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Topic: Pulse density modulation

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	Pulse-density modulation
		Pulse-density modulation, or PDM, is a form of modulation used to represent an analog signal in the digital domain.
		Instead it is the relative density of the pulses that corresponds to the analog signals amplitude.
		In a pulse-density modulation bitstream a 1 corresponds to a pulse and a 0 corresponds to the absence of a pulse.
	publicliterature.org /en/wikipedia/p/pu/pulse_density_modulation_1.html (438 words)

	Pulse-density modulation Information
		Pulse-width modulation (PWM) is the special case of PDM where all the pulses corresponding to one sample are contiguous in the digital signal.
		A PDM bitstream is encoded from an analog signal through the process of delta-sigma modulation.
		In pulse-density modulation, a high density of 1's occurs at the peaks of the sine wave, while a low density of 1's occurs at the troughs of the sine wave.
	www.bookrags.com /Pulse-density_modulation (412 words)

	Digital integrator for pulse-density modulation using an adder carry or an integrator overflow - Patent 5995546
		A clock (35) applies clock pulses to the latches (20, 22, 24, 30) at a frequency at least as high as the frequency at which the successive parallel digital input words are applied to the inputs (12) of the adders (14, 16, 18).
		Typically, the pulse density modulation of the input digital words involves framing the words, that is, treating each, word individually to produce a set output stream of pulses of length corresponding to the number of bit values that may be represented by the input word.
		The modulator includes an adder for adding and accumulating the successive digital input words, and a carry output and a latch for receiving the carry output of the adder, an output of the latch providing a pulse density modulated signal representing the input digital words.
	www.freepatentsonline.com /5995546.html (3045 words)

	Pulse-code modulation
		For binary PCM systems, the density of 1-symbols is called 'ones-density'.
		In other cases, the long term DC value of the modulated signal is important, as building up a DC offset will tend to bias detector circuits out of their operating range.
		Many of these codes are bipolar codes[?], where the pulses can be positive, negative or absent.
	www.ebroadcast.com.au /lookup/encyclopedia/ad/ADPCM.html (462 words)

	Modulation at AllExperts
		Modulation is the process of varying a carrier signal in order to use that signal to convey information.
		A device that performs modulation is known as a modulator and a device that performs the inverse operation of demodulation is known as a demodulator.
		These are the general steps used by the modulator to transmit data:# Accept incoming digital data;# Group the data into symbols;# Use these symbols to set or change the phase, frequency or amplitude of the reference signal appropriately;# Pass the modulated signal on for further processing, such as filtering and channel-coding, before transmission.
	en.allexperts.com /e/m/mo/modulation.htm (854 words)

	Modulation (Site not responding. Last check: 2007-10-11)
		Modulation describes a range of techniques for encoding information on a carrier signal, typically a sine-wave signal.
		When transmitting digital data, Modulation normally involves shifting one or more properties of the carrier wave between a set of states, a process referred to as keying.
		Modulation is frequently used in conjunction with various channel access methods.
	modulation.iqnaut.net (207 words)

	Onkyo Europe - Imaginative Sight & Sound
		In a digital amplifier, the analogue input signal is converted into a pulse (digital) signal, and then converted back into an analogue signal using a low-pass filter.
		On the other hand, with a digital amplifier, the signal consists of either a pulse (1) or no pulse (0)—there are no intermediate values.
		In digital amplifiers, there are two methods of pulse conversion: pulse width modulation (PWM), in which analogue quantity is represented by the width of the pulse, and pulse density modulation (PDM), in which analogue is represented by the number of pulses.
	www.eu.onkyo.com /article/article_en_1893452.html (1116 words)

	Spectral Analysis of a CW keying pulse
		I then calculate the spectrum of a pulse with an exponentially shaped rise and fall as would be produced by simple RC networks.
		Notice that the differences between the 20 millisecond and 50 millisecond pulses are first the energy near the carrier frequency is larger for the longer pulse as needed since it has about 2.5 times as much energy, and second the ``ringing'' has more oscillations for the longer pulse as expected.
		The first of the two factors is proportional to the Fourier transform squared of the square pulse and the second by the Fourier transform squared of the slope of the rise and fall.
	fermi.la.asu.edu /w9cf/articles/click/index.html (1309 words)

	SingaporeMoms - Parenting Encyclopedia - Pulse-code modulation (Site not responding. Last check: 2007-10-11)
		Pulse-code modulation (PCM) is a modulation technique invented by the Brit Alec Reeves in 1937.
		It is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals.
		The first transmission of speech by pulse code modulation was the SIGSALY voice encryption equipment used for high-level Allied communications during World War II.
	www.singaporemoms.com /parenting/PCM (778 words)

	Datapan.com - Pulse-code modulation
		Pulse-code modulation (PCM) is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals, then quantized to a series of symbols in a digital (usually binary) code.
		Several Pulse Code Modulation streams may be multiplexed into a larger aggregate data stream.
		The first transmission of speech by pulse code modulation was the SIGSALY voice encryption equipment used for high-level Allied communications during World War II from 1943.
	www.datapan.com /pulse.html (848 words)

	Spectral error density analysis—a new approach to identity jitter sources in SOC-devices - Test & Measurement ... (Site not responding. Last check: 2007-10-11)
		The Gaussian probability density distribution is a wide spread model for random jitter as it occurs at semiconductor junctions and is quantified by its rms-value.
		According to modulation theory the sinusoidal phase modulation of a sinusoidal carrier signal with small modulation depth results in a spectrum showing two side peaks to the left and right of the carrier.
		As a result we will see an error density that is non-zero for the negative half period of the jitter period and an error density of 0 for the positive half of the jitter period.
	www.reed-electronics.com /tmworld/article/CA376267 (3842 words)

	PDM Definition
		A PDM also manages the interrelationships between the data so that when changes are made to one database, the effects are highlighted in the others.
		Like its variable-width pulse width modulation (PWM) cousin, the output switching transistor is on more of the time for a high-amplitude input signal and off more of the time for a low-amplitude signal.
		PDM is used for audio signals in a variety of applications from cellphones to Sony's SACD music format.
	www.pcmag.com /encyclopedia_term/0,2542,t=PDM&i=49034,00.asp (754 words)

	baseband pulse shaping filter
		Pulse shaping filters are used to narrow bandwidth and improve bandwidth use.
		The spectral density of NRZ random data is given by [6] where Tb is the bit period, A is the amplitude of the signal and f is the frequency in Hertz.
		The shaped NRZ data using Gaussian pulse shaped filter are shown in Figure 10, and shaped NRZ data using new pulse shaping filter are shown in Figure 11.
	rfdesign.com /mag/radio_simulation_realization_baseband/index.html (1548 words)

	[Introduction --- PDM97(beta version)]
		The PDM (Pulse Density Modulating) digital neural network system is a neural network hardware which can simulate feedback and feedforward neural networks in a fully parallel and continuous manner.
		PDM is the acronym of Pulse Density Modulation.
		Analog output from each neuron is transmitted neither by analog voltage nor by binary digital data, but by a pulse stream whose frequency is proportinal to the output as our real neurons do.
	www.viplab.is.tsukuba.ac.jp /~hirai/PDM/English/intro.html (460 words)

	A Fundamental Introduction to the Compact Disc Player
		If the system clock pulse inaccurately (an unlikely event), if there is a glitch in the digital hardware, or if there is noise on a signal control line, the actual reading time will vary from sample to sample thus inducing noise and distortion in the extreme case.
		In this design, the width of the signal pulse represents the unique data word, thus it is critical that the PWM steps have exact width and minimum jitter to maximize accuracy and linearity of the output.
		In this technique, the density ratio of the sign of the pulses is related to the original 16-bit data word.
	www.amtechdisc.com /cdpaper.html (5442 words)

	[No title]
		The regular, recurrent, palpable wave of arterial distention due to the pressure of the blood ejected with each contraction of the heart.
		A radio or radar beam which is swept over a sector of space and is accompanied by a repeated pattern of pulses that is varied to indicate the position of the beam in space.
		] Modulation in which the peak-to-peak amplitude range of the signal to be transmitted is divided into a number of standard values, each having its own code; each sample of the signal is then transmitted as the code for the nearest standard amplitude.
	www.accessscience.com /Dictionary/P/P51/DictP51.html (1701 words)

	1-bit A/D and D/A Converters
		Differential pulse-code modulation is a technique in which the derivative of the signal is quantized.
		The input signal is compared to the integrated output pulses and the delta (difference) signal is applied to the quantizer.
		The quantizer generates a positive pulse when the difference signal is negative, and a negative pulse when the difference signal is positive.
	www.cs.tut.fi /sgn/arg/rosti/1-bit (1196 words)

	diyAudio Forums - A high-end digital amplifier for everyone
		The modulation scheme we have implemented is different from most of the existing PWM-based solutions; it is known as sigma-delta modulation (pulse-density modulation — PDM).
		Notwithstanding their high linearity and low clock frequency, sigma-delta modulators are generally not considered for digital power amplification because of their high pulse repetition frequency (PRF) and they encounter stability problems at high input amplitudes.
		One thing that has become apparent to me is that for any of these modulation conversion technologies that use an H-Bridge power output section without feedback, it would be very easy to use an FPGA as a switch for easy measurement and listening comparisons between the various commercial modulators and self-developed algorithms.
	www.diyaudio.com /forums/showthread.php?s=&threadid=22414 (2514 words)

	Welcome to HES Electronics
		A process which modulates the amplitude of a carrier wave according to a variation of the input voltage (signal).
		Bitstream Converter: A one-bit or low-bit A/D and D/A oversampling conversion method developed by Philips in which the audio signal is represented through PDM (pulse density modulation) or time averaging at a frequency of 11.3Mhz.
		Modulation: Variation of a wave parameter (such as amplitude or frequency) to carry information.
	www.heselectronics.com /libAudioVideo.htm (4241 words)

	Untitled Page
		PDM (Pulse Density Modulation) digital neural network system with 1000 neurons fully interconnected via one million 7-bit synapses.
		The same winner-take-all network was simulated by a workstation and it took 76 seconds to settle.
		The PDM system was 10000 times faster than a computer.
	www.viplab.is.tsukuba.ac.jp /~hirai/PDM.html (299 words)

	Product Review
		The samples are represented with a frequency modulated square wave, with pulses of equal duration.
		This is as compared to Pulse Width Modulation, where the duration of the pulses is modulated rather than the frequency of the pulses.
		This is referred to as 64 times oversampling, but the actual data density is only 4x that of regular CD, due to the higher resolution of the Redbook CD's PCM encoding.
	www.hometheaterhifi.com /volume_9_1/sharp-sm-sx100-digital-amp-1-2002.html (2429 words)

	Analog Devices : Analog Dialogue : Class D
		An alternative to PWM is pulse-density modulation (PDM), in which the number of pulses in a given time window is proportional to the average value of the input audio signal.
		Nonetheless 1-bit sigma-delta modulation is not often used in Class D amplifiers (Further Reading 4) because conventional 1-bit modulators are only stable to 50% modulation.
		Its 1-bit sigma-delta modulator is especially enhanced for the Class D application to achieve average data frequency of 500 kHz, with high loop gain to 90% modulation, and stability to full modulation.
	www.analog.com /library/analogDialogue/archives/40-06/class_d.html (5667 words)

	Electronic Products
		The result is high efficiency due to the output stage transistors being modulated either on or off.
		The modulation method also plays a role in determining the sound fidelity and output efficiency.
		PWM drive is often used, but more advanced designs sometimes employ pulse density modulation, in which an oversampling clock is used to generate pulses with a much higher transition frequency.
	www.electronicproducts.com /print.asp?ArticleURL=febevo1.feb2003 (610 words)

	GSM Physical Layer Modulation (Site not responding. Last check: 2007-10-11)
		MSK uses changes in phase to represent 0's and 1's, but unlike most other keying schemes we have seen in class, the pulse sent to represent a 0 or a 1, not only depends on what information is being sent, but what was previously sent.
		Even though MSK's power spectrum density falls quite fast, it does not fall fast enough so that interference between adjacent signals in the frequency band can be avoided.
		It happens that with lower time-bandwidth products the pulse is spread over a longer time, which can cause intersymbol interference.
	www.eecg.toronto.edu /~nazizi/gsm/modulation/index.html (749 words)

	techsacd12
		With such a Pulse Density Modulation (PDM) process, the instantaneous amplitude of the analog waveform is represented by the density of pulses.
		The pulse point up where the analog waveform approaches full positive and down where the analog wave approaches full negative.
		Like for PCM, such a PDM signal is highly resistant to distortion, noise, wow and flutter of recording media and transmission channels.
	www.daisy-laser.com /technology/techsacd/techsacd12.htm (264 words)

	[No title]
		On 4m it never disappeared on 70.26MHz in some areas but on 6m and 2m the level of AM activity dropped to almost zero with the advent of synthesised FM equipment produced in high volumes at increasingly attractive prices.
		Based on a kernel density estimation for approximating the symbol error rate (SER) from training data, a least mean squares (LMS) style stochastic gradient algorithm called the least SER (LSER) is developed for training linear MUDs.
		AM stands for Amplitude Modulation, a simple way of getting around the fact that radio waves at audio frequencies do not travel very far.
	www.lycos.com /info/amplitude-modulation--miscellaneous.html (464 words)

	frequency modulation in electromagnetic transformer
		It is well-known in radio-electronics that signal for modulation determines the "factor of noise protection" Usually a electromagnetic transformers are using the amplitude modulation when the strength of the primary current is changing by means of variable amplitude of voltage.
		Another type of modulation allows to get the signal/noise ratio less than unity, for example, it is the frequency modulated signal.
		For any pulse exist the front (density of current is increasing) and abatement (density of current is decreasing) but if the transformer is not high frequency the front and abatement changes are not connected with induction effect.
	www.fortunecity.com /tattooine/gargoyle/32/pulses.htm (242 words)

	The Compact Disc. How does it work?
		They interpret an electrical pulse to mean one of the figures of binary notation, a "1".
		The value of the signal is 1 V at the moment the measuring sample is taken (the moment of the sample pulse).
		In Philips PDM conversion, the 16-bit digital samples read from the CD are transformed into a high-speed, one-bit data stream (with 256 times oversampling).
	library.thinkquest.org /26171/gforce.html (3856 words)

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