Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. We can also get back our analog signal by demodulation. It is an analog signal thats sampled at uniform intervals and converted to a digital binary number. The application of the heterodyne principle to modulation is shown schematically in figure 143. With pcm, the analog signal is sampled and then converted to a serial nbit binary code for transmission. To ensure accurate reproduction of an analog signal. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Communications contents introduction to communication systems analogue modulation am, dsbsc, vsb, ssb, fm, pm, narrow band fm, pll demodulators, and fll loops sampling systems time and frequency division multiplexing systems, nyquist principle, pam, ppm, and pwm. The implementation of the pcm demodulator is similar to pcm modulation, which is ic cw6694 from conwise. Demodulation is extracting the original informationbearing signal from a carrier wave. Differential pulse code modulation is a technique of analog to digital signal conversion.
The signal output from a demodulator may represent sound an. In any radio that is designed to receive frequency modulated signals there is some form of fm demodulator or. Linear modulation one scheme is to simply square the received dsb signal x2 r. The transmitter section of a pulse code modulator circuit consists of sampling, quantizing and encoding, which are performed in the.
Short for pulse code modulation, pcm was first developed by alec reeves, a british engineer in 1937. The technology was originally developed for telephone communication system. We will consider the three basic digital data modulation methodsask, fsk, and psk. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. Note, when a modulator is set up, v dc is fixed at a particular value. Communication is a process by which information is exchanged between. Pass the recovered carrier phase into the demodulator model where it can be used directly as the reference phase. It is another type of ptm, where the amplitude and width of the pulses are kept constant and only. Using matlab mfile and simulink to implement fm modulation and. 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. Principles of noise random variables, white noise, shot, thermal and flicker noise, noise in cascade amplifiers pulse. Modulation and demodulation medium, it would be dif. Pulsedensity modulation, or pdm, is a form of modulation used to represent an analog signal with a binary signal.
Study and analysis of parallel to serial conversion by varying the line speed clock. The number of samples per second, ranging from 8,000 to 192,000, is usually. The sampled analog data is changed to, and then represented by, binary data. Pcm is in binary form, so there will be only two possible states high and low0 and 1. 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. A brief discussion about pulse code modulation and demodulation. There are many types of modulation so there are many types of demodulators. Fm modulation and demodulation electrical and computer. Content introduction what is modulation types of modulation amplitude modulation modulation index amplitude demodulation circuit diagram about project conclusion 3.
Therefore, before the pcm signal sends into the pcm demodulator, we\r utilize a comparator to recover the signal to the original level. 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. Pulse code modulation pcmfrequency modulation fm has been the most popular telemetry modulation since around 1970. Quadrature amplitude modulation qam pam signals occupy.
The meaning of source coding is the conversion from analog signal to digital signal. To understand the theoretical foundations for angle modulation as well as frequency modulation fm and demodulation. Request pdf digital phase modulation and demodulation digital phase modulation is a class of power and bandwidthefficient modulations widely used in telecommunications. Each channel sharing scheme a set of basis vectors. Pulse amplitude modulation is the basic form of pulse modulation. Build simple fm demodulator by using frequency discriminator 2. Performance of pulse code modulation phase modulation. A brief discussion about pulse code modulation and. Digital communication delta modulation tutorialspoint. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal.
In the following illustrations we will have a fixed message, v m cos m t and vary v dc to obtain different types of double sideband modulation. Pcm is in binary form,so there will be only two possible states high and low 0 and 1. Implementation of fsk modulation and demodulation using. Pulse code modulation is a method that is used to convert an analog signal into a digital signal so that a modified analog signal can be transmitted through the digital communication network. This application report discusses logiclevel implementation of fsk modulator and demodulator using a pll device hchct4046a. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. 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. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors.
Frequency modulation is a form of modulation, which represents information as. A demodulator is an electronic circuit or computer program in a softwaredefined radio that is used to recover the information content from the modulated carrier wave. Pcm modulation is commonly used in audio and telephone transmission. Phase shift keying modulation and demodulation trainer this trainer provides an opportunity to study carrier modulation of digital signals. There are various carrier modulation techniques required for transmission of digital information. Parallel to serial conversion by varying the line speed clock. In early days, the communication system is mostly using the analog signal to transmit signals.
The hchct4046a, pll with vco is a highspeed cmos ic designed for use in generalpurpose pll applications, including frequency modulation, demodulation, discrimination, synthesis, and multiplication. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Digital phase modulation and demodulation request pdf. Before we study in detail about pam lets know the concepts of modulation. Ask is the general term referring to modulation by changing the level of the rf carrier.
Pcm and delta modulation cse 32, fall 2010 instructor. Phase shift keying psk is one such modulation scheme. Fm demodulator circuits are found in any receiver that uses fm. The computational expense of this approach depends upon the particular modulation format and demodulation algorithm being implemented. There are many modulation techniques, which are classified according to the type of modulation employed. In fact, the pulse code modulation is quite complex as compared to the analog pulse modulation techniques i. Pam, pwm and ppm, in the sense that the message signal is subjected to a great number of operations. The goal of this experiment is to become familiar with fm modulation and demodulation.
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. Each code has the same number of bits and requires the same length of time for transmission. The pulse code modulation process is done in three steps sampling, quantization, and coding. The traditional modulation methods for aeronautical telemetry are frequency modulation fm and phase modulation pm. The fft core is clocked faster than the baseband data so that it can be shared, for instance, for fdd operation or by multiple antennas in mimo systems. Pdf the proposed model of pulse code modulation encoder for. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. Modulation translates a signal from its baseband to the operating. Am modulation and demodulation with circuit and output.
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. Fm modulation demodulation with pll general description package outline njw2307 is a fm modulation demodulation ic for audio signal in full duplex communication that operates from 3. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. There are different types of modulation and so are demodulators. Following is the block diagram of a delta modulator. Es442 lab 6 frequency modulation and demodulation objective 1. The type of modulation is determined by the modulation depth, which for a fixed mt depends on the dc offset, v dc. First of all is the lowpass filter, which is used to remove the noise in the audio signal. Pulse code modulation or pcm is known as a digital pulse modulation technique. First of all low pass filteris the, which is used to remove the noise in the audio signal. Digital modulation relies on digital signal processing, such as digitaltoanalog converters dacs at a receiver and analogtodigital converters adcs at a transmitter to transform analog information e. Pdf in this paper, we have developed a hardwarebased model of pulse code modulation pcm system for voice frequencies. To implement the simulink models for fm including a basic sinusoid and a multimedia file music to analyze each signal in time and frequency domains.
Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. Single bit pcm output at different line speed clock. 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. Modulation for analog communication yao wang, 2006 ee3414. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. In this article, you will find the study notes on types of modulation and demodulation which will cover the topics such as introduction to communication systems, amplitude and demodulation, classification of am, angle modulation and demodulation, generation of fm and pulse modulation. Figure 1 shows the block diagram of the top level integration of ofdm modulation and demodulation.
Am modulation and demodulation with circuit and output 1. Figure 2 lists the io ports of the modulation and demodulation modules. Storage oscilloscope is desired for satisfactory observation of pcm wave forms 4. 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. In addition to audio signal, it can also be used in data pulse. 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.
Pulse code modulation pcm is a method of converting an analog. Pam is used as an intermediate form of modulation with psk, qam, and pcm, although it is seldom used by itself. The pcmfm method could also be called filtered continuous phase frequency shift keying cpfsk. Pcm, dpcm, cvsd modulator and demodulator scientech2802. Using matlab mfile and simulink to implement fm modulation and demodulation. To implement the simulink models for fm including a basic sinusoid and a multimedia file music to analyze each signal in time and frequency domains using time scope and spectrum analyzer. Quadrature amplitude modulation qam pam signals occupy twice the bandwidth required for the baseband transmit two pam signals using carriers of the. 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 pulse code modulation and demodulation. Pulse code modulation pcm is a method used to digitally represent sampled analog signals. Understand the principle of amplitude modulation know how to modulate a signal to a certain frequency know how to demodulate a signal back to the baseband can write the equation and draw block diagram for both modulation and demodulation can plot the signal spectrum after modulation and demodulation.
Introduction to modulation and demodulation modulation. Pulse amplitude modulation pam theory of and its applications. Designing and analyzing frequency modulator and demodulator objective. Of them all, the digital modulation technique used is pulse code modulation pcm. 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. Delta modulation is a simplified form of dpcm technique, also viewed as 1bit dpcm scheme. Telo, chapter 9, modulation, demodulation, signal sampling 1 9. Therefore, before the pcm signal sends into the pcm demodulator, we\r\nutilize a comparator to recover the signal to the original level. The main advantage is the pcm modulation only needs 8 khz sampling frequency to maintain the original quality of audio. Digital modulation and demodulation fsk,psk,bpsk,qpsk techniques. Differential pulse code modulation dpcm circuit working. In a pcm stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to. As the sampling interval is reduced, the signal correlation will be higher.
166 1422 178 86 1042 1272 647 571 621 370 239 1248 936 657 198 983 457 541 710 973 733 12 807 360 1377 1076 98 549 1253 1405 914 39 421