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Questions tagged [reflection]

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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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1answer
33 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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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
75 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
62 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
56 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
47 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
41 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
87 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
47 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
72 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
336 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....
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1answer
39 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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86 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 ...
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1answer
54 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
139 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
54 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
288 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
262 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 ...
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2answers
82 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
197 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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0answers
145 views

Ethernet Transceiver Chip 100ohms impedance

I've designed a pcb which has a 10/100/1000 Mbps Ethernet Transceiver. It's been already manufactured and I am now testing it. I don't have much experience with electronic design therefore I didn't ...
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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
406 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
511 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
383 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. ...
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0answers
42 views

VNA reflection and transmission of stripline stub

Testing this stub board. I understand S12 is attenuated at 1.79GHz due L=λ/4. So I calculate relative permitivity: εr = (c / 4Lf)2 = 3.3 But what does (εr) represent in a ...
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2answers
496 views

Quarter Wavelength Matching : Missing Reflections?

With regards to the quarter wavelength impedance matcher, I understand it is used to correct a mismatch and looks as follows where \$ Z_T \$ is the matching line: I understand that we have set up the ...
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1answer
441 views

Negative reflection coefficient question

If I have a transmission line with a reflection coefficient of -0.3, and I feed it an input voltage of 5V, will my net voltage at the reflection point be (1 - 0.3)*5 = 3.5V or (1 + 0.3)*5 = 6.5V ...
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5answers
626 views

Why don't we talk about a signal reflection when we treat a lumped element model of a circuit?

I don't clearly understand why I have never seen a talk about a signal reflection in a lumped element model. When there is a transmission line connected to circuits A (signal emitter) and B (signal ...
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0answers
87 views

Understanding amplitude-time peaks in one dimensional reflection and transmission of sound waves

There is a one dimensional system of interfaces with a transducer sending and receiving sound wave (Plane wave) normal to the interface boundary. The system consists of two mediums, medium 1 & ...
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3answers
305 views

How to drive a SPI bus over 5 feet of 26AWG wire?

Below is the circuit I am trying to achieve. The endpoint is a 5V device but my microcontroller (SPI Master) is a 3.3V device so I have to do the voltage translation. My question is what kind of a ...
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2answers
1k views

How to get rid of this reflection on falling edge of i2c SDA line?

This is the scopeshot of the falling edge: How to get rid of the reflections on the falling edge of this SDA line?
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2answers
886 views

Reflection on SPI Clock Signal, termination or stub issue?

This is a SPI Clock. 6.25MHz frequency. I see something like a reflection. I don't think it's from cross talk on my board from another signal, not sure. Added as requested: This is my system diagram (...
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1answer
80 views

Mismatched transmission line at DC

The characteristic impedance equation in transmission line theory is this: $$Z_0 = \sqrt {\frac{R+j\omega L}{G+j\omega C}}$$ Take the case of a twisted pair transmission line, say the cat6 cable ...
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1answer
684 views

Reflectometer - directional coupler

I tried to use a single directional coupler to create a reflectometer and was hoping to measure both amplitude and phase of reflected signal. My setup is a follows: The directional coupler is from ...
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4answers
420 views

Transmission Line Question

I have a question concerning reflections due to impedance mismatching. Now, assuming a lossless TL, the latter is modelled by sections of lumped L-C segments where L in a series (sub)element of the ...
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4answers
3k views

purpose of termination resistor

My question is not about a particular bus or line and the termination I should put on it. I know some busses need termination resistors like CAN or address/data for memories. If I understood well ...
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1answer
140 views

In PSPICE how do I get a plot showing the reflection co efficient on the y axis?

I need to plot a graph of the reflection coefficient against the frequency.I ran an AC sweep of in the range of frequencies I need. However I am unsure of how to get the reflection coefficient on the ...
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1answer
167 views

Transmission lines and superposition

Below is the circuit in question. Good evening, I'm working on a problem that requires me to graph voltage at point A between -10 ns and 120 ns. I know that we must factor in wave reflections that ...
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1answer
223 views

Would low frequency signal (10kHz) have reflection on conducting wires as well?

I am connecting a signal source of 10kHz sine wave with a driver which is a voltage follower made by an OpAmp. The follower has one input and two identical outputs. One output is connected with a ...