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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Deriving power formulas for transmission lines

I'm trying to derive formulas for active power (\$P_s\$) and reactive power (\$Q_s\$) at the sending end of a transmission line shown below: Where: \$E_s\$ and \$E_r\$ are voltage magnitudes \$X\$ is ...
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Placing the BPF and impedance matching on the output and on the input

I am working on solving a problem, namely I need to add input and output matching to my circuit and I am not sure where I should put them. Additionally, in the circuit I want to use a bandpass filter ...
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Phase Constant of Transmission Lines when R, G, L and C values are unknown

A lossless transmission line of length 0.57 m is connected to a vector network analyser. When terminated in a short circuit the input impedance was measured to be: Zin (s/c) = j45 Ω. When terminated ...
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Lossless quarter wavelength transmission lines

so my lecturer released a past paper with the answers and I have no idea how he got the answer to this question. Please could someone explain it to me? Thanks. The question is: A lossless quarter-...
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148 views

When does one have to take cable capacitance into consideration?

When feeding an RF signal to a coaxial transmission line, when do you have to take into consideration the capacitance of the cable? I am working with a 36 MHz signal. The total cable length is ~3 ft (...
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Trace capacitance vs telegraphers equation

I haven't taken a course on transmission lines or RF so bear with me. Using EM we can calculate the capacitance and inductance of traces. I'm somewhat confused on the value of this calculation, though,...
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Voltage drop across a Power Transmission Line

For a short power transmission line (<80 km), the shunt capacitances/admittances are ignored, i.e. the transmission line model can be modelled using only the line resistance and line reactance. The ...
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47 views

Standing waves in dipole antennas as receivers

I am new to antennas design. When we use antenna as transmitter due to the open air at the end of the antenna we get full reflection of the current and voltage waves. However, when we use it as ...
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Elements of the amplifier - application and operation

I have a problem with a power amplifier from this application note. I am wondering about the elements shown in the circuit in the "Application Circuit" section. Can these elements be ...
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Problem with S parameter calculation

A load of 50Ω is connected in shunt in a 2-wire transmission line of Z0 = Ω 50 as shown in the figure. The 2-port scattering parameter matrix (S-matrix) of the shunt element is: Method 1 The line is ...
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Help needed with determining PCB trace termination for µC/SDRAM interface

I am trying to figure out whether I need termination resistors for my PCB routing between a µ-Controller and an SDRAM (IS42S32800J-6BLI) that I plan to clock at 166 MHz. According to Table 72 of ST's ...
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Coaxial Cable vs Shunt, path of least impedance

The website LearnEMC.com has a page called Identifying Current Paths which contains the following graphics. The graphic on the left shows a coaxial cable arranged in a "U" shape, with a ...
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Analog versus digital (I2S) audio transmission over 1-2m

I need to get a microphone signal to a microprocessor about 1-2m away via cable and I need it to be digitized at some point in this chain. I'm looking for a solution that draws something on the order ...
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How do you calculate the ABCD constants of a transmission line

[question I've been trying to solve this question for a few hours now and this is what i ve gotten so far from scouring the internet for similar questions inorder to be able to solve mine. My question ...
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Transmission Line Power Flow

Background: So, I recently watched Veritasium's video, "The Big Misconception About Electricity" and EEVblog's response to it. Here is the circuit in question: I think understand why the ...
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Why do we need to use transmission line theory?

I just started to learn transmission line theory. I'm still confused about a lot of things. Every source says that we need to use transmission line theory when the length of the wire is 1/4 or longer ...
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Guideline for Impedance Matching (simplified cases)

Dealing with impedance matching of RF networks one facing two common techniques: (a) maximize power transfer (b) minimize reflexion of signal waves In this question I have tried to develop some kind ...
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How long does it take for energy to propagate in a circuit?

The premise In a recent video by the pop-sci channel Veritasium, the concept of the flow of electricity and energy transmission in a circuit was discussed. In that video a thought experiment is ...
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Maximum power transfer and minimization of signal reflection: When should what be applied

Impedance matching is the practice of designing the input impedance of an electrical load or the output impedance of its corresponding signal source to maximize the power transfer or minimize signal ...
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Maximum power transfer and minimization of wave reflection: Understanding the difference on intuitive level

It is well known that there are two usual methods in impedance matching: if we have a network consisting of a source with impedance \$Z_S\$ and load with impedance \$Z_L\$ then we have two options to ...
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Is it ok to extend 16V AC output with 12V heavy duty electrical cable?

I have a AC 240V to AC 16V transformer to drive my gate opener. But the 240V power outlet is far from the gate. Is it ok to extend 16V AC output by using 12V heavy duty electrical cable? Transformer: ...
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145 views

How to terminate branches in a transmission line

some research has unfortunately not led to a clear result. Branches in transmission lines are not desirable, but if they are unavoidable the question arises how to properly terminate the individual ...
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Remote Sense Self Adjustable Power Supply

I been looking for an off the shelf power supply that can adjust its output voltage to compensate for losses, in my case in transmission line. Searching on DigiKey, I narrowed down my search to power ...
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Voltage drop impedance value

A single-phase circuit 60Hz transmission line is 45 miles long. Transmission line impedance z = 0.5 Ω/mi. The load on the transmission line is 75MW at 115kV with a 0.90 lagging power factor. Calculate ...
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RLGC extraction from the Asymmetric S-paramter

In the signal integrity of high speed interconnect, in case of extraction of RLGC from S-parameter of it, they assume the S-parameter is symmetric and reciprocal. but in practical case S-parameter of ...
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What is the meaning of Ω.mi?

In transmission line I see Ω.mi. I know that Ω/mi gives the value of impedance per mile. But Ω.mi gives impedance times mile!! Assume a conductor has z = 1 Ω.mi For a transmission line of 10 miles ...
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Proof of voltage in lossless line

I'm currently a newbie in electronics engineering, and I want to prove the formula for a lossless Transmission lines, but I'm struggling with it. Assuming we know the formulas for U(z) = Ud0(exp(-γ*z)+...
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Coaxial Transceiver - HF Signal & LF Signal on same cable

I have a project which needs a analog video signal & some control data sent on a coaxial cable, I came up with some ideas and I asked about it and some interesting answers were received (Multi &...
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104 views

S Parameters Channel Modelling Time domain representation of insertion loss

Below is the insertion loss waveform obtained after S parameter of a channel.The waveform is in frequency domain. May I know what is the equivalent time domain waveform and how to obtain it from this ...
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Transmission line at DC

Do we need to consider a PCB trace as a transmission line when the Input is a DC signal. As per my knowledge we used to consider PCB trace as a transmission line when length of the trace is more than ...
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What is the derivation of this formula of potential difference related to the capacitance of a two wire line?

From this lesson: https://circuitglobe.com/capacitance-of-transmission-line.html Basically, I don't get where the formula came from. I am aware of the V = Q / C but I'm not that familiar with ...
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Suppose there is a standing wave in a transmission line at high power. Will the nodes of a wave 1 ft apart be hotter than the antinodes?

I was looking around for an evening and could not find an answer. I am also fuzzy on the exact electromagnetic physics principle of why a reflection occurs (please do not say "because the ...
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116 views

Logical short-circuit vs. Physically short circuited

Can the logical short-circuit point on the transmission line with short-circuit terminal be physically short circuited? (By "logical short-circuit" I mean the position where the voltage is ...
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Transmission line and input impedance - Smith chart

According to "Smith Chart Supplement - Corrected Jan 2012" https://www.arrl.org/files/file/Antenna%20Book%20Supplemental%20Files/22nd%20Edition/Smith%20Chart%20Supplement%20-%20Corrected%...
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Attenuation for high frequency when using coaxial cable

Can someone tell me why high frequencies (1 MHz sine signals) are getting attenuated in the below case. I have a function generator with 600 Ω output impedence. I connect this output to a digitiser ...
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Capacitance of current carrying wires (Transmission Line)

Let me explain my primitive understanding of a capacitor. In electrostatics, a conductor containing accumulated charges attracts opposite charges in a conductor that's separated by an insulator, this ...
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Simulating crosstalk and reflection waves using the same lumped RLCG circuit in LTspice

Is it possible to add line delay to an RLCG type circuit? Using this type of circuit, I'm able to simulate capacitive and inductive coupling, but no reflection waves. Using a SPICE tline, however, ...
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How can I match a transmission line impedance on the source side?

Suppose that I want to transmit a signal by a coaxial cable to a high-impedance load. The signal is a single-ended TTL (3.3V) single square impulse from an FPGA output. The package of the FPGA is LQFP-...
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Slew rate in a transmission line

Let's say I have a 3km long transmission line with a capacitance of C = 50pF/m, the resistance is 100Ohm. The inductance and the conductance per unit length are negligible. If I want to receive the ...
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How can I relate input voltage, load voltage and reflection factor r?

I am given a circuit as given below. I have to find the relation between \$U_2\$ , \$U_1\$ and \$r_a\$ (reflection factor). I couldn't find the expression containing only these three terms as given ...
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263 views

Why is there no reactance in the impedance of a half wave dipole antenna?

For a resonant 1/2 wave dipole when used for transmitting, does the fact that the reflected waves on the antenna are in phase with the applied signal result in zero reactance at the feed point, or ...
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Why do some above-ground HV lines have mid-span insulators?

I was looking at these overhead power lines and wondering what the insulators and bypass cables (circled in red) are for? Are those five small discs in each segment ceramic insulators? Are the ...
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Is the increase of impedance over a small hatch area on a FlexPCB negligible?

I have a FlexPCB with 4 layers and total thickness of about 200 µm. The second layer is a ground plane that is solid copper over the entire FlexPCB. To increase flexibility of the FlexPCB, I want to ...
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How am I getting 1 Gbps through a CAT3 cable?

My work from home office, in a difficult-to-plumb part of my house, has an existing CAT3 running to it from the main part of the house. I wanted to use a wired connection because the Wifi flakes out ...
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Problem entering impedance values to calculate Zbus into Matlab

Im trying to compute the Zbus matrix using the next Matlab code: ...
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Impedance Matching Necessary for short HDMI trace?

So, I am working on a design that uses HDMI for media output. The PCB has a connector for the Raspberry Pi CM4, and usually what I would do, is to do a "differential pair route" where I do a ...
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Replace a short length of triaxial cable with a PCB transmission line

I am working on a project that benefits from a short (~1") length of triaxial cable. At first I was skeptical that the cable would have any effect given its short length, but the performance is ...
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CML pre driver tail node voltage

Please consider the following schematic. I want to understand the V(A) waveform, when D+ & D- are switching. My understanding is that during the switch, we will have overshoot on V(A), because ...
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Two transmission lines with different media

I have some questions about intrinsic impedance and characteristic impedance. I learned the reflection of a wave occurs if the intrinsic impedance of the materials is different. \$ \Gamma = \frac{\...
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Voltage Drop using DC transmission over large distances

I'm trying to figure out the voltage drop across a 2.5mm^2 (14 AWG) cable. The formula I've used is V_drop = (Length in Meters * Current * 0.017)/(area in mm^2). For a 14 AWG cable I understand the ...

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