Quadrature amplitude modulation ( QAM ) is both an analog and a digital modulation scheme.

QAM is used extensively as a modulation scheme for digital telecommunication systems.

An equivalent baseband signal or equivalent lowpass signal is – in analog and digital modulation methods with constant carrier frequency ( for example ASK, PSK and QAM, but not FSK ) – a complex valued representation of the modulated physical signal ( the so called passband signal or RF signal ).

These signal generators are capable of generating digitally-modulated radio signals that may use any of a large number of digital modulation formats such as QAM, QPSK, FSK, BPSK, and OFDM.

The signal is produced by means of a digital modulation method such as PSK, QAM or FSK.

For example, in a digital modulation scheme such as QAM where data is typically transmitted in symbols of 4 bits or more, the signal's constellation diagram is arranged so that the bit patterns conveyed by adjacent constellation points differ by only one bit.

ATSC and DVB-T specify the modulation used for over-the-air digital television ; by comparison, QAM is the modulation method used for cable.

16VSB was notably intended to be used for ATSC digital cable, but quadrature amplitude modulation ( QAM ) has become the de facto industry standard instead.

This system transmits an MPEG-2 or MPEG-4 family digital audio / digital video stream, using a QAM modulation with channel coding.

Most other digital carrier-modulated schemes, for example ASK, PSK, QAM and OFDM, can be characterized as double sideband modulation, resulting in the following relation:

Most digital cable providers use QAM for video services and DOCSIS standards for data services.

Some MATV systems may carry 8-VSB and QAM signals, mostly in apartment buildings and similar facilities that use a combination of terrestrial antennas and cable distribution sources ( such as HITS or " Headend in the Sky ", a unit of Comcast that delivers digital channels by satellite to small cable systems ).

Cobb edTV can be found on Comcast analog TV channel 24 for subscribers throughout Cobb County as a part of their basic cable package, and in the clear on QAM digital TV channel 81. 24 for digital basic.

On cable, it can be seen on Cox channel 6 and in high definition on digital channel 706 and clear QAM 6. 1.

The same general situation applies to digital cable service ; only DVD recorders with integrated digital cable (" QAM ") tuners can possibly avoid transcoding, and then only if the digital cable system is already sending a DVD-Video-compatible MPEG-2 stream, which again requires transcoding of all HD content and some if not all SD content.

) CableCARDs are not necessary for viewing unscrambled digital cable channels if the user has a QAM tuner — a feature in some televisions and DVRs.

* built-in support for receiving digital cable channels ( via an internal QAM tuner )

In his thesis he derived two-dimensional signal constellations that are similar to those used in the quadrature amplitude modulation ( QAM ) systems commonly used in high speed digital communications today.

TV23 is a Government-access television channel ( GATV ) cable TV channel in Cobb County, Georgia, seen on Comcast TV channel 23, and in ATSC clear QAM on digital cable channel 81. 23.

Thus, an analog signal is one represented by a continuous stream of data, in this case along an electrical circuit in the form of voltage, current or charge changes ( compare with digital signals below ).

The bilinear transform is a special case of a conformal mapping ( namely, the Möbius transformation ), often used to convert a transfer function of a linear, time-invariant ( LTI ) filter in the continuous-time domain ( often called an analog filter ) to a transfer function of a linear, shift-invariant filter in the discrete-time domain ( often called a digital filter although there are analog filters constructed with switched capacitors that are discrete-time filters ).

Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a series of discrete values representing the information.

The case was used by several academics in discussing such rights in the digital age.

Without this capacity, which is often the case in practice, to produce a representation with lower resolution or lower fidelity than a given one, one needs to start with the original source signal and encode, or start with a compressed representation and then decompress and re-encode it ( transcoding ), though the latter tends to cause digital generation loss.

This is the case for both physical film and digital cinema systems.

In case of digital video signal having 720 horizontal pixels, only the center 704 pixels contain actual 4: 3 or 16: 9 image, and the 8 pixel wide stripes from either side are called nominal analogue blanking and should be discarded before displaying the image.

The signals are usually processed in a digital representation, so speech processing can be regarded as a special case of digital signal processing, applied to speech signal.

Most mobile phones have a Firmware Over The Air firmware upgrade capability for much the same reasons ; some may even be upgraded to enhance reception or sound quality, illustrating the fact that firmware is used at more than one level in complex products ( in a CPU-like microcontroller versus in a digital signal processor, in this particular case ).

Quality criteria for such circuits may include equalization for amplitude over a specified band of frequencies, or in the case of digital data transported via analogue circuits, may include equalization for phase.

Moiré patterns are often an undesired artifact of images produced by various digital imaging and computer graphics techniques, for example when scanning a halftone picture or ray tracing a checkered plane ( the latter being a special case of aliasing, due to undersampling a fine regular pattern ).

For a variety of reasons ( including Mauchly's June 1941 examination of the Atanasoff – Berry Computer, prototyped in 1939 by John Atanasoff and Clifford Berry ), US patent 3, 120, 606 for ENIAC, granted in 1964, was voided by the 1973 decision of the landmark federal court case Honeywell v. Sperry Rand, putting the invention of the electronic digital computer in the public domain and providing legal recognition to Atanasoff as the inventor of the first electronic digital computer.

The analogue soundtrack provides a fall-back option in case of damage to the digital data or failure of the digital decoding, it also provides compatibility with projectors not equipped with digital soundheads.

Most CCTV systems record and store digital video and images to a Digital Video Recorder or in the case of IP cameras directly to a server, either on-site or offsite.

Atansoff invented the first digital computer in the world during the 1930s in the Iowa State College, but it took a lengthy court battle for achieving legal patent to 1973 when the case of Honeywell v. Sperry Rand was solved and the verdict named Atansoff with the title the inventor of the computer, the decision was never appealed, thus giving him the legal right to be called as such in the United States.

This is the case for earlier analogue trunks, MF and R2 digital trunks, and DSS1 / DASS PBX trunks.

Also, should the receiver lose power, even for a few milliseconds, or get ' swamped ' by 2. 4 GHz interference, it can take a few seconds for the receiver-which, in the case of 2. 4 GHz, is almost invariably a digital device-to re-sync.

In the case of 406 MHz beacons which transmit digital signals, the beacons can be uniquely identified almost instantly ( via GEOSAR ), and furthermore a GPS or GLONASS position can be encoded into the signal, which provides instantaneous identification of the registered user and its location.

Residents then had to dial " 8 " to reach Atlanta, which remained the case until digital equipment was installed in 1988

It differs from a digital signal, in which a continuous quantity is represented by a discrete function which can only take on one of a finite number of values.

In contrast, digital signals have a finite resolution.

Very different mathematical treatments apply to the design of filters termed infinite impulse response ( IIR ) filters, characteristic of mechanical and analog electronics systems, and finite impulse response ( FIR ) filters, which can be implemented by discrete time systems such as computers ( then termed digital signal processing ).

Although a digital filter can be an IIR filter if the algorithm implementing it includes feedback, it is also possible to easily implement a filter whose impulse truly goes to zero after N time steps ; this is called a finite impulse response ( FIR ) filter.

Quantization error is due to the finite resolution of the digital representation of the signal, and is an unavoidable imperfection in all types of ADCs.

Any digital modulation scheme uses a finite number of distinct signals to represent digital data.

Although physical modelling was not a new concept in acoustics and synthesis, having been implemented using finite difference approximations of the wave equation by Hiller and Ruiz in 1971, it was not until the development of the Karplus-Strong algorithm, the subsequent refinement and generalization of the algorithm into the extremely efficient digital waveguide synthesis by Julius O. Smith III and others, and the increase in DSP power in the late 1980s that commercial implementations became feasible.

In these cases, digital waveguides are often combined with FDTD, finite element or wave digital filter methods, increasing the computational demands of the model.

Sequential logic is used to construct finite state machines, a basic building block in all digital circuitry, as well as memory circuits and other devices.

The concept of state is formalized in an abstract mathematical model of computation called a finite state machine, used to design both sequential digital circuits and computer programs.

Local coordinates also afford digital designers a means around the finite limits of numerical representation.

However, as digital filters have a finite bandwidth, the response shape of the transformed Chebyshev will be warped.

However, digital signals are discrete in both of those respects – generally a finite sequence of integers – therefore a digitization can, in practical terms, only ever be an approximation of the signal it represents.

Discrete geometry has large overlap with convex geometry and computational geometry, and is closely related to subjects such as finite geometry, combinatorial optimization, digital geometry, discrete differential geometry, geometric graph theory, toric geometry, and combinatorial topology.

It has been argued that digital physics, grounded in the theory of finite state machines and hence discrete mathematics, cannot do justice to a physical theory whose mathematics requires the real numbers, which is the case for all physical theories having any credibility.

Nature is finite and digital.

* Moving average filter, a simple type of finite impulse response filter, in digital signal processing

Raster images have a finite set of digital values, called picture elements or pixels.

Also since a digital computer has finite precision ( See quantization ), extra care is needed to ensure the error in coefficients, A / D conversion, D / A conversion, etc.

If that discrete set is finite, the discrete values can be represented with digital words of a finite width.

The most well known of these algorithms are the Chirp z-Transform method ( CZT ) of spectral analysis, a range of optimal FIR ( finite impulse response ) digital filter design methods based on linear programming and Chebyshev approximation methods, and a class of decimation / interpolation methods for digital sampling rate conversion.