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What is digital modulation?


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Answered 2008-05-01 18:05:39

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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No modulation index for digital modulation .


presentation of analog digital hybrid modulation


1)digital modulation can easily detect and correct the noise. where as analog modulation has little complexity 2)security is more in digital modulation 3)digital modulated signal can traverse a long distance compared to analog modulation


How to Generate digital data for bpsk modulation?


The basic difference is that in analog modulation the modulating signal is analog signal and in digital modulation it is in digital form.


The Difference of two is only first digital has a transmission and second digital has modulation.....thats all....i think that's too clear ha...


Gordon Drury has written: 'Coding and modulation for digital television' -- subject(s): Digital modulation, Multiplexing, Digital television, Coding theory


—Analog digital hybrid modulation seeks the ways to eliminate the incoherent quantization noise component in digital communication, instead of conveniently making it minimal.


Analog is when audio or video is taken and translated into electronic pulses. Digital modulation is when audio or video is broken into binary codes and then transferred to the viewing device.


It is widely used, in various systems of modulation, to encode digital signals.


Kamilo Feher has written: 'Digital modulation techniques in an interference environment' -- subject(s): Digital modulation, Digital techniques, Radio noise, Signal processing


Delta modulation is not a type of quality conversion and runs on digital-to-analog, analog-to-digital. Differential pulse code modulation has a higher quality of conversion and runs on a 1-bit data stream.


There are 3 main types of digital pulse modulation:Pulse time modulation (PTM), somewhat similar to analog phase modulation.Pulse width modulation (PWM), the width of the pulse represents the signal.Pulse code modulation (PCM), serial transmission of binary bits forming numeric or character codes that represent the signal.All of these can be modulated on an RF carrier using any of the standard modulation techniques: AM, FM, Phase Modulation, etc. One advantage with AM digital pulse modulation techniques over AM analog is that the carrier can be 100% modulated, which cannot be done with analog, thereby allowing significant reductions in transmitter power without loss of coverage range. Sometimes FM digital pulse modulation techniques are referred to as Frequency Shift Keying (FSK). A very complex method of combining Phase Modulation and AM to increase the bit density of digital pulse modulation on an RF carrier is called Quadrature Amplitude Modulation (QAM).


because recieving hardwere is complex pm is used in digital synthesizers


Modulation may be defined as the process by which some characteristics of a signal called carrier is varied accordance with the instantaneous value of another signal called modulating signal. Types of Modulation: 1) Continuous Wave Modulation: ANALOG: AM, FM, PM DIGITAL : ASK, FSK, PSK 2) Pulse Modulation : ANALOG: PAM, PDM, PPM DIGITAL : PCM


Adaptive delta modulation is a analog-to-digital and digital-to-analog conversion technique which is primarily used for voice transmission data and can be used for multiple purposes.


The most fundamental difference, I would say, is that Amplitude Modulation (AM) is a kind of Analog Modulation Technique (the modulation is applied continuously in response to the analog information signal) where Amplitude Shift Keying is a type of Digital Modulation Technique ( an analog carrier signal is modulated by a discrete signal, 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 difference between pulse code modulation and delta modulation is that pulse code modulation is a method of encoding audio information digitally while delta modulation is a method that converts analog to digital signal.


Delta modulation is extremely important for high-tech lives that humans live today. Delta modulation is basically analog to digital and digital to analog signal providers, allowing for radio communication devices such as TV remotes.


i refered modulation is the sequence of message in to analog symbol( Simon haykin ,communication systems),,but i am not clear with this,couul u pls clarify?


In Pulse Amplitude Modulation, amplitude of pulse varies with signal. Theoretically in analog modulation there infinite levels of amplitudes or continuous amplitude. Two level PAM is digital modulation where only 2 number of levels are there. Thus signal is quantized to two discrete levels.


Analog Pulse modulation is discreet in time but the formation is transmitted in continuous form. In digital pulse modulation, not only the time axis is discreet but the information is also in digital form. Examples of Analog PM are PAM and PTM i.e pulse amplitude and pulse time modulations respectively. Examples of Digital PM are PCM and PDM i.e pulse code and pulse delta modulations respectively.


Frequency shift keying in digital communication and Frequency modulation in analog communication..........



BPSK Modulation can be done by using a multiplier. Digital data must be multiplied with the carrier frequency. In matlab simulink use a multiplier block to one input apply a sinusoidal generator & to the other a Pulse generator



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