Introduction
My Topic is dmux and its applications.There are many types of dmux for eg.1 to 4 line ,1 to 8 line,2 to 4 line etc.and dmux applications are used in varius branches for eg.in computer applications , in electronics,in tele communications.so I disscuss one by one.firstly what is dmux then its some typesand at last its some applications.
What Is Dmux?
Multiplexer
In electronics, a multiplexer or mux (occasionally the terms muldex or muldem are also found[1] for a combination multiplexer-demultiplexer) is a device that performs multiplexing; it selects one of many analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output.
An electronic multiplexer makes it possible for several signals to share one device or resource, for example one A/D converter or one communication line, instead of having one device per input signal.
Demultiplexer
On the other end, a demultiplexer (or demux) is a device taking a single input signal and selecting one of many data-output-lines, which is connected to the single input. A multiplexer is often used with a complementary demultiplexer on the receiving end.
Meaning of DeMux - "Demultiplexer", is a logical circuit that takes a single input source and sends it to one of several outputs. In networking, it is used to describe a device that receives a transmission of several signals over a single line and can properly decode the single line signal into multiple signals. The equipment used to de-multiplex the signals into several sources which were multiplexed before is called the De-Multiplexer. This is a reverse of Multiplexing where the analog / digital signals are combined for transmission over a single line or media. In electrical communications, the two basic forms of multiplexing are Time-Division Multiplexing (TDM) and Frequency-Division Multiplexing (FDM). In optical communications, the analog of FDM is referred to as Wavelength-Division Multiplexing (WDM) .
In digital signal processing, the multiplexer takes several separate digital data streams and combines them together into one data stream of a higher data rate. This allows multiple data streams to be carried from one place to another over one physical link, which saves cost. At the receiving end of the data link a complementary demultiplexer is normally required to break the high data rate stream back down into the original lower rate streams
Input/ Output diagram of dmux
Truth table of demux
Types of dmux
1-to-4 line demultiplexer
The opposite of the multiplexer circuit, logically enough, is the demultiplexer. This circuit takes a single data input and one or more address inputs, and selects which of multiple outputs will receive the input signal. The same circuit can also be used as a decoder, by using the address inputs as a binary number and producing an output signal on the single output that matches the binary address input. In this application, the data input line functions as a circuit enabler — if the circuit is disabled, no output will show activity regardless of the binary input number
A one-line to two-line decoder/demultiplexer is shown below.
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This circuit uses the same AND gates and the same addressing scheme as the two-input multiplexer circuit shown in these pages. The basic difference is that it is the inputs that are combined and the outputs that are separate. By making this change, we get a circuit that is the inverse of the two-input multiplexer. If you were to construct both circuits on a single breadboard, connect the multiplexer output to the data IN of the demultiplexer, and drive the (A)ddress inputs of both circuits with the same signal, you would find that the initial X0 input would be transmitted to OUT0 and the X1 input would reach only OUT1.
The one problem with this arrangement is that one of the two outputs will be inactive while the other is active. To retain the output signal, we need to add a latch circuit that can follow the data signal while it's active, but will hold the last signal state while the other data signal is active. An excellent circuit for this is the D (or Data) Latch. By placing a latch after each output and using the Addressing input (or its inverse) to control them, we can maintain both output signals at all times. If the Address input changes much more rapidly than the data inputs, the output signals will match the inputs faithfully.
2 –to- 4 line Demultiplexer
Like the multiplexer circuit, the decoder/demultiplexer is not limited to a single address line, and therefore can have more than two outputs. With two, three, or four addressing lines, this circuit can decode a two, three, or four-bit binary number, or can demultiplex up to four, eight, or sixteen time-multiplexed signals.
| As a decoder, this circuit takes an n-bit binary number and produces an output on one of 2n output lines. It is therefore commonly defined by the number of addressing input lines and the number of data output lines. Typical decoder/demultiplexer ICs might contain two 2-to-4 line circuits, a 3-to-8 line circuit, or a 4-to-16 line circuit. One exception to the binary nature of this circuit is the 4-to-10 line decoder/demultiplexer, which is intended to convert a BCD (Binary Coded Decimal) input to an output in the 0-9 range. If you use this circuit as a demultiplexer, you may want to add data latches at the outputs to retain each signal while the others are being transmitted. However, this does not apply when you are using this circuit as a decoder — then you will want only a single active output to match the input code. |
Applications of demux
1)How they use in digital logic gates?
Digital decoders and digital demultiplexers are integrated circuits (ICs) that move data between inputs and outputs. Digital decoders convert coded information into a familiar or uncoded form so that, for example, binary coded decimal (BCD) numbers can be converted into digits that display on a seven-segment calculator. Digital demultiplexers switch digital data from one input line to several output lines in a specific time sequence. They are often used in telecommunications applications. Digital decoders and digital demultiplexers are available with 1 to 4 input lines and 2, 4, 6, 8, 10, 14, or 16 output lines. Both types of devices have inverted outputs so that the selected output is set to 0, while all of the other outputs remain at 1. Digital decoders can be used individually, or connected together for use as demultiplexers.
Digital decoders and digital demultiplexers vary in terms of supply voltage, operating current, propagation delay, and power dissipation. Supply voltages range from - 5 V to 5 V and include intermediate voltages such as -4.5 V, -3.3 V, -3 V, 1.2 V, 1.5 V, 1.8 V, 2.5 V, 3 V, 3.3 V, and 3.6 V. The operating current is the minimum current needed for active operation. The propagation delay is the time interval between the application of an input signal and the occurrence of the corresponding output. Power dissipation, the total power consumption of the device, is generally expressed in watts or milliwatts. Some digital decoders and digital demultiplexers are radiation hardened or tolerant. Others include circuitry for protection against electrostatic discharge (ESD).
Selecting digital decoders and digital demultiplexers requires an analysis of logic families. Transistor-transistor logic (TTL) and related technologies such as Fairchild advanced Schottky TTL (FAST) use transistors as digital switches. By contrast, emitter coupled logic (ECL) uses transistors to steer current through gates that compute logical functions. Another logic family, complementary metal-oxide semiconductor (CMOS), uses a combination of p-type and n-type metal-oxide-semiconductor field effect transistors (MOSFETs) to implement logic gates and other digital circuits. Logic families for digital decoders and digital demultiplexers include cross-bar switch technology (CBT), Gallium arsenide (GaAs), integrated injection logic (I2L) and silicon on sapphire (SOS). Gunning with transceiver logic (GTL) and gunning with transceiver logic plus (GTLP) are also available.
Digital decoders and digital demultiplexers are available in a variety of IC package types and with different numbers of pins and flip-flops. Basic IC package types include ball grid array (BGA), quad flat package (QFP), single in-line package (SIP), and dual in-line package (DIP). Many packaging variants are available. For example, BGA variants include plastic-ball grid array (PBGA) and tape-ball grid array (TBGA). QFP variants include low-profile quad flat package (LQFP) and thin quad flat package (TQFP). DIPs are available in either ceramic (CDIP) or plastic (PDIP). Other IC package types include small outline package (SOP), thin small outline package (TSOP), and shrink small outline package (SSOP).
2)Fiber Bragg grating Application
A fiber Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by adding a periodic variation to the refractive index of the fiber core, which generates a wavelength specific dielectric mirror. A fiber Bragg grating can therefore be used as an inline optical filter to block certain wavelengths, or as a wavelength-specific reflector
The primary application of fiber Bragg gratings is in optical communications systems. They are specifically used as notch filters. They are also used in optical multiplexers and demultiplexers with an optical circulator, or Optical Add-Drop Multiplexer (OADM). Figure 5 shows 4 channels, depicted as 4 colours, impinging onto a FBG via an optical circulator. The FBG is set to reflect one of the channels, here channel 4. The signal is reflected back to the circulator where it is directed down and dropped out of the system. Since the channel has been dropped, another signal on that channel can be added at the same point in the network.
A demultiplexer can be achieved by cascading multiple drop sections of the OADM, where each drop element uses a FBG set to the wavelength to be demultiplexed. Conversely, a multiplexer can be achieved by cascading multiple add sections of the OADM. FBG demultiplexers and OADMs can also be tunable. In a tunable demultiplexer or OADM, the Bragg wavelength of the FBG can be tuned by strain applied by a piezoelectric transducer. The sensitivity of a FBG to strain is discussed below in fiber Bragg grating sensors.
3)DTV receiver application
A DTV receiver is a set-top box that permits the reception of Digital television. Its components are very similar to a desktop PC. The DTV receiver is a vital link in the chain of television system. The goal of a broadcasting system is to concentrate the hardware requirements at the source to simplify the receivers and makes it as inexpensive as possible.
It is usually connected to the TV set or incorporated in the TV set. The main features of a DTV receiver may be classified as follows:
• decodes the incoming digital signal;
• verifies access rights and security levels;
• displays cinema quality pictures on the TV set;
• outputs digital surround sound;
• processes and renders Internet and interactive TV services.
Basically, the tuner in the box receives a digital signal from a cable, a satellite, or terrestrial network and isolates a particular channel. The signal is then forwarded to a demodulator and converted to binary format. Once in binary format, the demodulator will check for error and forward the binary signal to a demultiplexer that will extract audio, video, and data from the binary stream. Once the demultiplexer has finished with the signal, the decoders will transform the digital bits bits into a format suitable for viewing on the television set.
As the architecture of a DTV receiver can vary in function of the network operator or the set-box manufacturer, we have chosen to divide the physical components into the following categories:
• system board,
• tuner,
• modulator and demodulator,
• demultiplexer and decryptor,
• decoders,
• graphics processor,
• CPU and memory,
• storage devices,
• physical interfaces,
• physical carcteristics.
Demultiplexer and decryptor
The technology used in DTV television is MPEG-2. The demultiplexer selects particular packets, decrypts, and forwards to a specific decoder.
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information".[1] It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission bandwidth.
4)Stepping switch application
(commonly called Strowger or step-by-step exchanges or steppers) to route telephone calls.
contact of the next, a counter could be constructed. Or by feeding the stepping contact with an endless pulse train via a relay, and controlling the relay from the switch's own output, it can be made to automatically hunt for the first unpowered line (or powered, depending on whether the relay is normally open or normally closed). They could also be used as a demultiplexer In electrical controls, a stepping switch, also known as a stepping relay, is an electromechanical device which allows an input connection to be connected to one of a number of possible output connections, under the control of a series of electrical pulses. It can step on one axis (called a uniselector), or on two axes (a Strowger switch). Stepping switches were invented by Almon Strowger in 1888. The major use for these devices was in early automatic telephone exchanges
As well as the decoding of pulses from telephones, stepping switches could be used for a variety of purposes, depending on how they were wired. By connecting several in series with the highest output of one going to the stepping, so
that two input lines could.
Bibiliography
1)http://www.play-hookey.com/digital/decoder_demux_four.html
2)http://en.wikipedia.org/wiki/DTV_Receiver#Demultiplexer_and_decryptor
3)http://en.wikipedia.org/wiki/MPEG-2
4)http://en.wikipedia.org/wiki/Fiber_Bragg_grating
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