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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How do utility lines wire transformers to go from 3-phase power to residential split phase?

I'm trying to understand how power distribution lines go from 3-phase to single-phase and haven't been able to find a concrete explanation. I understand that power companies transmit with 3-phase ...
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Voltage seen at load which has open circuit in parallel

If I send a sinusoidal signal down a transmission line, say with a source and line impedance of 50 ohms. Then if I have a 50 ohm load, in theory, there are absolutely no reflections. If however, I ...
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Transferring maximum power to multiplexed loads

I'm interested in creating a system driving 8 different loads from a single amplifier, at relatively high currents of few hundred mA I wish to do this utilising a 8:1 multiplexer IC (8* spst), where ...
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Evaluating antenna models as presented in a recent research paper

Here are lumped element equivalent circuit antenna models from a recent research paper (published in the INTERNATIONAL JOURNAL OF MICROWAVE AND OPTICAL TECHNOLOGY in 2019): Typical Approach of ...
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Antenna model by chatGPT AI - correct or not? [closed]

I asked chatGPT about a basic simplified model of an antenna according to my conception of it (pasted is the most relevant part of two separate answers). It would look like this: ChatGPT AI ...
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What is causing this resonance point in my S11 Trace?

Does anyone know what is causing the higher frequency occuring in the S11 trace of this simulation? I have checked all the capacitances and inductances associated with the transformer and ...
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1 answer
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Can a generator in an electrical grid be destroyed by disconnecting the power at a distant substation

I've read that if the length of a transmission line is a quarter wavelength then an open circuit at the sink would appear as a short at the source. Consider a real electrical power transmission line ...
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Calculate the sending-end line voltage for a long transmission line without being given shunt admittance

I have this question but I can't seem to figure out how to solve it. The question goes like so: For a three-phase long transmission line, Zc = 406.4∠-5.48°, VR = 215 kV and IR = 335.70 A, all per ...
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Do 50 Ω signal generators have a series resistor or not?

I am wondering about something really simple and silly. If functions generators have an internal series 50 Ω termination, then they would produce only half the set amplitude over a matched load. ...
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Cannot trigger digital logic because half of source voltage is lost in impedance matching

I am using a 3.3V output of an NI controller over a coax transmission line. I have matched the termination resistor to the 50 Ohm source resistance. I need to use this output signal to control three ...
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How to calculate voltage drop across a coaxial transmission line?

I am an engineering student and I want to ask a question for my assignment. How can I calculate voltage amplitude drop across a coaxial transmission line without input function? (How many percent of ...
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When should an unmatched antenna be measured with a cable length in even multiples of a half-wavelength?

A few years ago someone told me that if you use a cable which has a length of an even half-wavelength multiple for the frequency being tested, then the impedance measured at the end of that cable will ...
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Confusing about impedance termination

Datasheets by analog devices state that I must terminate IC (AD9910) impedance by input impedance of 50 Ω and placement near the balun. But here is the deal when I was looking for AD9912 datasheet (...
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Effect of a capacitor in a transmission line

What will the consequences be if I add a load capacitor in parallel with the load resistance in a simple transmission line? Here is the circuit.
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How do I calculate the anti pad of a via for high speed signals?

Lets say I have a signal that is X GHz, is there a specific anti pad size to ensure I have correct signal propagation? Does the anti pad only add a delay or extra capacitance?
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Effects of coax length in a 50 ohm/ 75 ohm mismatch

I am building a broadcast FM receiver (88MHz to 108MHz). My antenna is a 1/4 monopole with 4 quarter wave radials and has an impedance (Zsource) of 50 ohms. I am connecting it to a 75 ohm rg6 coax ...
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What happens to reflections when the distance between a capacitors plates is electrically long?

I understand what happens when a transmission line is terminated with a capacitor but what about when the distance between the plates becomes electrically long? For PCB mounted capacitors I know this ...
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What happens to the signal and antenna pattern when the coaxial shield of the feedline is severed?

Assuming a single-shielded coaxial cable connected between a transceiver and antenna, what would happen to transmitted signal and the antenna's radiation pattern if at some point along the feedline ...
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Possible purpose for a resistor and diode in parallel on a short transmission line to a digital input?

During some reverse engineering, I've come across circuits similar to this one shown, where a diode and a rather large resistor (mega-ohms) are in parallel across the source of a signal. Here, when ...
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Unequal resistive power splitter

I'm looking at a 3-port, unequal resistive power splitter design like the dashed-line box in the diagram. 1 is the source, whereas 2 and 3 are two loads of impedance, say Z0. All 1, 2, and 3 are ...
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How can I match the impedances in this circuit?

I have a pre-amplifier with 93.1 Ω output impedance connected to a main amplifier with input impedance of 1000 Ω via 75 Ω co-axial cable. The signals are very small pulses from a measurement device ...
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Kuroda Transformation of planar filter

I am reading about this Kuroda's' transform but I notice that they are 2 types of formulas on the internet. Which one is right? I'm so confused right now. Look at the (a) and (b) of these 2 pictures.
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How to amplify a square wave clock signal received from 50 ohm coax?

I want to use the signal from a GPS disciplined oscillator (GPSDO) as a clock signal for a microcontroller. The GPSDO outputs a 10 MHz square wave between 0 V and 3.3 V designed to drive into a 50 Ω ...
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Half power beamwidth of antenna

I was solving a problem regarding HPBW. From what I understood, HPBW of antenna is the angular separation on the beam where the radiation intensity is half of its maximum value. That means U(radiation ...
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Effect of surrounding material on microstrip impedance?

If you were to have a microstrip transmission line PCB trace, which then had a dielectric material run completely on top of the PCB track coverlayer. Would this surrounding material affect the ...
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S21 & S12 of a mismatched transmission line

I am trying to solve this problem: Since it is asking for a reference impedance of 50 Ω there will be a mismatch, and hence reflections at the Port 1 for calculation of S12. I already know S11 and ...
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How is the center pin supported in air-filled coaxial cables?

In SMA cables, the PTFE dielectric supports the center pin through the length of cable. How is the center pin supported in air-filled cables? E.g., 3.5mm, 2.9mm, K-connector, 1.8mm, V-connector, etc. ...
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A 200-mile-long neutral busbar doesn't sound real

In Chapter 1 of Power Systems Analysis (Grainger/Stevenson), the authors present a sequence of representations of the same power system (Fig 1.25 --> Fig 1.26 --> Fig 1.27). I am confused by the ...
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Is birefringence exploited or otherwise meaningfully observed anywhere in electronics?

Birefringence is a property of certain materials where the refractive index of the material is dependent upon the polarization and direction of propagation of light through it. I recently learned ...
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How is a fault location detected in a power system?

Electrical transmission lines can face various types of short-circuit faults, for example, line-to-ground, line-to-line, etc. How do power system engineers find the fault location by observing from ...
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How to include magnetic loss in transmission line equations for coaxial cable?

I'm trying to calculate the attenuation per unit length (\$\alpha\$) of a coaxial cable, including dielectric dissipation (\$\varepsilon^{\prime\prime}\$), magnetic dissipation (\$\mu^{\prime\prime}\$)...
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Impedance matching in 2-layer FR4 board

I'm not that familiar with high-speed boards designing. Here I want to route the PCB in a part of which I've used a LAN8720A as the PHY of the ethernet system. According to what I've read about ...
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Time domain reflectometer transmission line

I'm quite new to transmission line theory, so I decided to follow an introduction course online. I am struggling with understanding the solution to this question. Here is what the course is giving as ...
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Infinite transmission line connected to a generator

I am reading through a PDF of a book on transmission lines, and ran into a question in the book that kind of stumped me. A transmission line driven by 2.4 GHz generator has a Thevenin equivalent ...
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Can polarity protection circuit be useful for also data transmission?

For example, CANBUS has two transmission lines CAN_HIGH and CAN_LOW. Polarity matters. Would the performance be affected if a polarity protection circuit with couple of diodes would be implemented? ...
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Measuring the characteristic impedance of a transmission line with electrical components rather than a given VCCS Model

According to the transmission line fact mentioned at below paragraph. So I made a circuit using ADS as below to testified it. There is a voltage controlled current source (gain=1) that draw current (...
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Differential and single ended crosstalk and clearance

I know that there can be crosstalk between differential pairs (and you need at least a few lengths equal to the diff pair between diff pairs, usually 3 or more diff pair widths). What is the ...
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1 vote
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Finding total return loss between transceivers

I was wondering how one finds the total return loss between transceivers. In particular, how return losses of connectors are added. Say if I have two connectors with a return loss of -10dB. How do I ...
3 votes
5 answers
460 views

Impedance matching for short transmission lines

Why is it that impedance matching does not matter if the transmission line is shorter than the wavelenght of the signal? Why do you get zero reflection if the line is shorter than the wavelenght? Also,...
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Reflection of power at low frequency (non-transmission line)

Say you have a 1 kHz signal source with an impedance of 50 ohms and then connect a 100 ohm resistor between the terminals. Is the power that is reflected calculated in the same way as transmission ...
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Time step error after placing connection between component and transmission lines - ADS

I have recently created a project in ADS. It contains a couple of transmission lines, capacitors, and resistors. When I connect my transmission lines to the s2p file, transient simulation is done ...
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What type of PCB material should I use?

I'm making my first 4 layer PCB (1 signal, 2 GND plane, 3 PWR plane, 4 signal) with impedance control. I was checking the layer stack up for Altium to make sure the thickness and dielectric constant (...
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Distributed element low-pass filter simulation with microstrip lines in QUCS

I want to simulate the resulting circuit of "EXAMPLE 8.5 LOW-PASS FILTER DESIGN USING STUBS" from Microwave Engineering (4th edition) by David M. Pozar. Here is the targeted circuit: 4GHz ...
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PCB trace as transmission line: rise time vs propagation delay

I have seen the answer for when to consider PCB trace as a transmission line in many places. Typically, if the signal pulse rise time is ‘small’ compared to the time it takes for the signal pulse to ...
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What is the voltage angle?

I am trying to learn the basics of electricity. I came multiple times across the notion of a "voltage angle" of a node. For example, when sending \$f_{vw}\$ units of electricity on a line ...
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3 answers
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Effect of small length impedance discontinuity in a transmission line

Consider this arrangement of a radio, a long coax cable, a small length of "random" cable and an antenna. The radio, the coax and the antenna all have the same impedance, but the random ...
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Transmission Line model [closed]

Can some one explain me why exactly classical circuit theory fails to account for the wave nature of EM fields and how the transmission line model accounts for it better
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What would be the S-parameters for an "ideal" shorted transmission line?

I seem to remember that the shorted- vs open-transmission line reflection is out of phase by 180-degrees. I'm new to the mathematics behind transmission line theory and I'm trying to figure out how ...
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Current in a transmission line

I have a 6ft long SPI cable and I am trying to estimate the steady-state current demand on the driver. My transmission line is tuned to 100 Ω. That is, I've added a 50 Ω resistor in series with the ...
2 votes
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High voltage three phase power lines and ground danger

In Europe, most power lines have three cables for each phase and no neutral (usual UK line pictured): The three-phase AC generator at the power plant probably use a Δ-phase winding (simplified): (...
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