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	Frequency modulation - Wikipedia, the free encyclopedia
		Frequency modulation (FM) is a form of modulation which represents information as variations in the instantaneous frequency of a carrier wave.
		Note that frequency modulation can be regarded as a special case of phase modulation where the carrier phase modulation is the time integral of the FM modulating signal.
		With a tone-modulated FM wave, if the modulation frequency is held constant and the modulation index is increased, the (non-negligible) bandwidth of the FM signal increases, but the spacing between spectra stays the same.
	en.wikipedia.org /wiki/Frequency_modulation (927 words)

	Amateur Radio application of Frequency Modulation
		Phase Modulation (PM) is a similar system where the phase of the carrier wave is varied in sympathy with the voltage of the modulating signal, and as in frequency modulation, the amplitude of a carrier is held constant.
		The modulation index due to the noise voltage is constant for different noise frequencies, differently to the modulation index for the desired modulation signal which decreases with increasing modulating frequency (for FM).
		The modulation index is 2.4, and the deviation is 2.88kHz.
	www.vk1od.net /FM/FM.htm (3127 words)

	Phase modulation - Wikipedia, the free encyclopedia
		Phase modulation (PM) is a form of modulation which represents information as variations in the instantaneous phase of a carrier wave.
		Clearly, it could also be viewed as a change to the frequency of the signal and PM can be considered a special case of FM where the carrier frequency modulation is the time derivative of the modulating signal.
		For small amplitude signals, PM is similar to amplitude modulation (AM) and exhibits its unfortunate doubling of baseband bandwidth and poor efficiency.
	en.wikipedia.org /wiki/Phase_modulation (270 words)

	Lesson 2 - Modulation Techniques
		The modulation of digital signals with analogue carriers allows an improvement in signal to noise ratio as compared to analogue modulating schemes.
		Modulation of a carrier by a digital signal is denoted by shift keying because there is a discrete change in the carrier parameters.
		In this case the modulating signal is a binary bit train, which leads to a phase change of the carrier.
	users.deec.ist.utl.pt /~ineit/mt/chapter1/lesson3.htm (436 words)

	GMDSS (DM) FCC Element 3 Question Pool
		The modulation index increases as the RF carrier frequency (the modulated frequency) increases.
		The modulation index decreases as the RF carrier frequency (the modulated frequency) increases.
		The modulation index varies with the square root of the RF carrier frequency (the modulated frequency).
	members.aol.com /ab0di/el3c7.html (4892 words)

	Wireless transmission system for PM modulation signal - Patent 4799257
		A wireless transmitter for PM (phase modulation) signal with a spectrum scrambler for relocation of input spectrum for privacy purposes is comprised of a differential circuit coupled with an input terminal, a spectrum scrambler coupled with output of said differential circuit, and FM (frequency modulation) modulator coupled with output of the spectrum scrambler.
		3, the numeral 8 is an input terminal, 9 is a PM modulator, 10 is a transmission antenna, 11 is an attenuator, 12 is a spectrum invertor, 13 is a PM modulator, and 14 is a transmission antenna.
		Thus, the modulation index of Dev.sub.IE of the FM modulator 23 is defined by the power at the input point (g) of the modulator, and is expressed as follows.
	www.freepatentsonline.com /4799257.html (3671 words)

	Amplitude
		Note that the carrier frequency is modulated by the modulating signal to result in the modulated signal.
		In Figure 4 and 5, the peak voltage of the modulated signal is half the peak voltage of the modulating signal.
		The modulation index m is a dimensionless number, defined as the ratio of the sideband energy to the carrier energy:
	www.8vsb.com /Amplitude-Modulation.htm (2865 words)

	[No title] (Site not responding. Last check: 2007-10-12)
		The second analog feedback loop is used to regulate the modulation index, and requires a complex gain control stage to adjust the laser diode's extinction ratio ER Often, these analog feedback circuits require temperature compensation thermistors and multiple factory adjustments to control the extinction ratio.
		SUMMARY OF THE INVENTION A digital laser driver circuit is provided in which a digital synthesizer synthesizes a modulation index signal for precisely setting the modulation level of the laser, and a pair of feedback loops control the average power level and modulation index of the laser diode.
		The two comparators 168A, 168B compare the peak modulation signal on the resistor 162 to thresholds that are set by resistors 186,184, and 182 based on the reference voltage VR from the PWM.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/76023.011011&ELEMENT_SET=DECL (2284 words)

	[No title]
		The argument to the Bessel functions is the modulation index, which is directly proportional to the amplitude of the modulating signal.
		The modulation index is the amplitude of the modulator, measured in terms of the modulating frequency (i.e., when the modulation index and the modulating frequency are the same, the modulation index would have a value of 1).
		The modulator(s) determine the timbre of the tone, and the modulator envelope is the spectral envelope.
	qcpages.qc.cuny.edu /~howe/music726.1/FMSynthesis.html (4178 words)

	Course "Sound Design", Dik J. Hermes, 2005-2006 (Site not responding. Last check: 2007-10-12)
		When the modulation frequency is high enough, as in the last two examples, the spectral components are so far separated in frequency that the spectral resolution of the auditory system is good enough to resolve these three components.
		Compare an amplitude modulated 600-Hz sinusoid with a modulation frequency of 50 Hz with one with a modulation frequency of 70 Hz.
		In case the modulation frequency is not a good divisor of the carrier frequency, a inharmonic complex tone is perceived without a well defined pitch, e.g., in this 600-Hz sinusoid with a modulation frequency of 170 Hz.
	www.ipo.tue.nl /homepages/dhermes/lectures/SD/ChIII.html (1261 words)

	Lab2_Angle_Mod
		In angle modulation, the idea is to transmit the message signal in the frequency or the phase of the carrier signal.
		Similar to the FM, the phase modulation generally expands the bandwidth so that the effective bandwidth of the PM modulated signal is usually many times the bandwidth of the message signal.
		It is called as a narrowband angle modulated signal because its required bandwidth is narrower than the bandwidth of the general angle modulated signal.
	www.eas.asu.edu /~midle/jdsp/commex/LAB2_ANGLE_MOD.htm (1277 words)

	Frequency_Modulation
		Time-dependent spectra may be produced by varying the modulation index during the course of the sound.
		; this may be approximated by a sharp rise in the modulation index followed by a slower decay.
		Three examples of frequency modulated signals, where (A) the carrier frequency is higher than the modulating frequency (c:m = 10:1), (B) both frequencies are equal, and (C), the modulating frequency is higher than the carrier (c:m = 1:10).
	www2.sfu.ca /sonic-studio/handbook/Frequency_Modulation.html (452 words)

	Square One: FM Basic Training
		Modulation synthesis is a waveshaping technique in which an audio-rate signal called the modulator controls some parameter of another audio signal, called the carrier.
		The index is defined differently for AM and FM, but in both cases it is related to the amplitude of the modulator.
		The FM modulation index I is defined as the ratio of frequency deviation to modulator frequency: I = D/Fm.
	emusician.com /news/emusic_square_one_fm (2464 words)

	Wide modulation bandwidth measurements
		The result is an FM modulated signal at the output of the VCO and is given by equation 1 (due to string lengths, some of the formulas are at the end of the text).
		In an ideal VCO of infinite modulation bandwidth, if the amplitude of the modulating signal and f subscript mod are increased proportionally to keep the ratio v subscript mod/f subscript mod constant, the modulation index will remain constant and so will the amplitude of the carrier and sideband signals.
		When the modulation index is equal to 1.697, the carrier level (Equation 3) is 0.4 or it is -8 dBc with the reference to the unmodulated carrier.
	rfdesign.com /mag/radio_wide_modulation_bandwidth/index.html (1168 words)

	Digital Synthesis
		The regularity of the sidebands produces the strongly harmonic sound usually associated with synthesizers, but if the modulation index is changed during the note (dynamic modulation) the intensity of the sidebands will change in some very voicelike effects.
		At low modulation index, you will hear two distinct pitches in the tone; as the index is increased, the timbre of the upper pitch seems to become brighter.
		By applying an envelope function to the amount of modulation or the frequencies of carrier and modulator, sounds can be produced that have a life and excitement far beyond that available with the older synthesis methods.
	arts.ucsc.edu /ems/music/tech_background/TE-17/teces_17.html (876 words)

	ECE-S 306 Homework#3 Solution
		However, the sideband power is greatly affected by the choice of modulation index, as expected from the theory.
		It is known that it is desirable to have modulation index close to 1 to have as much power in the sideband as possible.
		Note that the magnitude spectra plots clearly show this, as the amplitude of the impulses at 90 Hz and 110 Hz (and the corresponding impulses at -90 Hz and -110 Hz) is substantially larger for modulation index of 0.9 compared to the other two cases (modulation index of 0.2 and 0.5).
	www.ece.drexel.edu /commweb/hw3nsolution.html (462 words)

	Amplitude Modulation
		The frequency of the modulating signal is chosen to be much smaller than that of the carrier signal.
		The bandwidth of an AM scheme which is the amount of space that it occupies in the Fourier domain is twice that of the modulating signal.
		The trick that is used to generate a modulating signal by adding a DSB version (carrier at 38 Khz suppressed) version of the output of the difference between the Left and Right channels added to the sum of the Left and Right channels unmodulated.
	robotics.eecs.berkeley.edu /~sastry/ee20/modulation/node3.html (437 words)

	[No title]
		Topic: FM, Tone Modulation, Modulation Index, Frequency Deviation, Sensitivity to a Change in the Amplitude and Frequency of the Modulating Signal.
		A carrier is FM modulated by a 3 kHz sinusoidal signal.
		Bw= The amplitude of the modulating signal is now increased by a factor of 4 and its frequency lowered by 1kHz.
	www.pupr.edu /mteixeir/comq3w01.doc (481 words)

	Using Bessel Functions in Frequency Modulation (Site not responding. Last check: 2007-10-12)
		Unlike amplitude modulation, prediction of the frequency spectrum occupied by an FM signal requires calculus.
		The left column represents the modulation index for a frequency modulated carrier.
		Since the modulation index is determined by carrier swing and signal frequency,and since you may desire a significant signal frequency, (audio goes to 15 KHz),it is necessary to limit your carrier swing, delta fc.In reality, the signal consists of higher frequency components due to stereo and a sub carrier authorization channel sometimes known as Musak.
	www.sunybroome.edu /~eet_dept/252/bessell.htm (485 words)

	amplitude modulation..?
		If you disconnect the modulating signal, the output of the modulator will be the a sine wave in wm.
		where m(t) is the modulating or baseband signal that is to be transmitted.
		In DSBTC modulation a nonlinear element (like diode) is used for modulation while in DSBSC a balnced modulator is used.
	www.edaboard.com /ftopic73756.html (835 words)

	Frequency Modulation
		To modulate the signal just means to systematically vary one of the three parameters of the signal: amplitude, frequency or phase.
		The carrier is at 65 Hz and the modulation index is 2.
		The modulation index is normally limited to a value between 1 and 5, depending on the application.
	www.fas.org /man/dod-101/navy/docs/es310/FM.htm (1801 words)

	Modulation Synthesis and Waveshaping
		The modulation index controls the "brightness" of the sound (the higher the index the brighter the resulting sound).
		ampo.cl is the amplitude modulation instrument definition and tester.cl is the "tester" instrument that will display the waveform and fft.
		One carrier is modulated by a modulator which in turn is modulated by another two modulators.
	ccrma.stanford.edu /CCRMA/Courses/220a:1998/Lectures/4/4.html (1334 words)

	Computer Music: FM Synthesis
		The intensity of the SIDEBAND frequencies is governed by the MODULATION INDEX which is in essence the depth or amount of the modulation.
		The actual MODULATION INDEX (I) is the ratio of the amplitude to the frequency of the modulating signal.
		The FREQUENCY DEVIATION is equivalent to the AMPLITUDE of the modulating signal.
	www.ec.vanderbilt.edu /computermusic/musc216site/FM.synthesis.html (1200 words)

	FM synthesis on SND
		If the mean frequency of the modulator reaches as high as audio frequency range, sidebands appear as partials of the new modulated sound.
		The position of each sideband is a function of the carrier modulator ratio or C:M ratio, and its number and amplitude change as function of the amplitude of the modulator or depth of the modulation.
		While the precise relationship between the sidebands, the c:m ratio and the amplitude of the modulator (better known as modulation index) is determined by the use of Bessel functions, it is common practice to say that the number of sidebands produced on either side of the carrier equals to the modulation index plus 2.
	ccrma.stanford.edu /guides/planetccrma/FM.html (2383 words)

	Phase-aligned formant (PAF) generator
		If the index of modulation exceeds the input range of the table (here set to stop at 10 as an example), the table lookup address should be clipped.
		Since the expansion of the waveshaping (modulator) signal consists of all cosine terms (i.e., since they all have initial phase zero), as do the two components of the carrier, it follows from the cosine product formula that the components of the result are all cosines as well.
		Our technique for superposing spectra does not work as predictably for phase modulation as it does for the PAF generator; the partials of the phase modulation output have complicated phase relationships and they seem difficult to combine coherently.
	www-crca.ucsd.edu /~msp/techniques/v0.05/book-html/node88.html (1022 words)

	Modulation Index (Site not responding. Last check: 2007-10-12)
		Recall from frequency modulation that modulation index is used to calculate the number of
		The modulation index is the ratio between the amount of oscillator deviation and the
		In frequency modulation, we saw that as the frequency of the modulating signal increased (assuming
	www.tpub.com /content/neets/14184/css/14184_112.htm (230 words)

	LAB405A - Modulation Analysis - FM
		The analysis of a 10 MHz FM signal with a 20 kHz sinewave modulation and 100 kHz deviation is shown in Figure 1.
		The frequency of the modulation waveform (20 kHz) is the modulation frequency.
		The FM modulation index is the ratio of deviation to modulating frequency (about 5:1 for this example).
	www.lecroy.com /tm/Library/LABs/LAB405A?menuid=2 (652 words)

	FM (Site not responding. Last check: 2007-10-12)
		--> In frequency modulation the amplitude is kept constant and the frequency is modulated by the amplitude of the modulating signal.
		The frequency spectrum can be found by rewriting the above expression as a sum of components of constant frequency using the properties of the Bessel Functions.
		Applet below shows a modulating signal in orange, the FM signal in red, the frequency spectrum in fl and how they vary with the modulation index and modulating frequency.
	cnyack.homestead.com /files/modulation/modfm.htm (101 words)

	Amplitude Modulation/Superheterodyne
		The interpretation of the modulation index, m, may be expressed as: The fraction (percentage if multiplied by 100) of the carrier amplitude that it varies by.
		We have already seen that the modulation index, m is the measure of how strongly you modulate.
		It may be interpreted at the fraction of the carrier amplitude that you modulate by.
	www.fas.org /man/dod-101/navy/docs/es310/AM.htm (2231 words)

	ipedia.com: Frequency modulation synthesis Article (Site not responding. Last check: 2007-10-12)
		Frequency modulation synthesis (or FM synthesis) is a form of audio synthesis where the timbre of a simple waveform is changed by frequency modulating it with a modulating frequency that is also in the audio range, resulting in a more complex waveform and a different-sounding tone.
		Use of modulators with frequencies that are non-integer multiples of the carrier signal (i.e., non harmonic), bell-like dissonant and percussive sounds can easily be created.
		The technique was invented by John Chowning at Stanford University in the early 1970s, was patented in 1975 and was later licensed to Yamaha.
	www.ipedia.com /frequency_modulation_synthesis.html (419 words)

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