Pdf analog and digital modulation techniques assignment 1. Looking at a graph of a signal is usually the easiest way to identify if its analog or digital. Analog data digital data digital signal encoding and. Am radio the bandwidth of an audio signal speech only is 5 khz. The other type of modulation in continuouswave modulation is angle modulation.
Phase modulation pm changes only the phase of the signal. In the real world, however, no system has infinite bandwidth, and analogue systems are limited to producing side bands within their finite bandwidth see later for more on bandwidth. Its signal amplitude can take on any number of values between the signal maximum and minimum. Modulation is one type of process used to change the properties of a periodic signal which is known as carrier signal with a modulating signal that normally contains data to be transferred. This chapter discusses the different modulation techniques that are used to convert a digital signal into an analog signal that is the appropriate form to either be transmitted down a twisted cable pair or to be applied to the radio frequency rf stage where it is modulated to a frequency that can be transmitted via microwave or satellite.
Pdf analog and digital modulation techniques assignment. A method of frequency translation, recovery of base band signal, amplitude modulation, spectrum of am signal, the balanced modulator, the square law demodulator, dsbsc, ssbsc and vsb, their methods of generation and demodulation, carrier acquisition, phaselocked loop pll,frequency division multiplexing. Frequency modulation is the process of varying the frequency of the carrier signal linearly with the message signal. New algorithms for automatic modulation recognition for. Analogue signal modulation telecommunications britannica. This produces a phase deviation of the resultant signal, v o, as shown in figure 18. Modulation is defined as the process by which some characteristics i. Pulse amplitude modulation pam theory of and its applications. Analog and digital modulation refers to how a carrier signal is modified in order to transmit information. Frequency versus amplitude modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal. In most modern systems these signals are digitized prior to transmission, but in some systems the analog signals are still transmitted directly without. As the resultant is a coded pulse train, this is called as pcm. For example, in an analog audio signal, the instantaneous voltage of the signal varies continuously with the pressure of the sound waves. For example, in an analog audio signal, the instantaneous voltage of the signal varies continuously with the pressure of the sound.
The carrier information can be defined in two forms, digital or analog. Analog and digital modulation techniques assignment 1. Analog communications 26 other modulation methods amplitude modulation the amplitude of the carrier signal is controlled by the modulating signal. A product modulator produces a dsbsc wave, as shown in figure 18. Jun 16, 2018 in this video, i have explained communication system by following outlines. An analog signal is a continuous wave denoted by a sine wave pictured below and may vary in signal strength amplitude or frequency waves per unit time. Modulation involved mixing, or multiplying, the input signal xn with a carrier signal cos. Broadcast television systems or terrestrial television systems outside the us and canada are the encoding or formatting standards for the transmission and reception of terrestrial television signals. The reason for that may be that the channel is bandlimited, or that we are assigned a certain frequency band and frequencies outside that band is supposed to be used by others. The government assigns a narrow bandwidth to each radio station. Most commonly, the audio and video are combined at the transmitter before being presented to the antenna, but separate aural and visual antennas can be used.
Analogue and digital communication techniques sciencedirect. Polar view of digital iq modulation contd transmission signal is sine wave at frequency f 0 with information encoded in discrete values of amplitude and phase. Connect the modulating signal generated in step 1 to the input of mod inout of function generator. Demodulation is the reverse process of modulation, which is used to get back the original message signal. When modulation is employed, a modulator is needed at the sending end of a channel and a demodulator at the receiving end recovers the baseband signal from the modulated carrier. In analog modulation, analog signal sinusoidal signal is used as a carrier signal that modulates the message signal or data signal. Therefore, analog modulation includes am, fm and pm and these are more sensitive to noise. In amplitude modulation, the amplitude of the carrier signal changes instantaneously with respect to the amplitude of the modulating signal. The following is an overview of some of the recently published analogue modulation recognition algorithms. The standard equation of the angle modulated wave is. As is noted in analogtodigital conversion, voice signals, as well as audio and video signals, are inherently analog in form. Now in digital terrestrial television dtt, there are four main. Input signal is information either in analog form or digital form which need to be transmitted. Analog to analog conversion techniques myreadingroom.
To achieve the amplitude modulation using modulation block of function generator, keep the following settings a. Sep 28, 2015 analog and digital modulation refers to how a carrier signal is modified in order to transmit information. Demodulation is the opposite process of modulation. These digital modulation techniques are discussed in our digital. The modulation index can be used to make the frequency deviation more. Amplitude modulation definition, types, solved examples. The analytical signal for double sideband, large carrier amplitude modulation dsblc am is. There are many modulation techniques, which are classified according to the type of modulation employed. The predetection part of an angle modulation receiver is the same as for amplitude modulation.
Joint acoustic and modulation frequency article pdf available in eurasip journal on advances in signal processing 20037 june 2003 with 5 reads how we measure reads. Phase modulation is used in many transmission applications, notably wifi and satellite tv. In all cases where negative video is used, fm is used for the standard. In analog television, the analog audio portion of a broadcast is invariably modulated separately from the video. The mathematical representation of frequency modulation consists of a sinusoidal expression with the integral of the baseband signal added to the argument of the sine or cosine function. 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. Also, consider reading our pulse width modulation pwm tutorial. Modulation, analog modulation, digital modulation, am,fm,pm. An introduction to frequency modulation sound on sound.
Phase modulation is the process of varying the phase of the carrier signal linearly with the message signal. Ee4512 analog and digital communications chapter 6 the baseband power spectral density psd spectrum of the information signal s t or sf for voice has significant. Analog communication angle modulation tutorialspoint. Amplitude modulation is a type of analog modulation in which the amplitude of the highfrequency carrier signal is changing with respect to the instantaneous amplitude of the modulating signal. If noise enters into a system, it persists and gets carried up to the end receiver. Analogtoanalog conversion, or analog modulation, is the representation of analog information by an analog signal. There are two types of modulation analog and digital. In the 20th century, most of the radio systems used am or fm for broadcasting. Modulation of analog data 2 why analog to analog modulation. This technique is frequently used in electronics as well as telecommunications. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download.
It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. The main difference between analog and digital modulation is that an analog modulated signal can take up any value in a possible range whereas a digitally modulated signal can only take up one of a discrete set of values. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Pwm stands for pulse width modulation where the width being modulated is that of a square wave.
Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Digital modulation types and relative efficiencies 3. Modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal. The circuit can be used as an extension shield for arduino or microcontroller mcu or ttlcmos signal generator. Phase modulation can be generated by armstrongs method shown in figure 18. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. There were three main analog television systems in use around the world until the late 2010s expected. Modulation is the process of modifying one signal based on another, and it is used mostly in the transmission of data from one point to another. The output of a pcm will resemble a binary sequence.
Modulation, analog modulation, digital modulation, am,fm. Of course, since n can take any integer value, in theory, applying frequency modulation to a signal produces an infinite series of side bands. Amplitude modulation is mostly used in the form of electronic communication. Input signal is designated as modulating waveform or modulating signal. Other articles where analogue signal modulation is discussed. Angle modulation is the process in which the frequency or the phase of the carrier signal varies according to the message signal. Any modulation block consists of input signal, carrier signal and output signal. Of them all, the digital modulation technique used is pulse code modulation pcm. Chapter 5 traditional analog modulation techniques mikael olofsson 20022007 modulation techniques are mainly used to transmit information in a given frequency band. Although there are many types of modulation, there are two basic types.
Digital modulation in communications systems an introduction. Angle modulation is further divided into frequency modulation and phase modulation. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Angle cw modulation with noise in the analysis of pm and fm systems, demodulation will be represented by yt. In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. There is a bit of grey area here, however, since even a dc signal is an analog signal that does not change and has zero slope. Pwm vs analog signals electrical engineering stack exchange. A signal is pulse code modulated to convert its analog information into a binary sequence, i. Analog signal graphs because a signal varies over time, its helpful to plot it on a graph where time is plotted on the horizontal, xaxis, and voltage on the vertical, yaxis. The continuous analog signal s t is a baseband signal with the information content voice or music to be transmitted. Phase modulation is a subcategory of frequency modulation, whereby the phase angle of the carrier envelope is modified in response to changes in the signal. The application of the heterodyne principle to modulation is shown schematically in figure 143. An analog signal is any continuous signal for which the timevarying feature variable of the signal is a representation of some other time varying quantity, i.
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. This article presents a simple circuit to convert transistortransistor logic ttl or pulse width modulation pwm signal to analogue signal using lm358 operational amplifier. In this video, i have explained communication system by following outlines. This method is only suitable for small values of modulation index.
Pdf analog communication system pdf notes ac notes sw. Generate the sinusoidal carrier signal of 2vpp, 10 khz from function generator. This type of modulation is used for signal generation in al synthesizers, such as the yamaha dx7 to implement fm synthesis. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal.
The main difference between analog modulation and digital modulation is in the manner. Pwmtoanalog signal converter electronics mini project. Analog modulation delas with the voice, video and regular waves of base band signals. 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.
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