Quadrature

Quadrature may refer to:

In signal processing:
 * Quadrature phase, oscillations that are said to be in quadrature if they are separated in phase by 90° ($\pi$/2, or 𝜆/4)
 * Quadrature component of a composite signal
 * Quadrature filter, the analytic signal of a real-valued filter
 * Quadrature amplitude modulation (QAM), a modulation method of using both an (in-phase) carrier wave and a 'quadrature' carrier wave that is 90° out of phase with the main, or in-phase, carrier
 * Quadrature phase-shift keying (QPSK), a phase-shift keying of using four quadrate points on the constellation diagram, equispaced around a circle

In mathematics:
 * Quadrature (geometry), drawing a square with the same area as a given plane figure (squaring) or computing that area
 * Quadrature of the circle
 * Numerical integration is often called "numerical quadrature" or simply "quadrature"
 * Gaussian quadrature, a special case of numerical integration
 * Quadrature (differential equations), expressing a differential equation solution in terms of integrals.
 * Formerly, a synonym for "integral"
 * Integral
 * Antiderivative
 * Addition in quadrature, combining the magnitude of uncorrelated signals by taking the square root of the sum of their squares

In physics:
 * Optical phase space quadratures, operators which represent the real and imaginary parts of the complex amplitude

In astronomy:
 * Quadrature (astronomy), the position of a body (moon or planet) such that its elongation is 90° or 270°; i.e., the body-earth-sun angle is 90°

In Hedge-funds:
 * Quadrature (hedge-fund), the quant hedge-fund created in 2010, in London, England.

Quadrature may also refer to:
 * Quadrature encoder, a device that detects mechanical position changes and direction of movement
 * Illusionistic ceiling painting, sometimes called quadrature after the Italian term, quadratura
 * La Quadrature du Net (Squaring of the Net in French), a French advocacy group that promotes digital rights and freedoms of citizens
 * "Quadrature", a song by Squarepusher from the album Just a Souvenir