Questions tagged [characteristic-impedance]

Characteristic impedance is the ratio of the amplitudes of voltage and current of a single wave propagating along a transmission line (i.e. without reflections traveling in the other direction). Its SI unit is the ohm.

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Characteristic impedance when routing differential

Can the characteristic impedance value of a single-ended transmissions line be omitted when the two transmissions lines of a differential pair are routed differentially (not two isolated lines)? I ask ...
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Voltage along transmission line with scattering parameters and VSWR given

A transmitter is connected to an antenna with a coaxial cable with length \$l=1.5 \:\text{m}\$. The characteristic impedance of the cable is \$Z_0 = 75 \: \Omega\$ and the scattering parameters are \$\...
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Lossless quarter wavelength transmission lines

so my lecturer released a past paper with the answers and I have no idea how he got the answer to this question. Please could someone explain it to me? Thanks. The question is: A lossless quarter-...
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Calculating the new per unit impedance of a transmission line

The per unit impedance of 98 km of 412 kV transmission line is (0.768 + 4.823i) x 10^-3 to bases of rated voltage and 115 MVA. Calculate the magnitude of the per unit impedance when the apparent power ...
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Why are we able to ignore the henries, Hz, farads, siemens and ohms when calculating the characteristic impedance of a transmission line? [closed]

I have seen calculations, and every time we just take the coefficents of these values and end up calculating a simple complex number. The units all equate to various exponents of area, second, metre ...
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What does a 50 ohm coax "look like" when neither the source nor the load are matched to it, and the center conductor and shield are used for signals?

Say I have a π-network filter for which the inductor is on a separate board. For convenience, I use a 50 ohm coax (4" long, frequency is 13.56 MHz) to connect to the inductor, using the center ...
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Output composite video (PAL) signal from FPGA DAC, totally lost in the analog domain

I'd like to start generating (and perhaps also capturing) composite video (PAL) signals from a digital source, eg. FPGA. However, while my digital logic/programming skills are covered, I'm lacking a ...
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is the characteristic impedance of a cable an actual impedance in the circuit?

Say you have this simple RF circuit : I "understand" that \$Z_0\$ must match \$Z_s\$ and \$Z_L\$ for maximum power transfer to the load. However, it has never been clear to me how to treat ...
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Transmission Line Step Response

This question seeks a canonical answer to a question regarding the transient response of a transmission line. Suppose one has a transmission line, long enough to be considered "infinite" for ...
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Thevenin equivalent of open ended transmission line Clarifications required

I am going through the below link for understanding about transmission line reflections. The below figure is an equivalent circuit of an open-ended transmission line. For finding the the voltage at V+ ...
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Via fence distance to the trace?

We have a board design with four layers that uses coplanar waveguide with ground plane: The trace has via fences. Originally, the design was: W=0.35mm, S=0.2mm, and H approximately 0.2mm (for one of ...
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Differential Impedance Matching

Below is a small portion of a schematic which I have seen It mentions that the transmission line will have a differential impedance of 100ohms between them. In case of Single ended it would be 50 ...
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Practical formula/method to predict the necessity of termination resistor

I am not into high frequency much and just know about ringing caused by reflections due to impedance mismatching in transmission lines. So I recently saw some non-engineer researchers in a lab that ...
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Using a miniature BNC connector on a PCB to measure high-frequency content with an oscilloscope

I am a power electronics engineer in R&D and often measure fast switching waveforms, specifically high bandwidth MOSFET gate signals. When connecting oscilloscope probes in the past I have found ...
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Calculating lengths of single-stub transmission line when all 3 characteristic impedances differ

Consider a transmission line circuit like the following but where \$Z_{o2}\$ was also unique (say \$Z_{o2}=7\,\Omega\$): I know how I would find \$l_1\$ and \$l_2\$ using smith charts: $$Re\left\{Y_n(...
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Transmission lines in paralell for RS485

I have a system with two RS485 transceivers connected by a 300 meters long cable, with 6 wires inside it. In this case, 3 paralell wires of this cable are being used for the "A" signal and ...
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Deriving the S-parameters, different Matched Loads possible?

I guess this is more of a conceptual question but for the problem below Im having trouble getting started on how to derive the S parameters for the network. I noticed that the network at 28.025 GHz ...
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J-Y(ST)Y..LG cable's charachteristic impedance

First: How to find out (e.g. calculate) the characteristic impedance for the cable mentioned? Id like to know how to model that cable in e.g. Ltspice, so I would like to know either Z or L' and C'. ...
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Characteristic Impedance vs Frequency

I am reading this paper and I see that characteristic impedance does not take frequency into account. I am surprised by this as I figured different rise time signals would have different frequency ...
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Impedance/Termination of Marvell PHY

I'm trying to understand the proper way to design a PCB to interface a Xilinx 7-series FPGA with a Marvell 88E1512 Ethernet PHY, without simply copying the design from an existing schematic. The ...
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Matching line driver output impedance over wideband

I'm designing a high impedance line tap for 10-10GBASE-T ethernet signaling. In the AFE I have a JFET LNA for high input Z which goes to a var. gain amplifier that is a fully differential ADC driver. ...
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How does wiring two LNAs in parallel affect charactaristic impedance?

It appears that wiring amplifiers in parallel improves the signal to noise ratio. I thought I would experiment with two SAV-541+ LNAs in parallel and see how they perform: How does wiring an LNA in ...
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Coax Cable Wave Impedance, Capacitive Load

I am studying the behaviour of cables over frequency, especially what a source sees, and have 2 Questions, as I did some simulations in LtSpice. As a model for the cable I used the "Lossy ...
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Load to Source impedance match for non-constant load impedance

i have a rf-system that is working in frequency range of 100 MHz and try to match the impedance of the load to the source system (50 Ohm). So, in general, i know that a network (P- or T-Network) has ...
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Impedance Matching of an Antenna

I am reading about antenna design and have a few questions which I could not get clarified. I read about "Stubs". I got to know that Stubs are used for impedance matching of an Antenna either by ...
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Stripline (with target impedance) between ground and power planes?

The common idea for a stripline is that the trace is sandwiched between two ground planes. My question: is it the same, for the purpose of characteristic impedance, to have a ground plane or a power (...
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Why is 50ohm sometimes used as a differential impedance?

I'm creating a design where I convert an RF single-ended signal to a differential signal with a 5400BL15B050E RF balun that is then fed to a ADL5802 RF mixer. The balun datasheet specifies the single ...
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The explanation about why do we define the formula of Characteristic impedance,propagation constant and Velocity propagation

There is a long transmission line 1.Characteristic impedance \$Z_C=\sqrt{\frac{z}{y}}=\sqrt{\frac{impedance}{admittance}}\$,and in the lossless line,\$Z_C=\sqrt{\frac{L}{C}}\$ 2.propagation ...
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Physics behind signal reflections and series termination

I have been looking for cause of signal reflections in transmission lines. Everywhere it is concluded that the reason is impedance mismatch. I can understand if the impedance changes in the path of ...
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Transmission Line Impedance 3 phase

I have the following question that I can't seem to figure out. The question ask to solve for the impedance of a 3ph transmission line. I've found the De (distance relative distance) and XL using the ...
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Confusion in understanding characteristic impedance and input impedance of an open circuited transmission line

The characteristic impedance Zo can be derived by considering LC sections throughout the line with open circuit at the end of the line, and this value is independent of length of the transmission line ...
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Impedance matching to minimize VSWR

I was trying to determine what the impact of impedance mismatching would be to an RF output and I came across this. About half way down the page, the author makes this claim. In general, if the ...
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Ringing problems on the output of inverter/comparator

I'm trying to drive some RF switches that need 0 to -5 V control logic with a 0 to 3.3 V signal. I found 2 topologies for this level shifting effect, one using a comparator and one using an inverter. ...
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How to estimate characteristic impedance for a random cable and tolerance of the termination resistor?

When we have a source with 50 Ohm output impedance we use a coaxial cable with a 50 Ohm characteristic impedance. And if we don’t know the output impedance then we use a 50 Ohm termination resistor at ...
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Twisted pair with shield and drain wire

Ive been posed with a problem regarding calculating the characteristic impedance of a shielded twisted pair with a drain wire. While I understand how to calculate this for a "normal" shielded twisted ...
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Characteristic Impedance of a port

I thought that the characteristic impedance was a parameter defined only for transmission lines. But now I have this question: is it defined also for a port? And, eventually, what does it represent ...
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LC Filter Design with coaxial input and output

I was trying to design a Chebychev high pass filter of 400MHz corner bandwidth, 0.2db ripple and 5 poles. I am confused with the proposed design in this filter design calculator. This calculator asks ...
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Velocity Factor in Transmission Line

For a lossless line, you have \$Z_0=\sqrt{\frac{L}{C}}\$ and \$VF=\frac{1}{c\sqrt{LC}}\$. For a line with R, L, G and C parameters, we have \$Z_0=\sqrt{\frac{R+j\omega L}{G+j\omega C}}\$. But how ...
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Why this evaluation board use different track impedance than the right one? Ethernet PHY, routing

Im doing a design with a implementation of 1Gb ethernet switch, for that I bought a evaluation board to do it well. The problem is that in the layout of the ev board I can check that the track ...
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What does line impedance stabilization mean?

What exactly does line impedance stabilization mean? What parameters of line impedance are stabilized and how? How does line impedance / source impedance vary with frequency?
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What exactly is Characteristic impedence in transmission lines? [duplicate]

Please help me to understand what does a characteristic impedance mean. I am unable to get the exact idea of what does it actually mean and its physical significance.
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USB cable characteristic impedance

Does differential impedance between D+ and D- not only depends on separation between and wire gauge of D+ and D-, dielectric constant of the insulation, but also the GND wire and shielding? I want to ...
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analog signal generator output in Volts vs dBm

I am connecting a mixer to a microwave source and need to be careful of how much power I am giving to the LO and RF of the mixer. If I just stay in the unit of dBm, it would be ok but I became ...
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Equivalent Characteristic Impedance for Different Trace Widths

Suppose I have a PCB trace that needs to be impedance matched, but the trace width changes as it travels from its source to its destination. Something like this: The 5mil trace would have a certain ...
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RF layout bend over Component

We lay out the RF trace for below model. GSM 900MHz RF trace maintain at 50Ω impedance. As I know, the RF trace needs to be as short as possible for better signal. Do we need to bend RF trace ...
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Routing large RF trace to small SMD pad

I am designing an RF board in Altium where due to the dielectric selected and its thickness, the trace width for a 50 ohm characteristic impedance is thicker than some of the SMD component pads. What ...
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Some calculations on Transmission Lines

I have to do some (simple) calculations for a transmission line. I was given a power supply of \$11V\$/\$22\Omega\$, \$Z_0 = 50\Omega\$, \$v = 2.2 \times 10^8 m/s\$, a load capacitance of \$1.124nF\$ ...
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Impedence Matching of Antenna and Coaxial Cable

There is a scenario based question which is confusing for me Antenna had four rods each 15cm arranged as a plus sign. its brass shielding was cut and it had two 75 ohm coaxial cables in it. one 10 cm ...
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What is the definition of characteristic impedance of a lattice network?

We were being taught about Lattice networks in class, today, and our professor mentioned that the characteristic impedance of a symmetrical lattice network like is given by: $$Z_0=\sqrt{Z_aZ_b}$$ I'...
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Difference in the characteristic impedance of a low frequency signal

In one of my PCB design, for a RS 485 signal termination resistor of 120 ohm is there. But the differential characteristics impedance of the signal is taken as 100 ohm instead of 120 and the signal ...
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