Questions tagged [reflection]

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610 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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1answer
51 views

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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0answers
57 views

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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2answers
38 views

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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1answer
55 views

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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0answers
60 views

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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2answers
121 views

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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2answers
63 views

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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4answers
134 views

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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4answers
142 views

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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1answer
74 views

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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0answers
65 views

Questions on ringing over square wave in transmission line

Considering a transmission line with open circuit termination at one end and a square wave voltage source with impedance not matching the characteristic impedance at the other end. Because of ...
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1answer
44 views

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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4answers
420 views

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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2answers
70 views

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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1answer
31 views

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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1answer
38 views

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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0answers
25 views

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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0answers
39 views

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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1answer
238 views

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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6answers
916 views

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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1answer
88 views

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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2answers
247 views

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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2answers
153 views

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 ...
2
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1answer
62 views

Calculate the voltage across a load resistor for complex transmission lines

The following parameters are given: 500m homogeneous transmission line. ...
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0answers
402 views

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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1answer
37 views

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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0answers
68 views

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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1answer
88 views

Maximum VSWR that can be tolerated?

I am trying to solve the 2013 paper set by ISRO for electrical engineers. I wanted to verify if my answer to Question no 14 is correct. The maximum RMS current is 20A, so maximum tolerable RMS ...
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1answer
121 views

When is it important to handle reflections in pcb design?

I am watching some videos explaining how reflection can affect a signal and how you should treat these signals as transmission lines to remove reflection. I wanted to understand a more practical ...
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1answer
80 views

Why is the pulse reflection becoming like this in pulse?

I use mosfet to generate a pulse, input the pulse into the transmission line, and after the reflection, test the waveform as shown. Why did the third reflected waveform become like this? I calculated ...
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1answer
276 views

Average Power of load conected to an Ideal Transformer

Where does the 1/2 come from in the power equation?
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1answer
296 views

Have you ever fried a wi-fi router by leaving it to work without its external antennas?

I wonder if a wi-fi router can be damaged if its external antennas are unscrewed? Have you ever damaged such a router leaving it to work without antennas, like this: Source I know that there are ...
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0answers
103 views

Reflection on a matched transmission line

A matched load with source using a transmission line (assume real load and matched using quarter wave transformer) should not have any reflection ideally. But we can see that the load impedance is ...
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1answer
85 views

S-Parameters, Smith Chart, and Reflection Coefficients

Please help guide my ignorance on this topic. From what I understand, S-parameters are reflection coefficients generalized to N-port systems (via an S matrix), but for a 1-port system, these converge ...
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0answers
147 views

Some calculations on Transmission Lines

I have to do some (simple) calculations for a transmission line. I was given a power supply of \$11V\$/\$22\Omega\$, \$Z_0 = 50\Omega\$, \$v = 2.2 \times 10^8 m/s\$, a load capacitance of \$1.124nF\$ ...
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2answers
779 views

Impedance Matching: Minimum Reflection vs Maximum Power Transfer

The minimum reflection is achieved when the two "circuits" being connected have the same impedance. This makes sense because all the components of the wave can propagate without needing to be modified....
1
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1answer
66 views

Different types of reflection/TDR casic

I am trying to understand the theory of operation of a time domain reflectometer (TDR). TDR is a time domain instrument with measurement the impedance versus the distance. If with a VNA one can ...
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0answers
127 views

Dipole antenna director

Say a free metal rod is placed at a distance λ/2 from a dipole antenna (fig), both being of same length. I understand it will reflect and dampen the signal going to the left. But how will it impact ...
2
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1answer
61 views

IR emmiter and reciever layouts for custom sensor

I'm having a hard time designing a PCB for a sensor array that need to detect if there is a small reflective object (3-20 mm section) in the way. That object can slowly rotate around a shaft. I have ...
2
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1answer
203 views

Why doesn't smaller Transmission Lines affect Signal Integrity? [duplicate]

I am reading High Speed Digital Design: A Handbook of Black Magic. It was mentioned that if length of transmission line (Microstrip or stripline) is less than 1/...
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1answer
69 views

RF PCB Design Inductor length conciderations

I am making a RF amplifier for my Communications Electronics course. I am looking at creating a PCB for it and figuring out how to get the desired reflection coefficient which I will most likely use a ...
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3answers
495 views

Is signal reflection dependent to PCB track length?

We add a termination resistor at the end of a transmission line in order to prevent its signal from reflecting back. I have deduced from some discussions that the termination resistor is not necessary ...
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1answer
489 views

How does short length of transmission line approximate to a wire?

Suppose I have a transmission line of length \$L\$ with characteristic impedance \$Z_0\$ and load voltage \$Z_L\$. If it is connected to a ideal sinusoidal voltage source \$V_s\$, then the voltage ...
2
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2answers
101 views

High-Speed electronics - Reflections in T-intersection

I'm currently attending a course on "experimental problem solving" and we just started talking about TDR (time domain reflectometry). I do understand that reflections occur whenever there is a change ...
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4answers
1k views

Physical meaning of reflection coefficient being complex

Below is a wikipedia section about reflection coefficient in electrical engineering: source: https://en.wikipedia.org/wiki/Reflection_coefficient It says that the incident to reflected wave ratio is ...
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3answers
2k views

whip effect in electric conductor

Some tiny background: The reflection coefficient, \$Γ\$ can be calculated according to this formula: $$Γ=\frac{Z_L-Z_S}{Z_L+Z_S}$$ For a transmission line, \$Z_S\$ is the impedance of the ...
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2answers
531 views

How to get complex reflection coefficients?

If I terminate a line with an open circuit, I'll get reflections of any incoming signals with the same phase (a reflection coefficient of 1). If I terminate the line with a short circuit, I'll get ...
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3answers
678 views

Impedance matching on DC voltage line to remove ringing/reflections

I'm generating a 6 MHz signal in an Altera FPGA. I am feeding this 1.8 V signal out through a level shifter to 3.3 V to a connector on the board. This is the signal at that connector: I am ...
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1answer
451 views

What is the mathematical equation to calculate the RSS or RSSI at a receiver, receiving a signal via single reflection ?

I have received certain answers on how to use your laptop or WARP or WLAN NIC to get the RSS or the RSSI, but what I'm interested in is the mathematics that is involved in calculating the RSS. ...