Quadrature

Quadrature may refer to:

Signal processing

• Quadrature phase, oscillations that are said to be in quadrature if they are separated in phase by 90° (π/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

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

Science

• Optical phase space quadratures, operators which represent the real and imaginary parts of the complex amplitude
• 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°

Other uses

• 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