Modulation and demodulation hold dominant positions in communication. Single sideband modulation, ssb demodulation electronics notes. 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. Bfsk modulation and demodulation file exchange matlab central. There are many types of modulation so there are many. For example, an am radio system transmits electromagnetic waves with frequencies of around a few hundred khz mf band the fm radio system must operate with frequencies in the range of 88108 mhz vhf band since the baseband signal contains frequencies in the audio. This principle is at the heart of amplitude modulation. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. Since, the two sidebands carry the same information, there is no need to transmit both sidebands. Observations usb and lsb are uniquely related to each.
Amplitude modulation am, demodulation and their circuit. In qpsk, the data bits to be modulated are grouped into. But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Frequency modulation and phase modulation are the two complementary principal methods of angle modulation. An ideal frequency modulated fm signal discriminators output is pro.
Demodulation is the opposite process of modulation. The signal output from a demodulator may represent sound an. Amplitude modulationdemodulation in matlab file exchange. If the received carrier phase is assumed to be constant, each of the seven reference values will have to be shifted only once at the beginning of the simulation. This application report discusses logic level implementation of binary fsk bfsk modulator and demodulator using a phaselocked loop pll device. As we mentioned before, well use dsbc modulation because of its ease in demodulation. In both cases the transmission bandwidth b t is occupied by the upper sideband usb and lower sideband lsb. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. To implement the simulink models for fm including a basic sinusoid and a multimedia file music to analyze each signal in time and frequency domains using time scope and spectrum analyzer. Analog modulation delas with the voice, video and regular waves of base band signals.
Frequency division multiplexing, fdma amplitude modulation and demodulation. Frequency modulation consists of encoding information onto a carrier signal by varying the frequency of the carrier. The process of suppressing one of the sidebands along with the carrier and transmitting a. There are many types of modulation so there are many types of demodulators.
Bandpass modulation and demodulation techniques communication systems, dept. Oct 25, 2015 implementation of bfsk modulation and demodulation. Ofdm is a combination of modulation and multiplexing. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. In the previous chapters, we have discussed dsbsc modulation and demodulation. Multiplexing generally refers to independent signals, those produced by different sources. Hi, im a beginner in matlab and im just wondering whether the modulation constant. To understand the theoretical foundations for angle modulation as well as frequency modulation fm and demodulation. Introduction frequency modulation is a form of modulation, which represents information as. The student will learn the basic concepts of ssb modulation.
In fm modulation when the bandwidth becomes so large that the input noise power is relatively large, the performance of the fm system degrades rapidly and the system exhibits a threshold. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. Frequencyshift keying fsk is the frequency modulation system in which digital information is transmitted through the discrete frequency change of a carrier wave. Is there a way i can vary it, say, to 100% modulation depth. Implementation of fsk modulation and demodulation using. The amplitude of the carrier remains constant phase modulation pm another form of analog modulation technique which we will not discuss. 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. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is sinusoidal. Each channel sharing scheme a set of basis vectors. First, just consider a simple example of throwing a paper for a much far distancecould u do that with ease. Ee4512 analog and digital communications chapter 5 chapter 5 digital bandpass modulation and demodulation techniques. Modulation, analog modulation, digital modulation, am,fm,pm. Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors.
Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Both processes aim to achieve transfer information with the minimum distortion, minimum loss and. In chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. The term detection is the older term dating back to the early days of radio. Frequency shift keying fsk modulation and demodulation. Then inner products dot products are 1 1 0 can interpret inner product as projection of vector 1 v1 onto vector 2 v2in other words, inner product of v1 and v2 tells us how much of vector 1 is there in the direction of vector 2. There are different types of modulation and so are demodulators. Ee4512 analog and digital communications chapter 6 the dsbsc am coherent receiver has a bandpass filter centered at f c and with a bandwidth of twice the bandwidth of st because of the lsb and usb. Source called v1 generates the message to be transmitted. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. Ssb sc modulation, and demodulation techniques for analog commu nication. Fsk frequency shift keying d1 63 fsk in f 1 f 2 decision out figure 4. There will be a minimum frequency separation required of the two tones. The next installment will examine some of the more complex forms of digital modulation, and explain the use of the time domain and pulsed signals in systems employing pulse modulation e.
Tcom 370 notes 995 modulation and demodulation modems for data transmission over analog links 1. 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. Using matlab mfile and simulink to implement fm modulation and demodulation. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. Modulation allows us to transmit multiple signals in the same medium i. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Terms like diode detector, synchronous detector and product detector are widely used. 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. Multiplexing method of sharing a bandwidth with other independent data channels. Chapter 7 singlesidebandmodulationssb andfrequency. The ad630 is a high precision balanced modulatordemodulator that combines a flexible.
In chapters 1 and 2 you studied how to apply intelligence modulation to an rf carrier wave. The goal of this experiment is to become familiar with fm modulation and demodulation. Carrier modulation allows the transmission of modulating frequencies. These methods contrast with amplitude modulation, in which the amplitude of the carrier wave varies, while the frequency and phase remain constant. The technology is used in communication systems such as amateur radio, caller id, and urgent situation broadcasts. In order to demodulate single sideband, ssb, it is necessary to reintroduce the carrier. Chapter 5 digital bandpass modulation and demodulation techniques. Frequency modulation fm frequency modulation is the process of varying the frequency of a carrier wave in proportion to the amplitude of a baseband signal.
Modulation and demodulation technology innovation and. The larger fraction of the pulse energy is near 0 frequency. A modem is an equipment that performs both modulation and demodulation. And the lower sideband ssb modulation uses the lowpass. When input noise power is quite large we would be inclined to use fm and allows a sacrifice of bandwidth for the sake of improved output signaltonoise ratio. Ssb modulation and demodulation pdf slide 9 coherent ssb demodulation. The carrier tone simplifies demodulation but carries no information. Demodulation is extracting the original informationbearing signal from a carrier wave. Here is the circuit used for modulation and its simulation. These modulation techniques form an integral part of academic curricula today. The bandwidth of each is dependent on the message bit rate. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation.
If not, what is the default depth of modulation for am here. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. This is part one of a twopart article on the basics of modulation and demodulation. Hapter modulation and demodulation mit opencourseware. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. This is called the process of modulationand demodulation remember the radio spectrum.
Bfsk modulation and demodulation keysight community. Circuit used suitable for envelope detector noncoherent diode with an rc. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Once a signal has been modulated, information is retrieved through a demodulation process. Tcom 370 notes 995 modulation and demodulation modems for. There are two types of modulation analog and digital. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Review pulse train bandwidth s ingle pulse of duration. This demodulator is more complex than most asynchronous demodulators.
1487 771 481 656 129 589 1263 1421 1143 497 868 1354 1303 835 46 1365 1215 1427 1038 338 1067 71 904 867 1332 64 204 890 218 80 910 1228 392 367 961