Costas Loop

A Costas loop is a phase-locked loop used for carrier phase recovery from suppressed-carrier modulation signals, such as from double-sideband suppressed carrier signals. It was invented by John P. Costas at General Electric in the 1950s. Its invention was described as having had "a profound effect on modern digital communications". The primary application of Costas loops is in wireless receivers. Its advantage over the PLL-based detectors is that at small deviations the Costas loop error voltage is sin(2(θiθf)) vs sin(θiθf). This translates to double the sensitivity and also makes the Costas loop uniquely suited for tracking doppler-shifted carriers esp. in OFDM and GPS receivers

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Other articles related to "costas loop, loop":

Carrier Recovery - Methods - Non-Data-Aided - Costas Loop
... Carrier frequency and phase recovery as well as demodulation can be accomplished using a Costas loop of the appropriate order ... A Costas loop is a cousin of the PLL that uses coherent quadrature signals to measure phase error ... phase error is used to discipline the loop's oscillator ...
Costas Loop - Implementation
... In the usual implementation of a Costas loop, a local voltage-controlled oscillator provides quadrature outputs, one to each of two phase detectors, e.g ... The overall loop response is controlled by the two individual low-pass filters that precede the third phase detector while the third low-pass filter serves a trivial role in terms of gain and ...