Frequency division multiplexing, fdma amplitude modulation and demodulation. The digital modulation techniques are amplitude shift keying ask, frequency shift keying fsk and phase shift keying psk. As we mentioned before, well use dsbc modulation because of its ease in demodulation. To understand the theory of pcm demodulation circuit. These methods contrast with amplitude modulation, in which the amplitude of the carrier wave varies, while the frequency and phase remain constant. To study amplitude demodulation by linear diode detector 3. The prediction may not be exact but it is very close to the actual sample value. Compare pulse code modulation and delta modulation. Phase modulation pm pm or phase modulation is the process of varying the instantaneous phase of carrier signal accordingly with instantaneous amplitude of message signal. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications.
Pulsecode modulation pcm is a method used to digitally represent sampled analog signals. In general, radio carrier generates at the transmission side of a telecommunication link. A signal is pulse code modulated to convert its analog information into a binary sequence, i. Of them all, the digital modulation technique used is pulse code modulation pcm. We can improve pcm by transmitting samples of d dtmtand integrating to. This type of digital pulse modulation technique is called as differential code modulation dpcm. Qpsk modulation and demodulation with matlab and python. Modulation, in electronics, technique for impressing information voice, music, picture, or data on a radiofrequency carrier wave by varying one or more characteristics of the wave in accordance with the intelligence signal. The result is that samples are highly correlated, so the previous sample is a good prediction of the next.
In this video, i have explained basics and advantages of dpcm differential pulse code modulation by following outlines. Pwm, or pulse width modulation is a powerful way of controlling analog circuits and systems, using the digital outputs of microprocessors. There are many modulation techniques, which are classified according to the type of modulation employed. Analyze single bit delta modulated pcm output, integrator output at the demodulator. Pulsecode modulation or pcm is known as a digital pulse modulation technique. Delta, adaptive, sigma delta modulator demodulator. Analyze the final delta demodulated output with second order low pass butterworth filter.
Pulse code modulation pcm is a digital representation of an analog signal that takes samples of the amplitude of the analog signal at regular. In fact, the pulsecode modulation is quite complex as compared to the analog pulse modulation techniques i. To perform the amplitude modulation and demodulation using am kit. This is further developed as delta modulation dm, which will be discussed in subsequent chapters. Pulse modulation can be categorized broadly into two. A brief discussion about pulse code modulation and demodulation.
A similar approach is then taken for developing models for multiple phase shift keying mpsk, minimum shift keying msk, and frequency shift. The phase locked loop pll as a demodulator will be studied in the next section. It is another type of ptm, where the amplitude and width of the pulses are kept constant and only the position of the pulses is varied. Modulation allows us to transmit multiple signals in the same medium i. Qam is composed of two independent pulse amplitude modulation pam baseband modulations placed on. Modulation and demodulation medium, it would be dif. Demodulationtechniques of pulse analog modulation is discussed. It is a modulation system in which the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the signal at the instant of sampling. The example goes on to quantize the training data itself. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. Pcm or pulse code modulation is a method to digitally represent sampled, analog signals, here its used in, requantizing the intensity values of an image.
In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Here is the circuit used for modulation and its simulation. Pulse code modulation pcm frequency modulation fm has been the most popular telemetry modulation since around 1970. The output of a pcm will resemble a binary sequence. Pam, pwm and ppm, in the sense that the message signal is subjected to a great number of operations. Then inner products dot products are 1 1 0 can interpret inner product as projection of vector 1 v1 onto vector 2 v2in other words, inner product of v1 and v2 tells us how much of vector 1 is there in the direction of vector 2.
To perform the pcm encoder and decoder and plot the characteristic of output wave form. Pulse code modulation pcm is a digital scheme for transmitting analog data. The amplitude of the carrier remains constant phase modulation pm another form of analog modulation technique which we will not discuss. Pulse code modulation pcm watch more videos at comvideotutorialsindex.
Circuit needed for fm modulation and demodulation is bit complicated than am. First, just consider a simple example of throwing a paper for a much far distancecould u do that with ease. This post discusses digital modulation techniques ask, fsk and psk. One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif. The differential pulse code modulation works on the principle of prediction. The discussion then moves to binary phase shift keying bpsk and shows how this simpler format is modeled using the generic quadrature modulation models. Study and analysis of pulse code modulation and demodulation. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. He described the theory and advantages, but no practical application resulted. You will find here the basic difference between digital modulation and analog modulation. Differential pulsecode modulation dpcm is a signal encoder that uses the baseline of pulsecode modulation pcm but adds some functionalities based on the prediction of the samples of the signal. So, for this image, if we apply a 1 bit per pixel uniform quantizer, here is the result we obtain.
Information is conveyed by modulating some parameter of the pulses with a set of discrete instantaneous samples of the messages signal. Pulse amplitude modulation is the basic form of pulse modulation. The pcmfm method could also be called filtered continuous phase frequency shift keying cpfsk. 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. To understand the operation theory of pulse coded modulation pcm. 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. Differential pulsecode modulation image compression. Nov, 2017 pulse code modulation pcm is a type of pulse modulation technique. May 12, 2017 pulse code modulation pcm is a digital representation of an analog signal that takes samples of the amplitude of the analog signal at regular intervals.
Study and analysis of parallel to serial conversion by varying the line speed clock. Differential pulse code modulation section overview. Pulse code modulation modulation is the process of varying one or more parameters of. Pulse code modulation is used in music play back cds and also used in dvd for data storing whose sampling rate is bit higher. Terms like diode detector, synchronous detector and product detector are widely used. The goal of this experiment is to become familiar with fm modulation and demodulation. We can also get back our analog signal by demodulation. Matlab program for pulse code modulation m file matlab. Ee4512 analog and digital communications chapter 6 the dsbsc am coherent receiver has a bandpass filter centered at f c and with a bandwidth of twice the bandwidth of st because of the lsb and usb. In a pcm stream, the amplitude of the analog signal is sampled regularly at uniform intervals. 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. Typical pcm communication system pulsecodemodulationanddemodulation. There are different types of modulation and so are demodulators.
The pcm fm method could also be called filtered continuous phase frequency shift keying cpfsk. The complete waveform simulation for the aforementioned qpsk modulation and demodulation is given next. Pulse code modulation pcmfrequency modulation fm has been the most popular telemetry modulation since around 1970. Apr 03, 2017 pulse code modulation demodulation trainer duration. By further processes, we can restore the original analog waveform. Phase modulation is the basis for many digital modulation formats, in which a modulated signal is divided into inphase 0. 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. Difference between modulation and demodulation compare the. Modulation, analog modulation, digital modulation, am,fm. Pulse code modulation pcm sampling and quantization of.
Pam, pwm and ppm modulations belong to analog modulation and the pcm modulation. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. Phase modulation and demodulation techniques are more complex than modulation and demodulation based on amplitude and frequency. The waveforms, definition and basic concepts of each digital modulation techniques are discussed here. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i.
Pulse code modulation is the procedure where each of the levels of an analog signal is assigned a value closest to a quantizer level used to quantize the signal. Modulation is defined as the process by which some characteristics of a carrier signal is varied in accordance with a modulating signal. The simulation involves, generating random message bits, modulating them using qpsk modulation, addition of awgn channel noise corresponding to the given signaltonoise ratio and demodulating the noisy signal using a coherent qpsk receiver. A form of modulation in which a pulse train is used as the carrier. This zerocrossingcounter demodulator will be modeled in the latter part of the experiment and used for demodulation low frequency fm. There are various forms of modulation, each designed to alter a. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. To understand the operation theory of pcm demodulator. But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal. Each channel sharing scheme a set of basis vectors. The operation theory of pcm demodulation figure 5 is the block diagram of pcm demodulation. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal.
Pcm is in binary form,so there will be only two possible states high and low0 and 1. Pcm, dpcm, cvsd modulator and demodulator scientech2802. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Modulation techniques pwm and pulse code modulation. This video also includes quantization in pcm and sampling of the signal. In a pcm stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to. Basics and advantages of dpcm differential pulse code. Pulse amplitude modulation pam theory of and its applications. Time division multiplexing 1 be ece 5th sem labtelugu version duration. Notice that the mean square distortion here is much less than the distortion in the previous example. Defining the term, we can say that pwm is the way we control a digital signal simulating an analog one, by means of altering its state and frequency of this.
Jul 19, 2011 the key difference between modulation and demodulation is that modulation is to transfer the message signal by adding it with the carrier signal while demodulation is the process of filtering out the actual message signal from the carrier signal. During transmission, the pcm signal is hard to avoid the noise interference. The spectral efficiency of the transmitted ask waveform is also a consideration and the m. Before we study in detail about pam lets know the concepts of modulation. Study and analysis of single bit pcm output by varying the sampling frequency. Delta modulation and demodulation delta modulation dm is a modulation scheme in which an incoming message signal is over sampled i. Source called v1 generates the message to be transmitted. Curriculum theory the operation theory of pcm modulation pcm modulation is a kind of source coding. Encoding information theory source coding theorem channel coding theorem. The circuit designed is simple, easy to understand and implement.
Essentially an amplitude modulated wave consists of a radio frequency carrier a sine wave at one frequency, typically in the radio frequency portion of the spectrum. Multiplexing of signals can also be done using pulse code modulation. Single bit pcm output at different line speed clock. This is mostly because audio has a large dynamic range and is weighted towards lower frequencies. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Introduction and overview of digital communication system. If the input is a continuoustime analog signal, it needs to be sampled first so that a. The term detection is the older term dating back to the early days of radio.
Previous years gate questions on random theory part 2. Pcm is in binary form,so there will be only two possible states high and low 0 and 1. Therefore, before the pcm signal sends into the pcm demodulator, we utilize a comparator to recover the signal to the original level. Frequency modulation and phase modulation are the two complementary principal methods of angle modulation. To understand the theory of pcm modulation circuit. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal.
Principles of communication modulation tutorialspoint. Here, the difference between the signals is encoded based on its magnitude. However, they provide the benefit of higher data rates for the amount of bandwidth consumed. To study sampling and reconstruction of pulse amplitude modulation system 6. The pulsecode modulator and demodulator were designed with. Pulse code modulation pcm is a type of pulse modulation technique. Amplitude modulation am, demodulation and their circuit. A modulation technique that allows variation in the position of the pulses according to the amplitude of the sampled modulating signal is known as pulse position modulation ppm.
To understand the operation theory of pcm demodulation circuit. To recover the original signal from the sampled data, a demodulator can apply the procedure of modulation in reverse. The sampled analog data is changed to, and then represented by, binary data. Pulse code modulation can be used in storing the data. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. Another method of pcm that can be confused with delta modulation is the d differential pcm. Frequency modulation fm frequency modulation is the process of varying the frequency of a carrier wave in proportion to the amplitude of a baseband signal. The basic theory and equations behind amplitude modulation are relatively straightforward and can be handled using straightforward trigonometric calculations and manipulation. The purpose of this lab is to introduce you to pulse code modulation and demodulation. The value of the present sample is predicted from the past samples. Storage oscilloscope is desired for satisfactory observation of pcm wave forms 4. This above block diagram describes the whole process of pcm.
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