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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Sequence Impedance/Zero Sequence Impedance of lines

I am trying to calculate the Sequence Impedance/Zero Sequence Impedance of couple of lines, but Im not sure if the calculation are right, and besides there are some tricky things on the data provided. ...
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What does pole rating and bipole rating mean for HVDC transmission cables?

I was just reading on HVDC underground cables. And according to the picture below, as they were listing out the parameters of the cables used, they mentioned pole ratings and bipole ratings. How are ...
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How do I determine the S-matrix for a combined series and shunt capacitors circuit?

I need to compute the S-parameters for the following two-port circuit, with combined series and shunt capacitors. simulate this circuit – Schematic created using CircuitLab I have tried ...
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SPI (15 MHz Signal) on two Layer PCB

I want to do a MIDI Controller which uses 15 MHz SPI between a Teensy 3.6 and 74HC595 / 74HC165 Shift Registers to read a button Matrix. The code is finished and the PCB would be the next step. I have ...
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When is it relevant to consider a trace as a RF transmission line

I'm building a simple Greinacher based RF Power meter for the PMR band i.e 446MHz. I intend it to work as a confirmation device and not something really acurate. The circuit is quite simple: The led ...
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Double Stub Matching Impedance

I'm trying to understand the double stub matching impedance using Smith Chart. Here is the diagram for the double stub impedance: The impedance on the right has to appear purely resistive. So ...
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Maximum Deliverable Power analysis for 2-bus system with Pi-model transmission line

In Chapter 2 of Voltage Stability of Electric Power Systems by Van Cutsem and Vournas, the maximum deliverable power for a fixed power factor is analyzed on a 2-bus (bus 1 is slack and bus 2 is PQ) ...
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RS-485 Connecting 100 devices - Avoid GND Loop

I'm new to community and it's my first question, so please forgive me for mistakes I could do referring to adding pictures and descriptions. I plan to use 100 devices and connect them via RS-485 in ...
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41 views

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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Transmission Lines:Standaing Wave Voltage Characteristic at Half Wavelength

The voltage equation for lossless transmission line that my professor has given me is : $$V(l)=V^+ e^{j\beta l} +V^- e^{-j\beta l}$$ and he says that when singals transits by half the wavelength the ...
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Are waves reflected off a transmission line when they reach the generator dissipate there?

There is a generator with ZG = 50 ohms connected to a transmission line of Z0 = 50 ohms, the length of the line can be any, the load is ZL = 200, this gives a reflection coefficient GammaL = 200-50 / ...
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Impedance Matching using Transmission line

Hi! I was looking at this research paper for Energy Harvesting through Rectanna and I stuck with this thing. The author, first, calculated the Rzin of the rectifier circuit. He had a source resistance ...
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Can reflection take place at the source in transmission lines?

I have read about the reflection of voltage and current, when passed through a transmission line through a load if the load is mismatched with the characteristic impedance. According to my ...
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Questions about RF ground plane and low frequency reflections

Why do RF signals on a microstrip/stripline require a ground plane to propagate within a circuit? When studying DC and low frequency AC circuits in school, it appears that ground is a particular point ...
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Why'd we have reflected waves in transmission lines?

I've learn today that when you applie a potencial V in a transmission line, we get a V in positive way, but we have to a V in negativa way, being reflected. What does it means? Like, I can understand ...
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Parameters affecting high-speed PCB transmission line design

I am designing an I/O board for an NVIDIA Jetson Nano SOM module. The board contains the HDMI, USB2.0, CSI, SD card and power system and GPIOs. As I am beginner with high-speed designs, I have a ...
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41 views

Opposite of reflection coefficient

The reflection coefficient (in circuits, for example) is generally given the symbol Gamma (\$\Gamma\$). What is the symbol given for the pass or transmission coefficient \$1-\Gamma\$? I've usually ...
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Parallel Termination in a Transmission Line

Suppose we have a parallel termination like this on a high-speed trace: If the line impedance \$ Z_o \$ and \$R \$ are matched, then there are no reflections from load to cause any ringing at the ...
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Confusion in modelling of total loop inductance of a rectangular loop

I was reading an article about partial and total loop inductances from this site and in a section where for calculation of total inductance of a rectangular loop is given as: In each portion of the ...
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2answers
54 views

In an open-circuited transmission line (microwave circuits) the current in the return path is completely zero?

Since the current meets the open boundary and gets reflected back does this mean that the return path has zero current always on it? Or there is also a standing wave there as well with a current with ...
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Parallel transmision lines reflection at the source

Question: There's a 9 V battery with output resistance of 50 Ω, at time t = 0 it is connected to two lossless transmission lines connected in parallel: LTx1 and LTx2. Both lines are identical, with ...
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Is it beneficial to use a taper for the feed input of a PCB antenna?

What is your opinion on using a taper for the feed input of a PCB antenna? Say the feed is 2mm wide and the transmission line is 0.45 mm. Would a taper just cause more impedance mismatch? Or would it ...
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ADS Gives Negative Input Impedance in Transmission Line Simulation

I am trying to get a very simple transmission line input impedance simulation right in ADS, but the result gives a negative real part of the impedance. This should be impossible. Any advice on how to ...
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Antenna Attenuation, Gain and RSSI calculation

I am using a RAK7258 LoRa gateway operating at EU-868MHz. I am looking to have the gateway and the antenna on each side of a wall (gateway inside, antenna outside) and receive some packets from some ...
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How to regulate the load node?

I was given the next assignment, but I dont know what to do. From the system showed there must be a regulation at the PQ node (3rd). But the course is starting and I have no idea what to do, it is ...
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Kirochoff's current law on Transmission line equation

In the figure above, for equation 2.1b i.e applying Kirchhoff's current law, why is not the resistance and inductance taken into consideration?
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What are the differential voltage technology used for PCIe gen 4, gen 5 and gen 6?

I have been studying various IO standards used for various PCIe generations? I understand that PCIe Gen-3 uses LVDS, LVPECL and PCML. I would like to learn what are the standards used for other ...
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Via stub resonance intuition of insertion loss drop by formula

Resonance in transmission line occurs when the capacitative part cancels the inductive part. Why in the case below at resonance does the S-param drop? Thanks.
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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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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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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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239 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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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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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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211 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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62 views

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
41 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
36 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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62 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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3answers
141 views

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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317 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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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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53 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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54 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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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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218 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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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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