# Questions tagged [reflection]

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38 questions
68 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 ...
57 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 ...
54 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 ...
34 views

### Average Power of load conected to an Ideal Transformer

Where does the 1/2 come from in the power equation?
40 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 ...
83 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 ...
43 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 ...
62 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 $1.124nF$ ...
270 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....
38 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 ...
76 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 ...
50 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 ...
123 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/...
51 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 ...
261 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 ...
225 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 ...
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 ...
170 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 ...
142 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 ...
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 ...
342 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 ...
478 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 ...
363 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. ...
39 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 ...
458 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 ...
392 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 ...
591 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 ...
86 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 & ...
263 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 ...
931 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?
830 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 (...
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 ...
643 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 ...
403 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 ...
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 ...
134 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 ...