Questions tagged [wave]

May refer to an electromagnetic wave (such as a radio wave) or the PCB manufacturing process of wave soldering.

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46 views

Electromagnetic waves antenna via microcontrollers (Transceiver and receiver)

I have two Arduinos: Mega and Nano, and 2 steel pieces of wire as an antennas which i sticked directly in the pins slots. I've setup my Mega2560 to generate an alternating current on one of its pin (...
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2answers
42 views

Why does lumped discipline not hold as dimension approaches operating signal wavelength?

I'm studying some basic introduction to the lumped matter discipline on my own. I completely understand where the first two constraints come from (i.e. lumped matter can only interact through their ...
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3k views

Why does 1/4 wavelength have a ground plane and 1/2 wavelength needs none?

Why does 1/4 wavelength have to have a ground plane and 1/2 doesn't? I know that an antenna that has half a wavelength does not need the ground plane (example a dipole antenna) and when using a ...
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64 views

Standing waves in Dipole antennas

I'm relatively new to antennas. In most of the textbooks, it is said that we want to minimize standing waves in the transmission lines by matching the characteristic impedance of the line with the ...
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2answers
90 views

Looking to generate 25 Hz square wave at about 90 V AC

I am looking to build a square signal generator tuned to ~25 Hz at a voltage of ~90 V AC that can output ~400 mA. I've searched around the internet and tried a few things but I've had no luck. My ...
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27 views

Based on \$f(f) = \phi_{\beta} \; \land \; f(t) = |\beta_u| \$ determine type of oscillator

Imagine the below characteristics of feedback circuit in sinewave oscillator are drawn: $$f(f) = \phi_{\beta}$$ $$f(t) = |\beta_u|$$ Based on the characteristics, how can I tell: Which type of an ...
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2answers
42 views

Non-sinusoidal waveforms: relationship (resistance, capacitance)\$\xrightarrow{\text{affects}}\$ (amplitude, frequency)

During the laboratory we have analyzed the following two non-sinusoidal generators: square-wave generator triangular-wave generator Sadly we didn't have enough time to complete the last task. My ...
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2answers
66 views

How to make a sawtooth waveform look less like a staircase (DAC)?

I am making a 4-bit digital-analogue converter using an adder circuit with four inputs. Each input is a square wave of a specific frequency. The output of the DAC is meant to be a sawtooth waveform ...
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1answer
67 views

Can the 1D wave equation be recreated in a conductive wire?

I am ignorant of EE, but not the wave equation, so bear with me. The (scalar) wave equation \$d_{tt} - c^2d_{xx} = 0\$ describes the displacement (and velocity) of some medium through space and time....
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3answers
410 views

What would cause a square wave to become rounded?

I have a square wave going through a thousand feet of cable. The cable has \$120 \,\Omega\$ characteristic impedance. I measured the capacitance and inductance of the cable and they are pretty close ...
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1answer
34 views

Magnetic field expression in a rectangular waveguide

I was reading the chapter of Fundations of Microwave Engineering (Robert E. Collin) about transmission lines and waveguides, and I have a question about the electromagnetic field in a rectangular ...
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1k views

Is there something as common frequency?

Let's say I have following three sinusoidal waves. ...
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11 views

Evaluation of Dominant Mode in a Circular Waveguide

I was doing the analysis of a circular waveguide (precisely, a wave guide with half - circular section of radius a, as shown in the following picture, and in which the shell is a Perfect Electric ...
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16 views

Error % for readings of average-sensing multimeters

Question: What is the error % in reading the voltage of a Square wave (1 Vpp) with an average-sensing multimeter with a half-wave rectifier, compared to a TRms multimeter The answer seems to be 11.1% ...
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2answers
58 views

Geometric spreading of an impulse antenna

I am new to radar and curious about the geometric spreading in free space. I set up an air-coupled antenna about a half meter above the ground, with a large PEC on the ground. Then I adjusted the ...
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1answer
25 views

Propagation Constant Expression in a Transmission Line

let's consider a generic transmission line: Its wave vector Kz is equal to: where Then, I read also that it is true that: where does this relation come from?
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Interface Conditions between Dielectrics inside a Waveguide

let's consider a general waveguide with two ideal dielectrics inside it: Let's consider the interface condition about the tangential electric field: Generally E = E(x,y,z), where z is the axis of ...
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81 views

Coaxial Cable Resonance

let's consider a coaxial cable of length L and see what happens at port 1 when port 2 is left open. Let's consider what is written on these slides: 1) I do not understand the reason of this graph. In ...
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3answers
83 views

Frequency dependence of S21

I have done a measurement with a vector analyzer in which I have connected a certain coaxial cable to the two port of the instrument. Precisely, I have got a measure of the phase of S21 of this type:...
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1answer
42 views

how to reduce signal noises

I am trying generate guided waves on simple metallic plate through piezo-ceramic material, I place two piezo on the surface of the plate at the different location and through Arbitrary pulse generator,...
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1answer
42 views

Conceptual question about Frii's equation

That's a pretty basic one but for some reason I am stuck now: Suppose I have a transmitter that transmits Ptx=4W_EIRP with an ideal, omni-directional antenna. The power applied to the antenna ...
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4answers
75 views

Average of flipped square wave

So I need to find what will be the average of a flipped square wave. I know that the high amplitude is 15V and the low amplitude is -9V and the average of the original signal is 2V. What will be the ...
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2answers
198 views

Propagation 'speed' of EM waves in air versus through conductive material

This paper I was reading said: "At a high level, the propagation speed of EM waves through conductive materials is SLOWER than their speed in air". Don't conductive materials intrinsically have less ...
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3answers
41 views

Why phase is the position of the waveform relative to time 0

I was reading a book which says: Phase describes the position of the waveform relative to time 0. It indicates the status of the first cycle. and below is a picture I am a little bit ...
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1answer
43 views

Cut-off frequency in ideal waveguides

it is known that in an ideal waveguide (with a perfect electric conductor and with non-dispersive and non-conductive dielectric) there is a cut-off frequency, for each mode, such that for higher ...
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65 views

Analogy to explain why an antenna must be (in order) size of wavelength

An antenna has to be sized on the order of the wavelength because we want waves to form. Waves mean, very roughly speaking, different "state" (current, voltage, water level, ...) at different ...
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81 views

Distance requirements in antenna arrays?

Antenna array is a broad term and it encompasses at least the following concepts: MIMO or massive MIMO: for spatial multiplexing beamforming: increasing the SNR (at transmitter or receiver) by ...
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2answers
99 views

Wave Propagation in Transmission Lines

let's consider this image (from AAC book, see here) The author wanted to show that a transmission line propagates not only voltage and current waves, but also an electromagnetic wave in the space ...
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1answer
40 views

Antenna's resistance: meaning and evaluation

When I studied elementary antenna's theory, I saw that the resistance (for simplicity let's consider only the resistive terms) of an antenna Ra is made of: 1) a parasitic resistance Rl, which causes ...
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2answers
126 views

Square wave generator won't work

I'm trying to generate a square wave at 21kHz (+13V,0V) using this schematic: I used formulas and this website to find the correct values for my components but it doesn't seem to work on Simetrix. ...
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1answer
83 views

Does a pcb as patch antenna isolate itself?

I'm currently working on a prototype patch antenna for UHF. Since I'm out of copper at the moment, I used empty PCB's as base material (don't mind the PCB in between, it's only a spacer): So now my ...
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2answers
86 views

1v square wave generator

I'm trying to create a square wave form from a single AA battery, say 1v. I came across an IC which is essentially a low voltage 555 timer: Semtech SX8122 however it is marked obsolete. I would like ...
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22 views

Complex vectors E and H

I have a doubt about the physical meaning of the complex representation of electric and magnetic fields. Let's consider an electromagnetic wave, in which both electric and magnetic fields propagate ...
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1answer
180 views

How to generate a controlled frequency sine wave using a microcontroller like PIC18F4550?

I'm designing a phonic wheel emulator. I have a PIC18F4550 and the following power supplies: +5V, -5V, 12V. I need to geneate a sine waves from frequencies near 500Hz up to approximately 8kHz. The ...
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1answer
48 views

Magnetic Monopoles and Magnetic Current Densities

I see that in electronic engineering the Maxwell equations are written with also some terms which represent the magnetic charge and the magnetic current densities. I was told they are inserted only to ...
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1answer
14 views

Voltage/Current waves on N port networks

I have a doubt about the sign convention for waves in an N port network. Consider for instance the following 2-port network: How should I fix the directions of voltage and current to calculate powers?...
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1answer
115 views

Quarter-wave impedance transformer working principle

consider the following scheme: A transmission line of length lambda/4 has been put before the load ZL in order to get an impedance matching. But, I do not understand how it works. Precisely, by the ...
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1answer
56 views

Rat Race (Hybrid 180°) Scattering Matrix

why the S matrix of a rat race is the following one? Which is the reasoning for determining it?
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1answer
82 views

Radar and Standing Waves

I have a doubt about the working principle of a simple Radar. Consider a stationary object, which does not move with respect to our transmitter. We send an electromagnetic wave to it, and it will ...
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19 views

Conductance curve for SPUDT with only one peak

I am trying to reproduce the results obtained by Morgan in his book on surface acoustic waves using the RAM model to analyze a DART kind IDT (p.270). In his book the curve he gets is double-peaked ...
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1answer
68 views

How to transmit a signal to a point [closed]

I have a signal generator (Digital Dual Channel Funktion Signal Generator) and want to generate two signals (530 and 550 Khz signal) and want to transmit these generated signals to the points on a ...
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1answer
92 views

Peak Detector with Reset

I'm trying to make a N.Peak Detector with reset functions. I've tried various modification to the classic peak detector without any success. What I'm trying to accomplish is: Detect the negative peak ...
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1answer
73 views

Triangular wave amplification

I've made a triangular wave by ICL8038 and it works perfectly at 15kHz with 15Vpp. I need to drive a 4 ohm load by that triangular wave. Could you please show me a solution/circuit to do that?
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1answer
28 views

Directional Coupler Terminals

I have a basic question about directional couplers. In this scheme each port is represented by one wire. What does it mean? The other terminal of each port is GND for all?
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3answers
346 views

How to produce sawtooth waveform from square waveform?

I have a question pertaining the changing of square waveform to sawtooth waveform using OpAmp. Following the picture below, I have to create a sawtooth waveform from a square waveform. It seems that ...
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2answers
70 views

I need an equation to calculate the time for a power percentage of a half cycle sine wave into a resistive load

I need to calculate the time a thyristor/triac needs to be on for a desired percentage of full power of each half cycle of the AC line input. On for the full half cycle will give me 100%. On for 1/2 ...
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3answers
224 views

How Much Current is Usually Used with IR Transmitting LEDs, in Remote Controls?

If you take various Remote Controls from your home, such as for a TV, Audio System, TV Box, etc, and measure the current that is supplied to the IR LED in the remote, what would be common current ...
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1answer
35 views

TOA distance resolution

As far as I could understand, TOA systems, abstractly, work by measuring the time it took the wave to transfer from a transmitter to a receiver and multiplying it by the speed of the wave in the ...
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43 views

What happens to a wave on a coaxial cable at low frequences?

I'm trying to understand the propagation of a sinus wave on a coaxial cable at very low frequences. But the problem is that I heard some people got a pi/2 dephasing, and some others got no dephasing....
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1answer
48 views

Alternating Voltage

Is AC the same as an alternating voltage ?

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