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In digital modulation, an analog carrier signal is modulated by a digital bit stream. Digital modulation methods can be considered as digital-to-analog conversion, and the corresponding demodulation or detection as analog-to-digital conversion. The changes in the carrier signal are chosen from a finite number of M alternative symbols (the modulation alphabet). These are the most fundamental digital modulation techniques: * In the case of PSK, a finite number of phases are used. * In the case of FSK, a finite number of frequencies are used. * In the case of ASK, a finite number of amplitudes are used. * In the case of QAM, a finite number of at least two phases, and at least two amplitudes are used. In QAM, an inphase signal (the I signal, for example a cosine waveform) and a quadrature phase signal (the Q signal, for example a sine wave) are amplitude modulated with a finite number of amplitudes, and summed. It can be seen as a two-channel system, each channel using ASK. The resulting signal is equivalent to a combination of PSK an In digital modulation, an analog carrier signal is modulated by a digital bit stream. Digital modulation methods can be considered as digital-to-analog conversion, and the corresponding demodulation or detection as analog-to-digital conversion. The changes in the carrier signal are chosen from a finite number of M alternative symbols (the modulation alphabet). These are the most fundamental digital modulation techniques: * In the case of PSK, a finite number of phases are used. * In the case of FSK, a finite number of frequencies are used. * In the case of ASK, a finite number of amplitudes are used. * In the case of QAM, a finite number of at least two phases, and at least two amplitudes are used. In QAM, an inphase signal (the I signal, for example a cosine waveform) and a quadrature phase signal (the Q signal, for example a sine wave) are amplitude modulated with a finite number of amplitudes, and summed. It can be seen as a two-channel system, each channel using ASK. The resulting signal is equivalent to a combination of PSK and ASK. In all of the above methods, each of these phases, frequencies or amplitudes are assigned a unique pattern of binary bits. Usually, each phase, frequency or amplitude encodes an equal number of bits. This number of bits comprises the symbol that is represented by the particular phase. If the alphabet consists of M = 2Nalternative symbols, each symbol represents a message consisting of N bits. If the symbol rate (also known as the baud rate) is fS symbols/second (or baud), the data rate is NfS bit/second. For example, with an alphabet consisting of 16 alternative symbols, each symbol represents 4 bits. Thus, the data rate is four times the baud rate. In the case of PSK, ASK or QAM, where the carrier frequency of the modulated signal is constant, the modulation alphabet is often conveniently represented on a constellation diagram, showing the amplitude of the I signal at the x-axis, and the amplitude of the Q signal at the y-axis, for each symbol. d ASK. In all of the above methods, each of these phases, frequencies or amplitudes are assigned a unique pattern of binary bits. Usually, each phase, frequency or amplitude encodes an equal number of bits. This number of bits comprises the symbol that is represented by the particular phase. If the alphabet consists of M = 2N alternative symbols, each symbol represents a message consisting of Nbits. If the symbol rate (also known as the baud rate) is fS symbols/second (or baud), the data rate is NfS bit/second. For example, with an alphabet consisting of 16 alternative symbols, each symbol represents 4 bits. Thus, the data rate is four times the baud rate. In the case of PSK, ASK or QAM, where the carrier frequency of the modulated signal is constant, the modulation alphabet is often conveniently represented on a constellation diagram, showing the amplitude of the I signal at the x-axis, and the amplitude of the Q signal at the y-axis, for each symbol.

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Q: What is digital modulator?

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modulator

Modem = modulator-demodulator, and is a tool for tweaking an analog signal so that it can be used in a digital device.

Pulse position modulation can be analog or digital, it depends on the signal and/or the modulator used to obtain the modulation. If an analog signal is applied at the input of the modulator, the position of the pulse can assume an infinity of different timing states (the signal vary continuously) and hence an analog modulation is realised in PPM. On the contrary if the signal is digitized previously in a series of discrete states, the pulse at the output will have discrete timing interval (not continuosly). Then a digital modulation is obtained. If the signal is analog, but the modulator is digital, we will have again a number of finite state in output timing, and the PPM will be digital. To be noted that, if the number of steps in the digital modulator, is higher then the dinamic range required, the performance of the digital and analog PPM will be exactly the same. Cecking the front of the pulse of PPM with a digital oscilloscope capable of jitter measurament, we will see immediately if the position of the pulses will be continuosly variable or a number of discrete steps will be presented. We can then consider analog and digital PPM physically different.

Naitram Persaud has written: 'An FM modulator by direct digital synthesis'

A modem (modulator-demodulator)See below links.

A modulator-demodulator is more commonly known as a modem. It is a device that enables digital data to be transmitted over analog communication lines, such as phone lines.

Modulating. The word modem comes from Modulator/Demodulator

The Full Form of Modem is : Modulator-demodulator. It is used to convert analog signals to digital signal and viceversa

The full form of Modem is Modulator-demodulator. Modulation is process of converting the digital computer signals to analog telephone signals. Demodulation is the opposite conversion, analog to digital.

An analog or digital modulator can perform amplitude, frequency, and phase modulation. These modulators are commonly used in communication systems to modulate a carrier signal in order to transmit information.

it stands for modulator - demodulatorit modulates and demodulates a signal.ie converts it from digital to analogue so it can be transmitted through wire and on the other side it is converted back to digital so a computer can read it

Did you mean "modem"- If it is modem it stands for MODULATOR/DEMODULATOR. In simple terms something that converts digital signal to analogue and back