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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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
16 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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94 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
94 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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83 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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58 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
50 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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0answers
112 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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54 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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31 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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61 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
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1answer
105 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
138 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
176 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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1answer
416 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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4answers
1k 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
195 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
71 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
201 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
198 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
49 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
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1answer
39 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
176 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 ...
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2answers
151 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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0answers
108 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
127 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
137 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
158 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
140 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 ...
2
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1answer
391 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 ...
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2answers
396 views

What is the purpose of the thin wire at the top of power transmission lines?

I know a power transmission line carries usually two sets of 3 phase conductors. But I have noticed a relatively thin wire at the center-top of the power transmission line. What is the purpose of this ...
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votes
3answers
200 views

What's the importance of source impedance termination?

Given a circuit like this: simulate this circuit – Schematic created using CircuitLab What's the importance of R1? One can guess that it's to make the output impedance of BUF1 equal to ...
18
votes
3answers
619 views

What happens at the end of a transmission line?

Let's say I wanted to make a widget containing a relay to switch between two antennas. There is a coax transmission line coming in from the transmitter, and two going out, each to a separate antenna. ...
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5answers
696 views

Can we measure reflected power in a transmission line?

This is a question related to radio transmission, I hope this is the proper forum to ask it. It relates to transmission lines connecting a radio transmitter to its antenna. In his book "Reflections", ...
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2answers
162 views

How does less cable impedance, source/termination impedance, lead to longer cable length for higher data rates?

This question is about high speed digital transmission on a transmission line, I need to know about how does the (1) impedance of the transmission line and the (2) source impedance and (3) ...
28
votes
2answers
704 views

If we could start our electrical grid from scratch with today's technology, which would be the most efficient choice? AC or DC?

Lately, I’ve been reading about the many advantages of HVDC transmission systems for long distance transmission, undersea links, and others. The historical reason of why AC was picked over DC was ...
18
votes
3answers
427 views

Transmission line reflection. I would like a non-mathematical explanation

I am a licensed radio amateur, and find bewildering the many different explanations, which range from folksy urban myth to Maxwell-Heaviside Equations, of what happens at the termination of a ...
5
votes
1answer
283 views

Cable Splitter Loss and Impedance Matching

From my memory, cable splitters (such as for splitting a cable tv coax cable into two televisions) provide impedance matching to prevent signal reflections, etc. If one 50 Ohm line is split into two ...
0
votes
1answer
240 views

What is a good tolerance for impedance matching or how to calculate losses?

If you build a microstrip on a silcon wafer, connected by picoprobes via SMA connector and cables to a VNA, what is actually a good match of the impedances of the cables and the waveguide. Is there a ...
4
votes
1answer
328 views

How does the addition of a bias-t circuit affect the impedance of a transmission line?

I've got a GPS circuit where the antenna is connected directly to the GPS receiver via a coplanar waveguide designed for an impedance of 50ohms. Unfortunately, I neglected to add the bias-t circuit ...
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1answer
159 views

Will an oscillator be able to drive a transmission line

I want to build a soil moisture measurement probe based on this idea: An oscillator feeds a transmission line burried in a soil via a termination resistor R1, XOR gate acts as a phase shift ...
3
votes
3answers
1k views

How does an swr meter directional coupler work?

How does the directional coupler in an swr meter work? How are the forward and reflected waves separated out from the standing wave on the feeder? I would like an answer in terms of sine (or cosine) ...
8
votes
3answers
1k views

How is rise time related to bandwidth of the signal?

Say, I want to limit the rise time of my digital signal edges to avoid dealing with transmission line effects. How do I determine the maximum frequency of harmonics in my signal knowing that my rise ...
0
votes
2answers
162 views

Multiple level signal transmission

I'm interested in increasing the transmission rate over Cat5 for a personal project. (Cat5/5e/6 will be chosen because of it's properties and obtainability but will not be used in the standard way) ...
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3answers
531 views

Why is impedance represented as a complex number?

Let me know one thing. Why is impedance represented by a complex number when considering loss? Usually it is said that imaginary part is because of loss. Is it True? If it is true then does that ...
15
votes
2answers
694 views

Why not use a ferrite bead around an RS-232 cable?

This is from the instruction manual of a printer: As you can see, one is not supposed to wrap the supplied bead around the serial cable. What is the reason for this?
5
votes
3answers
688 views

Long transmission line inductance with SPI

I have a PCI 5V GPIO card which bit-bangs SPI over a 10-foot cable. The SPI clock is running at 800Khz. The cable connects to a board and the SPI lines feed directly into the SPI IC's. I know SPI is a ...
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1answer
150 views

Power Grid in depth explanation [closed]

I am looking for links, books, papers, documents or any other reference type that allows me to get a very in depth overview of the power transmission and distribution network (preferably of the UK). ...
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1answer
141 views

Scattering matrix Transmission Matrix lasers

I would like to ask if anyone can suggest me a good tutorial about Scattering and transmission matrices for lasers. I am really struggling with some issues and the majority of the literature analyses ...
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2answers
602 views

source/output resistance

I was wondering why many generators ect. have 50 ohm output resistance. Before you answer here is what I know: Many transmission lines are 50 ohm, and terminated with a 50 ohms load to get maximum ...