Questions tagged [transmission-line]

A transmission line may refer to a cable or assembly that is designed to carry radio frequencies and must consider the wave nature of the signal. Coaxial cable is an example of a transmission line. It may also refer to high-voltage power transmission lines, used to transfer power from generating stations to consumers.

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Laplace vs Fourier Transforms in Transmission Lines

Consider an electric transmission line with transient equations $$\frac{\partial v}{\partial x} =-Ri -L\frac{\partial i}{\partial t}, \qquad \frac{\partial i}{\partial x} =-Gv -C\frac{\partial v}{\...
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Design guidelines for RF castellated edge connections

I've seen many examples online of castellated vias at board edges used for module connections. However, all of these seem to be for low frequency signals. When using a castellated via to connect an RF ...
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Can I calculate minimum rise time of a transmission line if I know the length and the loss tangent?

Overview: I am trying to work out if it's possible to transmit my 1.2Gbps MIPI data down a 600mm long flexible PCB strip. Assuming I have the impedance correct, will the signal still be degraded by ...
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Loading an FPGA pin at 20MHz in parallel

I'm designing a traction inverter controlled by the NI sbRIO-9627, which includes a Zynq-7020 FPGA. I am considering using a single FPGA pin to drive the external clocks of 14x ADuM7701 isolated ADCs ...
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Amplitude plot of voltage standing wave on a transmission line

edit: I just found a site almost perfectly describe the issue, https://ophysics.com/w3.html I found this graph on Google but couldn't find an explanation of it, it is similar to the one presented in ...
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Different results from Smith Chart and Transmission line impedance equation

I have the following question which I need to solve Use a short-circuited section of air-filled TEM, \$50\Omega\$ transmission line ( \$\beta= k_0 , \lambda_g = \lambda_0\$ ) to create an impedance ...
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Single wire earth return system

So, in a single wire transmission system, the earth acts as the return path for current to "flow back to source". Would this work for anywhere on earth, say, if we transmit current on a single wire ...
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Underwater communication trough cable

I wanted to build a device which can stay and move underwater (let's say, for instance, 15m underwater). Since RF frequencies are very attenuated by water and VLF antennas would be too high, I was ...
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Transmission line current magnitude

I want to compute the current magnitude in a transmission line. The line has properties b (total line charging susceptance, p.u.), ...
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ST ST25R95 - NFC chip - Impedance of transmission lines

I will supply the chip with 3.3V, and the datasheet of ST25R95 IC shows it has a ZOUT of 27R at this condition. There is a circuit between NFC antenna/coil/inductor and the IC, the LC filter and ...
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Couplers and dividers as baluns

Can every divider and coupler that provides 3dB amplitude divison and 180 degrees phase difference be used as balun? Rat race coupler and lange coupler provide the two conditions mentioned above. ...
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How to do via fencing of an RF trace with a 5V front copper plane and a GND back copper plane?

Background I am a building a board to send RTTY via a Radiometrix NTX2B as part of my final year High Altitude Balloon (HAB) project. I have just created a PCB which I uploaded to JLCPCB for ...
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What is happening, physically during a Transmission Line Reflection in a closed and open circuit scenario?

I am having trouble understanding what is happening physically during a transmission line reflection, in particular the short circuit and open circuit case. I understand that when when a transmission ...
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How can there be a zero sequence current in a single line to ground fault with an ungrounded neutral

The circuit that describes a single line to ground fault in a system with an ungrounded neutral is: I neglect capacitance between phases and only look at capacitance to ground. The definition of zero ...
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relation between transmission line & circuit impedance

What is the relation between the impedance of lumped components and the characteristic impedance of transmission lines? I have noticed that in some cases transmission lines are loaded with lumped ...
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How to demonstrate mathematically the conditions of reflection in transmission line?

We are all taught about transmission lines and its associates -- characteristic impedance, reflection, standing wave, etc. It is well known what happens when a transmission line is terminated with ...
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I have a hard time with determining the input impedance of the problem shown as well as the equivalent lumped circuit model with this Zin

This is the work I have done so far. I am not confident in my work and was having a hard time with determining the input impedance. If you have a correction or opinion on this work please comment.
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Multi Driver EJTAG interface routing considerations for better SI

we have a MIPS uP which has EJTAG interface. This needs to programmed from Both P1(by default) & P2 connectors This EJTAG interface needs to be shared between 3 drivers. Assembly Option1 in ...
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Can these S-parameters be derived?

I have been trying to derive the S-parameters of a lossless T-junction of transmission lines. Here's a diagram from Google: This is an exercise in microwave network analysis, not in design, so the ...
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Signal velocity in PCB traces

On what does the signal velocity depend for a signal traveling through a PCB trace? According to Wikipedia, it depends exclusively on the relative permittivity (ε_r) of the medium (well, it also ...
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Why single ended signal line is not immune to noise in RS232?

In single ended signal line the measurement is the difference between the signal and the ground. Isn't this way of calculation make it differential? Almost all the resource I have read says that ...
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Difference between single circuit and double circuit transmission line protection systems

I'm doing a research on long three phase transmission line protection systems and I found many schemes such as distance protection, merz-price voltage balance system, split-conductor, "translay" ...
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Understanding series open stub tuning

I recently had an assignment where I had to use open stub series tuning to find a way to maximize power delivered to the load from the generator. I understand that power delivered to the load is ...
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Length-matching microwave differential traces

I'm driving an RF mixer that takes differential input signals. My max signal frequency is \$6\,\text{GHz}\$. I understand that the differential input signals need to be length-matched, but what sort ...
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In a transmission line, does the real current interact with reactive impedances?

simulate this circuit – Schematic created using CircuitLab According to the diagram above, if real currents do not interact with reactive impedances, then reactive loads should not worry the ...
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Wire model RC vs LC/RLGC

The condition for using an LC/RLGC model over an RC model is when: f > R/(2*pi*L) (see for example http://www.ece.tamu.edu/~spalermo/ecen689/lecture2_ee720_channels.pdf slide 19). This explains why ...
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Microstrip skin effect

I've read that at high AC frequencies, current concentrates near the surface of a conductor, which is known as the skin effect. Does this also mean that current concentrates near the edge of thin ...
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Why should the protective angle on high voltage lines be kept as small as possible?

This website, https://circuitglobe.com/overhead-ground-wire-or-earth-wire.html, said for effective shielding, we should keep the protecting angle as small as possible, the angle between 20° and 30° is ...
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Trace width for breaking out 100Ω differential microstrip from 0.5mm pitch BGA

See bottom of post for the actual questions First, some context: I'm making a DisplayPort switch as a hobby project DisplayPort's high speed lines require 100Ω ± 10% differential impedance, which I'...
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How to estimate active-power transmission capacity based on voltage levels and line lengths

I know voltage levels and line lengths of high-voltage transmission lines and I am looking for a rough estimation of the maximum active-power transmission capacity during normal operation. By normal ...
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Meaning of S11 performing a clockwise arc circle about the smith chart origin?

I've tested a device with my VNA. It displays S11 in a Smith chart as a plot x(w) + iy(w) (w the frequency). Curiously, as w increases from 50KHz to 600MHz, the plot is an almost perfect 1/3 circle ...
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108 views

Grounded coplanar waveguide differential gap

I'm driving an ADL5802 RF mixer with a 5400BL15B050E RF balun. The balun turns a single ended signal into a differential signal on balanced lines for the mixer. In my attempt to match the balun ...
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The reason the advantage of Single conductor transmission line be changed to non-singular conductor transmission line

Question: If Single conductor of EHV(Extra high voltage) transmission line be changed to non-singular conductor of EHV transmission line,there are some advantages about this changing 1.Decrease the ...
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AC circuit analysis with a transmission line involved

I'm trying to perform an AC analysis of a circuit that contains a piece of coax cable. The input voltage 'Vs' is a swept frequency (1MHz-150MHz) voltage source with constant amplitude. What I'm ...
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Transmission & Distribution

During a recent job interview of mine, one of the panel asked me the following question Q) Why is the transmission voltage of overhead lines in our country in the multiples of 11? Some background ...
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Detecting an electrical connection without a complete circuit

Wired Fencing In a regular (wired) fencing system (for sabre and foil,) contact is determined simply by applying a current to the weapon through a wire and forming a circuit between a conductive ...
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transmission line parameters

I read that the propagation speed (m/s) of a lossless transmission line, which I know is equal to 1/sqrt(LC), is also equal to 1/sqrt(L'C') where L and C are distributed inductance and capacitance (...
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146 views

Is it better to route Ethernet on the top layer, or to use vias?

I'm making a circuit board with Ethernet (PoE if that makes a difference) coming in through an M12 connector, passing through magnetics and a PHY and going to a micro. I've always heard that there are ...
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Waveguide excitation through coaxial antenna

let's consider a waveguide excited with a coaxial cable antenna: You may see that this structure is sized with a distance between the antenna and the plate equal to \$\lambda/4\$. My professor has ...
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How to find the Fourier series of an output given input and transfer function

I have an input rectangle pulse, \$f(t) = rect(t/\tau) \$ and a transmission line whose transfer function depends on frequency. The transfer function of the t.l. is the transmitted wave divided by the ...
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Why longer stubs cause more intense ringing?

Why connection of longer stub lengths cause more intense ringing in a Communication Network like CAN? As stub lengths increase won't the attenuation increase and lead to less ringing? Also the time ...
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how to calculate DC resistance of transmission line from telegrapher's equation

Can someone explain to me how to use the transmission line (TL) formula (from telegrapher's equations) to calculate the DC resistance of the TL? Here's my work so far: V(x,s) = A * exp(-gamma*x) + ...
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Why is the amplitude of ringing in square wave independent of frequency of square wave?

Reflections in a transmission line is causing ringing in square wave because certain frequencies are getting enhanced, but when frequency of the square wave changes won't the amplitude of those ...
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Does the standard termination of 120 ohm really suppress reflections in recessive state in CAN?

Suppose we have a multi-node CAN network with the ends of transmission line terminated with the standard 120 ohm. When the recessive state is on the transmission line, the voltage on both CAN_H and ...
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Votage between ends of transmission line

I have two conductors forming a transmission line like in the figure below (left). Only B is grounded. What is the voltage between B and D at any given moment? If I use a transmission line model (...
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Attenuation and Insertion Loss for a 2 port network

in my university lectures the insertion loss and the attenuation of a 2 port network have been defined in the following way (and I have an extremely basic question about them): the Lnsertion Loss L ...
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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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Questions on ringing over square wave in transmission line

Considering a transmission line with open circuit termination at one end and a square wave voltage source with impedance not matching the characteristic impedance at the other end. Because of ...
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How will the proper termination at one end while the other end is kept open avoids reflections in transmission line?

Consider a transmission line which is terminated with characteristic impedance at one end but other end is kept open, the reflections are not observed. I don't understand the mechanism behind. Please ...
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How much RF power can a microstrip line handle?

Transmission lines on printed circuit boards must be impedance controlled lines since we want to transmit the full power and avoid the reflections. Microstrip lines have three parameters that we can ...

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