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. There are four ways to demodulate a transmitted single sideband ssb signal. Hapter modulation and demodulation mit opencourseware. 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. The type of modulation that will be studied in this chapter is called double sideband suppressedcarrier amplitude modulation dsbscam. In radio communications, single sideband modulation ssb or single sideband suppressedcarrier. Sc modulation, and demodulation techniques for analog communication. The following article gives an overview of the different methods for ssb demodulation and their use in software defined radios. Demodulation is extracting the original informationbearing signal from a carrier wave. External processing for controlled envelope single sideband pdf. In the above figure, the carrier and the lower sideband are suppressed. This chapter describes the essential principles behind. 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.
In order to demodulate single sideband, ssb, it is necessary to reintroduce the carrier. Pdf zero guard band multitwinssb system in single fiber. Process by which a property or a parameter of a signal is varied in proportion to a second signal. Generate 512 samples of a simulated broadband signal using the sinc function. The process of suppressing one of the sidebands along with the carrier and transmitting a. Hence, the upper sideband is used for transmission. Demonstrate the modulation and demodulation process of ssb. This points to a shortcoming of amplitude modulation, that only a fraction of the total. Fn 3 and 4 compares the phasor representation of am and ssb signals. To recover the modulating signal from the ssbsc signal, we require a phase coherent or synchronous demodulator. Since, the two sidebands carry the same information, there is no need to transmit both sidebands.
Why not just send the sidebands or just a 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. Single sideband modulation via the hilbert transform. But ssb demodulation information at that web site was terribly sparse. This example shows how to use the hilbert transform to carry out singlesideband ssb amplitude modulation am of a signal.
Fn 3 shows the sideband doubled for comparison with am. Double sideband dsb and amplitude modulation am modules. Singlesideband am signals have less bandwidth than normal am signals. I and q components in communications signals and single. Demodulation of a modulated amplitude synthesizes the upper and lower sidebands, and produces an output signal. Second, an optical single sideband signal can be self. The modulated signal has zero initial phase, and can be an upper or lower sideband signal. Abbreviated as ssb, single sideband modulation is a type modulation that eliminates all components of one sideband from an amplitudemodulated wave.
Single sideband amplitude demodulation matlab ssbdemod. The webs wikipedia single sideband modulation gives the mathematical details of ssb generation 1. Analog communication ssbsc modulation tutorialspoint. Media in category single sideband modulation the following 34 files are in this category, out of 34 total. There are many types of modulation so there are many types of demodulators. Finally, the qam signals were demodulated for bit error rate. I want to show mathematically in which case distortion would be more problematic. 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. One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif. Understanding the phasing method of single sideband demodulation. Aug 08, 2012 however, in searching the internet for tutorial ssb demodulation information i was shocked at how little information was available. Chapter 7 singlesidebandmodulationssb andfrequency. I and q components in communications signals and single sideband 7222010 1.
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. This example shows how to use the discrete hilbert transform to implement single sideband modulation. This is a modification of the ssb to ease the generation and reception of the signal. Pdf optical single sideband signal generation using phase. Using a pilot tone information cannot be derived by a system like the costas loop because the ssb signal is the sum. 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. 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. 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.
The modulated signal has the information in the whole band except at the carrier frequency. This thesis investigates the potential of optical single sideband signahg at 10 gb s. In both cases the transmission bandwidth b t is occupied by the upper sideband usb and lower sideband lsb. 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. Single sideband modulation or ssb is derived from amplitude modulation am and ssb modulation overcomes a number of the disadvantages of am. Each channel sharing scheme a set of basis vectors. 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.
Single sideband amplitude modulation pdf in single sideband ssb modulation only the upper sideband. 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. 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. A sideband is a band of frequencies, containing power, which are the lower and higher frequencies of the carrier frequency. Sep 15, 20 lecture 10 single sideband modulation nptelhrd. Modulation and demodulation medium, it would be dif.
In radio communications, singlesideband modulation ssb or singlesideband. The product modulator is a type of coherent ssb demodulator. An optical single sideband ossb generation method using phase modulation in semiconductor optical amplifier soa is proposed to overcome the dispersioninduced carrier suppression problem which. In the previous chapters, we have discussed dsbsc modulation and demodulation. In this modulation, only half of the signal of the dsbsc is used. Pdf we propose a novel zero guard band zgb multitwinssb bidirectional. And how exactly is the message recovered from the third diagram. This is the same as the am modulation above but without the carrier.
Doesnt the sideband modulated wave look like a regular sine wave from a generator. 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. 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. Ssb demodulation can be carried out with a synchronous demodulator. 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. By the end of this experiment, the student should be able to. Understanding the phasing method of single sideband.
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. Double sideband dsb and single sidebandssb sharlene katz james flynn 91608. In the process of amplitude modulation or phase modulation, the modulated wave consists of the carrier wave and two sidebands. The student will learn the basic concepts of ssb modulation and using the theoretical knowledge of courses.
Recall that our goal is to transmit data over a commu nication link, which we achieve by mapping the. Single sideband ssb is a common analog modulation scheme for voice communications. This expression is correct provided that we keep in the range. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. The carrier tone simplifies demodulation but carries no information. Ssb was used for long distance telephone communications. Mar 17, 2017 what does single sideband modulation mean. I and q components in communications signals and single sideband.
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