R3 and R4 are two load resistors put at the input of AD6641 to be the load of filter. Dielectric constant = 3. To make an effect transmission line with two wires it is best to create a twisted pair. The calculator is available in the Electrical Domain in Constraint Manager, from theDifferential signaling in flex circuits follows the design method of surface microstrip transmission lines. Copper thickness (t) = 18 micron. This assumes ~0 trace thickness. 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. e. - For the obtained Zo in your Smith Chart calculate the admittance. pair impedance with predifined traces’ gap. Terminating the cable with its characteristic impedance reduces reflections and increases the achievable data rate. g. 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. The calculator is available in the Electrical Domain in Constraint Manager, from the Differential signaling in flex circuits follows the design method of surface microstrip transmission lines. 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. The characteristic impedance (Z 0) of a transmission line is the resistance it would exhibit if it were infinite in length. Figure 5. 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. Press Analyze to see the results. Vias (plated holes) are used to route electrical signals among different layers of a multilayer. A Clemson ECE635 Project by Adam Schreiber and Jason Byers. But in your differential pair, each line will have its own characteristic impedance, lower than 100 Ohms but higher than 50 Ohms (for instance a quick computing in Saturn PCB give me 77. 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. Controlled impedance (CI) is the characteristic impedance of a transmission line. 0037” line/0. Description. Here, Z11 is the characteristic impedance looking into port 1 for one of the transmission lines. Dimensional units:. Cohn, Seymour B. Make sure the correct Layer is selected before changing this option. Characteristic Impedance (Z0) is the impedance of a transmission line when viewed from the perspective of the signal’s behavior. 4 Comments. Where. Microstrip Trace Impedance vs. You can use all the calculators you want if you don't know the exact board make up they're using; they should be able to help you. The tool implements numerical solutions of Maxwell’s equations to render accurate and consistent results. 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. 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. The stripline impedance calculator provided below is useful for gaining an initial estimate of trace impedance for striplines. Stable line source impedance 2. In the above equation, we’ve ignored losses (R and G in the transmission line impedance equation), but that’s okay, the point here is to pay attention to spacing. If there is an insulator around the wire then this calculator will be an estimate. Grounded Differential Coplanar Wave Guide. Differential Pair Impedance (Z_diff) = (2 × Z_single) / sqrt(1 + (2d / s)) Where: Differential Pair Impedance (Z_diff) represents the characteristic impedance of the differential. Specific Absorption Rate (SAR) Calculator. Wire Microstrip Impedance Calculator. Read more about designing to a differential impedance specification; Read more about the six important transmission. The single-ended impedance requires 60 Ohm, and the differential impedance requires 100 Ohm. Clemson Vehicular Electronics Laboratory: Transmission Line Impedance Calculator. This is the same reason we have to consider spacing between traces in differential pairs: the two conductors interact with each other to determine the odd-mode (and differential) impedance . This calculator is designed to calculate the characteristic impedance of a broadside couple stripline (see diagram below). Single-ended impedance of each data line (with respect to GND) should be 45 Ω +/- 15. The even mode impedance is measured across one line while an equivalent signal drives the other line. The user only needs to enter the attenuation in decibels (dB) and the given characteristic impedance of the transmission lines to. Microstrip construction consists of a. The amplitude of this crosstalk is what this tool calculates. Enter values for W and L for a microstrip line to determine its Zo and Electrical Length. Enter the relative permitivity, width of the trace, the ground plane spacing, and the substrate thickness to calculate the characteristic impedance. 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. While there are many 2D field solvers available, many are either bundled inside expensive tools, or have a user interface with a steep learning curve. Odd mode impedance is defined as impedance of a single transmission line when the two lines in a pair are driven differentially (with signals of the same amplitude and. We are now ready to calculate the microstrip characteristics. Otherwise you could lose data). By inputting the known values and leaving one variable blank, you can quickly calculate the missing parameter. This calculator allows you to add the impedance model and compute the desired trace geometry and spacing for a target impedance. Figure 1 shows the generic conduction paths of the common-mode and differential-mode noise of a dc-to-dc power supply (the DUT in an EMI lab). Multiply the result by the square root of the ratio of (1 + (2 * h / w)) to (1 – (2 * h / w)). Note that for the terminated case, the gain is measured with respect to the differential voltage at the termination, VIN = VD+ – VD– . Often when working with wires it is easy to create large return path loops if one is not paying close attention. 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. 1 to 2. It is only equal to double the characteristic impedance in certain cases. Edit: also, think ahead if you are going to use ground pours around the traces. The design inputs are the source impedance RS, the gain setting resistor RG1, and the desired gain G. These impedances are related to odd (ZO) and even model (ZE) impedances of a line. A stripline resembles a microstrip line and comprises a center conductor pattern symmetrically embedded completely within a dielectric, the top and bottom layers of which are conducting ground planes. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. Overview. Impedance Calculation for PCB Designers - Altium. Modeling approximation can be used to understand the impedance of. Note that the y-axis is on a logarithmic scale for clarity. All the math involved is well explained and documented by Dan AC6LA on his site. Differential Pair Impedance Calculator. Or the odd mode impedance is half of the differential impedance. Dual Stripline Impedance Calculator. Differential traces are intended to be coupled and therefore spaced as close as possible and since coupling reduces the differential impedance your single line impedance will need to be greater than 45 ohms (Zd < 2 x Zo). Solution of Wave Equations (cont. In other words, try to keep the length of D+ and D- the same. Re: Calculating Differential Impedance for USB Differential Pair. The input impedance, RIN, is equal to 2RG1 for a balanced differential drive. The Twisted Pair Impedance Calculator is able to compute the characteristic impedance Z 0(twisted pair) based on the dimensions of the twisted-pair cable. In this example, the. 8 substrates of various thicknesses. Z diff = 2* Z o (1 - 0. Figure 3. The odd mode impedance, Z 0,o, is given by the. If you have voltage and current measurements from a circuit network, you can calculate the network’s characteristic impedance using Ohm’s law. 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. 5 to 4. Question: The Zo in the matrix data: Zo mode 1 ==> Zcm(common mode) or Zoe(even mode). Differential impedance, Z diff, is the impedance between the two conductors. In some cases, users require a custom impedance value. where L is the inductance per meter and C is the capacitance per meter. The surface finish is neglected. Phone: +44 (0)1425 489 111 / +49 (0) 8104 628 0. 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. Typical values for most common differential signal types are 90 ohms differential, 100 ohms differential or 120 ohms differential. Tech Consultant Zach Peterson is talking Signal Integrity again today with a deep dive into Differential Impedance. Then calculate R T for impedance matching and the value of the R2 for differential balance. This is lower than the impedance of the line on its own as the influence of the equal and opposite polarity of the two propagating signals make the structure behave as though an extra ground plane has been added vertically between the traces. Driver output impedance: If too high, this limits drive capability. High speed measurement tools. The plots show the magnitude and phase of the input impedance. It is important to determine the characteristic impedance of a twisted-pair cable because this impedance should match the. The characteristic impedance (Z o) of coplanar waveguide with ground or microstrip lines with signal side ground plane can be calculated using the active calculator or the equations at the bottom of the page. Board thickness (h) = 50 micron. The differential impedance of MIPI tracks should be 100 Ohms, not 90 (USB requires 90). ) and the LOW level is defined as zero. 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. The new version includes: This software is intended to assist with microwave circuit design in predicting the impedance of a circuit made with Rogers High Frequency. A microstrip line is a type of electrical transmission line used to convey microwave-frequency signals and consists of a. Twisted pair: qquad footnotesize ext {Impedance} = frac {120 imes ln (2s/d)} {sqrt {varepsilon_r}} Impedance = εr120 × ln(2s/d) As you can see, it is not overly complicated to calculate by hand, but it will definitely take longer than using our calculator. Thus a "differential pair" any long distance apart will have an impedance of 98 ohms, without any coupling between the lines, i. When you click on the track, you can see the length of skew. The twisted pair helps create a more uniform inductance and capacitance per unit length of wire to ensure a constant impedance, by keeping the return path as close to the signal as possible. D = Separation between the differential traces. Edge Coupled Stripline Differential Impedance Calculator Broadside Coupled Stripline Impedance Calculator Symmetric Stripline Impedance Calculator Asymmetric Stripline. . Given the defaults (1. The differential impedance will be a bit less than 2x the single-ended impedance. Equation 3. 6mm, which is about 63mil. What this means to you is that at the resonant frequency, depending on whether the circuit is in parallel or series, the impedance is the highest or. make the assumption that you will get rid of transmission line effects and calculate based on a lumped-parameter system. Unfortunately, TxLine doesn't do coplanar waveguide for differential traces. The IPC Formulas and Wadell’s Method. Microstrip Characteristic Impedance Calculator Using a Formula by Brian C WadellEnter values for W and L for a microstrip line to determine its Zo and Electrical Length. Click the button corresponding to the unknown parameter to calculate its value ( w/ (h-t) <0. The Differential Pair Impedance Calculator is a specialized tool used in electrical engineering and signal integrity analysis to determine the characteristic impedance of a differential pair of transmission lines. 25; 1 < ε r <15 ). Receiver input impedance: If too low, this limits the number of receivers that the driver can handle. To avoid microstrip modes, have h >> (w+2g) and extend component side ground away from the trace by > (w+2g). The amplitude increases as the coupling length increases up to a point. Instruments is an example of a wideband, fully-differential amplifier with high input impedance that can drive 50-W lines. Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. Track width (w) = 137 micron. Measurements of S-parameters. 2 of the Microstrip Calculator, h=H1 and b=H2-H1. Therefore, for a Zd of 90 ohms a Zo target of 50 ohms is much more realistic. Picking from the CST Cable Studio Segments Navigation Tree. ; W is the width of the conductor (in meters). This calculator finds both odd and even transmission line impedance. Now as the driven signal propagates down the transmission line an impedance mismatch is still encountered at the far end of the cable (receiver inputs). Impedance Calculator. 5. Safe connection of measuring equipment 4. Using a differential pair to avoid common mode noise is common in audio circuits. 8. You will see the Differential Impedance Calculator interface with input fields for Characteristic Impedance (Z0) and Common Mode Impedance (Zc). , USB. reflection commonly used in transmission line analysis. This calculator is designed to find the characteristic impedance of an asymmetric stripline - a flat conductor between two ground planes. This planning tab is one of the most useful tabs as it enables you to calculate the optimal data when you need a specific target impedance for single and differential pair traces. 004” line/0. 1. One should always check carefully whether a calculator implements these equations under the appropriate approximations. ALGEBRAIC EQUATIONS Single Track For the stripline of Figure 2 with a symmetrically centredThe impedance is based on the cross-sectional geometry of the trace. ; H is the height of the dielectric layer (in meters). The calculator is set up to handle an asymmetric arrangement, where traces are not centrally located in the PCB layer stack. 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. Single Ended Impedance Ω. 25, but gives me nice trace from the module to the stub then to microcontroller. This calculator can calculate the impedance and propagation delay of any microstrip by taking its respective height, width, thickness & dielectric constant. 3. We care about maintaining the same differential impedance for the. 1 of the Microstrip Calculator using H2 in place of h, εr,eff can be computed as specified in Eq. This RLC impedance calculator will help you to determine the impedance formula for RLC, phase difference, and Q of RLC circuit for a given sinusoidal signal frequency. 6. The twisted pair helps create a more. This calculator can calculate the impedance and propagation delay of any microstrip by taking its respective height, width, thickness & dielectric constant. 6mm 4 layer PCB, 1oz outer copper, 0. A differential stripline pair refers to two traces located between two reference plane. 03556mm. Differential Impedance of Microstrip. The calculation looks correct, but the tracks are too wide. Isolation of power source noise 3. CPW T-Junction Power Divider. This transmission line calculator. •One or more transient voltage suppression devices if required. In this equation there is no dimension to the surface of the PCB. Single and differential coplanar structures are supported by the Simbeor impedance calculator. Note: valid for (w/h) from 0. Ask the board manufacturer for the values. Thermal Noise Power Calculator. INPUT DATA. Example. For example, if you wish to input "25000000", just type "25M" instead. A microstrip width calculator can calculate the width of a microstrip. This calculator requires symmetry in the trace widths and location between plane. This figure shows that the differential output equals 2 × R P in parallel with the effective value of R′O = 2(VOUT± FO – VO±)/IO±. 10. The impedance Z 0 of a transmission line consisting of a circular signal conductor having a diameter d and centered between parallel ground planes separated by a distance h is given by: Eq. 7. It seems I could largely do without any impedance matching considerations, given what the trace lengths are. GDCPW is known for its balanced configuration, which helps reduce common-mode noise and interference in high-frequency signal. Don’t forget to check out our other. Controlled impedance is important for solving signal integrity problems, which is the propagation of signals without distortion. This calculator is designed to calculate the characteristic impedance of a microstrip - a flat conductor suspended over a ground plane with a dielectric between. Free Trace Line Impedance Calculators that utilize the #3 approach. Figure 3. They will give very similar answers. The odd mode impedance, Z 0,o, is given by the following equation: Eq. φ = –90° if 1/2πfC > 2πfL and R = 0. The IPC Formulas and Wadell’s Method. I selected driven-modal solution for a number of modes of 2. Multiply the result by the square root of the ratio of (1 + (2 * h / w)) to (1 – (2 * h / w)). 0 mm and L (line length) to 100 mm and click on the Analyze button. These parameters include:No, the single-ended impedance provided in differential line calculators does not matter. 1. 3: Normalized characteristic impedance and normalized effective permittivity of a microstrip line as a function of u = w / h. Components such as capacitors, resistors or active devices are. See full list on resources. For PICMG COM Express designs, traces on the bus must. The differential impedance is the impedance measured across the two lines with the pair driven differentially. Line impedance stabilization network (LISN) 1. g. Simons, "Coplanar Waveguide Circuits, Components, and Systems", Wiley. Equivalent impedance aroused by via parasitic inductance can be figured out by the following formula: Rising time of test signals is 500ps and its equivalent impedance is 4. Actually the "odd impedance" is the correct impedance to look at for the USB requirement of 90 Ohms differential impedance. . These equations are relatively simple compared to other transmission line geometries, comprising only 2 interrelated equations for the microstrip impedance. This transmission line calculator calculates the impedance at input and attenuation of a given transmission line once terminated with the given load. 3: Normalized characteristic impedance and normalized effective permittivity of a microstrip line as a function of u = w / h. Microstrip Differential Impedance Formula. The USB 2. The Smith Chart achieves this by superimposing a grid on S11 that maps load impedance. 4mils = 0. altium. branch impedance and/or time to achieve selectivity. Design to make sure the tracks are as close together as possible and meet impedance requirements. 5 (FR-4) ! even for Conductor/Plane layers. Altium Designer’s differential line impedance calculator will set up your impedance-controlled differential pair routing widths for you. Perhaps the most common type of transmission line is the coax. USB 2. Spurious Free Dynamic Range Calculator. 2. Impedance (Ω): The desired impedance. Make sure the correct Layer is selected before changing this option. Re: Calculating Differential Impedance for USB Differential Pair. - For the obtained Zo in your Smith Chart calculate the admittance. Also, intuitively, from an examination of the field pattern, the even mode impedance Z 0e is likely to be high because the. Dielectric Thickness: mm. I am routing differential pairs in Altium 20 and using controlled impedance profiles. Differential traces are intended to be coupled and therefore spaced as close as possible and since coupling reduces the differential impedance your single line impedance will need to be greater than 45 ohms (Zd < 2 x Zo). 6 ohms and Z even = 110 ohms for your geometry, very close to your result. Differential Impedance ($$Z_{0_{diff}}$$): The impedance between the two lines with opposite polarity signals. 3. What is the characteristic impedance of twisted pair cables? 100 ohms. Go to Route > click tune differential pair skew/phase > click on any of the track. 75 mm track on a 0. Differential pair on a reference plane for differential mode (left picture) and common mode (right picture) line impedance In addition to the four line impedance types the Impedance Calculator is also able to calculate the Coupling Factor between two traces on either the same signal layer (horizontal coupling) or between two traces on different. 3. •One or two stage differential mode (line-to-line) low pass filter. The following are typical line widths and spacings for the more common impedance values when using ½ OZ copper: 50 Ohm Single Ended: 0. This type of noise is suppressed by installing a filter on the hot (VCC) side on the signal line or power supply line, as mentioned in the preceding chapter. The coax is a good way to create a transmission line. 05 that is free software and very famous among designers. 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. This is to accommodate users who found the original ranges too limiting. Distance between tracks (s) = 254 micron. Although widely applied to. 62 Ohms. The calculator shows 90 ohms can be achieved using. 5Ω, times 18 mA = 400 mV. h = Dielectric Thickness. Impedance (Ω): The desired impedance. 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. Differential impedance between the data lines should be 90 Ω +/- 15%. This calculator is designed to find the characteristic impedance of an asymmetric stripline - a flat conductor between two ground planes. These important design features are incorporated into your design rules, making impedance-controlled routing quick and easy. Skin effect: The skin effect in a PCB trace, including coplanar waveguides, adds additional AC and DC resistance to the total impedance. Steps in the Design of a Power Line EMI Filter •Calculate or measure the. All calculations use a frequency of 1 GHz. Differential Stripline Impedance Calculator. Backwards crosstalk creates a pulse width that is twice that of the propagation time of the pulse traveling the coupling distance. INPUT DATA. exe, Differential Impedance Transmission Line Calculator : This calculator has been upgraded to Version 3. There are a lot of online trace impedance calculators specifically designed for differential traces. this type of termination. In the limit of a very long transmission line (such as when the line length is many multiples of the wavelength), then the tanh function eventually converges to 1. Z diff equals Ra||(2Rb) (p model) or 2R 1 (T model). Suppose you have a test transmission line that you’ve simulated with a field solver or. If you put 10 in the Line Width, the calculator calculates the single ended as well as differential impedance. Reference: R. 035 mm) h is the Thickness of dielectric. When designing the trace configuration for your differential pairs, you are typically targeting 100 ohms differential. It is relevant when high-frequency signals are propagating on the PCB transmission line. UCCALC. Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. H 1 (Dielectric thickness) : mm mils. 3. But impedance change as a result of vias reaches more than 12Ω and it indicates that measured value features extreme variation with theory-calculated value. Commonly fabricated with printed circuit board (PCB) technology, a microstrip antenna calculator tool is an electrical transmission line that is. Agilent's LineCalc tool calculates Z odd = 50. Edge Coupled Microstrip Differential Impedance Calculator. Example. Impedance Calculators. The factors that influence differential pair via impedance will affect the input impedance seen at the vias. Simulation Setup. 5. 5oz inner copper, 8 mil trace spacing) and a target differential impedance of 100 ohms, JLC's calculator suggests a trace width of 8. 50. 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). Using Saturn's PCB Toolkit, it seems to be extremely difficult to achieve 100R. This is 1. Z 0 = ( Z 0o * Z 0e )^0. FWIW, the calculator I've used in the past is called Polar SI8000 which apparently has been superceded by Speedstack PCB. 347 e -2. As seen from the formula when D decreases, while keeping B. Where Z 0 is the characteristic impedance of the asymmetric. where . Differential Trace Impedance:. High-speed designs carry a requirement for controlled impedance, crosstalk control, and the need for interplane capacitance. 2. Calculates the differential pair impedance of a balanced line. The impedance Zo of a two-conductor transmission line, as well as the odd-mode, even-mode, differential. Learn how to design. Coaxial Line Impedance Calculator. The differential impedance depends upon the D/H ratio. What’s more, these calculators return an accurate impedance value when as per. 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. at the input end of the filter to maximize the impedance of the “outside” loop. 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. Overview. The second type is common mode noise which is. This calculator is designed to calculate the characteristic impedance of a broadside couple stripline (see diagram below). We recommend the software from Polar Instruments if you want to get exact impedance calculation. Using this calculator, I found 100 Ohms by giving 9 mils of track width, 5 mils of track separation, 8 mils of dielectric (prepregs usually have a dielectric constant of 3. (Sorry guys, I live and I have grown up in a metric world ) With these values, Saturn PCB's off-line calculator gives 57 Ohm differential impedance. , 10. A Grounded Differential Coplanar Waveguide (GDCPW) is a transmission line structure used in RF and microwave circuits. Coaxial Line Impedance. This is entirely different from leakage resistance of the dielectric separating the two conductors, and the metallic resistance of the wires themselves. L is the inductance in henries (H),. eu. Note: Units do not matter for this calculation as long as they are consistent. Coplanar Waveguide Calculator. Most often, the only specified requirement of a differential pair is its differential impedance. The concept of Shield Transfer Impedance (Zt), introduced by S. 100 Ohm Differential Pair: 0. Hence, without loss of generality, one. 0. It has been correlated many times. For coupled surface microstrip, Wadell[1] gives 7 pages of equations to evaluate the impedance. 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. 6. 50 - 55 ohms). d = Trace Separation. At high frequencies, PCB signal traces. Z d = Differential Impedance. It is relevant when high-frequency signals are propagating on the PCB transmission lines. Notice the increased amplitude at the receiving end. Any line condition placing the impedance phasor tip within this circle will cause the relay to trip. ; Er is the relative permittivity (dielectric constant) of the substrate material. Calculate the Differential Microstrip Impedance of a transmission line based on the the distance between the strips, height of the substrate, trace thickness and dielectric constant of the substrate. **Note: Like our stripline impedance calculator, all of our RF calculators allow SI prefix input. 2 Calculating Impedance The following equations can be used to calculate the differential impedance of the board. These calculators ALL use wrong naming for "differential impedance". The most commonly used twisted pair cable impedance is 100 ohms. Introducing the newest version of the Microwave Impedance Calculator from Rogers’ Advanced Connectivity Solutions. Most online calculators do not account for copper roughness. When you want to determine the width and length of a microstrip line for any given characteristic impedance and electrical length, or vice versa, a microstrip calculator is the right tool to do so. Visit to learn more about our other electrical engineering tools. So move to your left, use Omni's Cable impedance calculator and enjoy. Enter the Height, Width and Permittivity to get the Impedance of the Microstrip Note : The unit of the height and width entered must be the same. The source for formulas used in this calculator (except where otherwise noted) is the Design Guide for Electronic Packaging Utilizing High-Speed Techniques (4th Working Draft, IPC-2251, February 2001. EEWeb offers a free online twisted pair impedance (transmission line) calculator. The differential impedance depends upon the D/H ratio.