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 ...

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Impedance line matching and component value matching

I have the following circuit for the SIM900's antenna connection, using the A10393 antenna from digikey: In closer look: First of all my knowledge on RF design is not great. My questions now are ...
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84 views

When a voltage pulse is sent through an open transmission line, what happens to the voltage at the end of the line when the pulse is reflected?

From what I understand, the voltage doubles since the reflected and incident pulses add up. But then why don't all open terminations have double the source voltage since we can consider the voltage ...
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86 views

Using attenuators to damp reflections on transmission line?

I have a 3m long transmission line that transmits a 100ns bipolar square pulse every 200us. At the beginning of the coax cable is a pulsing circuit board, that generates the waveform, then it sends ...
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3answers
63 views

Simulate RF transmission lines at Low frequencies

I would like to simulate RF transmission lines in how they propagate, and how impedance mismatches at the end of the transmission line cause reflections and power transfer does not work. It would be ...
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55 views

Why is the data rate a function of the length of the transmission line?

The length of a transmission line is limiting the highest possible data rate on that line. Why are faster signals more likely to become corrupted on long transmission lines than on shorter ones, with ...
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192 views

PCB RF Layout Critique: Input on my radio-telescope PCB

I'm attempting to do the board layout for a radio-telescope we're building at one of my jobs. Here is the overall system topology: QRFH is for "Quad Ridged Feed Horn". It's a rather esoteric ...
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2answers
56 views

Why is there no voltage drop along a feedline

This page shows a graph of voltage along a transmission line by distance. Considering the case of a simple purely restive feedline of 50 ohms matched to a load of 50 ohms, I would expect the voltage ...
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1answer
66 views

Stripline reference plane discontinuity in reference design

According i.MX6 SMART DEVICE SYSTEM of freescale layout board, it uses 8 layers, my question is about the inner layers, they are striplines with a continuos GND plane in one side but in the other side ...
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3answers
221 views

Tapping energy from high voltage AC transmission lines

The details are hazy as I recollect this from my nipper days.Many, many years ago. “Persons were charged with stealing electricity by placing a large coil, somehow, near high voltage AC transmission ...
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409 views

Neophyte question about AC vs. DC (especially for powering a home)

Here in the United States the electricity grid is AC. I have heard that AC allows transmission of power at greater distances with less loss. However, with the advent of solar panels, it would seem ...
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80 views

The mathematics of saltatory neuronal action potential transmission [closed]

Some time ago, I tried to understand saltatory electrical potential transmission on a myelinated axon but have not found a clear mathematical model of this mechanism. The neuronal signal ...
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175 views

Coplanar waveguide for differential trace calculator

Although there are plenty of free impedance calculators out there, I'm struggling to find one that can solve impedances for a differential pair using coplanar waveguide. Anyone know of any free ...
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54 views

Impedance matching and calculating reactance

Design a reactive L network in order to provide impedance matching between transmission line of \$Z_o = 300 + j60\$ and an antenna having impedance of \$80 +j100\$ at the frequency of 1MHz. How ...
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27 views

How to find attenuation constant

Propagation constant is in the form P= a+jb (a= attenuation constant b = phase constant) a +jb = ln (x+ jy). How do I separate the real and imaginary part in the RHS so that I can equate the ...
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3answers
667 views

Why does the USA use 110V and UK use 230-240V?

Why does the USA use 110V and UK use 230-240V? What are the advantages? Explain me with calculation. Why do they use different frequencies like 50Hz, 60Hz? What is the reason?
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2answers
111 views

Best way to drive long signal cables

What is the best way to transmit analog signals between 100 Hz and 100 kHz over a distance of up to 6000 m with minimum frequency depending loss, the level is 50 uV to max 1V (always less than 100 mV ...
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1answer
62 views

Good book/reference for electromagnetism and distributed elements model

I am looking for a good explanation of what is in "between" of Maxwell's equations and the lumped model. I am talking specifically of RF electronics and the distributed elements model. I am ...
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2answers
76 views

Finite parallel impedance network general solution

Does anyone know if a finite number of parallel-series impedance has a general solution? I am trying to model a network flow problem that can be described in electrical terms and represented as a ...
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2answers
101 views

Finding exact breakpoint location in long wire

How can I find the exact location of breakpoint in my long transmission line? Please help with the methods.
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3answers
123 views

Conductance in a transmission line

I'm just trying to clarify the transmission line concepts in my head. Now wikipedia (that great source of always reliable information) defines the conductance in the transmission line as ...
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1answer
125 views

RF Circuit (what does capacitor do?)

I'm trying to work out why a 0.7pF capacitor was chosen. The circuit operates at 12GHz. At 12GHz, the capacitor has an impedance of about \$18\Omega\$. Also at 12GHz, ...
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1answer
46 views

CML signal to ground terminated line or peak sensing ADC for short pulse

I'm currently designing the prototype of a timing instrument. One sensor gives an analog CML (current-mode logic) signal, from an amplifier (ADN2880). One end of the pair is routed to a comparator ...
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2answers
277 views

Why does more bandwidth mean higher bit rate in digital transmission?

I understand that similar questions like this one have been asked before on this site, listed below. However, I am confused about the answers. If I explain what I think I understand, can somebody ...
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2answers
168 views

Minimal distortion in transmission line

In a transmission line, the condition for minimal distortion (caused by the line) are when (R/L = G/C) in the line, right? However, I don't see any reference to that in any application notes or ...
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1answer
129 views

1/4 wavelength case in transmission lines

I have studied that in transmission lines, if λ is the wavelength of the signal and L is the length of the conductor, then at L=λ/4 the transmission line act as an open circuit. So if we are ...
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1answer
92 views

Designing RJ45 connector to have 100Ω differential impedance

I'm designing two pairs of connectors that have same layout as RJ45 (just 2 inner pins) to have 100 ohm impedance deferentially. Are there tools that allow to calculate impedance or ...
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1answer
76 views

Radio antenna isolating transformer

I need to isolate galvanically my antenna from my RF transceiver. For this I have been recommended a transformer, I select a 1:1 transformer operating in high frequency range. Is it enough to wire it ...
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293 views

Plotting reflection coefficient magnitude vs frequency in MATLAB

I am trying to plot a function (t) with respect to w in MATLAB. However, the output that I am seeing is showing 0 for all w within the defined range. This is not what I am supposed to be seeing. The ...
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56 views

Circuit that behaves as a long transmission line. Any ideas? [duplicate]

I am in need of a circuit that would replicate the behavior of a very long coax cable (miles long). Namely, I am interested in how it would distort a relatively low-frequency signal and how it would ...
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37 views

Applying Transmission Line Theory To Plane Waves

I'm working on a project for my E&M class. Our goal is to use transmission line theory to design a "stealth" dielectric layer for some sort of aircraft. I can assume the radar wave is incident ...
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83 views

Can we draw analogy between em power flow through free space and ac power flow through a transmission line?

Knowing that the free space has a characteristic impedance (which is purely resistive, measured in ohms) I was wondering if I can model the free space as an infinitely long transmission line- ...
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1answer
189 views

What determines what type of short-circuit current is highest?

I'm doing a short-circuit analysis of a system, and started wondering about the following: What determines which type of fault current is the highest (and lowest)? The screenshot below shows the ...
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2answers
170 views

A transmission line with continuously varying impedance, how would reflection occur in this case?

Alright folks here it is, another transmission line question that has been bothering me. I understand the case where there is an abrupt change in impedance along a transmission line that leads to ...
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1answer
497 views

Derivation of Characteristic Impedance?

I start from the telegrapher's equation: \$-\frac{dV(z)}{dz}=(R'+j\omega L')I(z)\$, where \$V(z)\$ and \$I(z)\$ are the phasors of voltage and current respectively, in the transmission line model. ...
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544 views

Why does reflection off a PCB via look like this?

My question is related to http://mobius-semiconductor.com/whitepapers/ISSCC_2003_SerialBackplaneTXVRs.pdf. On the page 18 there are a few figures of "TDR off Diferent Types off Vias". I am confused ...
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How do transposition towers in transmission lines work?

There're such things as transposition towers in power distribution powerlines. The idea is that for example you have three conductors running in parallel at the same height and the leftmost of them is ...
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1answer
248 views

Does forcing a data line to a higher power make it more resistant to interference?

A device I'm working on as a hobby project requires me to transmit a HDMI signal over cat5. The TMDS lines in HDMI are balanced but in order for me to continue transmitting the DDC signal with the ...
3
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1answer
78 views

Regarding Transmission line

Is every wire a transmission line or a transmission line has a special manufacturing process? But why during analysis of normal electrical circuits we never consider parameters like characteric ...
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1answer
225 views

How short can an RF transmission line be?

Design for connecting transmitters to antennas often mentions the transmission line, and the standing wave ratio (SWR) for matching. But what if the transmitter is on the antenna? Background: I've ...
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2answers
225 views

Why a wave does not enter a cable? Understanding TDR (Time Domain Reflectometry)

I have been doing some TDR (Time Domain Reflectometry) measures which involves sending gaussian pulses through a cable and measuring the s11 (reflection) parameter. In this measure, I could see that ...
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1answer
51 views

Calculate balance between signal and noise to allow 32 kbit/s transfer

I have to calculate proper balance/ratio between signal and noise ( S/N ) in decibels ( dB ), to be able to transfer data over the channel at 32 kbit/s. Channels bandwidth is 100 kHz. I was given ...
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1answer
41 views

Calculate transmitting power of the Transmitter

I cannot get a hold of my professor and I'm stuck tyring to understand how to solve this problem. It's not homework or an assignment I'm preparing my self for a test. So as the title states I need ...
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3answers
229 views

Amplify .7Vpp square wave to 5Vpp square wave buffered to go over a 15-50 foot cable

I've got a sensor that outputs a .7Vpp square wave at 36kHz-60kHz. I need to take that square wave and amplify it to 5Vpp, as close to 0V to 5V rails as possible. Then I need to send that signal ...
2
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2answers
168 views

terminated cable capacitance

As much as I know, the input impedance of a coaxial cable with a characteristic impedance of 50 \$\Omega\$ which is terminated with a 50 \$\Omega\$ load resistor, should be 50 \$\Omega\$ as well. This ...
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1answer
195 views

Calculating reflections

I just solved a problem in my homework. I had to calculate the reflection waves and I was given the following data: // Resistance R0 = 120 Ω line impedance Ri = 90 Ω resistance at input Rb = 1 ...
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1answer
157 views

Confusion regarding considering a transmission line as lumped or distributed

I am just elaborating my question. I have came across different formula's to say whether a Transmission line is lumped or distributed. in one of the books i read " Effective length of a electrical ...
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3answers
170 views

understanding transmission line signal integrity through simulations

I need to simulate how signals are reflected based on the source, load and line impedances and how the signal integrity is effected by the spacing between different traces on a board, traces on the ...
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1answer
211 views

Do long transmission lines degrade rise/fall times, and if so, by what mechanism?

I remember someone telling me long ago that if a voltage step is sent down a transmission line, the step will become smeared as it travels down the line, and the rise time will become degraded. I'm ...
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2answers
184 views

Does the noise figure of a cable change if the load/source is mismatched?

I know that the noise figure of a transmission line is equal to its attenuation (usually expressed as dB/m or dB/100 ft). However, what if there is a mismatch between the line's characteristic ...
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680 views

How do different methods of transmission line termination compare?

It seems to me that there are three ways to terminate a transmission line: at both ends at the load only at the source only simulate this circuit – Schematic created using CircuitLab ...