Modulation demodulation maps retrieves the digital information into from an analog waveform appropriate for transmission over the channel. Nfm may have better spectrum efficiency than fm, but nfm just doesnt go as far. Modulation and demodulation summary figure 19 is a block diagram that summarizes the steps involved in modulating and demodulating a signal by a frequency f2. Ofdm is a combination of modulation and multiplexing. There will be a minimum frequency separation required of the two tones. Jun 17, 2014 introduction to modulation and demodulation 1. This site uses cookies to offer you a better browsing experience. To understand the theoretical foundations for angle modulation as well as frequency modulation fm and demodulation. Hapter modulation and demodulation mit opencourseware. The instructor would begin the demodulation demonstration by providing some background material on the concept of demodulation. The amfm modulation model and a multiband analysisdemodulation scheme is applied to speech formant frequency and bandwidth tracking. Ssbsc modulated signal has only one sideband frequency. A noncoherent detector has only one input, namely, the modulated signal port. Frequency modulation is widely used on frequencies above 30 mhz, and it is particularly well known for its use for vhf fm broadcasting.
Since frequency modulation is a nonlinear process, an exact description of the spectrum of an frequencymodulated signal for an arbitrary message signal is more complicated than linear process. There are many types of modulation so there are many types of demodulators. 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. The amfm modulation model and a multiband analysis demodulation scheme is applied to speech formant frequency and bandwidth tracking. Demodulation of vsbsc wave is similar to the demodulation of ssbsc wave. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation. Modulation types of modulation definition applications. The modulated signal y has zero initial phase and zero carrier amplitude, resulting from a.
Fm signals have the same peak frequency deviation, then when mt is a sinusoidal signal set such that the pm and note. The term and technology us used in both telecommunications and signal processing in analog frequency modulation, such as fm radio broadcasting of an audio signal representing voice or music, the instantaneous frequency deviation, the difference between the. Implementation of fsk modulation and demodulation using. Modulation damplitude demodulation damplitude pdf book. 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. Review pulse train bandwidth s ingle pulse of duration. If not, what is the default depth of modulation for am here. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. Fm versus nfm for best radio communications radiomaster. The carrier signal and y have sampling frequency fs. In an earlier semester project, four fm demodulation algorithms were developed and tested on their suitability. Frequency modulation and demodulation file exchange. The pdf describes a reyliegh distribution, where as pdf describes a uniform. But if u use a stone or any other object to wind the paper, then the paper reaches more t.
Theoretically, we can get one sideband frequency component completely by using an ideal band pass filter. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Modulation and demodulation principle borrow from radio telecommunication take a wide band signal few hz to khz modulate it with a single frequency the carrier signal which is the frequency associated to a given station emit the signal given the station frequency, a receiver follows a demodulation. This is the same as the am modulation above but without the carrier. 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 ssbsc modulation and demodulation. For a sine wave modulation, the modulation index is seen to be the ratio of the peak frequency deviation of the carrier wave to the frequency of the modulating sine wave. The vsbsc demodulator is shown in the following figure. It is also possible to change the frequency of a signal to give frequency modulation or fm. The signal output from a demodulator may represent sound an.
Analog communication vsbsc modulation tutorialspoint. Amplitude modulationdemodulation in matlab file exchange. Is there a way i can vary it, say, to 100% modulation depth. 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. Spectrum of angle modulated signals with different modulation index. Key differences between modulation and demodulation 1. Eee2009eee2009 communicationscommunications contents introduction to communication systems analogue modulation am, dsbsc, vsb, ssb, fm, pm, narrow band fm, pll demodulators, and fll loops sampling systems time and frequency division multiplexing systems, nyquist principle, pam, ppm, and pwm.
La72912v fm modulator and demodulator ic overview the la72912v is a fm modulation and demodulation singlechip ic. Multiplexing generally refers to independent signals, those produced by different sources. Hence, this process of detection is called as coherent or synchronous detection. The goal of this experiment is to become familiar with fm modulation and demodulation. Here, the same carrier signal which is used for generating vsbsc wave is used to detect the message signal. The demodulation demonstration is set up by configuring the board for 100% modulation and connecting one channel of the scope to the audio waveform at tp1 and the other channel the output.
Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. Lecture notes on analogue communication techniques. Hi, im a beginner in matlab and im just wondering whether the modulation constant. The amount of change in frequency is determined by the amplitude of the modulating signal. Once the signal has been received, filtered and amplified, it is necessary to recover the original modulation from the carrier. If poss explain me the working of each syntax in the program. Modulation of amsc and demodulation by modulating again. It is this process that is called demodulation or detection. Frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. Multiplexing method of sharing a bandwidth with other independent data channels. The 6 decibels reduction in nfm deviation and modulation index is sadly a 6 db decrease in signaltonoise ratio snr, and this unfortunately means that nfm causes a loss of about 30% of your distance coverage versus regular fm. 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.
Aly elosery october 25, 2010 this lab is divided into two parts. You will model the pll, and recover the message from the fm signal. First, just consider a simple example of throwing a paper for a much far distancecould u do that with ease. The technique of modulation helped humans to use wireless equipment in a bug way in their lives. Amplitude modulation is defined as the process in which the amplitude of the carrier wave ct is varied about a mean value, linearly with the baseband signal. This allows the demodulation of a vast variety of digital modulation protocols.
In fact, all radio channels in the am band use this type of modulation. Amplitude demodulation matlab amdemod mathworks india. The document that describes the process is digital demodulation project v242. Building the lif kit the latest version of the lif downconverter is the lif2012. Fsk frequency shift keying d1 61 conceptually, and in fact, the transmitter could consist of two oscillators on frequencies f1 and f2, with only one being connected to the output at any one time. The key difference between modulation and demodulation is that modulation is done at the transmitter side while demodulation is done at the receiver side of a communication system. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is sinusoidal. Today, phase locked loops pll are often used for fm demodulation. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. The fm modulation and demodulation process is identical in stereo and monaural processes. Modulation and demodulation techniques request pdf. 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.
Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. Introduction it is a process in which the frequency of the carrier is varied in accordance with the instantaneous value of modulating voltage. Pm and digital modulation s p where 2 is the pkpk phase change in one symbol duration, t for digital signals the modulation index. Remember to set up the vco module in 100 khz vco mode. There are different types of modulation and so are demodulators.
The bandwidth of each is dependent on the message bit rate. Implementation of fm demodulator algorithms on a high. Modulation and demodulation principle borrow from radio telecommunication take a wide band signal few hz to khz modulate it with a single frequency the carrier signal which is the frequency associated to a given station emit the signal given the station frequency, a receiver follows a. 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. Introduction frequency modulation fm has a long history of its application and is widely used in radio broadcast. Chapter 5 traditional analog modulation techniques commsys. Tcom 370 notes 995 modulation and demodulation modems for data transmission over analog links 1. The larger fraction of the pulse energy is near 0 frequency. Introduction frequency modulation is a form of modulation, which represents information as.
Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Modulation a mapping of the information on changes in the carrier phase, frequency or amplitude or combination. By using modulation to transmit the signals through space to long distances, we have removed the need for wires in the communication systems. A interesting solution is to solve this with digital signal processing. 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. The voltage controlled oscillator vco generates a center frequency locally. Demodulation is extracting the original informationbearing signal from a carrier wave.
Fsk frequency shift keying d1 63 fsk in f 1 f 2 decision out figure 4. This demodulator is more complex than most asynchronous demodulators. Fm demodulation using pll 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. Fm modulation and demodulation circuit multisim live. Download modulation damplitude demodulation damplitude book pdf free download link or read online here in pdf. Two of them mixed and pll demodulator are are implemented on the dsp tms320c6711dsk.
What is fm, frequency modulation electronics notes. 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. Frequency modulation fm is the encoding of information in a carrier wave by varying the. In part i you will learn how to design an amplitude modulator am and in part ii you will be able to demodulate an am signal. While changing the amplitude of a radio signal is the most obvious method to modulate it, it is by no means the only way. Using matlab mfile and simulink to implement fm modulation and demodulation. There are many types of modulation so there are many. Its adjustment free modulationdemodulation circuit significantly reduces the number of peripheral circuits required and can contribute to lower production costs. Eee2009eee2009 communicationscommunications contents introduction to communication systems analogue modulation am, dsbsc, vsb, ssb, fm, pm, narrow band fm, pll demodulators, and fll loops sampling systems time and frequency division multiplexing systems, nyquist principle, pam, ppm. Modulationsverfahren zur sprachubertragung pdf 186 kb.
We also consider methods to demodulate the modulated signals, i. Filtering is performed by a bank of gabor bandpass filters. Generally involve translating recovering the baseband digital information to from a bandpass analog signal at. Fm demodulation is a key process in the reception of a frequency modulated signal.
Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Each channel sharing scheme a set of basis vectors. Tcom 370 notes 995 modulation and demodulation modems for. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Modulation involves multiplying the input signal xt by a cosine with a frequency f2. All books are in clear copy here, and all files are secure so dont worry about it.
Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. In particular, we discuss first the nfm model, which represents the initial approach used to investigate the dynamics of spintronic modulators 9. Types of amplitude modulation am double sideband with carrier we will call it am. Modulation is the process of impressing a lowfrequency information signal baseband signal onto a higher frequency carrier signal modulation is done to bring information signals up to. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Wave fundamentals and modulation demonstration board. Read online modulation damplitude demodulation damplitude book pdf free download link book now. This is the most widely used type of am modulation. 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.
1257 1458 1416 36 1068 1381 444 594 230 1379 936 1507 1591 785 1319 1180 122 1170 1401 7 88 1245 828 550 463 1042 907 1446 166 188 390 1350 1255