Questions tagged [reflection]
The reflection tag has no usage guidance.
104
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Can a "sharp turn" on a trace with an SMD resistor also present a risk of reflection?
I'm aware that in transmission lines, taking sharp 90-degree angle turns are a bad idea. Below is an example of different current behaviors of high-speed transmission lines from various shapes of ...
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How important is a "no reflection" strategy for 1 Hz systems?
One of my colleagues claims that no matter what frequency the PCB board has, you cannot allow reflections inside the tracks. In this case, it's 1 Hz frequency that is going to turn a relay ON. The ...
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Is it possible to simulate reflections by designing an RLC transfer function?
Assume that you're knowing the PCB stack and the geometry of the conductor.
You're computing the capacitance per mm and inductance per mm and also the total resistance of the conductor.
That means you ...
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Reflection on PCB + antenna
I have a transducer with 64 outputs. I want to have 3 of the outputs on my amplifier input in a way that I can choose between them. My first idea for implementing this was to use jumpers as follows:
...
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Contradiction between wave impedance mismatch and transmission line theory
Suppose we have two transmission lines connected with each other, each transmission line has the same characteristic impedance: $$ Z_0 = \sqrt{\frac{L}{C}} $$ however they don't have the same ...
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How to calculate reflection coefficient of a transmission line with discontinuity [duplicate]
I have a question, let's say that we want to calculate the Reflection Coefficient that we see by watching from left to right of the red-line this circuit:
Let's say that:
...
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Will termination resistors help with USB data line "dead legs"?
I'm designing a USB switch, using small relays to connect a USB peripheral to any one of ten PCs.
The USB traces from the peripheral branch out to ten different relays. I anticipate these "dead ...
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Is there multipath inside a shield box?
Since metal surfaces reflect EM waves, if I put a transmitting antenna inside a shield box will the transmitted RF signal scatter everywhere inside the box?
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General guidelines to avoid damaging RF components
So, I am a young researcher in physics and use RF components like splitters, mixers, couplers, amplifiers, etc. These are not high voltage amplitudes at all - at most a few volts - often hundreds of ...
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Must the characteristic cable impedance match the series output impedance?
I have been working on a communication link between an FPGA and a SPI slave. The electrical connection between the two is done via a 2 metre cable composed of 42AWG wires with the following ...
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Even if source and load impedances are matched, and current is flowing, wouldn't power be dissipated at the source equal to the load?
Like for example a transmitter with 50 ohm impedance, I'm assuming this is real resistance, why would power not be dissipated also? Hope my question makes sense.
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Transmission Line simulation
Hello I am trying to understand the behaviour of a simulation of a simple transmission line.
Here is the Transmission line in question :
The behaviour is quite confusing to me so I would like if ...
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Impedance matching in RF and complex conjugate (Maximum power transfer theorem)
The "maximum power transfer theorem" states that "maximum power transfer occurs when the load impedance is equal to the complex conjugate of the source impedance", that "for ...
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How to avoid impedance discontinuity when a pcb trace is routed in multiple layers
What are the things to be take care to avoid reflections when a PCB trace is routed in multiple layers. I mean, How to achieve impedance control when trace moves from one layer to other.
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Max stub length on digital signals
I have one SPI port that I'd like to use for 2 or 3 devices with chip selects. I'm worried about signal integrity on the data lines with these stubs. I've tried depicting my question below.
Every ...
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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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Reflected wave phenomenon - transient response and steady state of a transmission line
I'm currently trying to design a PWM driver for an impedance-mismatched long cable.
Sending rectangular pulses (rise-fall time ~0s) over a long cable that is not matched with its impedance results in ...
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CAN Bus termination resistor in only 2 device connection
A termination resistor in CAN ( .. or other differential pair communication like RS485 ) is necessary to absorb reflection. The value is related to wire length, electrical frequency, baud rate. It ...
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How to plot the reflection coefficent at the load against frequency in ADS
The reflection coefficeint at the load is defined as
how do I plot the load reflection coefficent against frequency in ADS?
it is easy to plot the source reflection coefficient since it is just ...
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Can VSWR be complex-valued or is it always real?
This question is related to this one, but about VSWR instead of return loss:
Can VSWR be complex since it is based on a complex-valued \$\Gamma\$? If VSWR is complex then it is worth noting that:
\$\...
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What is the difference of meaning between the phase angle of S11 and the phase angle of Γ (Gamma)?
I realized recently that the Touchstone "DB" S-parameter format (.s1p, etc) uses the phase angle of \$\angle \Gamma\$ instead of \$\angle S_{11}\$ and wondered why it didn't use the phase ...
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Can \$\Gamma\$ remain complex while calculating return loss?
I'm working on adding .s1p touchstone export support to the xnec2c NEC2 antenna simulator for Linux. I would like the S11 dB values in the .s1p to have both real and imaginary values.
NEC2 calculates ...
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Maximum power transfer and minimization of signal reflection: When should what be applied
Impedance matching is the practice of designing the input impedance of an electrical load or the output impedance of its corresponding signal source to maximize the power transfer or minimize signal ...
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Maximum power transfer and minimization of wave reflection: Understanding the difference on intuitive level
It is well known that there are two usual methods in impedance matching: if we have a network consisting of a source with impedance \$Z_S\$ and load with impedance \$Z_L\$ then we have two options to ...
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Protect PCB from RF reflection
I am designing a system on megahertz frequency bands (~ 400-1000MHz.) This device is connected to a variable antenna which does not necessarily stay in match with the circuit so there will be some ...
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What does a 50 ohm coax "look like" when neither the source nor the load are matched to it, and the center conductor and shield are used for signals?
Say I have a π-network filter for which the inductor is on a separate board. For convenience, I use a 50 ohm coax (4" long, frequency is 13.56 MHz) to connect to the inductor, using the center ...
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What to do when studying "travelling wave" in a coaxial cable?
Propagation of travelling waves on cables may sometimes be difficult to apply and understand. There is a method called in french "abaque de Bewley" or "diagramme de Bergeron" (in ...
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Is there any relation between distance from source to reflector and standing waves?
When two electromagnetic waves (not considering mechanical waves) having the same amplitude and wavelength, moving in opposite directions are superimposed on each other and create standing waves. One ...
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Thevenin equivalent of open ended transmission line Clarifications required
I am going through the below link for understanding about transmission line reflections.
The below figure is an equivalent circuit of an open-ended transmission line. For finding the
the voltage at V+ ...
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Questions about RF ground plane and low frequency reflections
Why do RF signals on a microstrip/stripline require a ground plane to propagate within a circuit? When studying DC and low frequency AC circuits in school, it appears that ground is a particular point ...
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Are multiple reflections accounted for in S-parameters?
When the S-parameters of a 2-port device whose input and output impedance are different from 50 Ohm are calculated/measured in a 50-Ohm system, multiple reflections occur at port 1 and port 2.
Let's ...
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Parallel transmision lines reflection at the source
Question:
There's a 9 V battery with output resistance of 50 Ω, at time t = 0 it is connected to two lossless transmission lines connected in parallel: LTx1 and LTx2.
Both lines are identical, with ...
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How to find Z impedance if I have only S11 (db) and phase
I need to measure Z line impedance. Using VNA I measured S11 it is -53.8785 dB and phase at this point is 175.6706.
Could you explain using these numbers how to find R and jR
S11 = (Zx-Z0)/(Zx+z0) = -...
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Reflection coefficient in a microwave amplifier
I have a question about the reflection coefficient in a microwave amplifier (two-port network), what is it and what is it based on?
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How reflection occuring in antenna fed by transmission line affects performance?
Transmission line considered is lossless.
Basically the configuration is simple.
For transmitter side : a non ideal source (can be voltage current or power) feeding a transmission line (TL1) with ...
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Could a time-domain reflectometer, with no access to earth-ground, indicate if a long-wire is attached to the end of a long steel beam?
Without using any other wiring, optics, RF, sound, or vibration, I need to know if a 100 meter length of electrical wire is attached to the end of a 50 meter long steel beam.
I only have physical ...
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Typical power reflected off wall/window/wooden shelves etc
For interference purposes, I would like to quantify how much signal power I would receive back when my transmitted signal is reflected off an object (a wall, glass window, wooden shelf) at a distance ...
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Do surface charges exist when EM wave gets reflected by dielectric boundary?
If both the materials on a boundary are dielectric then do surface charge exists. I was solving using pillbox it showed that there should be surface charge on boundary to satisfy change in normal ...
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Refractive index, wavenumber, and wave impedance of the PEC that a plane wave is normally incident on
I am trying to find the refractive index \$n_t\$, wavenumber \$k_t\$, and wave impedance \$\eta_t\$ of a perfect electric conducting medium t. Here is my work so far:
The conductivity of the PEC is \$...
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Reflection in low frequency conductors (not transmission line)
Is the reflection phenomenon common in RF work with unmatched source/load pairs also present at low frequencies? Or are the wavelengths so much longer than the physical conductor lengths that ...
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Pullup resistors. Does it make any difference what side of the series resistor?
The line is high frequency digital line. It has to be pulled up. Does the side of the series resistor make any difference?
simulate this circuit – Schematic created using CircuitLab
or
...
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Is this signal reflection or a damaged transmitter?
This is (an isolated, differential) capture, 1µs/div, of some Profibus communication over about 10m of cable. The first image is typical for about 90% of packets and seem fine. Most are +/-5v with ...
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How do you calculate phase shift induced by a shunt capacitor?
Given a simple loaded-line shunt-capacitor phase shifter, how can I calculate the phase shift and insertion loss at S21 caused by the shunt capacitor (varicap in my case, but for any cap) assuming I ...
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Power waves and scattering matrix
I have some doubts about the concept of power waves used in the description of the scattering matrix of an N-port component. In particular, I was wondering what is the most general and correct ...
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Coax Cable Wave Impedance, Capacitive Load
I am studying the behaviour of cables over frequency, especially what a source sees, and have 2 Questions, as I did some simulations in LtSpice. As a model for the cable I used the "Lossy ...
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Impedance and resonance frequency of a bias tee
I am a beginner trying to learn about combining impedances and solving for the resonance frequency. I am solving a circuit:
simulate this circuit – Schematic created using CircuitLab
and I ...
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Signal reflections inside CPU?
Given the fact that the clock frequency is about one GHz and the corresponding wavelength is about the same order of magnitude (velocity of propagation is lower than 3 * 10^8 m/s inside the chip) with ...
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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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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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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 ...