What is Square wave: Definition and 78 Discussions

A square wave is a non-sinusoidal periodic waveform in which the amplitude alternates at a steady frequency between fixed minimum and maximum values, with the same duration at minimum and maximum. In an ideal square wave, the transitions between minimum and maximum are instantaneous.
The square wave is a special case of a pulse wave which allows arbitrary durations at minimum and maximum. The ratio of the high period to the total period of a pulse wave is called the duty cycle. A true square wave has a 50% duty cycle (equal high and low periods).
Square waves are often encountered in electronics and signal processing, particularly digital electronics and digital signal processing. Its stochastic counterpart is a two-state trajectory.

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  1. aagum_bae

    Square wave excitation for lock in amplifier?

    Why does square wave for both excitation and demodulation lead to demodulation at DC While using one of the signals sine the signal gets demodulated to odd harmonics? I'm unable to do the maths of Fourier expansion and multiplying and passing through low pass filter
  2. K

    Can a Square Wave Tachometer Drive be Powered by a Sine Waveform?

    I'm a marine engine mechanic, and as engine controls & sensor systems have gotten more complicated with current technology, my shop gets more & more requests for instrumentation & control system repairs. I have a lot of trouble getting technical info from suppliers, so I have been starting to...
  3. N

    Demodulation of modulating square wave

    Hi all There is RF signal in frequency range of 240 MHz to 500 MHz which has been amplitude modulated by 155 Hz square wave signal. The problem is to recover 155 Hz signal while exact RF Carrier frequency is unknown (240 MHz to 500 MHz). Is there any ready made COTs solution available for such...
  4. C

    Delaying/shifting the start of a square wave inverter

    I am trying to create a two phase type setup where I have a square wave in the multi-gigahertz frequency. However, I want the second wave to start once the first one reaches 90 degrees. How can the circuit be configured to do this? Will a phase shifter do or can a square wave be phase shifted at...
  5. M

    How a square or sawtooth wave can have a certain frequency?

    Hello! I know that a square or saw tooth wave consists of infinite amount of sinousoids each having different frequency and amplitude. But when I look at their plot they seem to have a well defined frequency or period. Which term in the Fourier series determines their frequency? Does a saw...
  6. jsg94

    Determine impulse response given input and output signals

    Homework Statement Hello everyone, In the following problem I have to find the unknown impulse response g1(t) given the input and output signals, as shown below: (the answer is already there, at the moment I am trying to understand how to get there). Homework Equations [/B] I have...
  7. T

    Understanding current measurement on an irregular waveform

    I hoped to use a Keithley 2400 source meter to generate a ~120Hz AC signal by outputting a 2-point sweep from 1A to -1A on an infinite trigger. The waveform image is attached below. The end goal is a resistance measurement for bulk semiconductor materials, we prefer AC measurement to avoid...
  8. M

    Question About Duty Cycle and Average Value of a Square Wave

    Homework Statement [/B] 1. Using the Schematic of a 555 in astable mode from the Wikipedia entry on '555 Timer IC," resistor R1 = 8 kOhms and capacitor C = 3 micro-Farads. Determine the value of R2 so that the output duty cycle is D = 0.7. Note that D is not expressed as a percentage here for...
  9. T

    B Simple double integration of square wave question

    Hi, Simple question, sort of: I see that according to the internet the mathematical description of a triangular wave is rather complex, so I'll try to stay as far away from that as I can, because I'm a bit rusty. I understand that if you integrate a square wave you get a triangular wave on the...
  10. Captain1024

    Fourier Series Coefficients of an Even Square Wave

    Homework Statement Link: http://i.imgur.com/klFmtTH.png Homework Equations a_0=\frac{1}{T_0}\int ^{T_0}_{0}x(t)dt a_n=\frac{2}{T_0}\int ^{\frac{T_0}{2}}_{\frac{-T_0}{2}}x(t)cos(n\omega t)dt \omega =2\pi f=\frac{2\pi}{T_0} The Attempt at a Solution Firstly, x(t) is an even function because...
  11. moenste

    RMS of square wave and alternating currents

    Homework Statement Find the value of the RMS current in the following cases: (a) a sinusoidally varying current with a peak value of 4.0 A, (b) a square wave current which has a constant value of 4.0 A for the first 3 ms and -2.4 A for the next 2 ms of each 5 ms cycle, (c) an alternating...
  12. F

    Engineering Circuit Analysis-Converting a square wave to a sine wave

    Homework Statement For an upcoming lab I've been asked to build a circuit to convert a square wave (vi(t))e into a sine wave (v0(t)) by selecting appropriate resistor/capacitor values for the circuit below (from what I know, it's impossible to produce an accurate sine wave with just this, I...
  13. J

    Fourier series of square wave on Matlab?

    Homework Statement How Can i do this on matlap the question in Attached files Homework Equations The Attempt at a Solution i try a lot but i failed
  14. B

    Can You Confirm My Fourier Series Calculation for a Square Wave?

    Hello, I think that I have done this correctly, but this is the first problem I have done on my own and would appreciate confirmation. 1. Homework Statement Find the Fourier series corresponding to the following functions that are periodic over the interval (−π, π) with: (a) f(x) = 1 for...
  15. P

    Graphing the V vs I relationship of diode using Square wave

    Homework Statement I am having trouble understanding what this picture is showing. [/B] I know that in the case of a sine wave, the voltage below zero will not conduct much if it does not drop past the breakdown region. On the other hand, it will start to conduct and grow exponentially at...
  16. H

    Square wave and sine wave -- How standing waves are formed?

    Why do the sound waves reflect and form standing wave when they travel along a string with sinusoidal waveform? But they do not reflect back when they are in square waveform ?
  17. B

    Who has experience with AD8333 to demodulate a square wave?

    I am wondering if anyone has used AD8333 to demodulate a square wave input (Not the LO, but the RF input).
  18. M

    The sound of a perfect square wave

    Hey guys, It is stated that a 100% perfect square shaped wave have infinite odd harmonics and it is impossible to produced theoretically. But, assuming if a perfect square wave is produced, what would it sound like? I remember someone said it in Youtube it would actually sound like a clarinet...
  19. G

    Fundamental frequencies of square wave and sine wave

    Homework Statement What are the fundamental frequencies for a 50 kHz square waveform of 50% duty cycle and a 25 kHz sinusoidal waveform, respectively? (The duty cycle of a square waveform is the ratio between the pulse duration and the pulse period.) Homework Equations My teacher then gave...
  20. D

    Best way to pulse a constant microcurrent square wave signal?

    I have a constant 100 uA square wave DC 10Hz signal that needs to have a pulse width of 50ms. I was reading up on using an electronic timer relay (recycle type) or a solid state relay controlled via PWM. I need some help choosing which route to take, or if there are better/easier ways to...
  21. R

    What Does a 22.5° Duty Cycle Mean in a Tachometer Square Wave Signal?

    I'm looking to get some help understanding the tachometer out specifications for an MSD 6AL ignition control unit. It specifies that "The Tach Output wire produces a 12 voltage square wave signal with a 22.5° duty cycle." I'm fine with the fact that its a 12 volt square wave, but I'm a...
  22. D

    Fourier Series - Asymmetric Square Wave

    Good morning everyone, I am taking a signals and systems course where we are now studying the Fourier series. I understand that this is for signals that are periodic. But I get hung up when determining the Fourier coefficients. In the video by Alan Oppenheim, he derives the equation for...
  23. A

    Would a square wave look like a sine passed through a material?

    Sorry for the wording of the topic- I couldn't figure out how to make it fit. If I passed a hypothetical square wave through a material- be it wood, glass, cotton, etc.- would it change to look more like a sine wave?
  24. J

    I understanding the Fourier components of a square wave

    In my physics book there is an example of making a square wave by "simply" summing up a few cosine waves. The book says these first three waves are the first three Fourier components of a square wave, yet when I sum the three wave functions up, I get something way off; as does my calculator...
  25. B

    How to calculate a harmonic of a square wave

    Hi, I'm a bit of a newbie to additive synthesis.. I just want to clarify that I am doing the correct calculation before continuing. If I wanted to calculate the 5th harmonic of a square wave (the fundamental freq. being 200Hz and the amplitude of the fundamental being 1) would the...
  26. J

    Power percentage, square wave, Fourier series

    Homework Statement What is the percentage of power (out of the total power) contained up to the third harmonic (power in DC component, a1 , a-1 , a2 , a-2 , a3 , a-3 ) of the square waveform shown above? (the duty cycle = D = τ/T0= 0.5) Homework EquationsThe Attempt at a Solution Hey all...
  27. F

    Square wave exponential fourier series

    This is A and B my friend is telling me that Co is actually 0 and I am getting 1/2 and i don't see exactly what I am doing wrong if i indeed am doing something wrong hopefully someone here can check this out and let me know exactly where i went wrong.. Thanks
  28. I

    Fourier Series Convergence for Square Wave Function

    Homework Statement what values does the Fourier series for f(t) converge to if t = 0 and t = 2? Homework Equations The Attempt at a Solution My answers the red rectangles for the even function t=0 >> 1 and t=2 -->1.5 and odd function t=0 >> 0 and t=2 -->1.5 because at t=0 is continuity...
  29. M

    Generating a square wave with a PIC12F

    Hi, using a PIC12F683 I'm attempting to toggle an IO pin every time the internal timer overflows (via the timer interrupt) but I can't seem to get it working. I'm viewing the voltage of the pin on a scope, expecting a square wave and getting a constant 5 volts. Also I've read the official...
  30. F

    Square wave, sampling and verilog clocks

    Homework Statement Homework Equations My question too :) The Attempt at a Solution Can anybody confirm whether I solved the problem right or wrong? As for the next question about verilog and many clocks I am unable to find a source with that information. Thanks a lot for any...
  31. M

    Best way to produce a 10-40kHz square wave

    Hi! I should probably start off by saying that I did attempt to search for this, but I wasn't able to find a thread that had a similar question. I'm driving an RLC network (in effect) with a square wave to saturate a ferrite core. The image is pretty close to what I'm trying to achieve. I...
  32. S

    Square wave symmetric around zero volts

    Hi everyone For a pre-lab, I am asked to draw a square wave symmetric around zero volts. I am not sure what this graph looks like, can someone give me an example? Thank You
  33. F

    Signal excited by square wave

    Homework Statement 11. What kind of frequency components can be observed in the output if a linear system is excited by a symmetric square wave? 12. What kind of frequency components can be observed in the output if a non-linear system is excited by a symmetric square wave? Homework...
  34. B

    Why Doesn't My Fourier Series Expansion Look Like a Square Wave?

    for a square wave function, f(x)= { -1, -∞ ≤ x ≤ 0; +1, 0 ≤ x ≤ ∞ Expanding it in Fourier series gives a function like, f(x) = (4/π) * Ʃn=0∞( (sin ((2n+1)x) / (2n+) ) Plotting a graph of the equation gives something like this, http://goo.gl/vFJhL which obviously doesn't look like a...
  35. J

    Creating a square wave pulse at the peak of a sin wave

    Hi all, I am trying to create a square wave pulse that lasts for a relatively small amnount of time which corresponds (as close as possible) to the peak of a sin wave input of period about 1 second. The only way that I can think of doing this is via a programmable device such as an arduino...
  36. Twinflower

    Calculate the amplitude of the fifth harmonic (square wave + HP filter)

    Homework Statement A high pass filter tuned for a corner freq. of 40 000 rad/sek and with a damping coeffisient of 1/sqrt(2) is being subjected to a square wave voltage with amplitide of 1 volt and 8000 rad/sek. What is the amplitude of the fifth harmonic on the output side of the filter...
  37. S

    Fourier Series of Even Square Wave

    Homework Statement -0.5\leq{t}\leq{1.5}, T=2 The wave is the attached picture. I need to determine the Fourier Series of the wave in the picture. I know that f(t)=a_0+{\sum}_{n=1}^{\infty}a_ncos(n\omega_0t)+{\sum}_{n=1}^{\infty}b_nsin(n\omega_0t) where a_0=\bar{f}=0 due to being an even...
  38. E

    How do you integrate a square wave?

    I'm doing homework where i have to find a function representation of the output signal from a simple op amp integrator circuit with a 4.7k resistor and a .01uf capacitor. I know I'm supposed to use the equation -1/rc * int vin(t) but the input is a square wave signal. I never learned how to...
  39. E

    Vary voltage and frequency of Square Wave

    Hi! I am using an AtMega32 to output a square wave. I am varying the frequency by toggling the output pin using Timer1. However, I also need to vary the voltage of the wave and frankly, have no idea how to. I tried looking up google but not much of it made sense to me thanks to my limited...
  40. S

    Square wave to sine wave conversion

    Hello guys i am very new to this forum. I am doing project in digital radio. can you tell me how to convert square wave into sine wave of frequency range 88 to 108 MHz. Thanks in advance.pls suggest me a circuit
  41. L

    Fundamental and harmonics of a square wave

    Homework Statement Measurements taken of a square-wave signal using a frequency-selective voltmeter (called a spectrum analyzer) show its spectrum to contain adjacent components (spectral lines) at 98kHz and 126kHz of amplitudes 63mV and 49mV, respectively. For this signal, what would direct...
  42. H

    Square wave and sine wave inverter

    Hello, Suppose we have a square wave inverter, and at the output we put a low pass filter with cut off frequency of 50 Hz, then the output is sinusoidal with frequency 50Hz. Now let's take a sine wave inverter and at the output we have a low pass filter with cut off frequency of 50Hz, then we...
  43. J

    Fourier series equation for a even square wave

    Can someone please help me with a Fourier series equation for a even square wave shown below: F(t) = 0 when -2ms <t < -1ms k when -1ms <t < 1ms 0 when 1ms <t < 2ms T=4 Im after finding the first 10 harmonic components. To be honest struggling with...
  44. S

    What is the wave function of a square wave in an infinite potential well?

    Alright, so here's my problem. I've got a wavefunction between -L/2 and L/2 (symmetric around 0). It's a square wave and it is in an infinite potential well. That's all I know about it. I need to find the wavefunction of it. I was thinking of doing a Fourier sine/cosine series but I'm stuck...
  45. G

    Square wave into a transformer, low impedance output needed

    I need to connect the transformer to an 5V open-collector source as shown below, but the load must not see a larger impedance than 50Ω. The 5V source is an internal source to the driver and not available outside of it. As it stands, the seen impedance will be 5k when the bjt is off, so this will...
  46. L

    Creating a square wave with current strong enough to light a powerful LED

    Hello! I haven't touched base in electronics in about a year (only took one course too) I'm currently working on a project and I'm wondering what the best solution might be to creating a square wave which is 5 milliseconds high, 12 milliseconds low (low as in ground not negative voltage)...
  47. A

    How can a square wave generator be used in a resonance inductive circuit?

    Square wave generator...what? Okay, so I built a square wave generator using a 555 timer and schematics that I found off the internet. Upon completion, I dumbly realized that there is only an output. I wanted to use the square wave generator in resonance inductive circuit, but seeing as there...
  48. genxium

    Could square wave propagate without modulation?

    Homework Statement I'm going to do the experiment that generates a square wave using the 555 timer this weekend, but I'm wondering why sometimes we have to modulate the square waves to sin waves, and decode them in the terminal receiver? Could square wave(or any other non-sin wave) itself...
  49. M

    Inverse laplace transform square wave

    can someone please help me find the inverse laplace transform of the following: http://www.webpagescreenshot.info/img/694286-34201141544am.png i do not know how to solve for this due to the e^-20s shift in the denominator... is there a way to change this function to make it easier to solve?