Single sideband modulation or ssb is derived from amplitude modulation am and ssb modulation overcomes a number of the disadvantages of am. Optical single sideband signal generation using phase modulation of semiconductor optical amplifier article pdf available in ieee photonics technology letters 165. Amplitude modulation definition, types, solved examples. Double sideband dsb is one of the easiest modulation techniques to understand, so it is a good starting point for the study of modulation. Chapter 7 singlesideband modulation and frequency translation. In am, the amplitude of the carrier is changed in accordance with the amplitude and frequency or the characteristics of the modulating signal. The webs wikipedia singlesideband modulation gives the mathematical details of ssb generation 1. We will assume that the baseband message signal mt is band limited with a. In the process of amplitude modulation or phase modulation, the modulated wave consists of the carrier wave and two sidebands. Generate 512 samples of a simulated broadband signal using the sinc function.
We generally assume the modulating signal is sinusoidal lets focus on the simplest case. In my internet searching, i found the ssb information available on the net to be either badly confusing in its notation or downright ambiguous. In radio communications, singlesideband modulation ssb or singlesideband suppressedcarrier modulation ssbsc is a type of modulation used to transmit information, such as an audio signal, by radio waves. The generated output y is a single side band signal with a suppressed carrier. Analog communication ssbsc modulation tutorialspoint. Single sideband quadrature amplitude modulation springerlink. Information content of amplitude modulation versus singlesideband transmission. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. 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. In fact, all radio channels in the am band use this type of modulation. Once a signal has been modulated, information is retrieved through a demodulation process. Amplitude modulation produces an output signal the bandwidth of which is twice the. Double sideband full carrier dsbfc also called the ordinary am modulation am double sideband suppressed carrier dsbsc singlesideband ssb vestigial sideband vsb not covered here.
When expressed as a percentage it is the same as the depth of modulation. Dsbsc is an amplitude modulated wave transmission scheme in which only sidebands are transmitted and the carrier is not transmitted as it gets suppressed. Amplitude modulation and singlesideband modulation from the book communications electronics by louis e. Similarly, we can suppress the carrier and the upper sideband while transmitting the lower sideband. One cosine term has 2 frequency spectral line, so 2 cosine terms have 4. This is the same as the am modulation above but without the carrier.
Am and dsbscam modulation do not use the frequency spectrum efficiently. In radio communications, singlesideband modulation ssb or singlesideband suppressedcarrier ssbsc is a refinement of amplitude modulation which. Besides just encoding voice information with variations in signal amplitude, or power, ssb consumes a little less than half the bandwidth of a full double band am signal. This allows more signals to be transmitted in the same frequency range. Ssb was used for long distance telephone communications. Overmodulation overmodulation is a condition that occurs when an excessive intelligence signal overdrives an am modulator making %m 100% because e i e c modulated carrier amplitude reach value greater than double of unmodulated value it produces a distortion known as sideband splatter, which results on transmission at frequencies outside. The carrier signal and x have sample frequency fs hz. Types of amplitude modulation am double sideband with carrier we will call it am. The advantages of single sideband ssb or single sideband suppressed carrier ssbsc modulation, such as spectral power efficiency, have long been known in all electronic communication systems. Amplitude modulation is a method of converting data into an alternatingcurrent carrier waveform.
I and q components in communications signals and single. Standard am and dsbsc techniques are wasteful of bandwidth because they both require transmission bandwidth of 2b. Single sideband modulation is normally used for voice transmission, but technically it can be used for many other applications where two way radio communication using analogue signals is required. What is double sideband suppressed carrier modulation dsb. The message signal is, for example, a function of the sound to be reproduced by a. Understanding single sideband modulation and demodulation. This can then be applied to use this type of mode to its best, whether as amplitude modulation, single sideband, or even giving abetter understanding of how qam operates. Pdf optical single sideband signal generation using. Ssb generation using hilbert transformmatlab code by dr.
This example shows how to use the hilbert transform to carry out singlesideband ssb amplitude modulation am of a signal. This is the most widely used type of am modulation. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Lets unfold that last statement for the uninitiated new hams. Ssb modulation by dsbscam and filtering in singlesideband ssb modulation only the upper sideband or the lower sideband is transmitted. External processing for controlled envelope single sideband pdf. This scheme allows to decrease the spectral width of the transferred signal by two times as opposed to the traditional quadrature amplitude modulation, while maintaining its spectral efficiency. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Singlesideband modulation wikimili, the best wikipedia. The primary benefit of an ssb signal is that the spectrum space it occupies is only onehalf that of am and dsb signals. A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. Linear modulation one scheme is to simply square the received dsb signal x2 r. Therefore, both these systems are bandwidth inefficient systems. Frequency modulation consists of encoding information onto a carrier signal by varying the frequency of the carrier.
But ssb demodulation information at that web site was terribly sparse. Chapter 7 singlesideband modulation ssb and frequency. As discussed earlier conventional am and dsbsc is wasteful from the band width point of view and requires a bandwidth equal to twice the message signal bandwidth. Single sideband modulation ssb standard am and dsbsc techniques are wasteful of bandwidth because they both require transmission bandwidth of 2b hz, where b is the bandwidth of the baseband modulating signal mt. Hence, the upper sideband is used for transmission.
Carrier is modulated by varying amplitude linearly proportional to intelligence baseband signal amplitude. We will assume that the baseband message signal mt is band limited with a cuto. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. In radio communications, singlesideband modulation ssb or singlesideband suppressedcarrier modulation ssb sc is a type of modulation used to transmit information, such as an audio signal, by radio waves. Chapter 6 doublesideband suppressedcarrier amplitude. This ssbsc system, which transmits a single sideband has high power, as the power allotted for both the carrier and the other sideband is utilized in transmitting this single sideband. Double sideband dsb and single sidebandssb sharlene katz james flynn 91608. Their spec tral components equal distances above and below the carrier.
A type of dsb, called binary phaseshift keying, is used for digital telemetry. The modulated signal has the information in the whole band except at the carrier frequency. In radio communications, singlesideband modulation ssb or singlesideband suppressedcarrier modulation ssbsc is a refinement of. Anew modulation schemesingle sideband quadrature amplitude modulation ssb qam is proposed. Modulation, singlesideband a method of controlling electrical waves by transmitting an information signal on only one sideband of frequencies. Understanding the phasing method of single sideband. Single sideband amplitude modulation matlab ssbmod. Frenzel selftest in amplitude modulation and single. Amplitude modulation produces an output signal the bandwidth of which is twice the maximum. Double sideband large carrier dsblc modultion for general message signal mt. The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. Amplitude spectrum of dsbsc signal with filter curve dashed.
Singlesideband am signals have less bandwidth than normal am signals. Doublesideband suppressedcarrier amplitude modulation contents slide 1 doublesideband suppressedcarrier amplitude modulation slide 2 spectrum of a dsbscam signal slide 3 why called doublesideband slide 4 ideal coherent receiver slide 5 coherent receiver analysis slide 6 spectra in dsbscam system slide 7 demodulator using the preenvelope. Electrical engineering stack exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. The modulated data generated, appears as a form of signal. Amplitude modulation early radio ee 442 spring semester. As we know, the transmission bandwidth of standard am as well as dsbsc modulated wave is 2w hz i. A refinement of amplitude modulation, it uses transmitter power and. Understanding how the modulating waveform not only generates undulations of the envelope, but also generates sidebands, etc enables the basic concepts behind am to be understood. Communications signals and single sideband 7222010 1. Amplitude modulation am is similar to dsb but has the advantage of permitting a simpler demodulator, the envelope detector. Thus, ssb modulation requires half the bandwidth of am or dsbscam modulation. Media in category singlesideband modulation the following 34 files are in this category, out of 34 total. A sideband is a band of frequencies, containing power, which are the lower and higher frequencies of the carrier frequency.
Amplitude modulation am is a modulation technique where the. Single sideband suppressed carrier ssbsc modulation. A modulation approach called singlesideband modulation omits either the frequencies below c or those above c, and simply transmits the others, on the basis that the frequencies on the other side of c are redundant. Second, an optical single sideband signal can be self homodyne. Abbreviated as ssb, single sideband modulation is a type modulation that eliminates all components of one sideband from an amplitudemodulated wave. Modulation is the process of having the information to be communicated modifies a higher frequency signal called a carrier 2. It would seem, though, that there is information content in. Amplitude modulation is mostly used in the form of electronic communication. Chapter 7 singlesidebandmodulationssb andfrequency. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal.
It consisted of groups of telephone conversations modulated on upper andor lower sidebands of contiguous suppressed carriers. This allows transmitting the modulated signal with the spectral width, which is equal to the spectral. Amplitude modulation am is the oldest and simplest form of modulation. In both cases the transmission bandwidth b t is occupied by the upper sideband usb and lower sideband lsb. Single sideband modulation article about single sideband. Ssb modulation by dsbscam and filtering in singlesidebandssb modulation only the upper sideband or the lower sideband is transmitted.
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