Although there are many types of modulation, there are two basic types. Demodulation is the reverse process of modulation, which is used to get back the original message signal. There are two types of modulation analog and digital. Its signal amplitude can take on any number of values between the signal maximum and minimum. This technique is frequently used in electronics as well as telecommunications. There are many modulation techniques, which are classified according to the type of modulation employed. Modulation is needed if the medium is bandpass in nature or if only a bandpass channel is available to us. 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. 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 analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Modulation, analog modulation, digital modulation, am,fm.
This method is only suitable for small values of modulation index. Now in digital terrestrial television dtt, there are four main. For example, in an analog audio signal, the instantaneous voltage of the signal varies continuously with the pressure of the sound waves. Analog data digital data digital signal encoding and. The government assigns a narrow bandwidth to each radio station. In amplitude modulation, the amplitude of the carrier signal changes instantaneously with respect to the amplitude of the modulating signal. Analog communications 26 other modulation methods amplitude modulation the amplitude of the carrier signal is controlled by the modulating signal. There are different types of modulation and so are demodulators. Modulation, analog modulation, digital modulation, am,fm,pm. The following is an overview of some of the recently published analogue modulation recognition algorithms. Pdf analog communication system pdf notes ac notes sw.
Analogtoanalog conversion, or analog modulation, is the representation of analog information by an analog signal. These digital modulation techniques are discussed in our digital. Chapter 5 traditional analog modulation techniques mikael olofsson 20022007 modulation techniques are mainly used to transmit information in a given frequency band. Of them all, the digital modulation technique used is pulse code modulation pcm. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. Sep 28, 2015 analog and digital modulation refers to how a carrier signal is modified in order to transmit information. Connect the modulating signal generated in step 1 to the input of mod inout of function generator.
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. A product modulator produces a dsbsc wave, as shown in figure 18. 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. Analog iq modulation transceiver iq signals take on a continuous range of values as viewed in the time domain used for amfm radios, television nonhdtv, and the first cell phones newer systems typically employ digital modulation instead receiver output 2cos2. 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 analog modulation, analog signal sinusoidal signal is used as a carrier signal that modulates the message signal or data signal. In analog television, the analog audio portion of a broadcast is invariably modulated separately from the video. The general function sinusoidal waves is shown in the figure below, in which, three parameters can be altered to get modulation they are amplitude, frequency and phase. 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 output of a pcm will resemble a binary sequence. This type of modulation is used for signal generation in al synthesizers, such as the yamaha dx7 to implement fm synthesis. A signal is pulse code modulated to convert its analog information into a binary sequence, i.
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. 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. Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc. Pulse amplitude modulation pam theory of and its applications. Digital modulation in communications systems an introduction. Analog and digital modulation techniques assignment 1. The application of the heterodyne principle to modulation is shown schematically in figure 143. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Phase modulation is used in many transmission applications, notably wifi and satellite tv. Also, consider reading our pulse width modulation pwm tutorial. 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. If noise enters into a system, it persists and gets carried up to the end receiver. The other type of modulation in continuouswave modulation is angle modulation.
Angle modulation is further divided into frequency modulation and phase modulation. The carrier information can be defined in two forms, digital or analog. Analog communication angle modulation tutorialspoint. Angle modulation is the process in which the frequency or the phase of the carrier signal varies according to the message signal. In this video, i have explained communication system by following outlines. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Input signal is designated as modulating waveform or modulating signal. In the 20th century, most of the radio systems used am or fm for broadcasting. The standard equation of the angle modulated wave is. Analogue signal modulation telecommunications britannica.
Any modulation block consists of input signal, carrier signal and output signal. To achieve the amplitude modulation using modulation block of function generator, keep the following settings a. Angle cw modulation with noise in the analysis of pm and fm systems, demodulation will be represented by yt. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. Digital modulation types and relative efficiencies 3. 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. Modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal.
Pwm vs analog signals electrical engineering stack exchange. Pdf analog and digital modulation techniques assignment 1. Pwm stands for pulse width modulation where the width being modulated is that of a square wave. 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.
Pwmtoanalog signal converter electronics mini project. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. The circuit can be used as an extension shield for arduino or microcontroller mcu or ttlcmos signal generator. Jul 30, 2019 in analog modulation, analog signal sinusoidal signal is used as a carrier signal that modulates the message signal or data signal. Chapter 6modulation techniques shandong university. 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. Amplitude modulation is mostly used in the form of electronic communication. There were three main analog television systems in use around the world until the late 2010s expected. Demodulation is the opposite process of modulation. New algorithms for automatic modulation recognition for. Jun 16, 2018 in this video, i have explained communication system by following outlines. Of course, since n can take any integer value, in theory, applying frequency modulation to a signal produces an infinite series of side bands. 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. Am radio the bandwidth of an audio signal speech only is 5 khz.
Input signal is information either in analog form or digital form which need to be transmitted. Phase modulation pm changes only the phase of the signal. In all cases where negative video is used, fm is used for the standard. Amplitude modulation definition, types, solved examples. 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. 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. Phase modulation is the process of varying the phase of the carrier signal linearly with the message signal.
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. This article presents a simple circuit to convert transistortransistor logic ttl or pulse width modulation pwm signal to analogue signal using lm358 operational amplifier. Generate the sinusoidal carrier signal of 2vpp, 10 khz from function generator. Amplitude and phase modulation can be used together. Therefore, analog modulation includes am, fm and pm and these are more sensitive to noise. Analog to analog conversion techniques myreadingroom. 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. Modulation involved mixing, or multiplying, the input signal xn with a carrier signal cos.
Modulation is defined as the process by which some characteristics i. Pdf analog and digital modulation techniques assignment. An introduction to frequency modulation sound on sound. 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. The predetection part of an angle modulation receiver is the same as for amplitude modulation.
Modulation of analog data 2 why analog to analog modulation. Analogue and digital communication techniques sciencedirect. 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 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.
Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. 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. 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. This produces a phase deviation of the resultant signal, v o, as shown in figure 18. 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. Looking at a graph of a signal is usually the easiest way to identify if its analog or digital. For example, in an analog audio signal, the instantaneous voltage of the signal varies continuously with the pressure of the sound. As the resultant is a coded pulse train, this is called as pcm.
Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast. Analog modulation delas with the voice, video and regular waves of base band signals. Analog and digital modulation refers to how a carrier signal is modified in order to transmit information. The modulation index can be used to make the frequency deviation more. The main difference between analog modulation and digital modulation is in the manner. 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. As is noted in analogtodigital conversion, voice signals, as well as audio and video signals, are inherently analog in form.