Tagged Questions

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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2answers
90 views

Very long transmission-line design tips

I'm designing a very long transmission line between a master node a some slaves far away connected by a bus where only 3 wires are used: - A DC power supply (24vdc) - B Digital comm - C Ground As ...
0
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1answer
64 views

Sending Signals over a Coaxial Cable [closed]

Recently I've been trying to understand how multiple signals can travel along a coax cable. Indeed, I have already read "How are multiple signals propagated in a coaxial cable?", but it doesn't seem ...
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2answers
60 views

How does the circuit fill up?

I came to know that in transmission line if I send only the phase to the houses and make the neutrals to ground then the circuit works. How does the circuit fill up without having any closed contact ...
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0answers
71 views

How long of a wire and how big of a load can I have for SPI bus?

I have a system where I will connect up to 128 identical magnometer ICs up to an FPGA. I am trying to decide between SPI and I2C for comms. If I use SPI the setup will require 128 + 3 wires IF all ...
2
votes
3answers
68 views

Do transmission lines induce electric or magnetic fields in towers?

Transmission lines have EM fields around them due to the high amount of current. Do these fields affect transmission towers (metal or otherwise)? If so, would it be possible to estimate the current ...
1
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1answer
48 views

How does the impedance that voltage “sees” while traveling down a tranmission line affect how the current move down the line?

It is well known that the voltage sees different impedances while traveling down a tramission line, and this impedance is a function of the intrinsic impedance of the line Zo and tangent of wave ...
1
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2answers
62 views

What is actually transformed in quarter wave transformer?

I'm reviewing some stuff on quarter wave transformer for a transmission line but since I have not had any experienced in handling these type of stuff, I am struggling to understand this concept ...
0
votes
1answer
44 views

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 ...
2
votes
2answers
100 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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2answers
117 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 ...
1
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3answers
77 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 ...
0
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2answers
66 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 ...
8
votes
3answers
215 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 ...
2
votes
2answers
58 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 ...
2
votes
1answer
72 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 ...
0
votes
3answers
248 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 ...
8
votes
8answers
422 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 ...
-1
votes
1answer
89 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 ...
0
votes
1answer
290 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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0answers
55 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 ...
0
votes
1answer
34 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 ...
1
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3answers
1k 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
112 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 ...
-4
votes
1answer
65 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 ...
3
votes
2answers
81 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 ...
3
votes
2answers
113 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
176 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 ...
3
votes
1answer
130 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, ...
2
votes
2answers
62 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 ...
5
votes
2answers
361 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 ...
2
votes
2answers
179 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 ...
3
votes
1answer
134 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 ...
1
vote
1answer
100 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 ...
1
vote
1answer
79 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 ...
0
votes
0answers
358 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 ...
0
votes
0answers
57 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 ...
0
votes
0answers
39 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 ...
1
vote
0answers
92 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- ...
3
votes
1answer
229 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 ...
7
votes
2answers
174 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 ...
1
vote
1answer
570 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. ...
10
votes
1answer
580 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 ...
22
votes
4answers
2k views

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 ...
3
votes
1answer
249 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
votes
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 ...
2
votes
1answer
230 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 ...
2
votes
2answers
231 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 ...
1
vote
1answer
52 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 ...
0
votes
1answer
45 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 ...
0
votes
3answers
259 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 ...