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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45 views

Controlled impedance traces necessary between line driver and series termination resistor?

I'm designing a line driver circuit with the SN74BCT25244 chip. The chip has a rise time of ~10 ns into an open circuit based on my own scope testing, but we are only wanting to drive the signal at a ...
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29 views

CAN Bus Nominal Impedance

I understand the reason for choosing a termination resistor of 120 Ohms for the CAN bus to avoid reflections but why was the nominal impedance of the CAN bus cables required to be 120 Ohms by the ISO ...
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Decoupling capacitors on bottom layer in non-BGA packages?

Typical advice on decoupling techniques usually gives highest priority to: always place the decoupling capacitors on the top layer, next to the pins. BGAs of course are a separate issue; I'll come ...
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68 views

Does matching impedance connectors matter in non-RF signals? Why?

I am designing a PCB which communicates with an encoder over RS422 at 2Mbps (15ns rise time typical in the MAX490's datasheet), and I am currently selecting the connectors. I have found 120Ohm twisted ...
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46 views

Why do ICs interconnects have squared corners

I was wondering, why do ICs interconnects have squared corners if they carry hi-frequency signals? (considering most transmission lines that handle high speed signals have chamfered/beveled corners ...
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Series connection of transmission lines described by telegrapher's equations

My issue concern the definition of series connection of multiple transmission lines described by the so called constant parameter model, to be next simulated in EMTP-RV. Let us take as an example two ...
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37 views

Laplace vs Fourier Transforms in Transmission Lines

Consider an electric transmission line with transient equations $$\frac{\partial v}{\partial x} =-Ri -L\frac{\partial i}{\partial t}, \qquad \frac{\partial i}{\partial x} =-Gv -C\frac{\partial v}{\...
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1answer
21 views

Design guidelines for RF castellated edge connections

I've seen many examples online of castellated vias at board edges used for module connections. However, all of these seem to be for low frequency signals. When using a castellated via to connect an RF ...
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Can I calculate minimum rise time of a transmission line if I know the length and the loss tangent?

Overview: I am trying to work out if it's possible to transmit my 1.2Gbps MIPI data down a 600mm long flexible PCB strip. Assuming I have the impedance correct, will the signal still be degraded by ...
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1answer
103 views

Loading an FPGA pin at 20MHz in parallel

I'm designing a traction inverter controlled by the NI sbRIO-9627, which includes a Zynq-7020 FPGA. I am considering using a single FPGA pin to drive the external clocks of 14x ADuM7701 isolated ADCs ...
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Amplitude plot of voltage standing wave on a transmission line

edit: I just found a site almost perfectly describe the issue, https://ophysics.com/w3.html I found this graph on Google but couldn't find an explanation of it, it is similar to the one presented in ...
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Different results from Smith Chart and Transmission line impedance equation

I have the following question which I need to solve Use a short-circuited section of air-filled TEM, \$50\Omega\$ transmission line ( \$\beta= k_0 , \lambda_g = \lambda_0\$ ) to create an impedance ...
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Single wire earth return system

So, in a single wire transmission system, the earth acts as the return path for current to "flow back to source". Would this work for anywhere on earth, say, if we transmit current on a single wire ...
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Underwater communication trough cable

I wanted to build a device which can stay and move underwater (let's say, for instance, 15m underwater). Since RF frequencies are very attenuated by water and VLF antennas would be too high, I was ...
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29 views

Transmission line current magnitude

I want to compute the current magnitude in a transmission line. The line has properties b (total line charging susceptance, p.u.), ...
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ST ST25R95 - NFC chip - Impedance of transmission lines

I will supply the chip with 3.3V, and the datasheet of ST25R95 IC shows it has a ZOUT of 27R at this condition. There is a circuit between NFC antenna/coil/inductor and the IC, the LC filter and ...
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Couplers and dividers as baluns

Can every divider and coupler that provides 3dB amplitude divison and 180 degrees phase difference be used as balun? Rat race coupler and lange coupler provide the two conditions mentioned above. ...
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How to do via fencing of an RF trace with a 5V front copper plane and a GND back copper plane?

Background I am a building a board to send RTTY via a Radiometrix NTX2B as part of my final year High Altitude Balloon (HAB) project. I have just created a PCB which I uploaded to JLCPCB for ...
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65 views

What is happening, physically during a Transmission Line Reflection in a closed and open circuit scenario?

I am having trouble understanding what is happening physically during a transmission line reflection, in particular the short circuit and open circuit case. I understand that when when a transmission ...
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1answer
66 views

How can there be a zero sequence current in a single line to ground fault with an ungrounded neutral

The circuit that describes a single line to ground fault in a system with an ungrounded neutral is: I neglect capacitance between phases and only look at capacitance to ground. The definition of zero ...
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relation between transmission line & circuit impedance

What is the relation between the impedance of lumped components and the characteristic impedance of transmission lines? I have noticed that in some cases transmission lines are loaded with lumped ...
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3answers
122 views

How to demonstrate mathematically the conditions of reflection in transmission line?

We are all taught about transmission lines and its associates -- characteristic impedance, reflection, standing wave, etc. It is well known what happens when a transmission line is terminated with ...
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I have a hard time with determining the input impedance of the problem shown as well as the equivalent lumped circuit model with this Zin

This is the work I have done so far. I am not confident in my work and was having a hard time with determining the input impedance. If you have a correction or opinion on this work please comment.
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Multi Driver EJTAG interface routing considerations for better SI

we have a MIPS uP which has EJTAG interface. This needs to programmed from Both P1(by default) & P2 connectors This EJTAG interface needs to be shared between 3 drivers. Assembly Option1 in ...
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51 views

Can these S-parameters be derived?

I have been trying to derive the S-parameters of a lossless T-junction of transmission lines. Here's a diagram from Google: This is an exercise in microwave network analysis, not in design, so the ...
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Signal velocity in PCB traces

On what does the signal velocity depend for a signal traveling through a PCB trace? According to Wikipedia, it depends exclusively on the relative permittivity (ε_r) of the medium (well, it also ...
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3answers
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Why single ended signal line is not immune to noise in RS232?

In single ended signal line the measurement is the difference between the signal and the ground. Isn't this way of calculation make it differential? Almost all the resource I have read says that ...
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1answer
59 views

Difference between single circuit and double circuit transmission line protection systems

I'm doing a research on long three phase transmission line protection systems and I found many schemes such as distance protection, merz-price voltage balance system, split-conductor, "translay" ...
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34 views

Understanding series open stub tuning

I recently had an assignment where I had to use open stub series tuning to find a way to maximize power delivered to the load from the generator. I understand that power delivered to the load is ...
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2answers
44 views

Length-matching microwave differential traces

I'm driving an RF mixer that takes differential input signals. My max signal frequency is \$6\,\text{GHz}\$. I understand that the differential input signals need to be length-matched, but what sort ...
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28 views

In a transmission line, does the real current interact with reactive impedances?

simulate this circuit – Schematic created using CircuitLab According to the diagram above, if real currents do not interact with reactive impedances, then reactive loads should not worry the ...
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Wire model RC vs LC/RLGC

The condition for using an LC/RLGC model over an RC model is when: f > R/(2*pi*L) (see for example http://www.ece.tamu.edu/~spalermo/ecen689/lecture2_ee720_channels.pdf slide 19). This explains why ...
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50 views

Microstrip skin effect

I've read that at high AC frequencies, current concentrates near the surface of a conductor, which is known as the skin effect. Does this also mean that current concentrates near the edge of thin ...
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59 views

Why should the protective angle on high voltage lines be kept as small as possible?

This website, https://circuitglobe.com/overhead-ground-wire-or-earth-wire.html, said for effective shielding, we should keep the protecting angle as small as possible, the angle between 20° and 30° is ...
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28 views

Trace width for breaking out 100Ω differential microstrip from 0.5mm pitch BGA

See bottom of post for the actual questions First, some context: I'm making a DisplayPort switch as a hobby project DisplayPort's high speed lines require 100Ω ± 10% differential impedance, which I'...
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1answer
31 views

How to estimate active-power transmission capacity based on voltage levels and line lengths

I know voltage levels and line lengths of high-voltage transmission lines and I am looking for a rough estimation of the maximum active-power transmission capacity during normal operation. By normal ...
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2answers
57 views

Meaning of S11 performing a clockwise arc circle about the smith chart origin?

I've tested a device with my VNA. It displays S11 in a Smith chart as a plot x(w) + iy(w) (w the frequency). Curiously, as w increases from 50KHz to 600MHz, the plot is an almost perfect 1/3 circle ...
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1answer
110 views

Grounded coplanar waveguide differential gap

I'm driving an ADL5802 RF mixer with a 5400BL15B050E RF balun. The balun turns a single ended signal into a differential signal on balanced lines for the mixer. In my attempt to match the balun ...
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1answer
26 views

The reason the advantage of Single conductor transmission line be changed to non-singular conductor transmission line

Question: If Single conductor of EHV(Extra high voltage) transmission line be changed to non-singular conductor of EHV transmission line,there are some advantages about this changing 1.Decrease the ...
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42 views

AC circuit analysis with a transmission line involved

I'm trying to perform an AC analysis of a circuit that contains a piece of coax cable. The input voltage 'Vs' is a swept frequency (1MHz-150MHz) voltage source with constant amplitude. What I'm ...
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56 views

Transmission & Distribution

During a recent job interview of mine, one of the panel asked me the following question Q) Why is the transmission voltage of overhead lines in our country in the multiples of 11? Some background ...
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62 views

Detecting an electrical connection without a complete circuit

Wired Fencing In a regular (wired) fencing system (for sabre and foil,) contact is determined simply by applying a current to the weapon through a wire and forming a circuit between a conductive ...
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1answer
52 views

transmission line parameters

I read that the propagation speed (m/s) of a lossless transmission line, which I know is equal to 1/sqrt(LC), is also equal to 1/sqrt(L'C') where L and C are distributed inductance and capacitance (...
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1answer
149 views

Is it better to route Ethernet on the top layer, or to use vias?

I'm making a circuit board with Ethernet (PoE if that makes a difference) coming in through an M12 connector, passing through magnetics and a PHY and going to a micro. I've always heard that there are ...
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52 views

Waveguide excitation through coaxial antenna

let's consider a waveguide excited with a coaxial cable antenna: You may see that this structure is sized with a distance between the antenna and the plate equal to \$\lambda/4\$. My professor has ...
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57 views

How to find the Fourier series of an output given input and transfer function

I have an input rectangle pulse, \$f(t) = rect(t/\tau) \$ and a transmission line whose transfer function depends on frequency. The transfer function of the t.l. is the transmitted wave divided by the ...
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4answers
125 views

Why longer stubs cause more intense ringing?

Why connection of longer stub lengths cause more intense ringing in a Communication Network like CAN? As stub lengths increase won't the attenuation increase and lead to less ringing? Also the time ...
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1answer
43 views

how to calculate DC resistance of transmission line from telegrapher's equation

Can someone explain to me how to use the transmission line (TL) formula (from telegrapher's equations) to calculate the DC resistance of the TL? Here's my work so far: V(x,s) = A * exp(-gamma*x) + ...
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130 views

Why is the amplitude of ringing in square wave independent of frequency of square wave?

Reflections in a transmission line is causing ringing in square wave because certain frequencies are getting enhanced, but when frequency of the square wave changes won't the amplitude of those ...
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1answer
70 views

Does the standard termination of 120 ohm really suppress reflections in recessive state in CAN?

Suppose we have a multi-node CAN network with the ends of transmission line terminated with the standard 120 ohm. When the recessive state is on the transmission line, the voltage on both CAN_H and ...

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