Questions tagged [reflection]

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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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3 votes
2 answers
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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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1 answer
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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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3 answers
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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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1 answer
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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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2 votes
2 answers
509 views

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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Two transmission lines with different media

I have some questions about intrinsic impedance and characteristic impedance. I learned the reflection of a wave occurs if the intrinsic impedance of the materials is different. \$ \Gamma = \frac{\...
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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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2 answers
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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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1 answer
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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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2 answers
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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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1 vote
1 answer
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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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1 vote
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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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1 answer
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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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2 answers
645 views

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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2 votes
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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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1 vote
1 answer
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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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1 vote
2 answers
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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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4 answers
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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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4 answers
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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 ...
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0 votes
1 answer
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Does the standard termination of 120 ohm really suppress reflections in recessive state in CAN?

Suppose we have a multi-node CAN network with the ends of transmission line terminated with the standard 120 ohm. When the recessive state is on the transmission line, the voltage on both CAN_H and ...
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1 answer
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How will the proper termination at one end while the other end is kept open avoids reflections in transmission line?

Consider a transmission line which is terminated with characteristic impedance at one end but other end is kept open, the reflections are not observed. I don't understand the mechanism behind. Please ...
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3 votes
4 answers
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How do reflections of a square wave cause ringing in transmission lines?

When a square wave is applied to a transmission line which is not terminated with its characteristic impedance, reflection and ringing occur. I don't understand how sinusoidal ringing occurs when I ...
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1 vote
2 answers
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Path of a signal traveling on a mismatched transmission line

I have a basic question about the path of a signal traveling on a transmission line with a short circuit as termination. Suppose that this line is driven by another line (at left) with Zc = 50 Ohm ...
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1 answer
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Falling and reflected impulse waveform - short circuit and void [closed]

What causes the signals to reflect differently when \$Z_L\$ = ∞ and when \$Z_L\$ = 0?
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Pads reflecting in controlled impedance strip?

Background I'm designing a controlled impedance line for a 1900MHz signal travelling between SIM7000A cellular chip and an antenna. Question Tuning circuits are recommended for antennas with series ...
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Time Domain Analysis with Vector Network Analyzer

I have done some measurements with a VNA in time domain (by using the transform operation of the instrument). Precisely, I have selected the measurement of S11 (reflection coefficient at port 1 of the ...
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Impedance matching to minimize VSWR

I was trying to determine what the impact of impedance mismatching would be to an RF output and I came across this. About half way down the page, the author makes this claim. In general, if the ...
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1 answer
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Input impedance of High - Frequency Amplifiers

I have a question about the choice of the input impedance of a high frequency amplifier. In general I know from elementary analog electronics courses that it is good for an amplifier (for instance an ...
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3 votes
8 answers
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Reflect IR beam off reflector instead of emitting straight to TSOP receiver

I have a working set-up to detect beam breaks using an IR LED, modulated at 36kHz, and a TSOP receiver connected to a comparator. It outputs the count via Arduino. The range is about the width of a ...
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1 vote
1 answer
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Refraction vs Reflection in Ultrasonic sensor for water level detection

I want to use ultrasonic module JSN-SR04 for detection of water level inside tank. The US module has single sensor for Transmission and Reception of US signals as shown below. I wonder if US sensor ...
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6 votes
2 answers
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How do wireless receivers reject noise created by the original signal reflecting off walls?

When a transmitter emits an RF signal it reflects and bounces around all over. If a receiver is line-of-sight with that transmitter then the original signal will hit it first but signals bouncing off ...
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How does risetime affect transmissionline effects?

How do rise and fall times affect reflection in a transmission line? Reflection will occur with shorter lengths as rise times becomes shorter, does this mean risetime effects the wavelength of a ...
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2 votes
1 answer
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Calculate the voltage across a load resistor for complex transmission lines

The following parameters are given: 500m homogeneous transmission line. ...
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1 vote
0 answers
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Unitary property of scattering matrix

From s-parameter lossless network definition , The sum of the incident powers at all ports is equal to the sum of the reflected powers at all ports. But how do we derive the above unitary property ...
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1 answer
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relation between reflexion coefficient and power ratio

Assume you have an intermediate input/outpout device connected to a coaxial line. For example, the device may be a DC-bloc, a bias tee, or simply a PCB microstrip transmission line. Using a signal ...
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Impedance Matching and Reflection Coefficient

Consider a real signal generator (Voltage Source Vs, output impedance Zs, reflection coefficient Γs) and a load Zl with reflection coefficient Γl. I was told that we have maximum power transfer when ...
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