I and q components in communications signals and single. The intelligence or information is in the sidebands. The carrier frequency, fc, should be larger than the highest spectral component. Single sideband modulation is a form of amplitude modulation.
The spectral components generated by a modulated signal are called sidebands. With this filter response, an optical single sideband suppressed carrier modulation is. Thus single sideband modulation requires only one sideband which is then demodulated into a full output signal whilst reducing the power demand of transferring a full signal 1. The purpose of this paper is the development of modulation and demodulation scheme of the single sideband qam signal ssb qam to eliminate the information redundancy in the spectrum of the transmitted signal. This technique contrasts with angle modulation, in which either the frequency of the. The relative height is 20logm db, where m is the nonnegative modulation index a.
Single sideband amplitude modulation matlab ssbmod. So we shall introduce to you the basic concepts of amplitude modulation then we. Chapter 3 will cover amplitude modulator and demodulator circuits. The equation above shows that the height of the sideband lines is different from that of the residual carrier. Amplitude modulation is a method of converting data into. Amplitude modulation am is the oldest and simplest form of modulation.
In this experiment, you will examine the characteristics of amplitude modulation am. Oct 12, 2020 am amplitude modulation double sideband wcarrier ssb usb single sideband upper sideband wsuppressed carrier ssb lsb single sideband lower sideband wsuppressed carrier fm frequency modulation lab demonstration to go along with questions. Sep 16, 2008 sideband modulation 91608 wheres the intelligence. The student will learn the basic concepts of ssb modulation and using the theoretical knowledge of courses. By removing some of the components of the ordinary am signal it is. To convert amdsbsc to am ssb sc either lsb or usb, the amdsbsc signal can be ltered with a bandpass. Thus, ssb modulation requires half the bandwidth of am or dsbscam modulation. It is based on the singlesideband suppressed carrier. Ssb reduces the transmitted bandwidth to b, but requires more complex modulator reduces snr for a. Forming qam signal with single sideband the ssb qam is a signal, which contains only a single sideband with frequencies 0. Notes and details about single sideband suppressed carrier, ssbsc widely used for analogue communications, especially on the hf portion of the radio. Change of any carrier parameter produces sidebands. It offers improved effective range over standard ssb modulation while simultaneously retaining backwards compatibility.
Ssb generation and demodulation salman ghafoor lecture aims phase shift method of ssb. 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. Carrier is modulated by varying amplitude linearly proportional to intelligence baseband signal amplitude. Consider a modulating wave mt that consists of a single tone or single frequency component. Phase modulation pm is a different form of frequency modulation and the carrier is similar in appearance to a frequencymodulated carrier. When a single frequency sine wave amplitude modulates a carrier, the modulating process. Characteristics of singlesideband systems in hf broadcasting itu. It is also known as ssb sc which is an acronym for single sideband suppressed carrier as it allows suppression of one sideband and carrier completely as we know, dsbsc modulation technique generates an output wave having twice the bandwidth as.
Single sideband ssb modulation, where only one sideband the lower sideband or the upper sideband is. Single sideband modulation assignment 1 yuhsien, chang. Ssb modulation by dsbscam and filtering in singlesideband ssb modulation only the upper sideband or the lower sideband is transmitted. As the name implies, single sideband, ssb uses only one sideband for a given audio path to. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio carrier wave. Amplitude modulation early radio ee 442 spring semester. 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 allocated range it is unacceptable because it causes severe interference with other stations and causes a loud splattering sound. The graphs above show the baseband signal, the signal of full amplitude modulation, the upper sideband and the lower sideband signals of. A signal carries useful information only when it changes.
Reviewer in amplitude and singlesideband modulation. Single sideband modulation ssb is an amplitude modulation scheme in which only a single sideband is transmitted through the channel. I and q components in communications signals and single sideband. There are three main techniques of amplitude modulation. This allows transmitting the modulated signal with the spectral width, which is equal to the spectral. In transmitted signal one half is occupied by usb, while the other half is occupied by lsb. R3e ssb, single sideband, reduced carrier j3e ssb, single sideband, suppressed carrier b8e isb, independent sideband c3f vsb, vestigial sideband table 21. We will study first the ssb baseband modulation and then single tone modulation. This harmonicgenerated sideband interference is called splatter.
Mar 25, 2015 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. Generate 512 samples of a simulated broadband signal using the sinc function. In both cases the transmission bandwidth b t is occupied by the upper sideband usb and lower sideband lsb. The modulating signal is split into two identical signal. Second, an optical single sideband signal can be self homodyne. Amplitude modulation am is similar to dsb but has the advantage of permitting a simpler demodulator, the envelope detector. Recognize an am signal in the time domain oscilloscope display, the frequency domain spectral display, or in trigonometric equation form. Quadrature amplitude modulation with amplitude modulation. Calculate the percentage of modulation of an am signal given waveform measurements.
The three principal types of electronic communications are amplitude modulation am, frequency modulation fm, and phase modulation pm. That is m t a f t cos2 m s m, where a m is the amplitude and f m is the frequency of the modulating wave respectively. As far as demodulation is concerned, we can coherently demodulate ssb as we did the. Chapter 7 singlesideband modulation ssb and frequency. Single sideband, ssb modulation is basically a derivative of amplitude modulation, am.
The following considerations will be concen trated on single sideband amplitude modulation with synchronous demodulation. 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. We will cover am along with a derivation known as singlesideband modulation in this chapter. Amplitude modulation, therefore, is the alteration of the amplitude of a carrier by a modulator.
A highresolution lownoise single laser photonic filter that can operate to high frequencies is presented. Double sideband dsb is one of the easiest modulation techniques to understand, so it is a good starting point for the study of modulation. Process by which a property or a parameter of a signal is varied in proportion to a second signal. For demodulation ssb can be coherently demodulated by multiplying with cos ct andfollowed by lpf. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal, such as an audio signal. Amplitude modulation and singlesideband modulation. A type of dsb, called binary phaseshift keying, is used for digital telemetry. Ece 453 single sideband modulation university of illinois. Let the message signal mt is band limited to w hz and its hilbert transform is mt h. For single sideband suppressed carrier of montone message, the wave form is xssbt acm 2 cos. Single sideband ssb modulation, where only one sideband the lower sideband or the upper sideband is transmitted. Chapter 7 singlesidebandmodulationssb andfrequency.
Amplitude companded single sideband is a narrowband modulation method using a single sideband with a pilot tone, allowing an expander in the receiver to restore the amplitude that was severely compressed by the transmitter. This is the ratio of the modulation amplitude and the amplitude of the unmodulated carrier. This example shows how to use the hilbert transform to carry out singlesideband ssb amplitude modulation am of a signal. Single sideband quadrature amplitude modulation springerlink. Amplitude modulation and singlesideband modulation chapter 2 chapter objectives this chapter will help you to. 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. That is m t a f t cos2 m s m, where a m is the amplitude and f m is. We will assume that the baseband message signal mt is band limited with a cuto. Single side band modulation ssb theoretical background single side band modulation is a type modulation that eliminates all components of one sideband from an amplitude modulated wave. The carrier signal and x have sample frequency fs hz. Sideband modulation 7222010 wheres the intelligence. Double sideband suppressed carrier dsbsc modulation, where only the upper and lower sidebands are transmitted. This is the ratio of the modulation amplitude and the amplitude. For a sinusoidal carrier, a general modulated carrier can be represented mathematically as xt atcos2.
Amplitude modulation produces an output signal the bandwidth of which is twice the maximum frequency of the original baseband signal. May 14, 2020 modulation is the process of having the information to be communicated modifies a higher frequency signal called a carrier. Special situations like single side band ssb and dsbsc. The following considerations will be concen trated on singlesideband amplitude modulation with synchronous demodulation. In both cases the transmission bandwidth is occupied by the upper sideband usb and lower sideband lsb. Amplitude modulation envelope detected signal f am, e.
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. The modulated data generated, appears as a form of signal. Singlesideband am signals have less bandwidth than normal am signals. Apr 21, 2017 anew modulation scheme single sideband quadrature amplitude modulation ssb qam is proposed. Amplitude modulation and dsbsc techniques require transmission bandwidth of twice the bandwidth of the modulating signal mt. Ssb was used for long distance telephone communications. Amplitude modulation is a method of converting data into an alternatingcurrent carrier waveform. In am, the amplitude of the carrier is changed in accordance with the amplitude and frequency or the characteristics of the modulating signal. Therefore, both fm and pm are often referred to as angle modulation. It is also known as ssb sc which is an acronym for single sideband suppressed carrier as it allows suppression of one sideband and carrier completely. Derivation of time and frequency domain expressions lsb and usb modulation. Why not just send the sidebands or just a sideband.
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