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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337 views

What is the meaning of “longer electrical length = more wavelengths”?

Reading a Keysight-note, not sure what is the following selected line means? I read and understood the meaning of electrical length, how it is related to bit in flight and wavelength is not clear.
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what role does transmission line termination take in long distance power lines?

Does transmission line theory and transmission line termination take any significance when dealing with long high-voltage power lines? Do power companies terminate their power lines to avoid ...
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43 views

Correct model for interference from an unterminated transmission line branch

Question about the correct mathematical model for a branched transmission line Baseline Setup Waveform generator: Output 10-60MHz sine wave, 8Vp-p, Output impedance 50Ohms RG58 50Ohm coax: ...
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25 views

VNA measurement of a domestic 3 wire AC cable used as a parallel transmission line

I am currently working on power line communication techniques for low and medium bandwidth applications. I was curious to calculate Z0 on a 3 wire, 1.5mm2 power cable. The theoretical impedance of a ...
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41 views

Inductance of composite conductor

Why L is calculated using average value and not by the formula 1/L = 1/L1 + 1/L2 + ...
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176 views

Why is a coaxial cable unbalanced?

Let's consider a coaxial cable which supplies a dipole antenna. My reference for all my statements is here. My reference says: Note that the current along a transmission line should be of equal ...
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1answer
31 views

Shorter transmission lines or nearer high frequency bypass caps

I have an application where I have a sensor which communicates with an FPGA with about 15 differential pairs of data clocking around 300 Mhz. Due to constraints, the board can't be taller than 35mm ...
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1answer
65 views

What really limits off-chip I/O? Capacitance or Inductance?

To my understanding, the crucial limiting factor for off-chip I/O is bondwire inductance, something that seeks to be minimized with BGA, flip-chip bonding etc. The rationale is that an RC wire model ...
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1answer
179 views

What is this structure on an RF PCB?

I'm looking at a picture of an RF PCB meant to operate at a few GHz, and I'm having trouble understanding exactly what this is: Obviously there are some transmission lines, and something that looks ...
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What type of wire does transmission tower use?

I learn form a more than 20years old book(South Korea text book) that high voltage transmission towers take Bare wire into service. But I saw some company take <...
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1answer
29 views

Governor Droop Response (Demand Balancing)

I am having trouble figuring out how to solve the governor droop response question in a textbook I am studying for a certification. This is the question: A 100 MW generator at 50 MW output that has 5%...
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1answer
33 views

Transmission line model VS lumped parameters models

Both the lumped parameters models vs transmission line models use RLC components for modelling. This is where I am confused and cannot see the difference between the two.
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59 views

How transmission line repeats after \$ \frac{\lambda}{2} \$ distance?

Following two statements made me think that the transmission line repeates after \$ \frac{ \lambda}{2} \$ distance: A complete revolution around the Smith chart corresponds to \$ \frac{ \lambda}{2} \$...
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How would superconducting circuits save a lot of power in a small electric car?

From the bottom of the New Scientist article called , 'The superconductor breakthrough that could mean an energy revolution.': Something like 10 per cent of electrical power is lost in long-distance, ...
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1answer
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Are there any special considerations for extending a UHF-carrying coax wire in a small device?

In the process of doing a repair on a mobile phone, I've tracked down a "no service" issue to an antenna lead inside the case. Specifically, it has detached from the U.FL/MMCX (I'm not sure ...
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307 views

Transmission lines with same impedance but different dimensions

Suppose we connect two transmission lines with characteristic impedances \$Z_1\$ and \$Z_2\$. The reflection coefficient looking into the transmission line with impedance \$Z_2\$ is $$ \Gamma=\frac{...
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28 views

Relation of Voltage of a line and its cross section area?

For a given power delivered, if the working voltage of line is raised to n times, then cross sectional area of line conductor would reduced to?
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1answer
39 views

Microstrip Transmission line characteristics impedance

The question is from GATE 2016-ECE-paper 2. Here in the question, we need to comment on the characteristics impedance of Microstrip line and we are given 4 options: The ANSWER GIVEN IS (B), My ...
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1answer
46 views

Multiple Resonances along a transmission line

in "Lessons in Electric Circuits", VOL III, ChPT 14, all the possible configurations of standing wave for a certain transmission line are shown. For instance, this is the case of a ...
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70 views

Reference node in a transmission line

in "Lessons in Electric Circuits", VOL III, ChPT 14, there is a SPICE simulation of this transmission line: The author writes: Running this simulation and plotting the source impedance ...
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80 views

Measuring inductance of a cable

Its a little thought experiment. Below you see a transmission line consisting of 2 parallel wires. With an LCR meter, I am measuring the inductance of the cable. On the left side, the LCR meter ...
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1answer
29 views

Referencing multiple differential pairs to ground before analog multiplexer

Yesterday I asked how to properly reference a differential signal (in my case from a current transformer) to ground, and got told that the impedance to ground should be matched at the location where ...
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1answer
30 views

Common mode noise rejection and grounding instrument current transformer

Suppose we have a signal from a current transformer over a pair of transmission lines. In order to prevent the voltage between the terminations of either of the transmission lines and ground from ...
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179 views

Qucs simulation of quarter wave microstrip stub doesn't match ideal calculaton

I'm trying to simulate the resonant frequency and insertion loss of a 3 mm open stub on a 10 mm microstrip transmission line (50 Ω) on a FR-4 PCB (εr = 4.0, height = 0.1 mm). I calculated that the ...
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1answer
52 views

In transmission line does reflected wave travel on the path before impedance or after impedance?

I was taught in class that 2 port RF networks have the following structure below, where V2+ is the reflected wave if load at end of port 2 does not match the characteristic impedance of lines at port ...
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Cable behaving like a low pass filter

In the transmission line theory you can use this circuit to describe a transmission line: So the resistor and the capacitor form together a low pass. So each cable has to have a cutoff frequency ...
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How neutral wire is obtained in three phase systems?

In India, we have only 3 transmission lines which are all live. But the domestic supply includes a neutral line along with that. How we can create a neutral in a transformer? Why don't we not need a ...
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What frequencies are usually used/most efficient for coaxial transmission lines/?

I was researching what frequencies are usually used for coaxial Tx. Most sources just says that at low f the length of the line doesn't matter and vice versa. However, I couldn't find a source that ...
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Why do not we carry energy as DC in dams? [closed]

If a wire's DC resistance is less than AC resistance, which it is, why do we carry energy as AC in dams? (high resistance means high loss, why do we carry it with higher losses?) Why don't we carry DC?...
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566 views

What exactly limits the signal frequency on transmission lines?

In practice, the frequency of a signal seems to have a significant impact on whether or not it can reasonable be transmitted over a line. As an example, consider the IEEE 802.3ab standard on Gigabit ...
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60 views

Time delay in lumped element delay line

I was trying to analyse a lumped element-delay line by changing the frequency and measuring \$ V_{in}\$ , as shown in the graph the goal of my analysis is to find the time-delay and the attenuation ...
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44 views

Characteristic Impedance of Multi-Dielectric Coplanar Waveguide

Background I've calculated the characteristic impedance of a CoPlanar Wave Guide (CPWG) type transmission line on my 8-layer stack-up between L1 - top layer and L2 - GND1 directly underneath it. The ...
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1answer
28 views

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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61 views

Characteristic impedance behavior with frequency

The characteristic impedance of any transmission line is derived as $$ Z_0= \sqrt{\frac{R+j \omega L}{G+j \omega C}} $$ where R is series resistance per unit length, L is series inductance per unit ...
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350 views

What is a guided mode?

I am currently reading my text, for my electromagnetics course, and we are discussing guided waves. The text casually mentions the term "guided modes", and never really defines what that ...
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67 views

At what distance(s), approximately, are high-voltage DC (HVDC) power lines more efficient than AC lines?

I hope this is not a duplicate, because I am sure other people have the same question... And could someone explain the reasons why? N.B. From the 'scienceabc' website linked to below: Despite being ...
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27 views

Frequency of the surge voltage

When analyzing an electrical circuit, and in the occurrence of an impedance mismatch between the supply voltage and the load (connected through a cable) + a high switching frequency, reflection ...
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46 views

Losses over frequency for microstrip vs. coplanar waveguide

At mmwave frequencies, coplanar waveguide transmission lines generally have lower loss than microstrip. What accounts for this, besides radiated losses? Or is the difference mostly related to the ...
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1answer
21 views

Impedance inverter transformation from series lumped resonators to lambda/2 resonators

Suppose I have the following series of filter transformations beginning with a lumped element bandpass filter and concluding with shunt susceptances- The transformation from step (a) to step (b), and ...
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49 views

What does it mean to short circuit a transmission line stub at a specific frequency?

I'm currently designing a microwave FET mixer right now, and I have to short-circuit the FET's drain at LO frequency and its harmonics. I've checked the "stub" article in wiki, and it says ...
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57 views

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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1answer
112 views

“The D-PHY specification defines the maximum lane flight time to 2 ns.” Why?

I'm hoping someone can explain to me why the maximum lane flight time matters. Impedance matching, skew, attenuation, etc. all make sense to me as a natural limitation to how long an interconnect can ...
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39 views

Voltage regulation at full load

The voltage regulation is I(Rcosa -Xsina)/Vr For leading pf Here %of regulation=(VRcosa-Vxsina)/Vr ×100 %=((4×0.8)-(6×0.6))/100 ×100% =-0.4 Where I am doing wrong?
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Why does the length of the wire matter to the value of the pull up resistors?

In this DHT-11 datasheet the following sentence was mentioned (on page 4) A typical application circuit recommended cable length shorter than 20 meters with a 5.1K pull-up resistor when greater than ...
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How far can radio signal be transmitted through a straight steel pipe?

We are needing to transmit data between a robot that will be traversing a pipe, and a base station located at the end of the pipe. The pipe is about 2 feet in diameter, made of steel, and is ...
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2answers
180 views

Please help me solve the below Directional coupler problem

I have tried and my answer keep coming 0db.I am not sure this answer is right as this is only kind of problem I have seen where port is short circuited.
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50 views

how do you model a transmission line at dc?

how do you model a transmission line at dc?
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What are these teardrop-shaped loops in power lines for?

I just happened to notice this along a road near where I live: So these were in a pair, oppositely facing, "tip" to "tip" of the teardrop. At first glance, this doesn't seem to be ...
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1answer
43 views

Crosstalk between transmission lines

I was reading these slides about crosstalk between transmission lines. At page 6 there is this circuital model to describe the effect of mutual coupling between these two lines: My doubt is: why \$I_{...
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91 views

Impedance of a lossless line

I am currently looking for a term for a lossless line with a wave resistance Zw which is open ended and I am not sure if I have calculated correctly. My thoughts about the calculation: If the line is ...

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