Ee4512 analog and digital communications chapter 8 chapter 8 analogtodigital and. The total bandwidth required for am can be determined from the bandwidth of the audio signal. Types of modulation amplitude modulation in this modulation, the amplitude of the carrier signal is modified to reflect the analog data. Amplitude modulation is implemented by means of a multiplier. Digitaltoanalog conversion is the process of changing one of the characteristics of an analog signal based on the information in digital data. Analog to analog conversion can be done in three ways. Output sine wave tuning has 32bit frequency resolution, 14bit phase resolution, and 10bit amplitude resolution. In digital modulation, an analog carrier signal is modulated by a discrete signal. By analyzing the cyclostationary nature of pulseamplitude modulation pam systems, two methods of quantization are proposed fixed and adaptive.
In this paper, a full analysis is presented on digitaltoanalog conversion for pulse amplitude modulated pam systems. The government assigns a narrow bandwidth to each radio station. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet. Digital to analog encoding modulation techniques ask. Analog modulation refers to the process of transferring digital low frequency baseband signal, like digital bitstream from computers over a higher frequency carrier signal such as a radio frequency band. Frequency versus amplitude modulation l frequency modulation fm l most popular analog modulation technique l amplitude of the carrier signal is kept constant constant envelope signal, the frequency of carrier is changed according to the amplitude of the modulating message signal. Analogtoanalog conversion, or modulation, is the representation of analog information by an analog signal. Amplitude shift keying amplitude shift keying is a technique in which carrier signal is analog and data to be modulated is digital. This conversion is also known as analog modulation. Analog to analog conversion techniques myreadingroom.
Phase modulation is a subcategory of frequency modulation, whereby the phase angle of the carrier envelope is modified in response to changes in the signal. Pam systems operate by passing informationbearing pulses through pulse. Amplitude modulation is a modulation conversion technique that is used mainly for the communication of data over the carrier wave. Analog modulation in analog modulation, the modulation is applied continuously in response to the analog information signal. Analog signal is converted into digital signal by using a digital code. Modulation is needed if the medium is bandpass in nature or if only a bandpass channel is available to us. Am radio the bandwidth of an audio signal speech only is 5 khz. Communication systemsanalog modulation introduction. Analog to digital conversion an overview sciencedirect. Us6191722b1 pulse width modulation digital to analog. Thus, it is possible to display up to 16,7 million different shades of color with multi color laser systems systems with more than one laser source color.
We can see 3 parameters that can be changed in this sine wave to send information. Phase modulation is also a technique that is been used for doing encoding in of analog signal into analog data using a digital transmission coding scheme that lie in the wide range of latest technologies like wifi,gsm and satellite television. The process of generating pulses of zero width and of amplitude equal to the instantaneous amplitude of the analog signal. The figure shows the relationship between the digital information, the digitaltoanalog modulating process, and the resultant analog signal. Analogtoanalog conversion can be accomplished in three ways. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Analog to analog conversion modulation geeksforgeeks. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion.
Analog to analog modulation in data communication dc10. Modulation process of varying one or more properties of a periodic waveform carrier signal, with a modulating signal that contains information to be transmitted. A pulse width modulation digital to analog converter includes a pulse generator, a combiner and a filter. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. Aspects of digitaltoanalog conversion amplitude shift keying. Ee4512 analog and digital communications chapter 6 the baseband power spectral density psd spectrum of. Analog modulation article about analog modulation by the. This term is called the amplitude, and changing it is called amplitude modulation am. It is a process by virtue of which a characteristic of carrier wave is varied according to the instantaneous amplitude of the modulating signal. These modulation techniques are continuous wave modulation amplitude modulation,frequency modulation,phase modulation and pulse modulations pam, pwm, ppm, pcm. Analogtoanalog conversion analogtoanalog conversion, or analog modulation, is the representation of analog information by an analog signal. Chapter 6modulation techniques shandong university.
In this modulation, the amplitude of the carrier signal is modified to reflect the analog data. The predetection part of an angle modulation receiver is the same as for amplitude modulation. Chapter 8 analogtodigital and digital to analog conversion. Introduction pulseamplitude modulation pam is a common transmission method used for digital communications. Analogtoanalog conversion, or analog modulation, is the representation of analog information by an analog signal. Types of modulation techniques am, fm, pm, pam, pwm, ppm. Angle cw modulation with noise in the analysis of pm and fm systems, demodulation will be represented by yt. Now consider the case of a signal with analog modulation. Analog to analog conversion amplitude modulation 1. Here we will discuss all types of pulse modulation techniques i. The continuous analog signal st is a baseband signal with the information content voice or music to be transmitted. Frequency modulation the frequency of the carrier signal is proportional to the modulating. Multichannel dds enables phasecoherent fsk modulation.
The simulink simulation uses the dsb am modulation block and the sum of three sinusoids source. An am radio station needs at least a minimum bandwidth of 10 khz. The amplitude of analog carrier signal is modified to reflect binary data. The signal becomes discrete both in amplitude and time. Mt031 tutorial, grounding data converters and solving the. So lets start with pulse amplitude modulation pam here we will see the definition of pulse amplitude modulation and waveform of pulse.
Hence info is carried in the phase or frequency of the carrier. The binary signal when modulated gives a zero value when the binary data represents 0 while gives the carrier output when data is 1. Phase modulation is used in many transmission applications, notably wifi and satellite tv. This modulation is generally needed when a bandpass channel is required. Digitaltoanalog conversion of pulse amplitude modulated. In pulse modulation, the signal is translated to a series o. Analog modulation definition of analog modulation by the. This set of data communication and networking multiple choice questions and answers mcqs focuses on digital to analog to encoding modulation techniques amplitudeshift keying ask frequencyshift keying fsk phaseshift keying psk quadrature amplitude modulationqam. Amplitude modulation frequency modulation phase modulation analogtoanalog conversion. Qam is the most efficient of these options and is the mechanism commonly used today see figure 5. If you continue browsing the site, you agree to the use of cookies on this website.
Digital modulation in somewhat similar to the analog modulation except base band signal is of discrete amplitude level. The pulse generator receives an nbit digital word, partitions the input digital word into a plurality of subwords, and produces a plurality of periodic pulse width modulated waveforms, each waveforms duty cycle and amplitude being representative of one of the plurality of subwords. In this particular topic you have learned the two types of conversion. What is analog pulse amplitude modulation and digital. Independent control of each channels frequency, phase, and amplitude allows the devices to correct for systemrelated mismatches.
In the show laser industry analog modulation defines the ability of a laser source to dim the output power of the laser beam, which means that the output power can be adjusted without stepping. Analog modulation is required when bandpass is used. This is the mcqs in analog transmission from book the data communications and networking 4th edition by behrouz a. Digitalto analog conversion bit rate and baud rate carrier signals ask fsk psk qam overview of lecture 17. Chapter 5 analog transmission kasetsart university. It is a method of encoding and transmitting data through a certain type of signal that can be deciphered at the receiving end. Analogto analog conversion amplitude modulation am frequency modulation fm phase modulation pm analog to analog conversion. In the analog transmission of digital data, the baud rate is less than or equal to the bit rate.
Analogtodigital conversion adc can be viewed as imposing a grid on a continuous signal fig. It is obvious that the grid must be sufficiently fine and must cover the full extent of the signal to avoid a significant loss of information. Analog communication basics, reference books, pdf, viva. Modulation, analog modulation, digital modulation, am,fm. First off, you have to understand what modulation refers to. Dclec17 analog to analog modulation am broadcasting.
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