Stack-up to tune Single/Differential impedances of my board in Allegro PCB 16. Impedance Calculators used by Mantaro engineers and provided here for your use freely. The first type is differential mode noise which is conducted on the signal (VCC) line and GND line in the opposite direction to each othe. In fact, striplines often make components such as band-pass filter's more accurately, with more symmetric roll-off and no lower cutoff frequency. 0075” spacing. Dimensional units:. e. Details: In the list below, [1] is the reference design stackup information; [2] and [3] are the processes to get the result close enough to the reference design target so as to know the tool is valid; and [4] is the calculation in question because it is either 5. 1. Often when working with wires it is easy to create large return path loops if one is not paying close attention. Characteristic impedance is purely a function of the capacitance and. calculate the impedance and capacitance of PCB traces. An example of a wire microstrip might most often be found in prototypes or reworked boards where a wire is used over the top of pcb or copper clad material. This calculator is designed to calculate the characteristic impedance of an embedded microstrip - a flat conductor suspended over a ground plane with a dielectric between it and another dielectric material. 1. For the odd mode, the differential impedance can be obtained by setting the integration region to enclose only one of the microstrips, and the characteristic impedance of the odd mode is half the differential impedance, approximately 22 ohms. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. 15 mm spacing. This calculator is designed to calculate the characteristic impedance of a broadside couple stripline (see diagram below). Example 7. My design requires that the pairs travel over very thin flexible PCB, about 50mm total transmission length. Clemson Vehicular Electronics Laboratory: Transmission Line Impedance Calculator. That means each trace would be a 50-ohm trace, if there were no coupling between the traces. 1. Re: Calculating Differential Impedance for USB Differential Pair. Introducing the newest version of the Microwave Impedance Calculator from Rogers’ Advanced Connectivity Solutions. If you select non-inverting op-amp, the calculator will show 11. Differential Impedance is the impedance between two differential pair signal traces. Coaxial Line Impedance. Moreover, this tool can also compute the signal propagation delay in inches per nanosecond (ns/in), the inductance per unit length in nano-Henrys per inch (nH/in), and. The required values are trace thickness, substrate heights, trace width, and subtrate dielectric in the calculator above and press the "calculate" button. If trace width is increased for the metal losses reduction, the single end impedance will be reduces. 8 substrates of various thicknesses. Impedance (Ω): The desired impedance. Note that for the terminated case, the gain is measured with respect to the differential voltage at the termination, VIN = VD+ – VD– . The input impedance of a line is a function not only of its characteristic impedance, but also of its loading impedance and electrical length (or physical length and frequency). Measurements of S-parameters. Z diff equals Ra||(2Rb) (p model) or 2R 1 (T model). This circuit only filters differential signals; if there is an in-phase signal (or interference) on both lines (called a common-mode signal/noise) it provides no filtering to it. Make sure the correct Layer is selected before changing this option. 71. You only need to know the resistance, the inductance, and the capacitance values connected in series or parallel. g. Microstrip Impedance Calculator. The specifications of my PCB are- the conductor thickness is 2oz(2. The best differential coplanar waveguide calculator can account for all of these effects simultaneously and without a complex 3D field solver. Imagine a differential pair made of two individually screened 50 ohm cables. To do this, keep the Impedance tab open and bring up the Properties panel. Also, I tried using 0 ohm resistor in between that didn’t help as well. The amplitude increases as the coupling length increases up to a point. To quantify conducted input EMI, a line impedance stabilization network (LISN) is placed at the regulator’s input, providing a standard input source impedance. , the structure is made up of two dielectric materials: air and the substrate material). Disc Air Capacitor Calculator; Impedance Calculator : XL, XC; Inductors, Transformers. L is the inductance in henries (H),. Figure 3 shows the respective p and T models used to calculate the differential impedance (Z diff). For coupled surface microstrip, Wadell[1] gives 7 pages of equations to evaluate the impedance. 3 Design Formulas for a Stripline. Enter values for W and L for a microstrip line to determine its Zo and Electrical Length. g. While commonly constructed using printed circuit boards, this structure can also be built using other materials as long as there is a conductor separated from. 035 mm) h is the Thickness of dielectric. The tool generates odd, even, common, and differential impedance as output values. Characteristic Impedance (Z0) is the impedance of a transmission line when viewed from the perspective of the signal’s behavior. The rules shown below are a rough approximation, and you should always check the approximation using an impedance calculator or field solver. 25, but gives me nice trace from the module to the stub then to microcontroller. You can interpret the name 'RLC circuit' to mean a circuit. This assumes ~0 trace thickness. ; This formula allows us to determine the. 3. Calculating the Differential impedance is a two-step process, first Calculate the single ended impedance Zo and then use this value to calculate the differential impedance. 6. Differential signalling is a method for electrically transmitting information using two complementary signals. The differential impedance depends upon the D/H ratio. w = Trace Width. 5oz inner copper, 8 mil trace spacing) and a target differential impedance of 100 ohms, JLC's calculator suggests a trace width of 8. For example, with microstrip, you can specify the substrate parameters (primarily thickness and dielectric constant) and use Linecalc to calculate the impedance for a given line width; this is the “analysis” mode. Track Thickness: mm. 3. A twisted-pair cable is simply two wires that are twisted together so as to reduce radiated EMI (electromagnetic interference) and mitigate the effects of received EMI. Just enter the given values for trace thickness, substrate heights, trace width, and substrate dielectric. The trace impedance (single-ended) in an individual trace is normally calculated by ignoring any neighboring traces, so no coupling to other conductors in the design will be. Reference: R. 1. In this section, we formally define this parameter and derive an. Using the formula, you can calculate the Differential Impedance (Zd) as follows: Zd = 2 * 100 / sqrt (1 + (2 * 100 / 20)) Zd = 200 / sqrt (1 + 10) Zd = 200 / sqrt (11) Zd ≈ 60. An asymmetric stripline is constructed between two plane layers, where the distance above the trace is not equal to the distance below. We are now ready to calculate the microstrip characteristics. Overview. The IPC Formulas and Wadell’s Method. •One or more transient voltage suppression devices if required. which is the characteristic impedance of the system. Vias (plated holes) are used to route electrical signals among different layers of a multilayer. Or the odd mode impedance is half of the differential impedance. Instruments is an example of a wideband, fully-differential amplifier with high input impedance that can drive 50-W lines. Determining trace impedance and propagation delay in PCB traces takes a trace length calculator and impedance profiler tool, and these features work best when they are integrated into your PCB design software. When we compare that with other calculators on the web and trustworthy tools like Saturn toolkit, we face lots of different results. 1 to 2. When designing the trace configuration for your differential pairs, you are typically targeting 100 ohms differential. In stripline specifically, the trace width (w), the trace thickness (t), the distance between ground plates (b), and the relative permittivity (better known as DK). This calculator is designed to help calculate the value of the resistors R1 and R2 to be used in T-pad attenuator. Skin Depth Calculator. It is widely accepted that the most accurate impedance calculations are produced with a 3D field solver due to the complex geometry in any PCB. With hundreds of coaxial RF cables in-stock and ready to ship worldwide immediately, our coax capacitance calculator lets you calculate the impedance of a coax by allowing you to enter the outer diameter dielectric width and inner conductor diameter. Instructions are below the calculator and don’t forget we can make and test your controlled impedance printed circuit boards too. Tools for Designers: Impedance Calculator Try This New Tool The Sierra Circuits Impedance Calculator uses the 2D numerical solution of Maxwell’s equations for PCB. H 1 (Dielectric thickness) : mm mils. 3 V, etc. "Shielded Coupled-Strip Transmission Line," IRE Transactions on Microwave. For a printed circuit board (PCB) this is a pair of traces, also known as a differential pair. Dimensional units: mm mils. These equations are relatively simple compared to other transmission line geometries, comprising only 2 interrelated equations for the microstrip impedance. Trace Height (H) Figure 4. The trace width (0. Learn how to design. B = separation between reference planes. •One or two stage differential mode (line-to-line) low pass filter. For PICMG COM Express designs, traces on the bus must. ( 0. Reset. Figure 5. The differential- and common-mode parameters of coupled lines can be derived from the odd- and even-mode parameters. PCB Structures / Discrete Structures / Signal Management. Coplanar Waveguide With Ground Characteristic Impedance Calculator. Note that the "h", for dielectric thickness in this formula is omitted in some other Polar publications. Twisted pairs are used with balanced signals. Impedance control in flex stack-ups is essential to reduce signal reflections and achieve dependable signal integrity. , 10. The common mode impedance is defined as the impedance of the lines connected in parallel, which is half of the even mode impedance. You can use Equation 5 to calculate the impedance of aA typical test network for a single-ended line is shown below (note; this can be easily extended to a differential line). The characteristic impedance is given by: Eq. 2 of the Microstrip Calculator, h=H1 and b=H2-H1. Our free impedance calculator for coplanar waveguide can help you with your design features to ensure your PCB is working as you intend. Edge Coupled Microstrip Differential Impedance Calculator. The odd mode impedance, Z 0,o, is given by the. The image below shows a typical 4-layer PCB stackup construction you’ll receive from most fabricators. In other words, try to keep the length of D+ and D- the same. The differential micro strip calculator requires some parameters. Figure 5. Calculating the Differential. Solution of Wave Equations (cont. . Edge Coupled Stripline Differential Impedance Calculator Broadside Coupled Stripline Impedance Calculator Symmetric Stripline Impedance Calculator Asymmetric Stripline. If you have voltage and current measurements from a circuit network, you can calculate the network’s characteristic impedance using Ohm’s law. At high frequencies, PCB signal traces. The stripline impedance calculator provided below is useful for gaining an initial estimate of trace impedance for striplines. 50 Ohms. Phone: +44 (0)1425 489 111 / +49 (0) 8104 628 0. Directional overcurrent elements improve on this by only responding to faults in one direction. So now you have the impedance looking into an infitely long line of cable. Wire Microstrip Impedance Calculator. Differential impedance, Z diff, is the impedance between the two conductors. Edit: also, think ahead if you are going to use ground pours around the traces. This calculator requires symmetry in the trace widths and location between plane. , DDR, HDMI, Gigabit Ethernet). ZC = 0. This assumes ~0 trace thickness. This calculator is designed to calculate the characteristic impedance of a microstrip - a flat conductor suspended over a ground plane with a dielectric between them (see diagram below). It is now a major exercise to evaluate the impedance using a calculator or spreadsheet. In differential pairs, each trace in the pair carries the same magnitude, but opposite polarity. A coplanar waveguide calculator will operate in one of two ways. where . Email: [email protected]. The tool implements numerical solutions of Maxwell’s equations to render accurate and consistent results. 5. Characteristic impedance is the ratio of voltage to current for a wave that is propagating in single direction on a transmission line. Sig± Differential input-signal source Z 0 Characteristic impedance of the balanced transmission line from the source to the amplifier input FDA circuit overview FDAs are broadband, DC-coupled amplifiers for balanced differential signals and have a unique ability to convert broadband, DC-coupled, single-ended signals into balanced differential. Pi-Matching Impedance Network Calculator. Cohn, Seymour B. The phase is mostly + 90 ∘ or − 90 ∘, indicating that Zin is mostly reactive. safety ground. Differential impedance between the data lines should be 90 Ω +/- 15%. This calculator is designed to calculate the characteristic impedance of an embedded microstrip - a flat conductor suspended over a ground plane with a dielectric between it and another dielectric material above the conductor (see diagram below). eu. 5) and 1. Yet I got a ZDiff CPW with ground capable calculator: Differential surface coplanar waveguide with ground calculations: *0. where L is the inductance per meter and C is the capacitance per meter. h = Dielectric Thickness. Read more about designing to a differential impedance specification; Read more about the six important transmission. Create a new impedance profile, then select Single-Coplanar or Differential-Coplanar from the Impedance Profile Type drop-down list. High-end calculators can rely on top-of-the-line systems to cover any computing speed deficiencies, but general impedance calculators must make a clear design tradeoff. 81 mm). Due to the parasitic capacitance provided by the PCB substrate and the mutual inductance between. - For the obtained Zo in your Smith Chart calculate the admittance. The differential impedance will be a bit less than 2x the single-ended impedance. For example, if u = 1 and ε r = 10, then from the figure, Z 0 ε e = 126 Ω and ε e / ε r = 0. trace geometry, and use this to calculate. Just as was the case with microstrip impedance calculators, stripline impedance calculators tend to rely on either the IPC-2141 formulas or on Wadell’s equations. Also note that your best bet may actually be VERY SHORT (few mm) traces, a thinner board or a 4 layer board :-) Thanks for your suggestions. The design inputs are the source impedance RS, the gain setting resistor RG1, and the desired gain G. 28Ω. Example. 25Distance units: Substrate Height, H Trace Width, W Thickness, TThe differential impedance depends upon the D/H ratio. Most online calculators do not account for copper roughness. The skew (difference between two lines of a pair) is not specified, even though it has a significantThe differential impedance between the positive and negative trace of the transmission line is slightly less than twice the impedance of the single ended impedance. 0 mm and L (line length) to 100 mm and click on the Analyze button. The most selective, however, are differential elements because theirUse a Numerical Field Solver for Impedance and Return Path Calculations. These equations are relatively simple compared to other transmission line geometries, comprising only 2 interrelated equations for the microstrip impedance and. ,Z0 Planning: Define the characteristic impedance of the stackup. It has a common mode impedance of 25 ohm and and a differential impedance of 100 ohm. Then the low-impedance termination resistors, connectingDifferential pairs are very simple: they are composed of two traces, routed side-by-side, and that carry equal magnitude and opposite polarity signals on each trace. To measure S-parameters, the preferred test equipment is a vector network analyzer (VNA). This calculator determines the differential microstrip impedance of a transmission line. You will see the Differential Impedance Calculator interface with input fields for Characteristic Impedance (Z0) and Common Mode Impedance (Zc). Terminating the cable with its characteristic impedance reduces reflections and increases the achievable data rate. Coplanar Waveguide Calculator.