|
|
Автор: Jesse Russel
Год: 2012
Издание:
Книга по Требованию
Страниц: 106
ISBN: 9785511805986
High Quality Content by WIKIPEDIA articles! Quadrature amplitude modulation (QAM) ( /?kw??m/ or /?k?m/ or simply "Q-A-M") is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing (modulating) the amplitudes of two carrier waves, using the amplitude-shift keying (ASK) digital modulation scheme or amplitude modulation (AM) analog modulation scheme. The two carrier waves, usually sinusoids, are out of phase with each other by 90° and are thus called quadrature carriers or quadrature components — hence the name of the scheme. The modulated waves are summed, and the resulting waveform is a combination of both phase-shift keying (PSK) and amplitude-shift keying (ASK), or (in the analog case) of phase modulation (PM) and amplitude modulation. In the digital QAM case, a finite number of at least two phases and at least two amplitudes are used. PSK modulators are often designed using the QAM principle, but are not...
|
|
Jesse RusselQuadrature amplitude modulation
Jesse RussellAmplitude modulation
Swarniv ChandraAmplitude Modulation in Electrostatic Plasma Waves