Multiplexing generally refers to independent signals, those produced by different sources. 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. Lecture 2829 fm frequency modulation pm phase modulation. In an emergency, you may need to communicate with others by radio the original source of this article is radiomaster reports. Usc sdr workshop fm if modulation index 1 wfm replacing back it will look similar to amdsbtc dr ing marcelo segura 4 narrow fm.
Frequency modulation wikimili, the free encyclopedia. In fm, the information of a signal is encoded in its frequency. Am fm pm modulation in matlab modulate matlab function. The latter two methods are closely related since both modulate. Multiplexing method of sharing a bandwidth with other independent data channels. Similar to this fm and pm modulation can also be carried out using modulate function by changing forth argument to fm or pm respectively. Circuit needed for fm modulation and demodulation is bit complicated than am. We have seen that an anglemodulated signal can be represented by 1 sct a cos 2. To extend the range of sound, we need to transmit it through a medium other than air, such as a phone. This page on amplitude modulation am vs frequency modulation fm vs phase modulation pm describes difference between amplitude modulation,frequency modulation and phase modulation types all these modulation types are analog modulation techniques. Frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave.
This chapter describes the essential principles behind. Also, the process of retrieving information from encoded signals will be discussed. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is sinusoidal. Pdf nonlinear frequency and amplitude modulation of a. Modulation and demodulation medium, it would be dif. Phase modulation is widely used for transmitting radio waves and is an integral part of many digital transmission coding schemes that underlie a wide range of technologies like wifi, gsm and satellite television.
Multiplexing, threshold infrequency modulation, the phase locked loop. Amamplitude modulation fmfrequency modulation pm phase modulation in phase modulation, modulation index is directly proportional to modulating voltage only while in frequency modulation, modulation index is also inversely proportional to modulat. Ofdm is a combination of modulation and multiplexing. Now that narrowband frequency and phase modulation may soon be. In this radiomaster reports article, we unravel the secrets of fm modes and. Introduction this application note describes how to make accurate modulation measurements using the anritsu eseries ms2712e and ms27e spectrum analyzers and s332e and s362e cableantennaspectrum analyzers, equipped with option 509, amfmpm analyzer. Pm and digital modulation s p where 2 is the pkpk phase change in one symbol duration, t for digital signals the modulation index. Hi in nfm the modulation index is very low, much lower than 1.
What is fm, frequency modulation electronics notes. This form of modulation was developed by the american electrical engineer edwin h. So can have amplitude modulation am frequency modulation fm phase modulation pm frequency and phase combined are known as angle modulation 8. Pm demodulation requires synchronous detection relatively expensive. Fm versus nfm for best radio communications radiomaster. Some phase modulation and quadrature amplitude modulation formats have a higher spectral efficiency for data transmission than frequency shift keying, a form of frequency modulation. In india, radio broadcasting is done through amplitude modulation. To the scanning hobbyist, the main concern with modulation methods is what method is used for the signal i am trying to receive. Phase modulation pm is another form of angle modulation. Fm modulators and demodulators are relatively more expensive that am hardware.
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. Or the process of modulation can be defined as varying the rf carrier wave in accordance with the intelligence or information in a low frequency signal. Narrowband frequency modulation nfm was a relatively new. Cs1 unit 1 fm free download as powerpoint presentation. Wbfm which provides better quality requires large transmission bandwidth. One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif. Features y excellent carrier suppression 65 db typical.
Phase modulation pm pm or phase modulation is the process of varying the instantaneous phase of carrier signal accordingly with instantaneous amplitude of message signal. Television broadcasting is done with amplitude modulation for video signals and frequency modulation for audio signals. The carrier has three parameters that could be modulated. Lecture notes on analogue communication techniques. The spectrum is a series of diracimpulse spaced by nfm and multiplied by the amplitude of.
This section sets out the basic properties of fmpm signals and how we can produce them. Modulationtypesamplitude,frequency,phase modulation. Additional techniques, such as preemphasis of higher audio frequencies with. In a classical linear fm process, the instantaneous frequency of the output signal undergoes a time variation proportional to the information contained in the input modulating signal. The user should have basic familiarity with the eseries spectrum analyzer operation. Author byron goodman provides some insight into the techniques. Similarly for pm, the information is encoded in its phase. In frequency modulation fm, unlike am, the amplitude of the carrier is kept constant, but its frequency is altered in accordance with variations in the audio signal being sent. Modulation a mapping of the information on changes in the carrier phase, frequency or amplitude or combination. Frequency modulation objectives upon completion of this chapter, the student should be able to. Modulation, analog modulation, digital modulation, am,fm. The class comprises frequency modulation fm and phase modulation pm, and is based on altering the frequency or the phase, respectively, of a.
Lecture 4 frequency modulation frequency modulation. Nfm is mainly used for speech communication systems like ham radios and police and other type of communication except airplane vhf communications, they use am for a very good reason. Phase modulation equation of phase modulation pm wave. Nfm is defined as narrowband frequency modulation rarely. Discuss the differences between am and angle modulation. Spectrum of a pm or fm signal with sinusoidal modulation. Frequency modulation is widely used in many areas of radio technology including broadcasting and areas of two way radio communication. Types of modulation sine wave carrier described by 3 parameters. Or modulation is defined as the precess by which some characteristics, usually amplitude, frequency or phase, of a carrier is varied in.
Modulation is the process of superimposing a low frequency signal on a high frequency carrier signal. For the most part the scanner manufacturers have already set the scanners to default to the proper type of modulation based on. Refer following as well as links mentioned on left side panel for useful matlab codes. Angle modulation consider a modulating signal mt and a carrier vct acos.
Frequency modulation fm is the encoding of information in a carrier wave by varying the. Frequency modulation and phase modulation are the two complementary principal. Frequency modulation fm phase modulation pm click on the links given above to know more. Slide 6 narrow band fm slide 7 bandwidth of an fm signal slide 8 demod. Additional techniques, such as preemphasis of higher audio frequencies. Frequency modulation, phase modulation, and fm spectra. Whilst other forms of modulation are being used in many areas, fm still offers the highest quality for broadcasting and many advantages. Calculate modulation index, signal bandwidth, sideband frequencies and. Amamplitude modulation fmfrequency modulation pmphase modulation in phase modulation, modulation index is directly proportional to modulating voltage only while in frequency modulation, modulation index is also inversely proportional to modulat.
Usc sdr workshop fm wfm is the standard used by commercial radio stations and it has a frequency deviation of 75khz and a. Frequency modulation fm angle modulation fm and pm spectral characteristics of fm signals fm modulator and demodulator lin dai city university of hong kong ee3008 principles of communications lecture 4. Explain the advantages and disadvantages of the different analog modulation techniques. Angle modulation is a class of carrier modulation that is used in telecommunications transmission systems. Lecture 4 frequency modulation free download as powerpoint presentation. Basic concepts of modulation three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Digital modulation in digital communications, the modulation process corresponds to switching or keying the amplitude, frequency, or phase of a sinusoidal carrier wave according to incoming digital data three basic digital modulation techniques amplitudeshift keying ask special case of am. Phase and frequency deviation for phase modulation and frequency modulation 78. In this radiomaster reports article, we unravel the secrets of fm modes and explain how to know when to use nfm and fm. Pm is used for signal and waveform generation in digital synthesizers, such as the yamaha dx7, to implement fm synthesis.
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