Analog communication dsbsc modulators in this chapter, let us discuss about the modulators, which generate dsbsc wave. Lab 2 dsbsc generation and demodulation nick patino ece 458. 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. Doublesideband suppressed carrier modulation dsb sc in full am dsb am, 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. Dsbsc and am modulation page 1 of 5 purpose the purpose of the lab is to examine the spectral content of an amplitude modulated carrier signal. In doing so, we explored the effects of both modulation and demodulation on the frequency spectrum of the signal,the. Fig 4 dsbsc modulation for a band limited message signal and its spectrum. Amplitude modulation am frequency modulation fm lin dai city university of hong kong ee3008 principles of communications lecture 3. In this experiment you will design an analog modulator and an analog demodulator. This is what i done with matlab coding for modulation and demodulation. In the course of demodulating, this block uses a filter whose order. Answer to here is the matlab code for dsbsc modulation.
Apr 14, 2016 this video is a part of the video series for analog communication course brought to you by mit ieee student branch. The voltage or current spectrum of dsb sc will be therefore no waste of power for discrete carrier component. It simply is an analysis of am and dsbsc modulation and demodulation of a periodic square wave. Ordinary am amplitude modulation as used in traditional am broadcasting results in a signal which, when analyzed as to its frequency spectrum is seen to consist of a centr. The acronym stands for double sidebandsuppressed carrier modulation. Double sideband suppressed carrier dsb sc modulation. A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. The process of modulation in a communication system increases its cost and complexity. In this chapter, let us discuss about the modulators, which generate dsbsc wave. Quadrature amplitude modulation qam is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. For demodulation, the modulation oscillators frequency and phase must be exactly the same as the demodulation oscillators otherwise, distortion andor attenuation will occur. It explains dsbsc generation using a balanced modulator. Fig 4 shows a base band signal, carrier and corresponding dsb sc modulated waves.
As we know, the transmission bandwidth of standard am as well as dsbsc modulated wave is 2w hz i. As with dsb sc, the modulating signal spectrum is shifted directly to the carrier frequency band without loss. Understanding the phasing method of single sideband modulation rick lyons. Dsbsc modulated signal as a function of time is represented by s t a m t f t cos2 ccs. Theory and experiment article january 2009 with 2,593 reads how we measure reads. Scientific offering dsbsc modulation and demodulation in bengaluru, karnataka. Below is what happen when you overmodulate a little bit, leaving some carrier behind but going beyond the am broadcast levels of modulation.
Double sideband modulation dsb and single sideband modulation ssb 45. Data communication using dsbsc am modulation demodulation of modified square wave. As expected from above, dsc sc system is usually not recommended for the general use since its demodulation is not as practical as in dsb and dsb rc systems. Doublesideband suppressedcarrier transmission dsbsc is transmission in which frequencies produced by amplitude modulation am are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest practical level, ideally being completely suppressed. Double sideband suppressed carrier dsb sc modulation objective. From this equation, it is obvious that the carrier component in am wave remains constant in amplitude and frequency.
Therefore, both these systems are bandwidth inefficient systems. Test the product detector by feeding in digitally synthesized singletone am and dsbsc signals with varying snr. But ssb demodulation information at that web site was terribly sparse. Read about company and get contact details and address. This points to a shortcoming of amplitude modulation, that only a. In order to demodulate single sideband, ssb, it is necessary to reintroduce the carrier.
The modified switchingmodulator for generation of am and. A normal system also termed as double sideband full carrier dsb fc system, transmits carrier along with the two sidebands. A regular am receiver will produce distortion as per the topright diagram due to the modulation being greater than 100%. Both simple multiplier type and nonlinear element type modulatorsdemodulators will be constructed. Ring modulator for the double sideband suppressed carrier generation.
Apr 28, 2016 hp deskjet 2, 25, 3630, 3635, 4720 ciss hp 63, 302, 123, 803. 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. Dsbsc phase demodulation application for vibration measurement. Dec 03, 2015 double sideband suppressed carrier dsb sc system definition and mathematical expression. Basic concepts of modulation three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Modulation is a process of translating information signal from low band frequency to high band frequency that is suits the transmission medium. Understanding the phasing method of single sideband demodulation. Double sideband dsb and amplitude modulation am modules. The modulator the modulator outputs two files, the first with the modulated signal exactly n real elements long and the. 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. Dsb sc modulated signal as a function of time is represented by s t a m t f t cos2 ccs.
Ssbsc modulation can be achieved with various systems, but in terms of hardware, usb or lsb can be used as a filter. 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. Ssb vs vsb difference between ssb and vsb modulation. Message signal embed into the amplitude of carrier simple am is also called. Introduction to double sideband suppressed carrier dsbsc. Pdf dsbsc phase demodulation application for vibration. Remember, neither yt, nor the oscillator signal, appears at the multiplier output. In both cases the transmission bandwidth b t is occupied by the upper sideband usb and lower sideband lsb.
Chapter 6 doublesideband suppressedcarrier amplitude. In the doublesideband suppressedcarrier transmission dsb sc modulation, unlike am, the wave carrier is not transmitted. Cw modulation is just a multiplication, for montone message and larger. Following is the block diagram of the balanced modulator. Dec 10, 2015 single sideband suppressed carrier ssbsc modulation. However, modulation is extensively used in most communication systems. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. 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.
Double sideband suppressed carrier dsbsc modulation. The dsb sc output is obtained at the secondary of the rf. Analog communication dsbsc modulators tutorialspoint. And the lower sideband ssb modulation uses the lowpass. The webs wikipedia singlesideband modulation gives the mathematical details of ssb generation 1. Unit 4 week3 power efficiency, dsbsc modulation and. Amplitude modulation a modulating signal, b carrier signal, c modulated. As expected from above, dscsc system is usually not recommended for the general use since its demodulation is not as practical as in dsb and dsbrc systems. It explains dsb sc generation using a balanced modulator.
Dsbsc modulation at a carrier frequency, kc, specified by the student. Before we start our discussion, it is recommended to understand concept of dsb sc vs ssb sc which mentions difference between dsb sc and ssb sc modulation types. The input is a passband representation of the modulated signal. Am modulation dsbfc free download as powerpoint presentation. Answer to here is the matlab code for dsb sc modulation. We once had a homework way back when decided to share it. Fig 4 dsb sc modulation for a band limited message signal and its spectrum. Test the circuit by feeding in an external modulation multitone am signal from the arb. The modulated signal s dsbsc amt looks similar to st but has a temporal but not spectral carrier component. Ring modulator for the double sideband suppressed carrier. The dsbsc am demodulator passband block demodulates a signal that was modulated using doublesideband suppressedcarrier amplitude modulation. Ssb modulation and demodulation pdf slide 9 coherent ssb demodulation. This page on ssb modulation vs vsb modulation describes difference between ssb and vsb modulation types. 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.
Hp deskjet 2, 25, 3630, 3635, 4720 ciss hp 63, 302, 123, 803. Dsb sc is useful to ensure the discrete carrier signal is suppressed. Analog communication dsbsc modulation tutorialspoint. To perform the doublesideband suppressedcarrier dsb sc amplitude modulation.
Am and dsbsc modulation and demodulation of a periodic. To extend the range of sound, we need to transmit it through a medium other than air, such as a phone. Single sideband modulation or ssb is derived from amplitude modulation am and ssb modulation overcomes a number of the disadvantages of am. Demodulation is done by multiplying the dsbsc signal with the carrier signal. Ssb sc modulation, and demodulation techniques for analog commu nication. Aug 08, 2012 however, in searching the internet for tutorial ssb demodulation information i was shocked at how little information was available. Process by which a property or a parameter of a signal is varied in proportion to a second signal. The modulated signal s dsb sc amt looks similar to st but has a temporal but not spectral carrier component.
Ring modulator for the double sideband suppressed carrier generation, wokring operation, carrier suppression, operation in presence of modulating signal. Dsbsc optical modulated signal by using mzm, and it suppresses one sideband. The student will be able to determine the modulation index, sideband power, and carrier power of a sine wave modulated am signal, and to identify the envelope of the modulated waveform on an. It conveys two analog message signals, or two digital bit streams, by changing modulating the amplitudes of two carrier waves, using the amplitudeshift keying ask digital modulation.
An outline of dsbscssbsc modulation and demodulation. This video is a part of the video series for analog communication course brought to you by mit ieee student branch. Dsb sc modulated signals undergo phase reversal when mt changes sign. Dsb sc and am modulation page 1 of 5 purpose the purpose of the lab is to examine the spectral content of an amplitude modulated carrier signal.
Thus, in order to save power and bandwidth, dsb sc modulation technique is adopted. Doublesideband suppressedcarrier transmission wikipedia. So, dsb sc system is used in order to overcome the drawback of dsb fc system. Doublesideband suppressedcarrier transmission dsb sc is transmission in which frequencies produced by amplitude modulation am are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest practical level, ideally being completely suppressed.
Dsbsc can be demodulated if modulation index is less than unity. Both the input and output signals are real scalar signals. The modulator outputs two files, the first with the modulated signal exactly n real elements long and the other a special trinary signal where 1 indicates time location of a 1 bit and 1 indicates. Analog communication dsbsc modulation in the process of amplitude modulation, the modulated wave consists of the carrier wave and two sidebands. Balanced modulator consists of two identical am modulators. Understanding the phasing method of single sideband.
The modified switchingmodulator for generation of am. This points to a shortcoming of amplitude modulation, that only a fraction of the total. Demodulation needs a digital costly system to restore the carrier both frequency and phase. Single sideband suppressed carrier ssbsc modulation. Amplitude modulation produces an output signal the bandwidth of which is twice the. Pdf a heterodyne interferometry with dsbsc performance is presented to measure small vibration signal. Modulation is also not difficult same as case 2 and 3. 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 modified switchingmodulator for generation of am and dsbsc. Single sideband modulation ssb standard am and dsb sc 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.
888 279 1381 1508 643 1157 123 47 326 319 1289 20 1306 445 1437 1529 1206 593 1304 771 539 451 388 687 1036 846 348 1162 87 727 212 1236 1068 589 604 454 218 309 1048 69 1000 610 1219 1350 974 413 856