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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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RF Differential and Single Ended Microstrip Impedance in PCB Design

In pcb design (using 4 layer osh park stack up) if the rf trace is single ended than i simply calculate microstrip impedance and draw copper trace with calculated width. For example for 50 ohm ...
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Deriving NEC wire reactance table values

I'm verifying the NEC impedance table manually (how it gets the values in the table). In the NEC list for AWG 1 above, the inductive reactance (Xl) for 1000 feet has value of 0.046 ohm for PVC ...
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Cutoff or Corner Frequency for Coax Cable

I'm trying to understand better what the significance of the cutoff frequency for coax cables is. I have a case where a cable is considered for use at frequencies up to 3% higher than the manufacturer'...
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Smith chart of λ/4 Transmission Line

I came across the following slide on power combiner circuit and I have questions about it. Why traverse across the upper half circle ? Why "ZT-line is the geometric mean of Zout and Zin." ?
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Reflection of Electric field in open-circuited transmission line

Consider a parallel-wire or parallel-plate or coaxial transmission line, carrying TEM wave, which we model as E,H,V,I, each having a forward(+) and backward(-) wave. In terms of V,I, we define ...
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How is Line and Phase Voltage the same for a Delta connected system?

I am having a little bit of confusion for some reason understanding how the phase and line voltage can be the same for a delta connected system, i understand why the current is different for the phase ...
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Maximum VSWR that can be tolerated?

I am trying to solve the 2013 paper set by ISRO for electrical engineers. I wanted to verify if my answer to Question no 14 is correct. The maximum RMS current is 20A, so maximum tolerable RMS ...
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Why current flows along a transmission line?

Say I don't have a ideal transmission line i.e resistance/length!=0. Also E-Field exists between the two conductor lines. How then current flows through the line? There is no E-Field along the line ...
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Lossless Transmission Line Length vs Rise Time

I am trying to answer the question - Does a signal's rise time increase with the length of a lossless transmission line? - using LTspice simulation. Some references say that lossless transmission line ...
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A source generator connected to a receiver with a lossy transmission line

Consider that we have a 50-ohm source generator that is connected to a 300 ohm transmission line. This line has a loss of 10 dB for every 100 ft and is connected to a 50 ohm receiver. The source ...
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ADS harmonic balance discrepancies with sawtooth waveform

I am using ADS for a simulation where I am biasing a diode with a sawtooth waveform. The sawtooth source provided by ADS, and 3 harmonics are specified There are different phase delays across the ...
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How do I stop signal looping with I/O port in this communication system

I am still a student. When I am designing communication system I am facing this problem: As shown in the figure I need to communicate with Master and Slave. But Master and Slave have single I/O port ...
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Matrix-Vector equation for active and reactive power in a transmission line

Suppose that we know vtilde (the complex voltage phasor vector at all buses), C the incidence matrix for a network, ...
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How much power can transit through a power line linking generation and load?

First things first I am not an electrical engineer at all so please bear that in mind when you reply/comment. I am looking at the following problem, I have a power line which connects a windfarm to a ...
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Transmission Line 2-Port Parameters

I am checking some Spice models of transmission lines. I have a Belden 1583A Ethernet Cable, with the following parameters \$R=93.8 \ \Omega\text{/km}\$ and \$Z_0=100 \Omega\$, hence \$C=47.652 \ \...
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Cut-Off Sinusoid or Sinuosoid?? - Standing Voltage Waves on Transmission Lines

My textbook shows two diagrams that appear to contradict each other to me. Each depict the magnitude of the standing voltage waves on a transmission line. The first, fig 2-14, shows a sinusoid bounded ...
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What are the s-parameters of a rg58 coaxial cable?

Can a the s-parameters of a rg58 coaxial transmission line be calculated. If yes, what are they?
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Maximum length of high-speed LVDS cable in automotive environment versus using SerDes

I would like to connect a small TFT display that uses LVDS, 4 channels for data and 1 channel for clock. Data rate is maximum 200 Mbps per lane. Very strict EMC requirements are applicable, namely ...
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How do the transfer functions of lumped and distributed circuit differ?

The transfer function of an electrical circuit can also be described as the \$S_{21}\$ parameter of the S-matrix. As far as I know the S-Matrix can be applied for both lumped and distributed circuits. ...
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Single-line power transmission of 1MW over 35,000km [closed]

This question posted on the physics stack exchange has not received much attention. I thought the audience here might be more able to answer it. Background A space elevator is mechanism to provide ...
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Microstrip transmission line impedance calculation

I'm attempting to calculate the necessary trace width of a PCB transmission line in order to have a characteristic impedance of 50ohm. However, different online calculators are giving me slightly ...
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Can I use a RF and/or Time-domain reflectometer to find 'wet contact'?

Friends of mine have a circuit where the RCD trips but only after prolonged rain. There are a number of garden and security lights on that circuit so I very much suspect there is a junction box where ...
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Why is the pulse reflection becoming like this in pulse?

I use mosfet to generate a pulse, input the pulse into the transmission line, and after the reflection, test the waveform as shown. Why did the third reflected waveform become like this? I calculated ...
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Cut-off frequency in coaxial cable

The cut-off frequency of an RL circuit is described by the following equation: $$f = \frac{R}{2\pi L}$$ where R is the resistance of the circuit and L is the inductance. Applying this equation to a ...
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Half-wavelength lossless transmission: magnetic energy and electric energy balance

I'm studying transmission lines and came up with a problem about a lossless transmission line that has a length equal to half the wavelength of the line. My book computes the complex power at the ...
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Effect of source output impedance on reflections in a transmission line

For preventing reflections when the frequencies are higher or close to the transmission line length, for a 50 Ohm coaxial cable a 50 Ohm termination resistor is recommended. simulate this circuit &...
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Paralleling LVPECL outputs?

I have a pretty unusual application here, where I need to drive a fast differential signal fanning out into 8+ 100ohm transmission lines. The unusual part is this: the transmission lines must be ...
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Open Neutral Service Detector/Disconnector

Who has built an open neutral service detector that can disable the 120v circuits when the neutral opens accidentally (in the USA 120/240v split ac system)? Remember these words by Mike Holt: https://...
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Transmission line with a resistor. What happens after a long time?

Ok so I'm analyzing a problem with a very simple lossless transmission line: In my case $$R=20 \Omega$$ and I have to find the evolution of uL(t) So I had no problem doing the first iterations. I ...
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65 views

Transmission Line: Converting from impedance to admittance. Why?

If we want to find the input impedance of this given transmission line problem, why is it advantageous to switch the quantities from impedance to admittance?
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Capacitance of short length transmission lines

I would like to simulate a short length transmission line in MATLAB/Simulink. In the library, there is a block that simulates a transmission line. The parameters that are required are the resistance R,...
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148 views

How to explain the reflected voltage on the oscilloscope when a pulse is sent through a transmission line with a capacitor at the load?

This is waveform that I got on the osciloscopewhen experimenting in the lab. A pulse was sent through the coaxial cable was used with a capacitor at the load. I have my own idea why is this happening ...
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Why is the top of the transmission line reflected pulse reduced?

I use this circuit to simulate the transmission line reflection, why the distortion occurs when the pulse signal is reflected back to the source. Only when the output impedance of the MOSFET pulse ...
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65 views

Creating chained digital current loop

I need to send some digital data and power for long distance (around 60 meters) using only 3 wires. Data speed is low, something like 100bps is enough, 1000bps would be perfect (12.5Bps and 125Bps). ...
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Connected RF Trace to Multiple Pads

I'm trying to improve my RF routing skills. I want to connect a 450 MHz trace (21mil width) to a RF6886TR13 power amplifier that has 6 RF_OUT pins. What is the best way to make this connection? I've ...
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Does LVDS always need 100 ohm differential impedance?

LVDS pairs need 100 ohms differential impedance. However, I am having trouble achieving that in my design. My design requires that the pairs travel over very thin flexible PCB, about 50mm total ...
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How to determine the frequencies in which the L&C model of an artificial transmission line works?

I want to model an artificial transmission line with L & C. So far I used the following circuit and used the values of L=400 pH and C=0.16 pF so that Z=sqrt(L/C)=50 ohms. So, expected S21 and S31 ...
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How to convert Inductor to series transmission line?

My objective is to understand the travelling wave amplifiers, but I am stuck on how to realize inductors in transmission lines. But, I am basically stuck on how to convert a series inductor to a ...
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Microwave transmission

I've just started learning microwave transmission in my engineering course, and the question that has been hovering over mind is, why do we need transmission lines( conductors) to transmit microwaves ...
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How to plot input reflection coefficient in dB scale using Matlab

So I have a problem that asks to plot the input reflection coefficient of a transformer in dB scale between 0.5 GHz and 4 GHz using Matlab. Here is the code I have thus far, it is plotting in ...
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87 views

Reference Plane In Impedance Calculation

I'm designing an 8-layer PCB with 10 distinct region of power. To attain 50Ohm trace I used Stripline calculators (like this fancy EEWeb) and they work great If you know that you have a complete solid ...
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Load Impedance Derivation

I'm having some trouble deriving this equation for transmission line theory: From: http://www.antenna-theory.com/tutorial/txline/transmission3.php When I sub the Telegrapher's equations into eqn ...
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Effects of frequently turning on and off power in the grid

What would happen to the infrastructure (transformer, transmission line etc) If I would turn on and off power frequently? Will it cause wear and tear? If so how? And how much? Also the effects of ...
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186 views

Effect of VIA fence on grounded coplanar waveguie (GCPW)

I'm working on a RF Frequency board with up to 6GHz signals. To connect components on the board (Mixer, Attenuator, ...) I decided on using GCPW. I designed my GCPW Using AppCad calculator (free ...
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Use of 3 phase transformers which are ∆-Y connected and Y-∆ connected

Different literatures say different things regarding ∆-Y and Y-∆ 3 phase transformer connection... Some say that ∆-Y is used for step down and Y-∆ is used for step up while others say just the ...
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Why the distribution network have 4 wires ( not neutral)?

In a real network the distribution lines were 3 lines (ABC). At one pole the lines became 4 lines which are ( ABBC) the phase B split to two lines . Could you please illustrate why they split them to ...
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1answer
87 views

spice transmission line error

I am trying to model a very lossy coax transmission line. As shown in the circuit, the top TL model includes the shield line; the bottom lumps the shield terms into the center conductor and looks more ...
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Determining the Impedance of the antenna on a known circuit

I am stuck on how to approach the following problem: I have a graph with both the response of a short-circuit and an unknown impedance antenna. The only information I have from this graph is the ...
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Parallel transmission lines impedance

I just want to know the correct way to calculate \$Z_{in}\$ in this network. It's very simple but I think I might be doing something wrong. Is it ok to calculate the impedance over one line and get \$...
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Calculation of transmission loss of a power plant

What is the transmission loss due to heat if my power station produces electricity at a power of \$5 kW\$ and the electricity consumer is \$1 km\$ away? It is a copper line with a material constant ...