Angle modulation basic definitions, frequency modulation, narrow band frequency modulation, wide band frequency modulation. Fm modulated signal st is a nonlinear function of the modulating signal mt, thus it is known as nonlinear modulation process. An introduction to orthogonal frequency division multiplexing. Phase modulation pm amount of phase change on angle of carrier is proportional to intelligence amplitude frequency modulation fm frequency change on angle. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Lecture notes on analogue communication techniques. Narrow band radio module is constituted of these discrete components, thus cost is higher and size is bigger than wideband onechip radio ic. Aug 04, 2017 wide band frequency modulation or wbfm is done when modulation index is greater than 1. Rapid amplitude and frequency modulation are characteristic of many songbird vocalizations. Readers who have some knowledge of the above topics will appreciate the clear manner in which they are presented and will also find the section most useful for reference purposes. In telecommunications and signal processing, frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave 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 frequency of the carrier and its center. But, the modulated wave produced by the narrowband fm differ from this ideal condition in two fundamental. Nbfm uses low modulation index values, with a much smaller range of modulation index across all values of the modulating signal an nbfm system restricts the modulating signal to the minimum acceptable value, which is 300 hz to 3 khz for intelligible voice used in.
The information signal is music and voice which falls in the audio spectrum. Introduction to modulation and demodulation free download as powerpoint presentation. This is useful in defining parameters like whether the signal is a narrow band or a wide band frequency modulated signal. Unit 7 week6 narrowband fm generation, spectrum of fm. Phase locked loops provide an excellent method of generating frequency modulation. May 10, 2017 introduction to ssbsc b techcommunication system4th sem. Frequency modulation is the process of varying the frequency of the carrier signal linearly with the message signal. Police communication ambulance communication walkie talkies bluetooth zigbee current cb radio. Pdf theoretical description of frequency modulation and. Introduction to communication system introduction, orientation introduction to communication system, need for modulation, amplitude modulation, time domain and frequency domain description, power relations in am wave, square law modulator, switching. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is. This is further divided into frequency and phase modulation.
Contents introduction to communication systems analogue modulation am, dsbsc, vsb, ssb, fm, pm, narrow band fm, pll demodulators, and fll loops. The result of modulating a bandlimited baseband signal on to a carrier is a signal that is. A narrow band fm is the fm wave with a small bandwidth. Frequency modulation, single tone frequency modulation, spectrum analysis of sinusoidal fm wave, narrow band fm, wide band fm, constant average power, transmission band width of fm wave, generation of fm waves, comparison of am. Introduction to ssbsc b techcommunication system4th sem. The process of superimposing a low frequency signal onto a high frequency signal three modulation schemes available. The subject of frequency modulation involves some con tradictions of existing practices and in general introduces new thoughts in connection with the operation of radio communication systems, transmitters and receivers alike. Wide band frequency modulation spectral analysis of the wide band fm wave or where is called complex envelope. An introduction to orthogonal frequency division multiplexing marius oltean universitatea politehnicatimisoara email. Sampling systems time and frequency division multiplexing systems, nyquist principle, pam, ppm, and pwm principles of noise random variables, white noise, shot, thermal and flicker. Difference between wide band and narrow band radio module by yukinaga koike, circuit design, inc. Pdf a new narrowband phase modulation mathematical identity. Timedomain description, frequencydomain description, generation of am wave. Frequency modulation is a powerful method of synthesis that is as relevant to analogue synthesizers as it is to.
The envelope contains a residual amplitude modulation that varies with time the angle contains harmonic distortion in the form of third and higher order harmonics of the modulation frequency it f m. One can take this sum and modulate it on a carrier signal of some other frequency in a simple way. Orthogonal frequency division multiplexing ofdm is one of the latest modulation techniques used in order to combat the frequencyselectivity of the transmission channels. Note that the complex envelope is a periodic function of time with a fundamental frequency which means where sta c cos2. Slide 6 narrow band fm slide 7 bandwidth of an fm signal slide 8 demod. Jun 03, 2015 narrow band fm is used mainly for things like. Noise introduction, short noise, thermal noise, white noise, noise equivalent bandwidth, narrowband noise, noise figure, equivalent noise temperature, cascade connection of twoport networks. An introduction to analog and digital communications, 2nd. The full audio spectrum ranges form 20 to 20,000 hz, but fm radio limits the upper modulating frequency to 15 khz cf. A method of frequency translation, recovery of base band. Fastl, in auditory physiology and perception, 1992.
Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal. Typically when crystal oscillators a re used the signal needs to be multiplied in frequency, and only narrow band fm is attainable. An fm spectrum is influenced by the modulation index as well as by the ratio of the amplitude of the modulating signal to the frequency of the modulating signal. Introduction to modulation and demodulation modulation. Look at the signal generator manual to see how to get an fm signal. Introduction manner in which it differs from amplitude modulation, and details associated with f m receiver servicing problems. The subject is new and all of its ramifications and prob lems are not known as yet, hence this volume of compara tively few pages is not intended as a complete exposition of the subject. Band introduction the department of defense dod uses the band 33003500 mhz for operating various types of shipborne, landbased, and aeronautical mobile radar systems for national defense purposes. Frequencymodulated broadcasting system used primarily for twoway voice communication, typically having a maximum deviation of 15 kilohertz or less explanation of narrowband frequency modulation. But, the modulated wave produced by the narrowband fm differ from this ideal condition in two fundamental respects. Introduction to rf simulation and its applications by kenneth s.
Slide 3 discretetime fm modulator slide 4 single tone fm modulation slide 5 single tone fm cont. These modulation techniques form an integral part of academic curricula today. Sampling systems time and frequency division multiplexing systems, nyquist principle, pam, ppm, and pwm principles of noise random variables, white noise, shot, thermal and flicker noise, noise in cascade amplifiers. The frequency band for fm radio is about 88 to 108 mhz. But, the modulated wave produced by the narrow band fm differ from this ideal condition in two fundamental respects. The carrier frequency, fc, should be larger than the highest spectral component. Narrowband frequency modulation article about narrowband. Frequency modulation fm is a method of modifying frequency of carrier signal in order that the receiver can obtain the desired transmitted information.
The second edition of introduction to digital and analog communications, 2e is written at an accessible level and serves as an introductory treatment of communication theory, both analog and. Figure a shows the transmission spectrum of narrow band radio module in the frequency of 434 mhz with. Scribd is the worlds largest social reading and publishing site. We have described our ultra high resolution spectrometer for molecular iodine at 501. Communications 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. Narrowband correction of the residual amplitude modulation in fm. Wide band frequency modulation or wbfm is done when modulation index is greater than 1. Rightclicking a modem frequency digit will enable frequency snap. However, using sectored antennas does not increase the number of slots and consequently the frequency reuse factor is not increased.
Frequency modulations are either upward or downward shifts in the pacemaker frequency, last seconds to minutes, and consist of small shifts in frequency long rises, lowfrequency modulations, warbles, and jamming avoidance responses or large shifts in rate sudden increases in frequency, followed by decrease, chirps, rasps, scallops, accelerations. Cellular systems accommodate a large number of mobile units over a large area within a limited frequency spectrum. Allocation table the frequency allocation table shown below is extracted from the manual of regulations. Frequency modulation frequency modulation is the process by which frequency of the carrier signal ct changes with respect to the modulating signal mt. Narrow band frequency modulation keee343 communication theory. Fm signal narrowband and wideband fm, bandwidth required for a. Frequency modulated broadcasting system used primarily for twoway voice communication, typically having a maximum deviation of 15 kilohertz or less explanation of narrow band frequency modulation. Aug 01, 2017 generation of fm signals narrow band frequency modulationnbfm.
The tuning bar provides a simple way to control the active modem frequency, bandwidth and the center frequency. Modeling auditory processing of amplitude modulation i. Amplitude modulation an overview sciencedirect topics. However, a small residual signal may remain due to noise. An introduction to frequency modulation sound on sound. A new mathematical identity is suggested to describe narrow band phase modulation and other similar physical problems instead of using the bessel function. Find out information about narrow band frequency modulation. Phase modulation on the other hand would instead move the phasor on a circle red line, with no changes to its radius. Bruce carlson, communication systems, an introduction to signals and noise in.
Frequency modulation is widely used for radio transmission due to the fact that the signaltonoise ratio snr is large in this method of modulation and hence radio frequency interference is minimized. Find out information about narrowband frequency modulation. Advantage of narrow band communication the merit of narrow band communication is to realize stable longrange communication. Difference between wide band and narrow band radio module. Introduction to semiconductor devices pdf free download. The modulation index for this fm signal is defined as. Leveraged in harmonic balance simulation methods f c 1 2ghz f s 10 30khz f c f s. Introduction to digital and analog communications, 2e is selfcontained and suited for a one or twosemester course in communication systems taken by electrical engineering juniors or seniors. Of course, since n can take any integer value, in theory, applying frequency modulation to a signal produces an infinite series of side bands.
Generation of narrowband frequency modulation nbfm. What is fm, frequency modulation electronics notes. Modeling auditory processing of amplitude modulation. Amplitude modulation am communication systems arose from the need to send an acoustic signal, the message, over the airwaves using a reasonably sized antenna to radiate it.
Fm signals are used in technology such as radars, telemeters, eeg, radio broadcasting, satellite communication and magnetic tape recording systems. Vmt to vary the carrier frequency within some small range about its original value. It is also very useful in ensuring that all transmitters or receivers in a system are set to accommodate a standardised level of modulation as it affects parameters like the receiver bandwidth, channel spacing and the like. Hapter modulation and demodulation mit opencourseware. Narrowband frequency modulation results in a translation of the spectrum of the integral of the baseband signal to a band surrounding the carrier frequency. What are the applications of narrow band frequency modulation.
The range of modulation frequencies found was between 109 and 358 hz. Nov 11, 2016 frequency modulation is widely used for radio transmission due to the fact that the signaltonoise ratio snr is large in this method of modulation and hence radio frequency interference is minimized. 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. The aim of the exercise is to demonstrate the process of frequency modulation on the basis of the available test circuit, illustrating in detail the attributes, which are characteristic for this type of oscillation modulation. The size of the antenna depends inversely on the frequencies present in the message, and voice and music have relatively low frequencies. The condition where only one sideband of the modulating frequencies is present is known as narrow band fm. Narrowband frequency modulation article about narrow. Frequency modulation an overview sciencedirect topics. Explain the difference between narrow band fm and wide band. Frequency modulation spectroscopy, wavelength modulation spectroscopy. In the file, you only need to change the value of the modulation index. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. Wide band frequency modulation wbfm learn by watch.
The next section deals with the effects of noise on. Noise in continuous wave modulation systems introduction, receiver model, noise in dsbsc receivers, noise in ssb receivers, noise in am receivers. Simon haykin has written two books with wiley for communications systems, introduction to digital and analog communications, 2e and the forthcoming revision of his classic communications systems, 5e. An important feature of angle modulation is that it can provide better. Principles of noise random variables, white noise, shot, thermal and flicker. Download product flyer is to download pdf in new tab. Hence, the spectrum of narrow band fm consists of the carrier and upper sideband and a lower sideband. Generation of fm signals narrow band frequency modulationnbfm.
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