# Questions tagged [reflection]

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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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1 vote
89 views

### 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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115 views

### 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: ...
• 938
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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 ...
• 511
1 vote
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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: ...
1 vote
85 views

### 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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156 views

### 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 ...
1 vote
150 views

### 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 ...
158 views

### 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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1 vote
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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 ...
• 461
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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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1 vote
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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 ...
362 views

### 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 ...
• 554
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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 ...
• 39
1 vote
2k views

### 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 ...
• 13
173 views

### 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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1 vote
330 views

### 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 ...
• 639
1 vote
801 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 ...
• 2,594
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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 ...
• 16.3k
325 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 ...
• 2,170
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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 ...
318 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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1 vote
472 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 ...
• 11
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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 ...
1 vote
426 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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