By the end of this experiment, the student should be able to. Since, the two sidebands carry the same information, there is no need to transmit both sidebands. The student will learn the basic concepts of ssb modulation and using the theoretical knowledge of courses. There are four ways to demodulate a transmitted single sideband ssb signal. 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. Abbreviated as ssb, single sideband modulation is a type modulation that eliminates all components of one sideband from an amplitudemodulated wave. This example shows how to use the discrete hilbert transform to implement single sideband modulation. One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif.
Chapter 7 singlesidebandmodulationssb andfrequency. A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. Double sideband dsb and single sidebandssb sharlene katz james flynn 91608. 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. Understanding single sideband modulation and demodulation. Doublesideband suppressedcarrier amplitude modulation and. The webs wikipedia single sideband modulation gives the mathematical details of ssb generation 1. Fn 3 and 4 compares the phasor representation of am and ssb signals. Double sideband dsb and amplitude modulation am modules. Singlesideband am signals have less bandwidth than normal am signals. The modulated signal has the information in the whole band except at the carrier frequency. In radio communications, single sideband modulation ssb or single sideband suppressedcarrier.
Ssb demodulation can be carried out with a synchronous demodulator. Aug 08, 2012 however, in searching the internet for tutorial ssb demodulation information i was shocked at how little information was available. This expression is correct provided that we keep in the range. Pdf zero guard band multitwinssb system in single fiber. Please focus on conceptual treatment rather than individual techniques of modulation and demodulation. Recall that our goal is to transmit data over a commu nication link, which we achieve by mapping the. In radio communications, singlesideband modulation ssb or singlesideband.
Sep 15, 20 lecture 10 single sideband modulation nptelhrd. The following article gives an overview of the different methods for ssb demodulation and their use in software defined radios. In the above figure, the carrier and the lower sideband are suppressed. I and q components in communications signals and single. I am trying to compare the demodulation for single sideband ssb and dual sideband modulation formats dsb when the reconstructed carrier is not perfect i. Hence, the upper sideband is used for transmission.
Using a pilot tone information cannot be derived by a system like the costas loop because the ssb signal is the sum. In fact, it can be shown that a coherent demodulator performs better than an envelope detector when the received signal is corrupted by additive noise. Modulation and demodulation methods are different when i and q representation is used x t t k x t dt fm c m cos z. Single sideband amplitude demodulation matlab ssbdemod. Finally, the qam signals were demodulated for bit error rate. Each channel sharing scheme a set of basis vectors. A sideband is a band of frequencies, containing power, which are the lower and higher frequencies of the carrier frequency. Single sideband ssb is a common analog modulation scheme for voice communications. The hilbert transform finds applications in modulators and demodulators, speech processing, medical imaging, direction of arrival doa measurements, essentially anywhere complexsignal quadrature processing simplifies the design. In both cases the transmission bandwidth b t is occupied by the upper sideband usb and lower sideband lsb. Fn 3 shows the sideband doubled for comparison with am.
Understanding the phasing method of single sideband demodulation. Understanding the phasing method of single sideband. This is the same as the am modulation above but without the carrier. Media in category single sideband modulation the following 34 files are in this category, out of 34 total. Mar 17, 2017 what does single sideband modulation mean. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. In the previous chapters, we have discussed dsbsc modulation and demodulation. Ssb was used for long distance telephone communications. Single sideband amplitude modulation pdf in single sideband ssb modulation only the upper sideband. Modulation index for some common functions using frequency and phase modulation abstract the equations defining the amplitude of sidebands resulting from either frequency modulation or phase modulation by either squarewave, sinewave, sawtooth or triangular modulating functions are presented.
To recover the modulating signal from the ssbsc signal, we require a phase coherent or synchronous demodulator. Second, an optical single sideband signal can be self. Modulation and demodulation medium, it would be dif. Generate 512 samples of a simulated broadband signal using the sinc function. The analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Single sidebandmodulation ssb andfrequency translation contents slide 1 singlesideband modulation slide 2 ssb by dsbscam and filtering.
External processing for controlled envelope single sideband pdf. Pdf we propose a novel zero guard band zgb multitwinssb bidirectional. This points to a shortcoming of amplitude modulation, that only a fraction of the total. But ssb demodulation information at that web site was terribly sparse. Double sideband suppressed carrier modulation dsbsc in full am dsbam, the carrier wave ct is completely independent of the message signal mt, which means that the transmission of carrier wave represents a waste of power. 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. If there are two gaussian noise signals, n1 and n2, with the variance of n2 being greater than the variance of n1, then the pdf of n2 pdf 2 has a wider spread around its mean than n1s pdf pdf 1 see fig. Demodulation is extracting the original informationbearing signal from a carrier wave. This thesis investigates the potential of optical single sideband signahg at 10 gb s.
There are many types of modulation so there are many types of demodulators. The carrier tone simplifies demodulation but carries no information. As described in previous pages, single sideband is a form of amplitude modulation where the carrier and one sideband have been suppressed or reduced in level. Why not just send the sidebands or just a sideband. This chapter describes the essential principles behind. I want to show mathematically in which case distortion would be more problematic. Doesnt the sideband modulated wave look like a regular sine wave from a generator. In the process of amplitude modulation or phase modulation, the modulated wave consists of the carrier wave and two sidebands.
In this modulation, only half of the signal of the dsbsc is used. The modulated signal has zero initial phase, and can be an upper or lower sideband signal. And how exactly is the message recovered from the third diagram. Fn 1 and 2 shows the amplitude and phase distortion which is a consequence of using only one sideband fn 1 shows upper sideband and fn 2 shows lower sideband distortion. Demodulation of a modulated amplitude synthesizes the upper and lower sidebands, and produces an output signal. Sc modulation, and demodulation techniques for analog communication. Pdf optical single sideband signal generation using phase. I and q components in communications signals and single sideband. Audio oscillator, wideband true rms meter, multiplier, adder, utilities, phase shifter, tuneable lpf, quadrature utilities, noise generator, speech, headphones 0 prelaboratory reading double sideband dsb is one of the easiest modulation techniques to understand, so it is a good. A modem is an equipment that performs both modulation and demodulation. The process of suppressing one of the sidebands along with the carrier and transmitting a single sideband is called as single sideband suppressed carrier system or simply ssbsc. The type of modulation that will be studied in this chapter is called double sideband suppressedcarrier amplitude modulation dsbscam. The product modulator is a type of coherent ssb demodulator.
Single sideband modulation via the hilbert transform. This example shows how to use the hilbert transform to carry out singlesideband ssb amplitude modulation am of a signal. The process of suppressing one of the sidebands along with the carrier and transmitting a. In order to demodulate single sideband, ssb, it is necessary to reintroduce the carrier. Hapter modulation and demodulation mit opencourseware. Process by which a property or a parameter of a signal is varied in proportion to a second signal. Demonstrate the modulation and demodulation process of ssb. Ssb demodulation can use a dsbsc demodulator with no change. In radio communications, single sideband modulation ssb or single sideband suppressedcarrier modulation ssbsc is a type of modulation used to transmit information, such as an audio signal, by radio waves. 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. The demodulation of single sideband ssb signals requires special attention, because simple mixing leads to superposition of the upper and lower sidebands at audio frequencies.
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