# Difference between revisions of "Quadrature Phase Shift Keying"

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A [[Modulation Scheme]] where the [[Phase]] of the modulated signal is shifted depending on the incoming bitstream by an angle of -135°, -45°, +45° or +135°. Thus 4 states (a two-digit binary symbol) can get expressed in every transition. | A [[Modulation Scheme]] where the [[Phase]] of the modulated signal is shifted depending on the incoming bitstream by an angle of -135°, -45°, +45° or +135°. Thus 4 states (a two-digit binary symbol) can get expressed in every transition. | ||

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+ | [[Image:Qpsk.jpg|QPSK in time domain]] | ||

In order to minimize the used [[Bandwidth]] allocated on the [[Transponder]] the outgoing signal is usually filtered using digital low-pass [[FIR Filter]]s with smooth roll-off so that the high-order noise of the sudden state changes gets removed. | In order to minimize the used [[Bandwidth]] allocated on the [[Transponder]] the outgoing signal is usually filtered using digital low-pass [[FIR Filter]]s with smooth roll-off so that the high-order noise of the sudden state changes gets removed. | ||

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## Revision as of 22:06, 23 September 2004

A Modulation Scheme where the Phase of the modulated signal is shifted depending on the incoming bitstream by an angle of -135°, -45°, +45° or +135°. Thus 4 states (a two-digit binary symbol) can get expressed in every transition.

In order to minimize the used Bandwidth allocated on the Transponder the outgoing signal is usually filtered using digital low-pass FIR Filters with smooth roll-off so that the high-order noise of the sudden state changes gets removed.