Pdf 4amplitude modulator and demodulator circuits appi t. The original waveform amplitude is quantized with a resulting loss of information. Demodulation of pam for demodulation of the pulse amplitude modulated signal, pam is fed to the low pass filter as shown in fig3 below. A two bit modulator pam4 will take two bits at a time and will map the signal amplitude to one of four possible levels, for example. In ppm modulation technique the power required for transmitting individual pulses are constant, but synchronization of transmitter and receiver are required. Quadrature amplitude modulation qam pam signals occupy. Remote controlled cars, planes, trains use pulse code modulations. A demodulator sometimes detector or demod is a device that performs demodulation, the inverse of modulation. There is a simple pulse modulation technique called pulse amplitude modulation pam which is proved to be more power efficient than the pwm and consumes constant power for individual pulses. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Ask fsk psk modulation digital modulation techniques amplitude, frequency and phase shift keying duration. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave.
Pulse amplitude modulation pam linkedin slideshare. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. Digital demodulator of the quadrature amplitude modulation. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. Pulse amplitude demodulation peak detection is used to detect pam.
The depth of modulation can be varied using the variable knob provided at a. Pulseamplitude modulation, acronym pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. The following gives implementation of amplitude modulation demodulation double. Pulse modulation may be used to transmitting analog information, such as continuous speech signal or data. It is another type of ptm, where the amplitude and width of the pulses are kept constant and only. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. To study sampling and reconstruction of pulse amplitude modulation system. Modulator for testing demodulator demodulator simulate 8pam comm. 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. Pulse amplitude modulation has some applications, but it is not used by itself in data communication. The goal of this experiment is to become familiar with fm modulation and demodulation. The pulse amplitude modulated signal, will follow the amplitude of the original signal, as the signal traces out the path of the whole wave. Pulse amplitude modulation pam is the transmission of data by varying the amplitude s voltage or power levels of the individual pulses in a regularly timed sequence of electrical or electromagnetic pulses. Fm demodulator circuits are found in any receiver that uses fm.
Modulation is the process of changing the characteristics of the carrier signal in accordance with the instantaneous values of the modulating signal message signal. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. The purpose of a communication system is to transfer information from a source to a destination. The pam modulator and demodulator circuits simple compared to other kinds of modulation and demodulation techniques. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulses are varied according to the sample value of the message signal. The simple pulse modulation technique called pulse amplitude modulation pam proved to be more power efficient than the pwm and consumes constant power for individual pulses like ppm. The pulse may take any real voltage value that is proportional to the value of the original waveform. To study and perform pulse position 6 to study and perform pulse code modulation. It is a simple process for both modulation and demodulation. Types of modulation 6 flynnkatz 7810 analog modulation amplitude modulation, am frequency modulation, fm double and single sideband, dsb and ssb digital modulation phase shift keying. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. Modulation allows us to transmit multiple signals in the same medium i. Pulse amplitude modulation pulse code modulation sampling.
Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. Analog communication pulse modulation tutorialspoint. Consequently, the constellation points lie on the horizontal line. Pulse position modulation ppm is an analog modulation scheme in which, the amplitude and the width of the pulses are kept constant, while the position of each pulse, with reference to the position of a reference pulse varies according to the instantaneous sampled value of the message signal. 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. Request pdf pulse amplitude modulation pulse amplitude modulation pam. Telo, chapter 9, modulation, demodulation, signal sampling 1 9. To study and perform amplitude modulation 2 to study and perform frequency modulation and demodulation. 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. Frequency division multiplexing, fdma amplitude modulation and demodulation. 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. The pulse amplitude modulated signal, will follow the amplitude of the original signal, as. Pulse amplitude modulation pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses.
No information is lost, but the energy is redistributed in the frequency domain. Pulse amplitude modulation an overview sciencedirect topics. The modulation processisprobablyeasier tounderstand whenviewed fromthe perspective of amplitude modulation. In pulse amplitude modulation pam, the a m are purely real, that is im a m 0 for m 1, 2, m. The process of demodulation for signals using amplitude modulation can be achieved in a number of different techniques, each of which has its own advantage. Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. In particular, we consider pam signal demodulation and detection and give a. Pulse amplitude modulation pam is an analog modulating scheme in which the amplitude of the pulse carrier varies proportional to the instantaneous amplitude of the message signal. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. Feb 12, 2014 pulseamplitude modulation, acronym pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Difference between pam, pwm, and ppm comparison of pwm. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. There are two categories of pam techniques, one is the pulses have the same polarity and the other in which the pulses can have both positive and.
The ideal modulated signal should have a minimum euclidean distance of 2. However, it is the first step in another very popular conversion method called pulse code modulation. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. Pulse amplitude modulation request pdf researchgate.
Sampling theorem and pulse amplitude modulation pam. System in simulink and decode the secret message 10 build the following. Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. Pam underlies the operation of a wide variety of modems. There are many types of modulation so there are many types of demodulators. Pam can be timedivision multiplexed tdm, as can pulse code modulation pcm. Another binary modulation format is binary phaseshift keying bpsk, which can be. Pdf pulseposition and pulseamplitude modulation interface for. The pam modulator and demodulator circuits simple compared to other kind of modulation and. 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. 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. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast.
There are different types of modulation and so are demodulators. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. Pulse code modulation is used in mobile phones, normal telephones etc. In pulse amplitude modulation, the amplitude of regular interval of periodic pulses or electromagnetic. Pulse amplitude modulation pam theory of and its applications. Laboratory exercise on demodulation of pam signal asee peer. It is customary to arrange the points so that they are equally spaced and centered at zero. Explain generation and demodulation of pam, ppm and pwm. The term demodulator is used because the demodulation process is considered to be the opposite of modulation. The demodulator is the circuit, or for a software defined radio, the software that is used to recover the information content from the overall incoming modulated signal.
If the negative symbol is transmitted, the pdf for z will be as sketched below. Demodulation is extracting the original informationbearing signal from a carrier wave. Pulseamplitude demodulation peak detection is used to detect pam. Modulation, demodulation, signal sampling time of study. The number of possible pulse amplitudes can be infinite in the case of analog pam, but it is usually some power of two so that the. The percentage modulation can be calculated using the formula. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Modulator for testing demodulator demodulator submit the following. Explain generation and demodulation of pam, ppm and pwm with.
In any radio that is designed to receive frequency modulated signals there is some form of fm demodulator or. Fig2 shows the spectrum of pulse amplitude modulated signal along with the message signal and the sampling signal which is the carrier train of pulses with the help of the waveform plotted in time domain. In pam the amplitude of the individual pulses are varied according to the amplitude of the modulating signals. Vary the modulating frequency and amplitude and observe the effects on the modulated waveform. For the example above, the carrier signal is p es cos2. Difference between pam, pwm, and ppm comparison of pwm and pam.