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. Pcm is in binary form,so there will be only two possible states high and low 0 and 1. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. In both the modulation and demodulation, it is assumed that the bandwidth of. Oct 12, 2018 frequency modulation and phase modulation is a system in which the amplitude of the modulated carrier is kept constant, while its frequency and rate of change are varied by the modulating signal. As we mentioned before, well use dsbc modulation because of its ease in demodulation. Pcm is in binary form, so there will be only two possible states high and low0 and 1. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. Pulse amplitude modulation an overview sciencedirect. 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. Transmitter and receiver circuits are simple and easy to construct. Once the signal has been received, filtered and amplified, it is necessary to recover the original modulation from the carrier.
Principles of communication modulation tutorialspoint. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. Amplitude modulation definition, types, solved examples. 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. For the baseband digital transmission, pulse amplitude modulation pam is the most efficient in terms of power and bandwidth utilization. Pulse amplitude modulation pam, is a form of signal modulation where the message. We can define amplitude modulation by saying that a modulating signal, should produce an am wave of the form well use s instead of v or e to indicate that were talking about a modulated quantity and that it can be either a field or a voltage. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors.
Amplitude modulation is mostly used in the form of electronic communication. This lab introduces students to communications theory with amplitude modulation and demodulation. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. To study sampling and reconstruction of pulse amplitude modulation system 6. In practice, the carrier may be highfrequency hf while the modulation is audio. Pulse amplitude modulation pam theory of and its applications. A brief discussion about pulse code modulation and demodulation. 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. Angle modulation ch16 angle modulation host modulation therapy digital modulation schemes ch16 angle modulation detection estimation and modulation theory part i pdf sinusoidal pulse width modulation inverter arduino. This lecture introduces the principle of digital modulation, which serves as the bridge. Oct 09, 2018 amplitude modulation theory may be represented in any of three ways, depending on the point of view. 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.
Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. 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. Here is the circuit used for modulation and its simulation. We can also get back our analog signal by demodulation. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Vestigial sideband amplitude modulation vsbam is a modulation that improves the spectral e. In analog modulation technique, if the amplitude, duration or position of a pulse is varied in accordance with the instantaneous values of the baseband modulating signal, then such a technique is called as pulse amplitude modulation pam or pulse durationwidth modulation pdmpwm, or pulse position modulation ppm. In quadrature modulation, we use baseband iq signals to create an amplitude, frequency, or phasemodulated waveform that will be amplified and transmitted. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. The signal output from a demodulator may represent sound an. 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 pulse may take any real voltage value that is proportional to the value of the original waveform. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave.
Theory of frequency modulation and phase modulation. Each channel sharing scheme a set of basis vectors. Pulse amplitude demodulation peak detection is used to detect pam. Demodulation is a key process in the reception of any amplitude modulated signals whether used for broadcast or two way radio communication systems. Quadrature amplitude modulation qam pam signals occupy. 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. It is this process that is called demodulation or detection. In pam the amplitude of the individual pulses are varied according to the amplitude of the modulating signals. 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. 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. A form of modulation in which a pulse train is used as the carrier. The minimum sampling frequency is the minimum frequency at which the modulating waveform can be. In the positive half cycle of pam signal, diode conducts and current flows through r, whereas in negative half cycle, the diode is reversed biased and.
Modulation and demodulation amplitude modulation is the process of varying the amplitude of a carrier wave in proportion to the amplitude of a baseband 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. To study frequency modulation and determine its modulation factor 4. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn. Fm demodulation is a key process in the reception of a frequency modulated signal. Amplitude modulation am, demodulation and their circuit. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation.
An am wave may thus be dscribed, in the most general form, as a function of time as follows. The pam modulator and demodulator circuits simple compared to other kind of modulation and. The amfm modulation model and a multiband analysisdemodulation scheme is applied to speech formant frequency and bandwidth tracking. Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. A modem is an equipment that performs both modulation and demodulation. To study amplitude demodulation by linear diode detector. Amplitude, frequency and phase modulation can be applied directly by software to the generated signals, which gives great flexibility where complicated and precise waveforms are required. Pulse amplitude modulation pam, quadrature amplitude modulation qam. Ee3 lab 1 amplitude modulation and demodulation broadcast analog television tv signals have a bandwidth of approximately 6mhz and this is achieved with a quadrature modulation. Source called v1 generates the message to be transmitted. Pulseamplitude demodulation peak detection is used to detect pam. To transform the input signal e t into a succession of. Amplitude and phase modulation information can be carried in m is the size of constellation amplitude only. The term demodulator is used because the demodulation process is considered to be the opposite of modulation.
Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. Modulation and demodulation pdf modulation and demodulation ch16 modulator demodulation 16. Am is shown simply as consisting of three discrete frequencies. Modulation is defined as the process of transmission of information such as images or videos on an electrical signal. There are many types of modulation so there are many types of demodulators. Pulse amplitude modulation pam, pulse shaping, and the nyquist criterion. To study and perform pulse width modulation and demodulation. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. The channel noise is neglected in this lecture, and how to demodulate the. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation.
Understanding quadrature demodulation radio frequency. In quadrature demodulation, we are converting the existing modulation into the corresponding iq baseband signals. The goal of this experiment is to become familiar with fm modulation and demodulation. Demodulation is defined as the process of extracting this information. The amfm modulation model and a multiband analysis demodulation scheme is applied to speech formant frequency and bandwidth tracking. The spectral efficiency of the transmitted ask waveform is also a consideration and the m. Modulation is a process of translating information signal from. 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. Information is conveyed by modulating some parameter of the pulses with a set of discrete instantaneous samples of the messages signal. 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.
In amplitude modulation, it is the voltage level of the signal to be transmitted. Demodulation is extracting the original informationbearing signal from a carrier wave. The original waveform amplitude is quantized with a resulting loss of information. In amplitude modulation theory, the amplitude of a carrier signal is varied by the modulating voltage, whose frequency is invariably lower than that of the carrier. Qam is composed of two independent pulse amplitude modulation pam baseband modulations placed on. In pulse position modulation the amplitude of the pulse is kept constant as in the case of the fm and pwm to avoid noise interference. Frenzeljr, in handbook of serial communications interfaces, 2016. Each part may be of any convenient amplitude at the input to an adder. The pulse position modulation ppm is a modulation technique designed to achieve the goals like simple transmitter and receiver circuitry, noise performance, constant bandwidth and the power efficiency and constant transmitter power. Frequency modulation and phase modulation is a system in which the amplitude of the modulated carrier is kept constant, while its frequency and rate of change are varied by the modulating signal.
Its important to understand that the received signal could be from. A group of theoretical papers in the early 1960s 4567. In this video, i have explained amplitude modulation by following outlines. No information is lost, but the energy is redistributed in the frequency domain. Jun 17, 2018 in this video, i have explained amplitude modulation by following outlines. Modulation allows us to transmit multiple signals in the same medium i. 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.
There are different types of modulation and so are demodulators. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Amplitude modulation an overview sciencedirect topics. Demodulation is the process by which the original information bearing signal, i. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Request pdf pulse amplitude modulation pulse amplitude modulation pam. Pradeep kshetrapal, tutorials point india private limited. The frequency double sideband dsb is one of the easiest modulation techniques to understand, so it is a good starting point for the study of modulation. Modulation and demodulation techniques request pdf. The first practical system was put forward in 1936 as an alternative to am in an effort to make radio transmissions more resistant to noise.
Filtering is performed by a bank of gabor bandpass filters. Figure 32 shows the frequency spectrum and so illustrates equation 37. Pulse amplitude modulation request pdf researchgate. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. It is a simple process for both modulation and demodulation. The idea is simple, though the notion that it can be used to modulate signals. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation.
Students will explore the mathematical theory behind amplitude modulation and use the analog discovery 2 to visualize the effects of amplitude modulation in the time and frequency domains. To study amplitude demodulation by linear diode detector 3. Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. Frequency division multiplexing, fdma amplitude modulation and demodulation. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave.
Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier. If the negative symbol is transmitted, the pdf for z will be as sketched below. Amplitude modulation theory frequency spectrum power. 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. In particular, we consider pam signal demodulation and detection and give a. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Both processes aim to achieve transfer information with the minimum distortion, minimum loss and. Then, students will use labview to program an am demodulator and use it to explore and visualize the.
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