Digital signal (signal processing)

The red digital signal is the sampled and quantized repred analog signal. A digital signal consists of a sequence of samples, which in this case are integers: 4, 5, 4, 3, 4, 6...
Discrete cosine waveform with frequency of 50 Hz and a sampling rate of 1000 samples/sec, easily satisfying the sampling theorem for reconstruction of the original cosine function from samples. (The effects of quantization are too subtle to be seen in this graph.)

Discrete time, quantized amplitude signal.

- Digital signal (signal processing)
The red digital signal is the sampled and quantized repred analog signal. A digital signal consists of a sequence of samples, which in this case are integers: 4, 5, 4, 3, 4, 6...

50 related topics

Relevance

coding tube

Pulse-code modulation

coding tube
Sampling and quantization of a signal (red) for 4-bit LPCM

Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals.

In The Signal by William Powell Frith, a woman sends a signal by waving a white handkerchief.

Signal

Function that conveys information about a phenomenon.

Function that conveys information about a phenomenon.

In The Signal by William Powell Frith, a woman sends a signal by waving a white handkerchief.
A digital signal has two or more distinguishable waveforms, in this example, high voltage and low voltages, each of which can be mapped onto a digit. Characteristically, noise can be removed from digital signals provided it is not too extreme.
A binary signal, also known as a logic signal, is a digital signal with two distinguishable levels
Discrete-time signal created from a continuous signal by sampling
Signal transmission using electronic signals

Particularly in digital signal processing, a digital signal may be defined as a sequence of discrete values, typically associated with an underlying continuous-valued physical process.

4-channel stereo multiplexed analog-to-digital converter WM8775SEDS made by Wolfson Microelectronics placed on an X-Fi Fatal1ty Pro sound card

Analog-to-digital converter

4-channel stereo multiplexed analog-to-digital converter WM8775SEDS made by Wolfson Microelectronics placed on an X-Fi Fatal1ty Pro sound card
AD570 8-bit successive-approximation analog-to-digital converter
AD570/AD571 silicon die
INTERSIL ICL7107. 31/2 digit single-chip A/D converter
ICL7107 silicon die
Fig. 1. An 8-level ADC coding scheme
Comparison of quantizing a sinusoid to 64 levels (6 bits) and 256 levels (8 bits). The additive noise created by 6-bit quantization is 12 dB greater than the noise created by 8-bit quantization. When the spectral distribution is flat, as in this example, the 12 dB difference manifests as a measurable difference in the noise floors.
Analog to digital conversion as shown with fig. 1 and fig. 2.

In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal.

A Sound Blaster Live! Value card, a typical (circa 2000) PCI sound card.

Sound card

Internal expansion card that provides input and output of audio signals to and from a computer under control of computer programs.

Internal expansion card that provides input and output of audio signals to and from a computer under control of computer programs.

A Sound Blaster Live! Value card, a typical (circa 2000) PCI sound card.
Close-up of a sound card PCB, showing electrolytic capacitors, SMT capacitors and resistors, and a YAC512 two-channel 16-bit DAC
8-channel DAC Cirrus Logic CS4382 placed on Sound Blaster X-Fi Fatal1ty
The AdLib Music Synthesizer Card, was one of the first sound cards circa 1990. Note the manual volume adjustment knob. ISA-8 bus.
Sound card Mozart 16 for ISA-16 bus
A Turtle Beach sound card for PCI bus
Echo Digital Audio's Indigo IO – PCMCIA card -bit 96 kHz stereo in/out sound card
A VIA Technologies Envy sound card for PC, 5.1 channel for PCI slot
Three early ISA (16-bit) PC sound cards showing the progression toward integrated chipsets
A pair of professional rackmount audio interfaces
Professional audio interfaces often have industry-standard inputs in addition to analogue audio, in this case ADAT, TDIF, and S/PDIF
USB sound card

Sound cards use a digital-to-analog converter (DAC), which converts recorded or generated digital signal data into an analog format.

A commercial IP telephone, with keypad, control keys, and screen functions to perform configuration and user features.

Telephony

Field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties.

Field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties.

A commercial IP telephone, with keypad, control keys, and screen functions to perform configuration and user features.
Fixed telephone lines per 100 inhabitants 1997–2007

Telephone calls can be provided digitally, but may be restricted to cases in which the last mile is digital, or where the conversion between digital and analog signals takes place inside the telephone.

The Haar wavelet

Haar wavelet

Sequence of rescaled "square-shaped" functions which together form a wavelet family or basis.

Sequence of rescaled "square-shaped" functions which together form a wavelet family or basis.

The Haar wavelet

This property can, however, be an advantage for the analysis of signals with sudden transitions (discrete signals), such as monitoring of tool failure in machines.

Audio levels display on a digital audio recorder (Zoom H4n)

Digital audio

Audio levels display on a digital audio recorder (Zoom H4n)
A sound wave, in red, represented digitally, in blue (after sampling and 4-bit quantization).
The lifecycle of sound from its source, through an ADC, digital processing, a DAC, and finally as sound again.
Sony digital audio tape recorder PCM-7030
Focusrite USB Interfaces

Digital audio is a representation of sound recorded in, or converted into, digital form.

The sinc function, the time-domain impulse response of an ideal low-pass filter.

Low-pass filter

Filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency.

Filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency.

The sinc function, the time-domain impulse response of an ideal low-pass filter.
The gain-magnitude frequency response of a first-order (one-pole) low-pass filter. Power gain is shown in decibels (i.e., a 3 dB decline reflects an additional half-power attenuation). Angular frequency is shown on a logarithmic scale in units of radians per second.
A simple low-pass RC filter
Plot of the gain of Butterworth low-pass filters of orders 1 through 5, with cutoff frequency . Note that the slope is 20n dB/decade where n is the filter order.
Passive, first order low-pass RC filter
RLC circuit as a low-pass filter
A third-order low-pass filter (Cauer topology). The filter becomes a Butterworth filter with cutoff frequency ωc=1 when (for example) C2=4/3 farad, R4=1 ohm, L1=3/2 henry and L3=1/2 henry.
An active low-pass filter

The Whittaker–Shannon interpolation formula describes how to use a perfect low-pass filter to reconstruct a continuous signal from a sampled digital signal.

Commercial FM broadcasting transmitter at radio station WDET-FM, Wayne State University, Detroit, USA. It broadcasts at 101.9 MHz with a radiated power of 48 kW.

Transmitter

Electronic device which produces radio waves with an antenna.

Electronic device which produces radio waves with an antenna.

Commercial FM broadcasting transmitter at radio station WDET-FM, Wayne State University, Detroit, USA. It broadcasts at 101.9 MHz with a radiated power of 48 kW.
A radio transmitter is usually part of a radio communication system which uses electromagnetic waves (radio waves) to transport information (in this case sound) over a distance.
Animation of a half-wave dipole antenna transmitting radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). The voltage charges the two sides of the antenna alternately positive  (+)  and negative   (−) .  Loops of electric field (black lines) leave the antenna and travel away at the speed of light; these are the radio waves.  This animation shows the action slowed enormously
Hertz discovering radio waves in 1887 with his first primitive radio transmitter (background).
Guglielmo Marconi's spark gap transmitter, with which he performed the first experiments in practical Morse code radiotelegraphy communication in 1895-1897
High power spark gap radiotelegraphy transmitter in Australia around 1910.
1 MW US Navy Poulsen arc transmitter which generated continuous waves using an electric arc in a magnetic field, a technology used for a brief period from 1903 until vacuum tubes took over in the 20s
An Alexanderson alternator, a huge rotating machine used as a radio transmitter at very low frequency from about 1910 until World War 2
One of the first vacuum tube AM radio transmitters, built by Lee De Forest in 1914. The early Audion (triode) tube is visible at right.
One of the BBC's first broadcast transmitters, early 1920s, London. The 4 triode tubes, connected in parallel to form an oscillator, each produced around 4 kilowatts with 12 thousand volts on their anodes.
Armstrong's first experimental FM broadcast transmitter W2XDG, in the Empire State Building, New York City, used for secret tests 1934–1935. It transmitted on 41 MHz at a power of 2 kW.
Transmitter assembly of a 20 kW, 9.375 GHz air traffic control radar, 1947. The magnetron tube mounted between two magnets (right) produces microwaves which pass from the aperture (left) into a waveguide which conducts them to the dish antenna.

A related trend has been an ongoing transition from analog to digital radio transmission methods.

Typical 1980s CB base station, used with outdoor antenna. This radio may also be used in an automobile, since it is powered by 13.8 V DC. Shown with Astatic Power D-104 desk mic

Citizens band radio

Land mobile radio system, a system allowing short-distance person-to-many persons bidirectional voice communication among individuals, using two way radios operating on 40 channels near 27 MHz (11 m) in the high frequency (a.k.a. shortwave) band.

Land mobile radio system, a system allowing short-distance person-to-many persons bidirectional voice communication among individuals, using two way radios operating on 40 channels near 27 MHz (11 m) in the high frequency (a.k.a. shortwave) band.

Typical 1980s CB base station, used with outdoor antenna. This radio may also be used in an automobile, since it is powered by 13.8 V DC. Shown with Astatic Power D-104 desk mic
Cobra 18 WX ST II mobile CB radio with microphone
A QSL card issued by a US CB station in 1963.
Image of Citizens Radio license 1972 issued by the United States Federal Communication Commission.
Hand-held CB transceiver; antenna not shown
Typical center-loaded mobile CB antenna. Note the loading coil, which shortens the antenna's overall length.

This includes a new UHF PMR 446 MHz allocation: an eight-channel analog Personal Mobile Radio 446 MHz (Analog PMR446) with frequencies from 446.00625 to 446.09375 MHz (12.5 kHz spacing) FM with 0.5 watt power output, and 16 channels for Digital Personal Mobile Radio 446 MHz (Digital PMR 446).