. The normalized input impedance for that transmission line is read from the Smith Chart to be 1 - j0. In this paper, the uncertainty and the impact of imperfect load calibration standard for on-wafer Through-Reflect-Match calibration method are analyzed with the help of 3D electromagnetic simulations. The end of the transmission line is hooked to an antenna with impedance ZA. The K values for the various transmission lines are also copied from his Transmission Line Details windows. trace geometry, and use this to. A transmission line can be used instead (Fig. Key Takeaways. Mismatch Loss When Both Ports are Mismatched. 3. Real part is to around 50 and imaginary part should be around 0. A 9:1 transformer will yield a 50-Ohm match to a 450-Ohm impedance. 1) describes the series connection of short- and open-circuited stubs having characteristic impedances of Z 0 / 2 and half the original electrical length. Enter all the Resistive values in ohms, C in pF and L in nH. To find the length of the series line, d, we can draw lines from the center through z L and point A outward to the edge of the chart and measure the corresponding arc, leading to d = λ/8. An audio transformer with an impedance ratio of 15:1 is to be used to match the output of a power amplifier to a loudspeaker. The LNA is designed to the target gain and noise figure specifications over a specified bandwidth. The simplest termination is either a short circuit or an open circuit. 4 j Plot this at point z1. In solving problems around matching, the smith chart is used to determine the value of the component (capacitor or inductor) to use to ensure the line is perfectly matched, that is, ensuring the reflection coefficient is zero. F. 338λ - 0. on the line. Figure 2. The characteristic impedance of a transmission line is purely resistive; no phase shift is introduced, and all signal frequencies propagate at the same speed. The drawback of this approach is that if the load is changed, the location of insertion may have to be moved. Understanding coax can be helpful when working with it. 2 (b). 5. A Clemson ECE635 Project by Adam Schreiber and Jason Byers. It’s crucial that the reactive components cancel each other. Also, what is the ECE145A/ECE218A Impedance Matching Notes set #5 Page 13 Basis for distributed matching using transmission line segments: the equivalent circuit model of a short transmission line. The required values are trace thickness, substrate heights, trace width, and subtrate dielectric in the calculator above and press the "calculate" button. 86 nH. Why is it that impedance matching does not matter if the transmission line is shorter than the wavelenght of the signal? Consider a couple of wires twisted together, about 1 inch long. In Figure 6, we implicitly assumed that the impedance of the signal source (not shown) is matched to the line characteristic impedance. the source impedance g Z. Frequency-dependent transmission line behavior can also be introduced by loss, as discussed in Section 8. To simplify our analysis, we can model the input of the device receiving the power with it input impedance (e. Dielectric Thickness: mm. On the other hand, 75 Ω products are best suited for applications that involve transmitting or routing video signals (e. , one that does not use length), you only need to know impedance and velocity. Z g. Figure (PageIndex{4}) Solution. Another common application is the balancing and impedance matching of wideband converters to unbalanced sources, which generally exhibit port. 19. To stick closests to the lossless approximation, we pick n. Frequency span ±. 9 Ω and a positive imaginary part (+j99 Ω) to ensure maximum power transfer will be achieved. 8. 19. 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. A simple form of variable impedance matching device is the single stub tuner. A Transmission Line Connecting Source & Load We can think of a transmission line as a conduit that allows power to flow from an output of one device/network to an input of another. 1. a. With a two-section cascaded quarter-wave transformer an appropriate matching network is shown in Figure 7. Conductor size, space between conductors, what plastic was used in the insulation — all affect line impedance. Description. Pick a signal frequency for your taper. stubTL4 = rfckt. Select a trace impedance profile over the length of the taper. Users need only specify the material properties for. 39 for the effective dielectric constant. I am planning to use coplanar waveguide with bottom ground layer as transmission line. Return loss is an important parameter to measure in transmission systems because it can affect the system's performance. 9 Ω and a negative imaginary part (–j99 Ω), we need a source impedance with a real part of 9. 1 (a). You can easily construct your own transmission lines with a. Next, substitute the values into the formula: Z0 = sqrt ( (R + jwL) / (G + jwC)). g. 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. I'm designing a circuit with RFICs using differential signaling. 2 Figure 1-2: Circuits with simple reactive loads. At f=0 Hz: input: V=0, I=13. The nice part about coax is that it can be bent and flexible unlike most pcb transmission lines. Theoretically this is true only for lossless transmission lines—i. This can be built into a FLEXI-BOX and a transmission line (50 Ohm track) PCB is available which easily adapts for this circuit with one simple trimming. A two-port impedance model represents the voltages of a system as a function of currents. 57 pF can be used. 1 (a) presents the problem of matching to the input of a transistor which is modeled here as a capacitor in series with a resistive load. Coverage. I used an online. In addition to the characteristic impedance of a transmission line, the tool also calculates. The tool implements numerical solutions of Maxwell’s equations to render accurate and consistent results. Input impedance (Ohms) Desired output impedance (Ohms)Transmission-line impedance matching circuits are used at higher frequencies where the lumped elements become very small and impractical to use. The Sierra Circuits Impedance Calculator uses the 2D numerical solution of Maxwell’s equations for PCB transmission lines. The circuit got its name because the inductor and the capacitor form a Pi symbol (see schematic below). This has been found practical for testing 50-ohm to 75-ohm transformers, for which matching pads are readily available. Assuming you chose a transmission line topology, then you would need to compute the electrical lengths and impedances to use. To verify the design, assemble a circuit using 50-Ohm microstrip transmission lines for the matching networks. That is, we want ZL=Z0 (or Zin=Z0). Figure 6. This is read from the point where the circle you drew intersects the Re{ Z N} = 1 circle. Let's use the mixer (LT5560) as an example. 5 + 12. 585° long line moves us from the constant-resistance circle of r = 2 to the r = 0. In Figure 3. The green boxes turn red if the numbers are outside the range for reliable calculation. Calculate Reset Result Characteristic Impedance ( (Z o) Ohms Formula for Quarter Wave Transformer Impedance Calculator Derevation of the Quarter Wave Transformer. Single-stub matching is a very common method for impedance matching using microstrip lines at frequences in the UHF band (300-3000 MHz) and above. 7. 7 gives 49. Reflection-less match. One commonly used formula for calculating the characteristic impedance of a PCB trace or transmission line is the capacitance per unit length formula: Z0 = 1 / (C / L) where Z0 is the. The purpose of integrating output-damping resistors in line buffers and drivers is to suppress signal undershoots and overshoots on the transmission line through what is usually referred to as line-impedance matching (see Figure 1). Output-Damping Resistors. The Z-parameter matrix of a two-port model is of order 2 2. Stub Matching - Impedance (Z) over a 180 degree cycle along a lossless transmission line. The following parameters are fixed values: Parameter. This example is to design a single section quarter-wave transformer to match the 100 Ω load to a 50 Ω transmission line at an operating frequency of 2 GHz. In coaxial cable or two-wire line applications. referred to as a balun. Using a transmission line as an impedance transformer. It's also explained on our DK and DF Extraction page. 41)] * ln. In some cases, users require a custom impedance value. All of the reference schematics match to 50 ohms and use a balun to convert the differential inputs and outputs to single ended. 1, the top (visible) traces comprise one conductor, whereas the ground plane (underneath, so not visible. 45 GHz. . This article offers an introduction to the Smith chart and how it’s used to make transmission-line calculations and fundamental impedance-matching circuits. This calculator is designed to calculate the characteristic impedance of a broadside couple stripline (see diagram below). Coplanar Waveguide Calculator. 16. 5 GHz. Fig. It’s simply defined as the process of making one impedance look like another. 15. 1. View All Tools. The values of Lp = 11. A common dipole, driven from the center and 1/2 λ above ground, will exhibit approximately 72 Ω of impedance. 1x the wavelength of the signal. The green boxes turn red if the numbers are outside the range for reliable calculation. How much power does the generator deliver? Answer: The diagram for this problem is given in the following diagram:Rho: Conductor resistivity relative to copper. In most cases, the impedances are purely real (not inductive or capacitive). Characteristic impedance is purely a function of the capacitance and. Reflection-less match. 1 6. The voltage is maximimum at one end and minimum at the other end, and the opposite is true for the current. Given impedancesZ, Z1 and Z2, deduce the lengths l1 and l2 of the matching sections. While transferring this energy, it is important to zero or minimize energy losses that occur. For this to be possible, we should match the source and load impedances to the transmission line being used. 6. A PCB transmission line calculator you'll find online or in many design applications can't be used to get accurate impedance values because they do. Also, what is theFigure 2. The lateral dimensions, however, are well controlled being photolithographically defined and then etched. 1, which shows an impedance matching network placed between a load impedance and a transmission line. Given a characteristic impedance of Z 0 and a load with complex impedance Z L , this application will calculate. 5mm pitch. 15. 4. Although implementations vary, the wire diameter is usually about 1 mm and and the wire spacing is usually about 6 mm. With the transmission line clearly defined as a circuit element, it can now be analyzed when a load is attached. Such equipment is best suited for communications applications, which make up the bulk of RF applications. Based on the number of stubs used, the stub impedance matching can be. Perhaps the most common type of transmission line is the coax. Figure 3: Finalized lumped-element impedance-matching. RF impedance matching can be implemented in two different ways -. 037λ and 0. 6 Summary. Tutorial on RF impedance matching using the Smith chart. The complex (R ± jX) input impedance of amplifier B should be matched to the complex output impedance of amplifier A. The chart is used during RF simulation by RF engineers and is displayed by vector network. There are a lot of online trace impedance calculators specifically designed for differential traces. 3 and 12. To find the length of the stub, we should consider the impedance of point A. This impedance matching calculator calculates either the turns ratio or the impedance which will allow for impedance matching between primary and secondary circuits. Calculate the impedance of a coaxial transmission line. The calculator produces more accurate results than the IPC formulas for impedance because it. 6 GHz over more than 10 GHz of bandwidth, providing a 4:1 impedance transforma-tion from 25 to 6. Also, what is theECE145A/ECE218A Impedance Matching Notes set #5 Page 13 Basis for distributed matching using transmission line segments: the equivalent circuit model of a short transmission line. To use this calculator, simply input your microstrip geometry and Dk value, and the tool will return the differential impedance value for a pair of microstrip traces. Find coefficient of reflection (mag, & angle) and SWR. Thickness: Thickness of the microstrip conductor. The free end of the stub is either left open-circuit or (always in the case of waveguides) short-circuited. Some of its key features are; displays insertion. The effective output impedance of the line driver (ZO) is matched with the line. You can plot the VSWR circles. The edge couple differential microstrip transmission line is a common technique for routing differential traces. Maximum power transfer. It is improved for Rev 3 (July 2017. Key parameters for a transmission line-Characteristic impedance (only impacts S-parameter -calculations)The calculator below uses Wadell’s equations to determine the differential impedance of symmetric striplines, which can be found in the seminal textbook Transmission Line Design Handbook. Note the stub is attached in parallel at the source end of the primary line. The input impedance is purely real since the line length is one quarter wavelength: This impedance is used to calculate the depth ( D) into the patch antenna. 13. Mismatch Loss (dB) Γ = Z L-Z O Z L +Z O Where: ZL = Load Impedance ZO = Characteristic Impedance From the above equations, it can be seen that when ZL = ZO (Load impedance is matched to the characteristic impedance), the reflec- tion coefficient (Γ) = 0, making VSWR = 1. A Delta Match is intended for matching a driven element to 300-600 Ω balanced feed line. between a t ransmi ssion line of characteristic impedance Z o and a real load i mp edan ce R L1 yields a matched system. 6. This calculator finds both odd and even transmission line impedance. e. The first thing to know when calculating the impedance of a wire is whether it's a coaxial or twisted pair cable. In this case, the line length will always be 1/8th of the signal wavelength: Complex-to-real impedance transformer line length when the matching line’s impedance equals the magnitude of the load impedance. tline is intended to calculate various transmission line parameters. At low frequencies near 0 GHz, the input impedance is inductive since. Although implementations vary, the wire diameter is usually about 1 mm and and the wire spacing is usually about 6 mm. View All Tools. In terms of how these calculators work, the impedance of a transmission line in a PCB can be calculated in four ways: Use the R, L, C, G parameters from the Telegrapher’s equations to calculate the impedance of the transmission line. The term “impedance matching” is rather straightforward. Impact of characteristic impedance (Z 0) on tpd. Secondary impedance, Z S: 2000Ω. Click the Z_Load buttons to see impedance examples; A Match is at dead center (reference impedance Z0 ) A Short is at the far left; An Open is at the far right; Pure real. Relative Dielectric Constant ( εr ): Track Width. The impedance seen by the source is simply given by Z= jωL+ 1 jωC +R= R+jωL 1− 1 ω2LC (7. 1: 300 Ω 300 Ω twin-lead. 2. Zin = ZS Z in = Z S. 6(b) (red), imple-the transmission line. The actual input impedance to the terminated line isSo, the dielectric at my 5-6GHz frequency range is 3. The TEM mode exists down to DC. Is it matched well? 2- For a 50 ohm lossless transmission line terminated in a load impedance ZL=100 + j50 ohm, determine the fraction of the average incident power reflected by the load. 2: Matching Network Design With Complex Impedances. Therefore, next part is divided in two parts as detailed below. Variation of impedance with track width (Pitch fixed at 200um, so reducing the track width will increase the separation. First, determine if the microstrip line is a suitable choice by analyzing the default microstrip transmission line at a design frequency of 1. Note the stub is attached in parallel at the source end of the primary line. or any device with a web browser. L/2 L/2 C L C/ 2 C/ 2 Z0 , τ L = τ Z0 C = τ/ Z0 τ=A/vp Let’s approximate a shunt inductor with a transmission line section. This will also provide the time delay the cable provides for a signal and also the capacitance and inductance per. SMITH CHART AND IMPEDANCE MATCHING Impedance matching: lumped elements Example: Matching a dipole. Both cases will be considered. Figure 25. 6. Calculate the Transmission Line impedance Z0 for a large variety of mechanical structures. 338λ - 0. Example 3. They consist of shorted or opened segments of the. Press Analyze to see the results. This online RF transformer calculator calculates the turn ratio (Np/Ns) and (Ns/Np) of an RF transformer by entering input/primary impedance Zp (O) and output/secondary impedance Zs (O). Most importantly, it computes the critical length of the trace. Since the line is 7. The Smith Chart graphically maps S11=reflection coefficient= (ZL-Z0)/ (ZL+Z0) to Load Impedance (ZL), normalized to Z0 (source impedance = center of chart). Single Stub Matching. The quality of an impedance match can be expressed mathematically by the reflection coefficient (Γ). The voltage reflection coefficient Γ, given by Equation 3. In addition, the calculation takes into account the effect of signal attenuation in the transmission line. Ω/mΩ/in. This calculator allows you to calculate the input impedance of a transmission line, as well as the VSWR, return loss, and mismatch loss at the input point. The characteristic impedance (Z o) of a microstrip transmission line can be calculated using the active calculator or the equations at the bottom of the page. The matching network design described in this section is. This can be achieved by regulating the inner and outer diameter of the coaxial cable, along with the. 2 Matching using Cascaded Transmission Lines and Constant Q Circles. trace geometry, and use this to calculate impedance. The characteristic impedance represents the ratio of voltage to current in a transmission line and is a critical parameter in ensuring signal integrity and impedance matching in high-frequency electronic circuits. 3 3. The phase is mostly + 90 ∘ or − 90 ∘, indicating that Zin is mostly reactive. 71 Ω. The calculator shown below uses Wadell’s equations for differential impedance, which can be found in the seminal textbook Transmission Line Design Handbook. 1: 300 Ω 300 Ω twin-lead. Here, the antenna impedance matches the transmitter output impedance. 1. These equations are relatively simple compared to other transmission line geometries, comprising only 2 interrelated equations for the microstrip impedance. The default units for all given values, except the. 75. Calculates the resistor values, attenuation, minimum attenuation, 'impedance', reflection coefficient, VSWR and return loss of a matching Pi attenuator. One other example is the delivery of maximum power to an antenna . USB data lines have 90 ohm wave impedance so a transmission line with infinite length would look like a 90 ohm resistor for a DC signal that is applied forever as. Shunt Capacitance –accounts for Line-Charging Currents d. It is tempting to think that a better result could be obtained by having sections of various lengths. For lossless transmission line, characteristic impedance, Z 0 =√(𝑳/𝑪)This calculator will help you determine the correct values for the inductor and capacitor in an L-match impedance matching circuit. Transmission of electrical energy from the source to the load is done using a transmission line. Single Stub Matching using parallel connection. This calculator is designed to help calculate the value of the resistors R1 and R2 to be used in T-pad attenuator. A tapered impedance matching network is defined by two characteristics—its length L and its taper function Zz 1 (): z −3A −2A −A 0 Z 0 Z 1 Z 2 Z 3 R L Z Multi-section impedance taper Continuous impedance taper1- Assume the load is 100 + j50 connected to a 50 ohm line. Press Analyze to see the results. All we need to do is calculate the proper transmission line impedance (Z 0 ), and length so that exactly 1/4 of a wave will “stand” on the line at a frequency of 50 MHz. . Realization of Accurate Load Impedance Characterization for On-Wafer TRM Calibration. Consider a voltage source, with generator impedance Zg, hooked to an antenna with impedance ZA via a transmission line. Step 2: Use a shunt (series) reactive element to resonate with (or cancel) the imaginary part of the impedance that results from Step 1. 4. To arrive at the correct positive value, simply. Draw a circle through this point around the center. Series Impedance –accounts for series voltage drops Resistive Inductive reactance c. (In fact, there are installations that use such transformers at both the shack and tower ends of long runs of 450-Ohm transmission line to reduce losses that would be incurred with an all-coax system. A great example is the surface microstrip which forms on the outer layers of the PCB. com Antenna/filter, power combiner/divider, coupler. V~(z) = V~+ 0 (ejβz +ΓLe−jβz) I(z) = V~+ 0 Z0 (ejβz − Γe−jβz) (1) (2. Generally, the cable manufac-Online calculators will generally use Wadell's equations to determine the transmission line impedance numerically. ; Z 0 is the characteristic impedance of free space (approximately 377 ohms). Most RF Coaxial Cables have an impedance of 50 ohms or 75 ohms. 7, as shown in Figure 6. It’s worthwhile to investigate theThe goal is to match the input impedance (Zin) to the transmission line (Z0). If the line impedance is closer to the target impedance, then the critical length will be longer. 6. The complex conjugate of z S is marked as point A on the Smith chart. 1 shows the two typical situations that arise. e. Here lies the challenge: impedance calculators must balance speed and accuracy. 7. 4 6. The lines operate at 300 MHz. In general, θ = ( π / 2) ( f / f 0). 2 are defined as. In simple terms power transfer takes place. Z0 = SQRT ( ZL * Zin) Z 0 = SQRT (Z L ∗Z in) Where Z0 is the characteristic impedance (ohms) ZL is the load impedance (ohms) Zin is the input impedance. In this section the four main impedance transformers are compared: the linear taper, the Klopfenstein taper, the quarter-wave transformer and the. 6. 331 1 2 5. 7. Learn about why matching networks are used and how they are designed. Most RF test and measurement equipment manufactured today has a characteristic impedance of 50 Ω. The input impedance and load impedance are on the same SWR circle. High Frequency Example. In some cases, a calculator will return a negative value for the electrical length of L1. One of the features of this type of microstrip is the coupling between lines. This is the typical model for the input of a FET. The Er (relative permittivity) is set as a common factor for all the possible mechanical designs and calculations. Figure 1: An impedance matching network matching an arbitrary load impedance to a transmission line Impedance matching is needed according to [1, 5] for the following reasons: i. These include series, shorted shunt section, and open shunt section. if Re( Z / Z 0 )>1), network (a) can be used; otherwise network (b) can be used. It displays the impedance of the input and output match in a 50Ω test environment as measured on a network analyzer. Critical length depends on the allowed impedance deviation between the line and its target impedance. TX-LINE software is a FREE and interactive transmission-line utility for the analysis and synthesis of transmission-line structures that can be used directly in Cadence ® AWR ® Microwave Office ® software for matching-circuits, couplers, and other high-frequency designs. RF transformers are ideal for use in impedance matching to maximize the power transfer & suppress signal reflection, step-up/step-down. 3, respectively. "Series-Section Transmission-Line Impedance Matching," QST (July, 1978), 14-16. The result here reduces to any odd multiple of 1/8th the signal’s wavelength. 1. Suppose that Zg=50 Ohms, ZA=50 Ohms, Z0=200 Ohm, and that the line is a quarterwavelength long. 7 + −1. This calculator will help you determine the correct values for the inductor and capacitor in a Pi match impedance matching. With a two-section cascaded quarter-wave transformer an appropriate matching network is shown in Figure 7. The required parameters are the signal (or source) frequency, the impedance of the source and the impedance of the load. The basic idea of impedance matching is illustrated in Figure 5. The ideal lossless transmission line (TL) block is designed for a characteristic impedance of 50 Ω at 3 GHz and an electrical length of 0. Impedance matching is a fundamental concept in electrical engineering that often presents challenges for even the most experienced practitioners in the field. Such a stripline is constructed with two traces referenced to the same reference planes above and below the traces with a dielectric material between them. Then use an L-pad calculator like this: - You can double check the formula derivation on that site. There are some advantages to using a. Cable Impedance Calculator. Fig. To locate this point the arcs corresponding to the real and imaginary parts of (z_{L}) are considered. By tapering a transmission line, a very broadband impedance match (low VSWR) can be realized over a wide bandwidth, the longer the taper, the wider the frequency band. Matching the characteristic impedance with load impedance [ Z0=ZL] Stub impedance matching utilizes transmission line segments called stubs. We now consider values Γ that arise for commonly-encountered terminations. com. Sending-end port A ~ A' B B' Transmission line Generator. The microstrip is a very simple yet useful way to create a transmission line with a PCB. antenna impedance, Za*SU, shunted by the inductance impedance, j X , of the short transmission line formed by the added gamma rod as seen at the input end of the gamma rod. Basic Appl. A quarter-wave impedance transformer, often written as λ/4 impedance transformer, is a transmission line or waveguide used in electrical engineering of length one-quarter wavelength (λ), terminated with some known impedance . 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. This calculator finds both odd and even transmission line impedance. When in doubt, use 1 for copper, . When Z = Z2 is real, then the lengths of the matching sections. To achieve matched impedance, multi-section transformers are connected between the feeder transmission line of characteristic impedance Z 0 and the load impedance Z L. 6. Home. The edge couple differential microstrip transmission line is a common technique for routing differential traces. Suppose our unmatched load impedance is Z = 60 - i35 Ohms; if the system impedance is 50 Ohms, then we divide. Note: Units do not matter for this calculation as long as they are consistent. 2 and 3. This transmission line calculator calculates the impedance at input and attenuation of a given transmission line once terminated with the given load. In DC circuits, the source and load should be equal. For 25 ohms, we calculate 31 mils line width and 7. Most formulas calculate impedance from width. Mismatch Loss When Both Ports are Mismatched. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. 718. e. . 301λ can do the job. We know that ZL in this case is 50 ohms, due to the. Z 0 A V g g. 86 L ≈ 9. 2. Design broadband matching networks for a low noise amplifier (LNA) with ideal and real-world lumped LC elements. We recommend the software from Polar Instruments if you want to get exact impedance calculation. The wideband matching techniques described in this section use multiple quarter-wavelength-long transmission line sections with the lines. Calculate the nominal impedance of the loudspeaker required for maximum power transfer. Let’s consider a transmission line of length L with characteristic impedance Z C and load impedance Z L, as shown in Figure 25. Calculates the. 66, the trace height is 1. 4. Step 2: Use a shunt (series) reactive element to resonate with (or cancel) the imaginary part of the impedance that results from Step 1. To determine the characteristic impedance of the parallel-plate waveguide first calculate the voltage of the top plate with respect to the bottom plate. 1: A source with Thevenin equivalent impedance ZS Z S and load with impedance ZL Z L interfaced by a matching network presenting an impedance Zin Z in to the source. It consists of a transmission line with a sliding short circuit (similar to a trombone) that can be used as the reactive element in the impedance matching method shown in the Smith charts above. L/2 L/2 C L C/ 2 C/ 2 Z0 , τ L = τ Z0 C = τ/ Z0 τ=A/vp Let’s approximate a shunt inductor with a transmission line section. L networks for narrowband matching a source or load impedance Z to a transmission line with characteristic impedance Z 0. From this equation, we get that the inductance is L ≈ 9. The majority of impedance matching designs are based on a combination of resonance and absorption. Feedline Impedance (Z (Feedline)) Ohms. In that case I need to design a transmission line which has characteristic impedance of 50 ohms.