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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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: $$C=B \cdot log_2(1 + S/N)\text{ bits/sec}$$ ...
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34k views

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?
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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 ...
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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 ...
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18k views

Easiest way to extend a pulse

I have been messing around with my cars ignition. I know a lot about cars, but I haven't learned much about electronics. When I did study electoincs it was almost 20 years ago. Anyways. The car's ...
5k views

Why emitter follower is so noisy and distorted in large signal?

I have a signal around 20 V peak-peak. I want to feed it into an emitter follower BJT and I have no experience in working with such large signals. The BJT is well in bias point ( I tested the ...
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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 ...
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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?...
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24k views

Speed of electricity (signal propagation?) through copper for communications delay

I would like to be be able to calculate the delay for communications data within TCP/IP networking through cat5e networking cable. That is a pretty vague ...
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What component to use for audio signal switching?

I'm looking to build a guitar pedal switcher based on a Raspberry Pi or Arduino (have not yet decided, but I have an unused Raspberry around and I lean towards that). Anyway, digital logic. Now, I ...
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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 ...
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Series resistor on digital signal lines [duplicate]

I have seen many schematics using 22 ohm resistor in series with digital signal lines. I was wondering is this always a MUST or there are there some special scenarios where we don't need them since ...
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Reconstructing Clock for Serial Signal

Suppose that I have a serial signal (example below), which is transmitted without an accompanying clock signal, I would like find a circuit (using discrete components / ICs, possibly an FPGA, but not ...
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What's the purpose of the diode at the JFET gate in this Hartley oscillator?

This is something of a follow-up question to one I asked a few days back (Original JFET Hartley Question). Having made the changes suggested in the comments (i.e., changing Rd/R3 to 270 ohms, instead ...
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1 vote
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Solving Difference Equation Using Z-Transform

I was trying to solve a problem given in my textbook. I have attached the solution given in the book. I thought some modifications where needed to it and tried to solve in a different way. I ended up ...
1k views

Time limited and band limited signal

How can a time limited signal be of infinite bandwidth and a finite bandwidth signal be of infinite duration?
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How to know the kind of filter from the transfer function [closed]

I got that system $x_n \to x_n-x_{n-1}$, so $h_n=[.....,0,1,-1,0,...]$, with $h_0=1$ and $h_1=-1$, so the transfer function given by: H(\omega)=\sum_{i=-\infty}^{\infty} h_ne^{-jwn} = h_0e^{...
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_{...
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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 ...
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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 ...
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How do I build a TRRS headphone jack with a jack that is detectable by an iPhone

I have a circuit and I am trying to integrate it with an iPhone via a TRRS headphone jack's microphone input. I have a generic TRRS cord and am trying to send a signal through it. However, the iPhone ...
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What is signal ground

I encountered signal ground symbol while studying 555 IC Please explain why isn't a simple ground connection used and how does signal ground differ from normal ground. I am a first year undergraduate, ...
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Trouble with Schimtt trigger settings for varying sinusoidal inputs

To make my problem easier to describe, I drew the above figures (abbreviated as Fig.). The sinusoidal input comes from a rotating device, from a small alternator(a permanent magnet AC generator). ...
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Scope probe having ringing with 10x option

I did a bit of a search in the forum but despite there being a few related topics related I couldn't find the specific answer for this question. Using a 50Mz scope I connected the probe to an FPGA ...
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3k views

How do signal reflections work?

How do reflections work, physically to the charge carriers level? Considering a square wave generator connected to a long, open cable, I've made a quick chronological diagram of the propagation of ...
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4k views

Sending signal over long distance wire

I need to control a remote relay over a 1km (max) distance. Here is a simple block diagram that represents what I'm trying to achieve: simulate this circuit – Schematic created using CircuitLab ...
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Question about differential signals as input of an operational amplifier

I'm studying the circuits which are used to implement operational amplifiers. For example, I've studied the two stages amplifier (in which the first stage is a differential amplifier with differential ...
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What is the difference between signal and symbol in wireless communications?

What are the definitions of signal and symbol in wireless communications, respectively? Often when I read books and papers I see things like "transmitted signal" and "transmitted symbol". Is there a ...
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362 views

looking to capture an infared code

I am trying to get an infared signal being sent from an emitter (think along the lines of a remote control). I know I can use a fotoransistor on a breadboard to capture/detect the signal, but I have ...
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569 views

Noise can be Differential or Common!

I have a basic understanding on this topic but i still have some doubts, my text books says Differential means it will have impact on one of the 2 signal nodes. and Common will have a common impact on ...
10k views

Square Wave Amplifier - 5VDC -> 13VDC

I want to have a square wave that goes from 0 VDC to 5VDC go through some sort of amplifier and that amplification takes that same wave ( at a frequency of 1200Hz but could also be adjusted later ) ...
1 vote
2k views

resistor value in wheatstone bridge

I have a resistance based sensor which gives the resistance change when the strain/force is applied. How to measure the unknown resistance change using the Wheatstone bridge circuit.? I mean what are ...
1 vote
801 views

Differential Pairs and GND

I have some doubts about different configurations of differential pair I have seen in many cases: In these schemes, biasing network for the gate is not shown for simplicity. All of them are excited ...
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1 vote
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Microphone peak detector circuit no signal response

I have built a peak detector circuit using op-amps/comparators to amplify the signal from an electret microphone, hold the peak signal and create a sharp logic edge when a peak is detected to be sent ...
2k views

Parallel OpAmp configuration

I am finding it very strange what is the role of R1 in this circuit, and what would happen if I would just remove R1 along with ...
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367 views

Square wave from comparator drifts and the integrated square wave doesn't yield a triangle wave

I am trying to make a function generator. The generator runs on 16kHz, the rails are +12/-12V for test purposes. I basically obtain a sine wave with an oscillator, drive a comparator (LM311) with the ...
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How to decrease nrf24l01 transceiver range?

I've just got my Nrf24l01 but then I found out that the working signal range for the module is 100m and above. Our real intention for the module is to let the nrf24l01(Receiver) out of range for about ...
237 views

Amplify AC signal only

I amplify a signal which including AC and DC.Why is the output waveform changed when C1 is 0.1u?And how to decide the value of C1?
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Can't understand concept, range of the pulse (waveform)

I am working on the lab which is allowed to ask other people for hints. In the image, program called "Audacity" is used to capture that waveform. Question 1 In the image it says, "The peak-to-...
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254 views

Maximum power transfer of transformer [closed]

We have this transformer: simulate this circuit – Schematic created using CircuitLab The power transfered to R1 resistor is maximized when the frequency of the signal is very big.This means ...
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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 (...
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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
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 ...
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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 ...
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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 ...
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? ...
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886 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 ...
882 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 ...
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 ...
14k views

How does a coaxial aerial cable work?

My family and I managed to break the aerial cable of our TV a few days ago. The cable is of this kind of design: And I believe its called a coaxial cable. Fortunately, someone more practical than ...
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