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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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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25 views
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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47 views
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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2answers
59 views
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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2answers
47 views
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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1answer
45 views
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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1answer
36 views
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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1answer
74 views
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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37 views
Injection of active and reactive power for votlage regulation
I am currently investigating voltage regulation by injecting/absorbing active/reactive power through grid-tie inverters as you can see in the figure below.
So, I am conducting some simulations in ...
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1answer
36 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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1answer
38 views
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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Signal from point a to point b
Signal travels in a system shown in the picture:
Find signal to noise ratio at the point b if following values are known:
\$\ N_0 \$ - noise power of the amplifier at it's entrance (noise over ...
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Is this a two capacitor reactance matching network? And is there anyway we can determine the source impedance of the nfc chip device?
My teammate found this configuration from a paper:
http://infocenter.nordicsemi.com/pdf/nwp_026.pdf
, and there is no explanation for the two Cp capacitors connected to ground. We needed to do ...
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1answer
118 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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42 views
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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1answer
63 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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1answer
17 views
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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1answer
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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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1answer
39 views
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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1answer
100 views
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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1answer
67 views
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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1answer
59 views
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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1answer
60 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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1answer
32 views
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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1answer
111 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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75 views
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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1answer
53 views
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
67 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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0answers
112 views
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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1answer
63 views
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 ...
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2answers
178 views
SPI bus multi-slave termination
I have been using a Tiva C microcontroller (TM4C1294NCPDT) as master to communicate with 6 SPI devices (slaves). The SPI clock is 8 MHz with 1.5 ns rise time. My idea is depicted bellow.
My design do ...
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2answers
61 views
Transmission Line Model, Symmetric vs Unsymmetric
Can someone please explain what's the difference between a symmetric vs unsymmetric transmission line model ?
The normal un-symmetric one has R and L in series with G, C in parallel. While the ...
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2answers
115 views
How can I make a model of a single wire CAN bus cable?
I'm currently working on a project of analyzing the latency of a CAN bus network with transceivers and without transceivers. The latency parameter here will be analyzed with the effect of bus line ...
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Reflection on a matched transmission line
A matched load with source using a transmission line (assume real load and matched using quarter wave transformer) should not have any reflection ideally.
But we can see that the load impedance is ...
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3answers
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Transmission Line Effects
My question has to do with the rule of thumb we generally use when dealing with transmission lines.
We say that if the length of the line is 10% or less of the wavelength, we could neglect the ...
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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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Why real part of load change as we look through transmission line?
As we move from an imaginary load towards generator through a transmission line, we can see that real and imaginary part of that impedance changes. In fact, an ideal transmission line is comprised of ...
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Why does the solution to the wave equation define two directions?
I've been studying transmission lines recently and I'm struggling to reconcile my intuition with the derivations. Take the form of the general solution to the wave equation given on this page antenna ...
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1answer
48 views
How does the power station compensates for the current that flows down to earth due to domestic body-current faults?
I know current flows in a loop and energy is used to move it in a loop. Now suppose we get a single phase AC (220/120V) electricity supply for our home and we have earth connection to prevent shocks ...
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1answer
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Reasons and assumptions behind the use of per unit length quantities in the telegraph equations
I am working out the derivations of the telegraph equations of a transmission line
$$\begin{gathered}
\frac{{\partial V}}{{\partial x}} = - L\frac{{\partial I}}{{\partial t}} - RI \hfill \\
\...
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If a Power System is not loaded, do shunt components still cause bus voltage to increase?
TL;DR: Title.
If any bus of a Power System is connected to a load, shunt components such as transmission line capacitance tend to inject reactive power into the system. This increase of local ...
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1answer
74 views
Do I need an impedance controlled connector for RS422?
I've never implemented RS422 before (crazy right?). Since the impedance of the line is controlled to 120Ω do I need an impedance controlled connector for that? If anyone has implemented RS422 which ...
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34 views
What effects limit throughput of a short channel?
In a short channel, e.g. a 1" long Ethernet cable, which effects are most likely to reduce throughput and why? What would the nature of the throughput reduction be? Specifically, I am wondering about ...
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2answers
56 views
how can I get leakage current in tlp?
I got tlp test data and found that the current at vertical line means leakage current.
But I don't understand the method how does the tlp-test measure the leakage current.
I tried to search the ...
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25 views
Power Outages and Surges
I live in South Africa where we experience frequent power outages due to so-called "loadshedding". With this, there have been numerous cases of damage to appliances due to surges, usually when power ...
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Impedance Expression for a Transmission Line
I'm studying transmission line theory and this is the expression I derived for the input impedance for a lossless transmission line:
$$
Z(\omega) = Z_{\inf} \frac{1+e^{i\frac{\pi\omega}{\omega_{0}}}}{...
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151 views
Capacitance of a particular transmission line
Is it possible to derive the expressione of the equivalent capacitance seen by AB for this kind of transmission line, where w is the width of the wire, d the spacing, l the length of the repeated part ...
