Quadrature amplitude modulation (QAM) 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 final 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 considered as QAM since the amplitude of the modulated carrier signal is constant. QAM is used extensively as a modulation scheme for digital telecommunication systems. Arbitrarily high spectral efficiencies can be achieved with QAM by setting a suitable constellation size, limited only by the noise level and linearity of the communications channel.
QAM may refer to:
QAM stands for quadrature amplitude modulation, the format by which digital cable channels are encoded and transmitted via cable television providers. QAM is used in a variety of communications systems such as Dial-up modems and WiFi. In cable systems, a QAM tuner is linked to the cable in a manner that is equivalent to an ATSC tuner which is required to receive over-the-air (OTA) digital channels broadcast by local television stations when attached to an antenna. Most new HDTV digital televisions support both of these standards. QAM uses the same 6 MHz bandwidth as ATSC, using a standard known as ITU-T Recommendation J.83 Annex B ("J.83b").
QAM is a modulation format and does not specify the format of the digital data being carried. However, when used in the context of US digital cable television, the format of the data transmitted using this modulation is based on ITU-T J.83 Annex B ("J.83b"). This is in contrast to DVB-C which is also based on QAM modulation, but uses a DVB-based data format which is incompatible with North American receivers.
I'm sittin' here thinkin' about you tonight
And all that you mean to me
I used to think I would never fall in love again
I guess I was wrong
When your heart was broken
When your wounded pride was laid to rest, baby
You'll never open your heart to anyone else you said
But you lied, I know you're lyin' tome
You see your mind might be made up, mmm
But your heart has got it's own plans
There's no one to blame for false pride, tellin' lies,
tryin' to hide
From feelin' the pain, I know you don't wanna feel it
There's nowhere to hide when the love is callin' your
name, yeah
From the dark, babe, nowhere to hide, baby
There's nowhere to hide, so let love have it's way
with your heart
When love calls, love calls, love calls your name
It's on my lips
And I wish that you were still here
To take me away with your kiss
And take me away from all this crazy, crazy
'Cause too many words have been spoken, mmm
Too many lies have been told, baby
You'll never do it again you told yourself over and
over and over
You're wrong, dead wrong, babe, yeah
There's nowhere to hide, mmm, when love is callin'
your name
In from the dark, baby, nowhere to run, girl
There's nowhere to hide, yeah, so let love have its
way, girl, with your heart, babe
Love calls, love calls
There's nowhere to hide, yeah, when love calls your
name
You fall apart, baby
Nowhere to hide, nowhere to run when love is on its
way, girl, to your heart, baby
When love calls, love calls your name, babe
Love's callin' your name, hey, hey
It's callin' out for, callin' out for me, baby
Love's on its way, baby, yeah, yeah, yeah, yeah
I'm sittin' here thinkin' about you tonight
And how you make me feel
The sweetness of your touch
The softness of your voice, mmm
You make me wanna be a better man, baby
And I wanna thank you for calling me into your life