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• Amplitude-shift_keying abstract "Amplitude-shift keying (ASK) is a form of amplitude modulation that represents digital data as variations in the amplitude of a carrier wave.In an ASK system, the binary symbol 1 is represented by transmitting a fixed-amplitude carrier wave and fixed frequency for a bit duration of T seconds. If the signal value is 1 then the carrier signal will be transmitted; otherwise, a signal value of 0 will not be transmitted.Any digital modulation scheme uses a finite number of distinct signals to represent digital data. ASK uses a finite number of amplitudes, each assigned a unique pattern of binary digits. Usually, each amplitude encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular amplitude. The demodulator, which is designed specifically for the symbol-set used by the modulator, determines the amplitude of the received signal and maps it back to the symbol it represents, thus recovering the original data. Frequency and phase of the carrier are kept constant.Like AM, ASK is also linear and sensitive to atmospheric noise, distortions, propagation conditions on different routes in PSTN, etc. Both ASK modulation and demodulation processes are relatively inexpensive. The ASK technique is also commonly used to transmit digital data over optical fiber. For LED transmitters, binary 1 is represented by a short pulse of light and binary 0 by the absence of light. Laser transmitters normally have a fixed "bias" current that causes the device to emit a low light level. This low level represents binary 0, while a higher-amplitude lightwave represents binary 1.The simplest and most common form of ASK operates as a switch, using the presence of a carrier wave to indicate a binary one and its absence to indicate a binary zero. This type of modulation is called on-off keying, and is used at radio frequencies to transmit Morse code (referred to as continuous wave operation),More sophisticated encoding schemes have been developed which represent data in groups using additional amplitude levels. For instance, a four-level encoding scheme can represent two bits with each shift in amplitude; an eight-level scheme can represent three bits; and so on. These forms of amplitude-shift keying require a high signal-to-noise ratio for their recovery, as by their nature much of the signal is transmitted at reduced power.ASK system can be divided into three blocks. The first one represents the transmitter, the second one is a linear model of the effects of the channel, the third one shows the structure of the receiver. The following notation is used:ht(f) is the carrier signal for the transmissionhc(f) is the impulse response of the channeln(t) is the noise introduced by the channelhr(f) is the filter at the receiverL is the number of levels that are used for transmissionTs is the time between the generation of two symbolsDifferent symbols are represented with different voltages. If the maximum allowed value for the voltage is A, then all the possible values are in the range [−A, A] and they are given by:the difference between one voltage and the other is:Considering the picture, the symbols v[n] are generated randomly by the source S, then the impulse generator creates impulses with an area of v[n]. These impulses are sent to the filter ht to be sent through the channel. In other words, for each symbol a different carrier wave is sent with the relative amplitude.Out of the transmitter, the signal s(t) can be expressed in the form:In the receiver, after the filtering through hr (t) the signal is:where we use the notation:where * indicates the convolution between two signals. After the A/D conversion the signal z[k] can be expressed in the form:In this relationship, the second term represents the symbol to be extracted. The others are unwanted: the first one is the effect of noise, the third one is due to the intersymbol interference.If the filters are chosen so that g(t) will satisfy the Nyquist ISI criterion, then there will be no intersymbol interference and the value of the sum will be zero, so:the transmission will be affected only by noise.".
• Amplitude-shift_keying thumbnail Ask_ideal_diagram.png?width=300.
• Amplitude-shift_keying wikiPageExternalLink WP-21.
• Amplitude-shift_keying wikiPageID "946426".
• Amplitude-shift_keying wikiPageRevisionID "605301448".
• Amplitude-shift_keying date "November 2012".
• Amplitude-shift_keying hasPhotoCollection Amplitude-shift_keying.
• Amplitude-shift_keying reason "this article need neutral and better phrasing".
• Amplitude-shift_keying subject Category:Applied_probability.
• Amplitude-shift_keying subject Category:Fault_tolerance.
• Amplitude-shift_keying subject Category:Quantized_radio_modulation_modes.
• Amplitude-shift_keying type Abstraction100002137.
• Amplitude-shift_keying type Attribute100024264.
• Amplitude-shift_keying type Manner104928903.
• Amplitude-shift_keying type Property104916342.
• Amplitude-shift_keying type QuantizedRadioModulationModes.
• Amplitude-shift_keying comment "Amplitude-shift keying (ASK) is a form of amplitude modulation that represents digital data as variations in the amplitude of a carrier wave.In an ASK system, the binary symbol 1 is represented by transmitting a fixed-amplitude carrier wave and fixed frequency for a bit duration of T seconds.".
• Amplitude-shift_keying label "ASK".
• Amplitude-shift_keying label "Amplitude-shift keying".
• Amplitude-shift_keying label "Amplitude-shift keying".
• Amplitude-shift_keying label "Amplitudenumtastung".
• Amplitude-shift_keying label "Modulación por desplazamiento de amplitud".
• Amplitude-shift_keying label "Modulation par déplacement d'amplitude".
• Amplitude-shift_keying label "Modulação por chaveamento de amplitude".
• Amplitude-shift_keying label "Амплитудная манипуляция".
• Amplitude-shift_keying label "تضمين إزاحة السعة".
• Amplitude-shift_keying label "振幅偏移変調".
• Amplitude-shift_keying sameAs Klíčování_amplitudovým_posuvem.
• Amplitude-shift_keying sameAs Amplitudenumtastung.
• Amplitude-shift_keying sameAs Διαμόρφωση_μετατόπισης_πλάτους.
• Amplitude-shift_keying sameAs Modulación_por_desplazamiento_de_amplitud.
• Amplitude-shift_keying sameAs Modulation_par_déplacement_d'amplitude.
• Amplitude-shift_keying sameAs Amplitude-shift_keying.
• Amplitude-shift_keying sameAs 振幅偏移変調.
• Amplitude-shift_keying sameAs 진폭_편이_방식.
• Amplitude-shift_keying sameAs ASK.
• Amplitude-shift_keying sameAs Modulação_por_chaveamento_de_amplitude.
• Amplitude-shift_keying sameAs m.03sbc0.
• Amplitude-shift_keying sameAs Q477284.
• Amplitude-shift_keying sameAs Q477284.
• Amplitude-shift_keying sameAs Amplitude-shift_keying.
• Amplitude-shift_keying wasDerivedFrom Amplitude-shift_keying?oldid=605301448.
• Amplitude-shift_keying depiction Ask_ideal_diagram.png.
• Amplitude-shift_keying isPrimaryTopicOf Amplitude-shift_keying.