Rectangular function

Rectangular function

The rectangular function (also known as the rectangle function, rect function, unit pulse, or the normalized boxcar function) is defined as:

:mathrm{rect}(t) = sqcap(t) = egin{cases}0 & mbox{if } |t| > frac{1}{2} \ [3pt] frac{1}{2} & mbox{if } |t| = frac{1}{2} \ [3pt] 1 & mbox{if } |t| < frac{1}{2}.end{cases}

Alternate definitions of the function define mathrm{rect}(pm egin{matrix} frac{1}{2} end{matrix}) to be 0, 1, or undefined. We can also express the rectangular function in terms of the Heaviside step function, u(t):

:mathrm{rect}left(frac{t}{ au} ight) = u left( t + frac{ au}{2} ight) - u left( t - frac{ au}{2} ight),,

or, alternatively:

:mathrm{rect}(t) = u left( t + frac{1}{2} ight) cdot u left( frac{1}{2} - t ight).,

The unitary Fourier transforms of the rectangular function are:

:int_{-infty}^infty mathrm{rect}(t)cdot e^{-i 2pi f t} , dt=frac{sin(pi f)}{pi f} = mathrm{sinc}(f),,

and:

:frac{1}{sqrt{2piint_{-infty}^infty mathrm{rect}(t)cdot e^{-i omega t} , dt=frac{1}{sqrt{2picdot mathrm{sinc}left(frac{omega}{2pi} ight),,

where mathrm{sinc} is the normalized form.

We can define the triangular function as the convolution of two rectangular functions:

:mathrm{tri}(t) = mathrm{rect}(t) * mathrm{rect}(t).,

Viewing the rectangular function as a probability distribution function, its characteristic function is:

:varphi(k) = frac{sin(k/2)}{k/2},,

and its moment generating function is:

:M(k)=frac{mathrm{sinh}(k/2)}{k/2},,

where mathrm{sinh}(t) is the hyperbolic sine function.

ee also

*Fourier transform
*Square wave
*Triangular function


Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • Triangular function — The triangular function (also known as the triangle function, hat function, or tent function) is defined either as::egin{align}operatorname{tri}(t) = and (t) quad overset{underset{mathrm{def{{=} max(1 |t|, 0) = egin{cases}1 |t|, |t| < 1 ,… …   Wikipedia

  • Dirac delta function — Schematic representation of the Dirac delta function by a line surmounted by an arrow. The height of the arrow is usually used to specify the value of any multiplicative constant, which will give the area under the function. The other convention… …   Wikipedia

  • Heaviside step function — The Heaviside step function, H , also called the unit step function, is a discontinuous function whose value is zero for negative argument and one for positive argument.It seldom matters what value is used for H (0), since H is mostly used as a… …   Wikipedia

  • Sign function — In mathematics, the sign function is a mathematical function that extracts the sign of a real number. To avoid confusion with the sine function, this function is often called the signum function (after the Latin form of sign ).In mathematical… …   Wikipedia

  • Sinc function — In mathematics, the sinc function, denoted by scriptstylemathrm{sinc}(x), and sometimes as scriptstylemathrm{Sa}(x),, has two definitions, sometimes distinguished as the normalized sinc function and unnormalized sinc function. In digital signal… …   Wikipedia

  • Wigner distribution function — The Wigner distribution function (WDF), named after Eugene Wigner, was first proposed for corrections to classical statistical mechanics in 1932 by Eugene Wigner. But the Wigner distribution function is also a good transform for time frequency… …   Wikipedia

  • Boxcar function — In mathematics, a boxcar function is any function which is zero over the entire real line except for a single interval where it is equal to a constant, A . The boxcar function can be expressed in terms of the uniform distribution… …   Wikipedia

  • Window function — For the term used in SQL statements, see Window function (SQL) In signal processing, a window function (also known as an apodization function or tapering function[1]) is a mathematical function that is zero valued outside of some chosen interval …   Wikipedia

  • Holomorphic function — A rectangular grid (top) and its image under a holomorphic function f (bottom). In mathematics, holomorphic functions are the central objects of study in complex analysis. A holomorphic function is a complex valued function of one or more complex …   Wikipedia

  • special function — ▪ mathematics       any of a class of mathematical functions (function) that arise in the solution of various classical problems of physics. These problems generally involve the flow of electromagnetic, acoustic, or thermal energy. Different… …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”