If you use a microstrip trace impedance calculator, you’ll find that a trace thickness of 2 mils requires a trace width of 6. a 50 ohm impedance is often the required matching characteristic. This impedance is used to calculate the depth ( D) into the patch antenna. How can PCB trace have 50 ohm impedance regardless of length and signal frequency? 23. Below ~5GBps not something to worry about at all. This flow is outlined below. 45 Ohms for the following specs. This can be done by using a thinner board, or going to four layers (signal / plane / plane. Ohm’s Law provides the framework for solving network analysis problems; when the curtain gets pulled back, Ohm’s Law updates to become the relationship between voltage, current, and impedance, not resistance. My boards are usually 2 layers and no impedance control so this is all new stuff for me. where 1. 062" double sided finished board The numbers work out. g. To use it, first select the. 6mm pcb thickness ) with 8 mil trace width, 8 mil trace spacing , 1. 0048, while for internal traces, K equals 0. Or at least use thin FR4, if you can afford the losses. Cloose one. After quite a reading I got to know that as the track width of a cline is decreased, there is a decrease in the impedance, Trace width is indirectly proportional to impedance. 1mm, so trace width can also go down: with Er=4. The spacing ( S) is determined. I'm attaching a 50 Ω external antenna to uFL connector on board. Choose a calculator to tune your PCB design. This is more practical for construction at home, and with our newfound details, we can get to work on PCB layout. QUESTION: Very cool PCB width tool! I would like to know its limits though. You will need accurate models for the input impedance of the load and the output impedance of the source. dielectric constant er is 4. This says that ALL 50 Ohm transmission lines in FR4 have exactly the same capacitance per length. The image given below is depicting an example of a stack-up. 429 Mils. 254-0. PaulRB August 4, 2018, 6:51am 2. 5 ohms is close to the measurement of the trace impedance on the initial PCB design of 38 ohms. Trace width and copper weight;. Equation 4: Length of the trace . 11. What is the formula for PCB trace resistance? The formula for calculating the resistance of a PCB trace is: R = (ρ × L) / A. All 4 layers had ground pour on them. We can divide this trace into a series of squares, each 1 inch on a side. That means each trace would be a 50-ohm trace, if there were no coupling between the traces. As a second opinion, here is what Saturn PCB toolkit says: If a 120 thou trace is too wide, moving the plane closer to the trace will help. Therefore, the IPC-2141 equations are only accurate when attempting to calculate a trace width corresponding to a 50 Ohm single-ended impedance. 3) Longer traces will not limit the. For this reason, the 50 ohms impedance traces should be 5. If this is a standard PCB they. Step 4. 8: 3: 3. Therefore, the IPC-2141 equations are only accurate when attempting to calculate a trace width corresponding to a 50 Ohm single-ended. when I calculate required trace width for 50 Ohm impedance for 0. 378 [mils/oz/ft. Which standard should you use? Rf trace width calculator. Trace Layout. The close trace to plane coupling will decrease the crosstalk between traces and allow us to maintain the impedance at an acceptable value. **Note: Like our stripline impedance calculator, all of our RF. How do you calculate temperature rise in PCB trace? Temperature rise in a PCB trace can be estimated using the following formula: Temperature Rise (ΔT) = I^2 * R * t / (k * A) Where: ΔT is the temperature rise in degrees Celsius. *DK above Trace is Air ( = 1. 5,115. In this calculator, we will show you how to calculate the trace width of a PCB for both internal and external traces. 2. I used trace widths that result in 50 Ohms. 9 x 10-3 ohm/ohm/C Applications The microstrip is a popular device in microwave radio technology. Try running a 10 GHz signal through that path and you will see loss. ) May 17, 2006 - Added (lateral) thermal resistance calculations. The calculator shown below uses Wadell’s equations for differential impedance, which can be found in the seminal textbook Transmission Line Design Handbook. PCB Toolkit with IPC-2152 modifiers Internal Trace 22 mils PCB Toolkit with IPC-2152 without modifiers Internal Trace 55 mils Circuit Calculator Internal Trace 52. Trace width is 4. This calculator determines the resistance of a PCB trace based on its dimensions and copper properties: python import math def calculate_trace_resistance(length_m, width_m, thickness_m, rho=0. For example: Yellow Violet Red Gold: 4 7 x100 ±5% = 4700 Ohm, 5% tolerance 1kOhm, 1% tolerance: Brown Black Black Brown Brown. 9843 mil-thickness: 1. Note that there are many international standard for this sort of thing, e. But if that is what you have, and with FR4, your microtrace width should be around 1. The answer to this question, Characteristic impedance of a trace, shows that a 120 mil trace is required to get this impedance. To use it, first select the. Try This New Tool. This calculator computes the trace width of a microstrip given the following information: maximum current, trace thickness, temperature rise, ambient temperature, and length. substrate. 0). Figure 2. Figure 2: A Rectangular Copper Trace50 ohm pcb trace width calculatorFor a 0. The better solution is to have at least a 4 layer PCB, with a thick core, each side with a GND reference plane close enough (4 mils will be great). A Target Impedance of 50 Ω gives a width of 81. This can bea straight trace inverted F, -type trace,. ”Critical Length. It proved very useful for me when I had to design a board with surface-mount power transistors on. substrate. Designing a plan B is cheap while laying out the circuit board. W = Width of the trace H = Height of dielectric above theThis calculator calculate the resistance of a copper trace based on width, length, thickness and temperature. 79um/60um) = 0. 19mm) traces with 7. *H 5 2. 5A and the material has bulk resistivity 3 times that of copper and it's 60um thick, then it's the same as a copper trace carrying 0. Calculators include PCB Trace Width, Ohm’s Law, Parallel Resistor and many more. If you’re designing an RF PCB for microwave or. Inputs. Peak Voltage: Volts. A 20 mil trace will have a much greater tolerance for losing metal than a 3 mil trace would. To find out the width of the microstrip, enter the target impedance (zo), trace thickness (t),. Propagation delay (t pd) in PCBs is the time taken by a signal to travel through a unit length of a transmission line . Thank you. In this stack-up, the layers are given, the required impedances are given, and the trace width and spacing between the traces are also given. If we make the line width wider, we have to make the dielectric thicker to preserve the 50 Ohms, and this keeps the capacitance the same. Width (W) Thickness (T) Substrate Dielectric (Er) These elements refer to the following diagram : On this list, many are constants and depends on the PCB making process and components. High-quality circuit boards as prototype and series at reasonable prices. Impedance. 5 * sqrt (3) * sqrt (34. This 8W rule also applies to ground planes on the same layer. e. This trace width has been chosen as the narrowest trace width that can be practically achieved in volume manufacturing operations. Why does a 4 layer PCB board significantly reduce the trace Width needed for a 50 ohm transmission line when compared to a 2 layer PCB board? Hot Network QuestionsIt should draw about 1. One thing is for sure: When you are routing a high-speed PCB design you are going to be working with. 3. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. The Smith Chart graphically maps S11=reflection coefficient= (ZL-Z0)/ (ZL+Z0) to Load Impedance (ZL), normalized to Z0 (source impedance = center of chart). There are calculators though, based on formulas presented in the same standard I mentioned before (IPC-2221. 7 10^ (-6) Ohm-cm. 4 mil trace thickness. 9. Impedance. After changing W to 14 mil click “Analyze” and you can see Zo is now calculated to be 49 ohms. This calculator helps translating the color bars from the resistor to its value. What trace width for 100A PCB? Estimation: For a 100-ampere current on a 1 oz copper PCB, you might need a trace width of approximately 300-400 mils (0. W [oz/ft 2] is the track width. 0 and 3. How do I create a tapered trace?The Differential microstrip impedance calculator is used to compute the differential (Zd) and single-ended impedance (Zo) of an edge-coupled microstrip line just by entering the width, separation and thickness of the trace along with the dielectric thickness and constant of the coupled line. The width of the trace you need is in the "W" box. The minimum trace width should be 6 mil or 0. You can certainly size the traces in the SPI bus such that their impedance is 50 Ohms, but this is not required. 300-0. There are four different types of impedance used in characterizing differential trace impedances. The width of the conducting layer is important to. 048, b = 0. from one edge to the other as long as they are squares and the current is distributed evenly. Trace width and spacing depend on your PCB stackup. 'Fast' depends on the frequency and the length of the trace. For the signal trace of width W and thickness T, separated by distance H from a ground (or power) plane by a PCB dielectric with dielectric constant εr, the characteristic impedance isImpedance Matching and Large Trace Widths. $$Z_{0}$$ = characteristic impedance of the microstrip in ohms (Ω). 2. 400 inches). The KiCad PCB Calculator is a set of utilities to help you find the values of components or other parameters of a layout. Now, to get to 0. So, if we route the differential pair in an FR-4 board with 35um copper and plating thickness the targeted impedance will be close to 90 Ohms. More important will be to avoid longer stubs. 5 mil which we can round to 14 mil. 25 mils , t = 1. Now also calculates DC resistance with. from one edge to the other as long as they are squares and the current is distributed evenly. Here, you’ll see a maximum current calculation for that section of trace. via stitching to GND plane. With PCBWay impedance calculator, you can calculate the approximate impedance of your PCB / high frequency circuit board. Therefore, there is a rise in characteristic impedance of 3. 1. Inputs. The next graph investigates this further. The important things are the w/h width to height ratio and also the er constant of the material and the thickness of the conductor. I am just guessing on the Ohms. Use an impedance calculator to determine the trace width (W) and spacing (S) required for the specific board stack-up being used. 6mm thickness and the connector is a SMA. Assuming a standard 0. So Adjust trace width to match the impedance to 50 Ω Ω. The above basic example was to show you how you can calculate the. Impedance calculators or formulas like the one mentioned earlier can help determine the required trace width. For example on 0. For CW (which is indeed the worst-case), the calculations is the same as for DC. No ground plane under Antenna. I am developing a 4-layer FR-4 board containing a GNSS receiver (L1 + L2). Power Loss: Watts. Therefore, the trace height and width you choose for 1 GHz will be a slightly different impedance at 10 GHz (if you need to worry about the difference, you probably already know about the difference!) This model was originally developed by analyzing trace impedance measurements using a regression model. This makes the design very unpredictable due to extra parasitic inductances added to the filter circuit. 18. A is the cross-section area [mils 2], I is the maximum current [A], T RISE is the maximum desired temperature rise [°C], W is the trace width [mils], T is the trace thickness [oz/ft 2], k, b and c are constants. Digi-Key. Click into the Routing -> Width option. For this reason, trace width is important in the design of striplines. 001-91445 Rev. PCB Trace Width Calculator Trace width is an important design parameter in PCB design. As you adjust the width of the line, you can eventually get the microstrip impedance calculator to converge on the. The resistance in real life will vary a bit since. 363A, 1oz, 20c gives 5 mil trace width. The main takeaway for me: To get to around 80 ohms, I should not pull ground on the signal. they normally use 7. 4 GHz -> wavelength in air is 122mm -> wavelength in FR4 is approx. The PCB internal/external trace resistance shall be calculated according to the following formula: R = (ρ * L / (T * W)) * (1 + α * (TAMB – 25 °C)) Where: R is the trace resistance [Ω] ρ is the resistivity parameter, whose value for copper is 1. Use this tool to calculate relationships between current, voltage, resistance, and power in resistive circuits. 3 as fr4 material with 1. The nearby ground planes will be the dominant factor determining the impedance whenever the planes are close to the traces. 6 mm is used) can anybody help me how to calculate 100 ohm impedance. The characteristic impedance of the signal path is a continuous 50 ohm path relative to the closest ground. An air-filled coaxial line has min attenuation when Zo is 77ohm, while max power capacity occurs when zo is 30 ohm. 567 1. Antenna Design and RF Layout Guidelines Document No. I am more interested in the impedance, reactance and resistance of traces in my question for given frequencies in pcbcad softwares for a given layer stackup than the antenna shapes. Effortlessly design and analyze PCB microstrip transmission lines with our Microstrip Transmission Line Calculator. A temperature rise in PCB trace width calculator is a tool or software that helps engineers and designers estimate the temperature rise in a PCB trace based on the trace width, current, and other parameters. Your trace width and spacing calculate out as a 50 ohm trace on a couple of calculators I checked, so that should be okay. Conversely, the spacing might end up being very large for a thicker dielectric. Width of track = 1,65 mm trace thickness = 0,2 mm (from pcb datasheet) height of dielectric above return plane = 1,6 mm (from datasheet) I obtain a Z0 of 70,8 ohm. Just as important as determining an appropriate trace width for a single-ended trace. It’s a three-in-one. 8 Characteristic Impedance: 50 With my values, with a non-standard thickness board (31 mils thick), I arrived at 55 mils. 7 x 10-6 ohm-cm αcopper (temperature coefficient) = 3. Use a 4-layer board so you can achieve h ~= 0. (dielectric constant Dk=4. ) I found AN10778, Sect. 50 Ohm Transmission Line Calculator; Circuit Board Trace Width Calculator; 50 Ohm Pcb Trace; 50 Ohm Trace Width Calculator Formula; The above screen shows that the target parameter is 'Trace Width (W)' and the fixed parameters are 50 ohm Char. Or at least use thin FR4, if you can afford the losses. 000500 ohms per square, or 0. Figure 4. PCB traces - a brief overview Output Impedance (Z): 138 Ohms Choose Type Microstrip Impedance Calculator Edge Coupled Microstrip Differential Impedance Calculator Wire Microstrip Impedance Calculator Embedded Microstrip Impedance Calculator Wire Stripline Impedance Calculator Edge Coupled Stripline Differential Impedance Calculator The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a calculated impedance according to the IPC-2141 standard. Saturn PCB tools Z0=84. I am creating an RF PCB and require my RF signal coplanar trace to have a 50 ohm impedance. 79um/60um) = 0. 3. 9 mil. If the line (or part of it) is short compared to the wavelength, then it is not critical to have the exact width. According to JLCPCB's "impedance calculator" for their JLC7628 stackup, a trace of 11. 127mm. In the image below, the single-ended. I managed so far (using Altium) to setup profiles for a 50 Ω (GPS Antenna) and 90 Ω (USB 2. Schematic:Calculate trace width values based using the IPC-2221 charts by providing inputs such as current thickness and temperature values. Click Synthesize 7. 378 is related to standard 1 ounce pour thickness. RF IC -> Balun N/W -> PCB antenna or Chip Antenna. W = Width of the trace H = Height of dielectric above theThere are also calculators and plugins for common PCB design software that uses IPC-2152 charts to calculate width for you. 9mm. You will need the following information to then obtain certain parameters such as dielectric thickness etc to estimate your 50 Ohms impedance : Work out if you can the required PCB stack-up for the 6-layer PCB. PCB manufacturing tolerance exacerbates the problem, as traces on dual-. You can follow the same procedure to calculate maximum voltage and minimum spacing for all the. It's free to sign up and bid on jobs. The trace is 1 inch wide and 12 inches long. So, you need to calculate how much resistance a PCB trace can provide. In order for an individual trace to have an odd-mode impedance that is equal to the characteristic impedance,. The required inputs are the Dk value for the dielectric constant of the PCB substrate, and the. As a second opinion, here is what Saturn PCB toolkit says: If a 120 thou trace is too wide, moving the plane closer to the trace will help. What is the width of a trace for 100 ohm impedance? The width of a PCB trace for a specific impedance depends on factors like dielectric material and thickness. This will work with the controlled dielectric approach, where you specify the stackup, and then you adjust the width and dielectric constant to hit a trace width and impedance target. I used a similar calculator when I wanted a 50ohm trace for an 868MHz LoRa circuit. The JLCPCB results are more reliable than (some of) the simple formula-based approaches. 7 ohms; common impedance: 19. If you use the same width on different sites,. The PCB trace to the flex cable 4. 254mm, spacing between both is required 0. 5mm FR4, but be careful with discontinuities at the connectors. 7mil is the upper trace width, after etching the trace will be like a Trapezoid,this. 6. This rule maintains the desired signal impedance. We specialize in both Small quantity, Quckturn, and Production printed circuit board Quantities. , 0. Some guidelines: 0. Trace Width: Leave this blank so it calculates it. 1. You can calculate the maximum current using the formula below. from one edge to the other as long as they are squares and the current is distributed evenly. Download Presentation. PCB trace resistance is determined by the thickness, width, and length of the trace. For the other points, the reflections are a result of impedance mismatching. The PCB material will be FR-4 with 1. Figure- Allegro automatically assigns trace width 12. 4 ohms; differential impedance: 90. 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). This tool calculates the matching network necessary to terminate a line of the specified characteristic impedence (Z o) in a specific complex load impedence (R L + jX L) at a specified frequency. The application below provides a simple way to calculate the required trace width (in mil) for a given input current and temperature. 5 mils above ground. The microstrip calculator determines the width and length of a microstrip line for a given characteristic impedance (Zo) and electrical length or vice versa. The total current of this circuit is 1A. 7E-6. 5. Use the max current (Imax) and max current density (J) to determine minimum trace width: Trace Width (mils) = Imax (A) / J (mA/mil2) Add margin of 20% for reliability. We will also. Also, standard FR4 is very lossy at GHz frequencies. First, we would like to know the critical length for a USB signal being routed on a typical 2-layer PCB. This is in parallel to your 50 Ohm lines connecting the high pass section. The tools shows that the required minimum spacing is 160 mils. You should enter the height of the outer layer, presuming you have a ground plane in layer 2. Click here to see the user guide of our impedance calculator. 41] (Section 2. 38. At higher frequencies, the PCB signal trace impedance will depend on the geometry of the circuit, so it has to be calculated. Staff member. We specialize in both Small quantity, Quckturn, and Production printed circuit board Quantities. 062" thick board. ANSI PCB Trace Width Calculator. “Good design practices with FR4 will usually do the trick. When using 4-layer PCB, the gap between Top layer and Internal Layer 1 is only about 0. required current rating, copper weight, the allowable temperature rise of your board). If the length of the trace is also provided, the total resistance, voltage drop, and. The resistance of a trace is important to estimate the power dissipate in a trace or to estimate roughly the voltage drop from a voltage supply based on the current flowing through the trace. I guess, it is only taking resistance in consideration but then , that would depend on the length too?. The legend for all three curves is shown on the middle curve and that is a transmission line built on a 10mil thick RO4350B. Ethernet: Ethernet lines. PCB Impedance-Calculation: Help with the dimensioning of the impedances of your circuit board. ductor Width & Thickness and a Function of the Dielectric Constant ( ) of the Mat-erial surrounding the Lines. You can access serveral online sites to help calculate a trace with Z0 of 50 Ohm. 1. These cables would also span long distances, reaching hundreds of miles. So you will find the elements on your PCB provider website. copper CPWG, using solder mask on top Trace width: 35 mils, Clearance to adjacent ground plane: 8 mils This gives an impedance of 52. You can better understand your calculator results by becoming familiar with the following formulas. nrd_au. PCB Trace Power Handling Calculator. 6mm. 6%. The resistance of a trace on a PCB depends on several factors, including the width and thickness of the trace, the length of the trace. e. 3 mm traces. 2mm and trace-to-trace clearance 0. A basic rule of thumb is that the width of the trace is about equal to the thickness of the dielectric material to achieve a 50 ohm impedance on the line. I can’t select all lines at once and change the track as normally done because some parts of generated impedance matching tracks are also selected and don’t let me using the PCB filter to change all tracks at once!Now, hit calculate spacing to compute the required minimum spacing value. First, for 2. While trying to route a eMMC (for data, clk, etc. 69 volts. RF tracks must have an impedance of 50 ohms. Advanced Circuits is MIL-PRF-31032, MIL-PRF-55110G, AS9100C, ISO 9001:2008 Certified, IPC 6012 Class 2, 3 and 3A Qualified, and ITAR Registered. Mar 11, 2011 #8 FvM Super Moderator. Email: info@multi-circuit-boards. 5. t olera n ce. What is the width of a trace for 100 ohm impedance? The width of a trace for a 100-ohm impedance depends on the PCB. . 9 mil. Coplanar Waveguide With Ground Characteristic Impedance Calculator. For a Dk = 4. One solution is to reduce the dielectric thicknesses. A Target Impedance of 50 Ω gives a forward calculated width (W1) of 94. 16 mm. 127mm. Altium Designer users can access an automated IPC-2221 calculator inside the routing tools in the PCB Editor window. Overview. Enter into the calculator with other parameters like allowable temperature rise. . 38. 0. When I use Jean Nicolle calculator Z0=89. 725. A 50-ohm trace on a typical two-layer board is around 110 mils wide. On each site, the trace width that results approximately 50 Ohms is different. PCB Impedance Calculation. 50 Ohms. This is good enough so we can now switch to the “Coupled Microstrip Line” calculator. trace. 8 mil traces, and that is assuming no space. A = (T x W x 1. I used some online calculator to calculate parameters of trace so it has 50 Ohm impedance. If you reduce this trace width to 19 mils, the characteristic impedance will result in about 52. 100 Ohms was had to achieve on PCBs at that time since trace widths were greater than 6 mils usually. At an impedance mismatch, a portion of the transmitted signal isYes, and the substrate height is wrong in the calculation input. However, other impedance values are possible. 000000017): if width_m > 2*thickness_m: area_m = thickness_m * width_m else: area_m =. The IC only has room for 18. Phone: +44 (0)1425 489 111 / +49 (0) 8104 628 0. Standard FR4 1. I am developing a 4-layer FR-4 board containing a GNSS receiver (L1 + L2). Datasheets. 254mm,. 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. It is one of the most crucial factors that should be calculated and analyzed when designing a PCB. I MAX = (K x T RISEb) x A C. The PCB internal/external trace resistance shall be calculated according to the following formula: R = (ρ * L / (T * W)) * (1 + α * (TAMB – 25 °C)) Where: R is the trace resistance [Ω] ρ is the resistivity parameter, whose value for copper is 1. 3. 005' trace for 50 ohms) T = Trace thickness in inches (usually ½ oz to 10 oz ie. 11mm) you get very narrow 50 ohms transmission lines (0. This tool will also compute the resistance of the stripline, the voltage drop on it, and the resulting power dissipation. 4 mils or 0. Class creation for controlled impedance routing using Altium Designer Classes for 50 and 100-ohm traces. 1 Ohm, the trace length must be about 8. On a typical high speed multilayer board you may have something around 100um trace width and 100um dielectric thickness. T. 1 mm gap (x2), and even 1 mm ground width (x2) is less than the 2. 4 mil trace thickness. 3 as fr4 material with 1. Phone: +44 (0)1425 489 111 / +49 (0) 8104 628 0. $egingroup$ Thanks @KH ! If you will focus on the questions that are in the body and not in the title, I guess the answer will be a bit shorter. PCB Impedance-Calculation: Help with the dimensioning of the impedances of your circuit board. We get a lot of questions about trace impedance and how to calculate the right trace size to hit a specific impedance in a manufacturable PCB. 6 mm thickness, 1 oz. 6mm thickness ,signal trace thickness is 1oz. −PCB 50 ohms, 4 x 1 pF loads: 41 ohms −PCB 45 ohms, 4 x 1 pF loads: 37 ohms −PCB 40 ohms, 4 x 1 pF loads: 34 ohms −PCB 62 ohms, 4 x 2 pF loads: 41 ohms −PCB 50 ohms, 4 x 2 pF loads: 35 ohms −PCB 45 ohms, 4 x 2 pF loads: 33 ohms * depends on length of loaded region (pF/length) All PCB impedance = Rtt Tune Lead In Zo and RttAs logic circuits developed, the need for faster interconnects increased, making impedance levels increasingly important. 7E-6 [Ω · cm] L is the trace length [cm] T is the trace thickness [cm] W is the trace width. These calculations are complex. 5 mil which we can round to 14 mil. You. . It made sense to have 2 50-Ohm traces (50 was a good round number for most VNAs, too. 5: 5. 3 can then be used to design a PCB trace to match the impedance required by the circuit. The bottom line is: check with your fabricator when planning a 4-layer PCB stackup with 50 Ohm impedance. Let the PCB manufacturer know of your intention to request the manufacture of a 6-layer board. I wanted to use Altium to calculate the width of the trace automatically, so that it had a 50 Ohm impedance. This is the reason why engineers specify the trace width in their designs. Let's calculate the trace thickness and trace spacing- Som with a 15% tolerance and 90 Ohms targeted impedance, the conductor width required 0. except for W, the width of the signal trace. 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. Doubt about 50 ohm impedance calculation. Instructions. 020-0. It shows the minimum trace-to-ground spacing required to produce a 50 Ohm. The calculator shown below uses Wadell’s equations for differential impedance, which can be found in the seminal textbook Transmission Line Design Handbook.