Pulse code modulation pcm and its derivatives, quantising noise, and examples digital communication techniques ask, fsk, psk, qpsk, qam, and mary qam. Pulsecode modulation pcm is a method used to digitally represent sampled analog signals. Performance of pulse code modulation phase modulation receivers with nonideal data l. Pulse code modulation is used in compressing the data that is why it is used in storing data in optical disks like dvd, cds etc. In fact, the pulsecode modulation is quite complex as compared to the analog pulse modulation techniques i. Pulse code modulation is the heart of technology in communications in. But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal. Storage oscilloscope is desired for satisfactory observation of pcm wave forms 4. Differential pulse code modulation dpcm circuit working. Each one of these digits, though in binary code, represent the approximate amplitude of the signal sample at that instant.
Pulse code modulation modulation is the process of varying one or more parameters of a carrier signal in accordance with the instantaneous values of the. The purpose of this lab is to introduce you to pulse code modulation and demodulation. It explains what is modulation and classification of modulation. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. Then the msd demodulation under low snr synchronous implementation.
We can also get back our analog signal by demodulation. For the baseband digital transmission, pulse amplitude modulation pam is the most efficient in terms of power and bandwidth utilization. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Pulse code modulationpcm is different from the other forms of pulse modulation studied so far, pcm also uses sampling techniques, but it differs from the others in that it is a digital process. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. Radio waves can carry audio, video, and digital information over great distances by using changes in a carrier waves amplitude, frequency, or phase to represent the information being transmitted. Introduction to modulation and demodulation free download as powerpoint presentation. Multiple choice questions and answers on modulation and demodulation. Performance of pulse code modulation phase modulation.
Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. The pulse code modulator technique samples the input signal xt at a sampling frequency. Pulse modulation techniques pam, pwm, ppm, pcm pulse. Demodulation is the reverse process to modulation to recover the message signal mt or dt at the receiver. It is the base for all digital modulation techniques and it is simple process for both modulation and demodulation technique.
Capacityapproaching codes demodulation line coding modem anm pom pam. Amplitude modulation is defined as the process in which the amplitude of the carrier wave ct is varied about a mean value, linearly with the baseband signal. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Modulation, analog modulation, digital modulation, am,fm. One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif. Pam, pwm and ppm, in the sense that the message signal is subjected to a great number of operations. Single bit pcm output at different line speed clock.
Explain generation and demodulation of pam, ppm and pwm. B audio visual application format specifications for bdrom pdf. Demodulation is the opposite process of modulation. The ramp will attain different heights in each cycle since the widths are different and the heights attained are directly proportional to the. Modulation and demodulation medium, it would be dif. Study of pcmfm telemetry sequence soft demodulation. Types of modulation techniques am, fm, pm, pam, pwm, ppm. Sound transmission in air has limited range for the amount of power your lungs can generate. Principles of communication modulation tutorialspoint. Pulse code modulation pcm is a digital pulse modulation technique. Pulsecode modulation pcm is a technique that aims at representing an. To analyze a pcm system and interpret the modulated and demodulated waveforms for. Of gaza 2010 figure 7 encoding process demodulation process to produce.
That is, there are only two possible states, represented by logic 1 high and logic 0 low. Design and simulation of pulse code modulation multiplexing. The pulse may take any real voltage value that is proportional to the value of the original waveform. Linear modulation we are typically interested in locating a messagesignal to some new frequency location, where it can be ef. Qam transmitter implementation qam is widely used method for transmitting digital.
Pulse code modulation pcm pcm is commonly used for digital audio windows pcs, cds, digital telephony pcm. Pulse code modulation pulse code modulation pcm is a digital scheme for transmitting analog data. Then the signal will pass through r6 and feedback to pin 9. In pulse code modulation, the message signal is represented by a sequence of coded pulses.
Differential pulse code modulation is a technique of analog to digital signal conversion. You can see the classification of pulse modulation to see the classification of all types of modulations including pulse. This is true no matter how complex the analog waveform happens to be. The rf and if sections of the receiver are common to a wide range of system types, but the demodulator is specific to the type of modulation used. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am to make the carrier carry the radio broadcast. To extend the range your voice can reach, we need to. In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. This technique samples the analog signal and then quantizes the difference between the sampled value and its predicted value, then encodes the signal to form a digital value.
In addition to reading the questions and answers on my site, i would suggest you to check the following, on amazon, as well. Pulsecode modulation or pcm is known as a digital pulse modulation technique. Analog modulation delas with the voice, video and regular waves of base band signals. Quadrature amplitude modulation qam pam signals occupy twice the bandwidth required for the baseband transmit two pam signals using carriers of the same frequency but in phase and quadrature demodulation.
The goal of this experiment is to become familiar with fm modulation and demodulation. There are two types of modulation analog and digital. Implementation of fsk modulation and demodulation using. As the resultant is a coded pulse train, this is called as pcm. Implementation of fsk modulation and demodulation using cd74hc4046a mahendra patel standard linear and logic abstract in telecommunications and signal processing, frequency modulation fm is encoding of information on a. Multiple choice questions and answers on modulation and. In digital modulation, an analog carrier signal is modulated by a discrete signal. Pcm is in binary form,so there will be only two possible states high and low0 and 1. The input sequence b k consists of binary digits bits 1 and 0 with a bit duration of t b and a bit rate of r b 1 t b. As part of performing this lab you will investigate the digitization of an analog signal, the reconstruction of the original analog signal, the measurement of quantizing noise. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors.
It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. This article discusses about pulse code modulation and demodulation processes in detail with all its steps, sampling, quantization and coding. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet. Analog signal such as voice or music is converted to discrete samples and then quantized to bits after quantization, companding compressing and expanding takes place. Pulse code modulation file exchange matlab central. Terms like diode detector, synchronous detector and product detector are widely used. This video lecture discusses different types of modulation techniques. Million communications systems and research section in pulse code modulationphase modulation systems, the nonreturntozero or biphase data are directly modulated onto the residual carrier.
Parallel to serial conversion by varying the line speed clock. This sampled variable amplitude pulse is then digitalized by the analog to digital converter. It is the standard form of digital audio in computers, cds, digital telephony and other digital audio. Three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Switch to qam modulation you can proceed with hilbert. Pulse code modulation pcm is a method of converting an analog signal into a digital signal ad. Modulation techniques pwm and pulse code modulation. The term detection is the older term dating back to the early days of radio. Introduction to modulation and demodulation modulation. This is the code for pulse code modulation, where u can observe for n bit pcm system. Coded modulation pcm is a form of modulation where there is no carrier, so.
Telo, chapter 9, modulation, demodulation, signal sampling 2 as an example let us describe fet amplitude modulator. Fm modulationdemodulation with pll general description package outline njw2307 is a fm modulation demodulation ic for audio signal in full duplex communication that operates from 3. The original waveform amplitude is quantized with a resulting loss of. The analog signal will pass through r5 and input to pin 10, which is the inverting input terminal. Pcm is even used in the database management systems. A brief discussion about pulse code modulation and demodulation. Ask is the general term referring to modulation by changing the level of the rf carrier.
In addition to audio signal, it can also be used in data pulse. Digital modulation and demodulation fsk,psk,bpsk,qpsk techniques. In a pcm stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. Instead of a pulse train, pcm produces a series of numbers or digits, and hence this process is called as digital. Pulse code modulation is a method that is used to convert an analog signal into a digital signal, so that modified analog signal can be transmitted through the digital communication network. No information is lost, but the energy is redistributed in the frequency domain. Abstract pulse code modulation multiplexing pcmm is a part of transmitting multi. We will consider the three basic digital data modulation methodsask, fsk, and psk. Pulse amplitude modulation an overview sciencedirect. In digital modulation, the modulation technique used is pulse code modulation pcm where the analog signal is converted into digital form of 1s and 0s.
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