Questions tagged [signal]

A signal is a stream of information in the form of a varying quantity. Usually in electronics, signals can be in the form of voltages, currents, or radiated electromagnetic fields.

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In a USB cable, is it OK to swap the D+ and D- wires?

I heard that D+ and D- are differential signals, does it matter if I swap them when connecting a USB device to the computer?
Yan King Yin's user avatar
53 votes
11 answers
13k views

Can a radio transmitter somehow detect the number of receivers in its area?

During conversation, a colleague proposed that over-the-air television and radio broadcasters can determine the number of viewers or listeners based on the "load" on their signal. This seems to me ...
ghaberek's user avatar
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41 votes
8 answers
80k views

Why put a resistor in series with signal line?

A lot of times in circuits I see a resistor placed in series in a signal line and sometimes even in series with an MCU's VDD line. Is the intention of this to smooth out noise in the line? How is this ...
PICyourBrain's user avatar
  • 3,745
32 votes
7 answers
81k views

What exactly are harmonics and how do they "appear"?

From reading so many sources online, I still cannot grasp why a different waveforms have harmonics. For example: when designing a silly amplitude modulation (AM) circuit that puts a square wave from ...
John Quinn's user avatar
26 votes
8 answers
9k views

Is it possible to receive information if the received power is below the noise floor?

This relates to my previous question, which I think I have asked in the wrong way: How to insert background EM noise into pathloss equation? I wasn't really interested in detectability of the signal,...
David K.'s user avatar
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24 votes
5 answers
61k views

How termination resistors work; what happens if I use lower values?

I am going to try to interface low-speed 8bit DDR2 chip to FPGA, and I've got some questions crucial to make it work :-) Is that correct that the idea of termination resistor is to sink most of the ...
BarsMonster's user avatar
  • 3,327
24 votes
3 answers
52k views

How does data travel inside a wire?

I know this is a very basic question but the answers returned by google are way too complicated for me to understand. I am not asking about modulation here. What I want to know is what exactly is ...
Sunshine's user avatar
  • 351
23 votes
8 answers
6k views

In which direction do electric signals flow?

We know that electrons move from the negative to positive terminal, and that holes flow in the conventional direction of current - from the positive to negative terminal. I've always assumed that this ...
slebetman's user avatar
  • 1,680
21 votes
3 answers
5k views

Difference between bit rate and baud rate and its origins?

Everyone seems to have different definitions everywhere I look. According to my lecturer: \$ R_{bit} = \frac{bits}{time} \$ \$ R_{baud} = \frac{data}{time} \$ According to manufacturers : \$ R_{...
Psi's user avatar
  • 409
20 votes
4 answers
2k views

Do you recognise this signal?

The story for this signal is the following. I've bought an NAD C 356BEE amplifier with an integrated MDC DAC module. It has optical and USB input. The optical is OK, but if I connect the DAC to my PC ...
csadam's user avatar
  • 1,646
19 votes
2 answers
17k views

transmitting 5v signal over a long cable

I'm seeking for help here as I need a reliable answer to this. I need to get an input signal (low frequency 5v digital pulse), to a micro-controller from a (...
Codenamed SC's user avatar
18 votes
3 answers
6k views

Why does a female-female coupler break the USB-C standard?

I'm working on a project which uses a PCBA which basically acts as a USB-C extension. It has 2 USB-C receptacles (female) connectors. The mapping between the two receptacles is one to one. The pair of ...
Frenetique's user avatar
17 votes
2 answers
21k views

What generates the clock signal in a fast CPU and how does it work?

Often, for integrated circuits, a quartz crystal is used to generate the clock signal. However, this only reaches speeds in MHz. What component, or what circuit, generates signals up to 5 GHz ...
Markinson's user avatar
  • 317
16 votes
3 answers
12k views

Why are flip-flops usually triggered on the rising edge of the clock?

Usually in digital design, we deal with flip-flops that are triggered on a 0-to-1 clock signal transition (positive-edge triggered) as opposed to on a 1-to-0 transition (negative-edge triggered). I ...
travisbartley's user avatar
15 votes
4 answers
3k views

How is it possible to drive VGA displays at such high pixel clock frequencies?

I'm working on a digital circuit using discrete components to drive a 640x480 VGA display in a 80x30 text mode. For a 640x480 display, the pixel clock is 25.175MHz, which has a period around 40ns. I ...
supershirobon's user avatar
15 votes
1 answer
2k views

How do receivers decode multiple GPS signals on the same carrier frequency?

I'm currently researching GPS signals and am trying to fully understand the path of a signal from satellite to receiver. I understand that mixed into the GPS signal is a C/A code as well as a PRN ...
Justanothermatt's user avatar
15 votes
3 answers
37k views

Changing a Signal's DC Offset

I have a square wave being generated from a waveform generator oscillating between 0 V and 5 V. The generator does not support negative DC offsets. I need to shift this signal down to be centered ...
Präriewolf's user avatar
14 votes
9 answers
6k views

Is this an AC or DC signal?

My teacher says that this signal is DC, but if the polarity varies from 0V to -8V , shouldn't it be AC? He says that DC + AC = DC
JEAN LEONARDO 's user avatar
14 votes
4 answers
4k views

What is the purpose of a carrier signal in communication technology?

What is the carrier signal for when we actually do not care about this but only about the other signal (the useful signal?) Why isn't only the useful signal used instead of mixing it with the carrier?...
Ben's user avatar
  • 625
14 votes
5 answers
16k views

Analyzing Accelerometer data characteristics and designing a filter

I have about 32 seconds worth of accelerometer data of a basic driving scenario 25MPH normal roads along with hitting about 7 potholes and a rough patch of road. The accelerometer is mounted on the ...
13 votes
4 answers
3k views

What is causing this distortion of a pulse wave when recorded to a reel-to-reel tape?

I'm currently trying to record a pulse train used as a tempo clock for music instruments (e.g. output of Korg Volca 'sync out') onto my Fostex M-8 reel-to-reel recorder, with the aims to then ...
Rasmus Källqvist's user avatar
13 votes
2 answers
25k views

How does a signal travel down a telephone wire?

Supposing a computer gets data over telephone wire, it has to send/recieve signals, but how do things work? Does it use analog signal or a digital bits? How does it send/recieve "1"s and "0"s?
cursious10's user avatar
13 votes
4 answers
2k views

Signal Processing with Op Amps

I'm tasked to reproduce the following signal using only Op Amps (and resistors). I'm pretty sure I must add two signals, the square and triangular waveforms, it is just pretty hard to figure out ...
Favner's user avatar
  • 143
13 votes
4 answers
3k views

General question about analog and digital signals

Newbie alert: I am not an electrical engineer, nor have I ever taken electrical engineering, so please bear with me. Whenever I read about the distinction between digital and analog signals, a ...
so.very.tired's user avatar
13 votes
3 answers
11k views

Using an op amp as a buffer

Working on a project where we're using a couple of OP470 Quad Op amps. There are 2 unused op amps, and I need to buffer a signal coming from a sensor (this is according to the sensor's data-sheet). I'...
Skaevola's user avatar
  • 668
13 votes
2 answers
2k views

Differential Signals - Why is having an equal impedance an advantage?

I lately heard in a course that a main advantage of differential signals is that both signals show the same impedance, whereas a single-ended signal, which is measured against ground, has a high ...
Daiz's user avatar
  • 477
13 votes
3 answers
9k views

Coaxial cable signal and ground

How does a coaxial cable carry RF, audio and low freq. signals? I understand there must be a difference between all these, for example the return path being through the shield or not. Can someone ...
1p2r3k4t's user avatar
  • 716
12 votes
3 answers
3k views

If one sends short bursts of electric current that abruptly turn on and off, why does the receiver receive a smoothed-out current?

An Introduction to Information Theory: Symbols, Signals and Noise, by John R. Pierce, says the following: The difficulty which Morse encountered with his underground wire remained an important ...
The Pointer's user avatar
  • 1,271
12 votes
1 answer
9k views

Why isn't the Fourier transform of a single sine wave cycle a single bar?

I have tried different Fourier transform codes out there on single sine waves, and all of them produce a distributed spectrum with a resonance at the signal frequency when they should theoretically ...
Mister Mystère's user avatar
12 votes
2 answers
7k views

Why is channel capacity a factor of bandwidth instead of frequency?

I'm trying to understand the concept of capacity for a wireless channel. Some help would be appreciated. For a AWGN channel capacity is calculated as: $$C=B \cdot log_2(1 + S/N)\text{ bits/sec}$$ ...
Drew's user avatar
  • 123
12 votes
3 answers
3k views

Why is a signal that is finite in time domain, infinite in its frequency domain?

Why does every single band-limited signal in frequency have an infinite time domain and vice versa (As it's a symmetric relation, inf in one is finite in the other). I understand how a digital signal ...
JustLearning321's user avatar
12 votes
3 answers
2k views

What is mecca ground?

I came across few different ground names (digital, analog, signal, power, mecca, EM, shield, etc). I do understand most of them - but mecca is a new one for me. Can someone please explain this mecca ...
KingsInnerSoul's user avatar
12 votes
3 answers
15k views

Which one is better as voltage divider: resistive, capacitive , low pass filter,...?

There are different types of voltage attenuators for AC signals ( a short explanation is here). The most well known is a resistive one. Others like capacitive, inductive or low pass filters are ...
Aug's user avatar
  • 1,571
12 votes
1 answer
4k views

CAN bus signal integrity

The channels are CAN_H (red), CAN_L (blue), and CAN_H-CAN_L (brown). It can be observed in the diagram below that CAN_H-CAN_L has an acceptable signal shape. However, both CAN_H and CAN_L look poorly ...
richieqianle's user avatar
  • 1,612
12 votes
1 answer
5k views

What separates a "good" eye diagram from a "bad" one?

I'm running some USB verification testing at work, and the Agilent oscilloscope I'm working with returns a nice summary of pass/fail statistics along with a pretty eye diagram. Since the pass/fail is ...
Jay Greco's user avatar
  • 1,847
12 votes
3 answers
2k views

How to add a controlled amount of jitter to a signal

Background I am developing a digital clock and data recovery circuit and am now getting into the evaluation phase, focusing on testing the limits of the design and finding potential strengths and ...
travisbartley's user avatar
11 votes
6 answers
3k views

Why can the effective number of bits be a non-integer? What does this physically represent?

The effective number of bits (ENOB) describes the "real" resolution of an ADC. I paid no attention to it when I was first taking the class but now when I think about it I cant really make ...
Emre Mutlu's user avatar
11 votes
2 answers
3k views

Ground Symbol, which one I should use?

I normally use this symbol in my schematic as my signal ground. But recently my manager asked me to use this symbol instead because the one that I am using is the earth ground and I should use the ...
user3562851's user avatar
11 votes
3 answers
3k views

SDRAM Prototype vs Production Woes

I have a design using an LPC1788 together with a SDRAM module from ISSI (IS42S32800D). This is a 32bit interface. I have routed this design out and had a prototype made with a PCB manufacturer that ...
James's user avatar
  • 759
10 votes
6 answers
6k views

Generating a differential signal

I was given a small task (actually it's part of a much larger task) where the requirement is to generate a signal which looks like it came from a microphone. The following requirements needs to be ...
Tom L.'s user avatar
  • 8,059
10 votes
2 answers
2k views

Help with or hints for decoding an IR protocol

Some time ago I bought a simple and cheap little IR-controlled toy helicopter (same as this one - it's called "Diamond Gyro" or "Diamond Force"). For fun, I've been looking into controlling it via an ...
9 votes
4 answers
3k views

What's the difference between a power rail and a signal line?

I've been educating myself on the fundamentals of integrated circuit design, and I've come across the terms power rail and signal line. It seems that both of these things are moving energy around the ...
Connor's user avatar
  • 399
9 votes
4 answers
17k views

What is the difference in meaning of a voltage signal and current signal?

This might sound like a crazy bad question. But I'm wondering even though current and voltage inevitability co-exist, why do we use the term for one concept(current or voltage)? If there is a signal ...
user16307's user avatar
  • 12.1k
9 votes
4 answers
4k views

Does there exist an IC that allows on-the-fly routing of signals?

Do there exist ICs with N input pins and N output pins which, either via EEPROM setting or via on-the-fly control by a microcontroller, allow one to route each of the N inputs to ANY of the N outputs? ...
boardbite's user avatar
  • 4,922
9 votes
5 answers
5k views

Detect electrical signals from plants

My daughter wants to do a science fair experiment that involves reading the electrical signals in plants, but the cost of a multi voltmeter with data logging is very high. Can anyone suggest a setup ...
Catherine Gruber's user avatar
9 votes
3 answers
9k views

Why does more bandwidth mean higher bit rate in digital transmission?

I understand that similar questions like this one have been asked before on this site, listed below. However, I am confused about the answers. If I explain what I think I understand, can somebody ...
Blue7's user avatar
  • 1,655
9 votes
1 answer
883 views

Optimize signal return path with decoupling capacitors in a two layer board

I'm designing a pretty complex two layer board - I should really go for a 4 layer one, but that's not the point here. I'm done with component placing and routing and I'm doing the finishing touches ...
user avatar
9 votes
4 answers
881 views

RS485 minimum node spacing - 3 x RS485 device on PCB

I would like to ask something about RS485 minimum node spacing which is described in (Page 5) TI Design guide I would like to create device which consists from 3 existing RS485 devices. My plan was ...
Wojtkingson's user avatar
8 votes
7 answers
1k views

Why is one return conductor for each forward conductor in a ribbon cable better than a shared return conductor?

I don't understand why second way of implementing is better than the first one? I have my own basic logic regarding this topic, but i am not confident if what i think is correct! so i was looking ...
Hilton Khadka's user avatar
8 votes
4 answers
3k views

Why do OOK transmissions have bandwidth?

With on-off keying, you have a single carrier wave at a constant frequency transmitting its presence or absence. Now I understand that the crystal will not be perfect so you will have some minimal ...
Aidan's user avatar
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