A modem is an equipment that performs both modulation and demodulation. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. In practice, the carrier may be highfrequency hf while the modulation is audio. Pulse amplitude modulation request pdf researchgate. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. The minimum sampling frequency is the minimum frequency at which the modulating waveform can be. 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. 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. 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. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. Am is shown simply as consisting of three discrete frequencies. Demodulation is a key process in the reception of any amplitude modulated signals whether used for broadcast or two way radio communication systems.
It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. Here is the circuit used for modulation and its simulation. For the baseband digital transmission, pulse amplitude modulation pam is the most efficient in terms of power and bandwidth utilization. Amplitude modulation theory frequency spectrum power. Understanding quadrature demodulation radio frequency. The pulse may take any real voltage value that is proportional to the value of the original waveform. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Each channel sharing scheme a set of basis vectors. Frequency division multiplexing, fdma amplitude modulation and demodulation. It is this process that is called demodulation or detection. In this video, i have explained amplitude modulation by following outlines. Amplitude modulation an overview sciencedirect topics.
Frenzeljr, in handbook of serial communications interfaces, 2016. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. 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. Modulation is a process of translating information signal from. In amplitude modulation, it is the voltage level of the signal to be transmitted. 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. A form of modulation in which a pulse train is used as the carrier. This lab introduces students to communications theory with amplitude modulation and demodulation. 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. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation.
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. To study frequency modulation and determine its modulation factor 4. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Pradeep kshetrapal, tutorials point india private limited. Its important to understand that the received signal could be from. To transform the input signal e t into a succession of. 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. Modulation and demodulation pdf modulation and demodulation ch16 modulator demodulation 16. 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. Quadrature amplitude modulation qam pam signals occupy. 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. Modulation is defined as the process of transmission of information such as images or videos on an electrical signal.
The amfm modulation model and a multiband analysis demodulation scheme is applied to speech formant frequency and bandwidth tracking. Amplitude modulation definition, types, solved examples. In pam the amplitude of the individual pulses are varied according to the amplitude of the modulating signals. 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. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. Once the signal has been received, filtered and amplified, it is necessary to recover the original modulation from the carrier. Oct 09, 2018 amplitude modulation theory may be represented in any of three ways, depending on the point of view.
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 amfm modulation model and a multiband analysisdemodulation scheme is applied to speech formant frequency and bandwidth tracking. Fm demodulation is a key process in the reception of a frequency modulated signal. To study and perform pulse width modulation and demodulation. Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. Demodulation is extracting the original informationbearing signal from a carrier wave. Pulseamplitude demodulation peak detection is used to detect pam. In quadrature demodulation, we are converting the existing modulation into the corresponding iq baseband signals. 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. Pulse amplitude modulation pam, quadrature amplitude modulation qam. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn. 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.
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. Pulse amplitude demodulation peak detection is used to detect pam. There are many types of modulation so there are many types of demodulators. 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. 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. A group of theoretical papers in the early 1960s 4567. 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. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%.
Qam is composed of two independent pulse amplitude modulation pam baseband modulations placed on. To study sampling and reconstruction of pulse amplitude modulation system 6. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. There are different types of modulation and so are demodulators. The pam modulator and demodulator circuits simple compared to other kind of modulation and.
Each part may be of any convenient amplitude at the input to an adder. We can also get back our analog signal by demodulation. As we mentioned before, well use dsbc modulation because of its ease in demodulation. The original waveform amplitude is quantized with a resulting loss of information. This lecture introduces the principle of digital modulation, which serves as the bridge. Pcm is in binary form,so there will be only two possible states high and low 0 and 1. 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. Capacityapproaching codes demodulation line coding modem anm pom.
To study amplitude demodulation by linear diode detector. Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. In quadrature modulation, we use baseband iq signals to create an amplitude, frequency, or phasemodulated waveform that will be amplified and transmitted. A brief discussion about pulse code modulation and demodulation. The signal output from a demodulator may represent sound an. Figure 32 shows the frequency spectrum and so illustrates equation 37. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. The term demodulator is used because the demodulation process is considered to be the opposite of modulation. 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. Pulse amplitude modulation pam theory of and its applications. Principles of communication modulation tutorialspoint. Amplitude modulation is mostly used in the form of electronic communication.
Pulse amplitude modulation pam, pulse shaping, and the nyquist criterion. In both the modulation and demodulation, it is assumed that the bandwidth of. Vestigial sideband amplitude modulation vsbam is a modulation that improves the spectral e. 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. 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 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. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Information is conveyed by modulating some parameter of the pulses with a set of discrete instantaneous samples of the messages signal. Amplitude and phase modulation information can be carried in m is the size of constellation amplitude only. 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. Theory of frequency modulation and phase modulation.
Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. The goal of this experiment is to become familiar with fm modulation and demodulation. Amplitude modulation am, demodulation and their circuit. 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. Filtering is performed by a bank of gabor bandpass filters. 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. The channel noise is neglected in this lecture, and how to demodulate the.
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. Demodulation is defined as the process of extracting this information. Jun 17, 2018 in this video, i have explained amplitude modulation by following outlines. 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. Transmitter and receiver circuits are simple and easy to construct. If the negative symbol is transmitted, the pdf for z will be as sketched below.
In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. 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. 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. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Source called v1 generates the message to be transmitted. To study amplitude demodulation by linear diode detector 3. Then, students will use labview to program an am demodulator and use it to explore and visualize the.
Modulation allows us to transmit multiple signals in the same medium i. No information is lost, but the energy is redistributed in the frequency domain. 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. Pulse amplitude modulation pam, is a form of signal modulation where the message. Pulse amplitude modulation an overview sciencedirect. In particular, we consider pam signal demodulation and detection and give a. Modulation and demodulation techniques request pdf. Both processes aim to achieve transfer information with the minimum distortion, minimum loss and.
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