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Topic: Characteristic impedance

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Nominal impedance

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	Acoustic impedance - Wikipedia, the free encyclopedia
		The acoustic impedance Z (or sound impedance) is the ratio of sound pressure p to particle velocity v in a medium or acoustic component.
		The characteristic impedance of a medium (usually air, but also for instance exhaust gases in a muffler) is the ratio of sound pressure p to particle velocity v in open field (i.e.
		The acoustic impedance Z of an acoustic component (in Pa·s/m) is the ratio of sound pressure p to particle velocity v at a transition with a previous component:
	en.wikipedia.org /wiki/Acoustic_impedance (304 words)

	Cable impedance
		Characteristic impedance is determined by the size and spacing of the conductors and the type of dielectric used between them.
		For ordinary coaxial cable used at reasonable frequency, the characteristic impedance depends on the dimensions of the inner and outer conductors, and on the characteristics of the dielectric material between the inner and outer conductors.
		In a nut shell the characteristic impedance of a coax cable is the square root of (the per unit length inductance divide by the per unit length capacitance).
	www.epanorama.net /documents/wiring/cable_impedance.html (4288 words)

	Characteristic impedance - Wikipedia, the free encyclopedia
		The SI unit of characteristic impedance is the ohm.
		Applying the transmission line model based on the telegrapher equations, the general expression for the characteristic impedance of a transmission line is:
		The voltage and current phasors on the line are related by the characteristic impedance as:
	en.wikipedia.org /wiki/Characteristic_impedance (174 words)

	Characteristic Impedance - Microwave Encyclopedia - Microwaves101.com
		Characteristic impedance is a measure of the balance between the two.
		Characteristic impedance does not even need a transmission line, there is a characteristic impedance associated with wave propagation in any uniform medium.
		The intrinsic impedance is a measure of the ratio of the electric field to the magnetic field.
	www.microwaves101.com /encyclopedia/Z0.cfm (808 words)

	Package-Level Interconnect Design for Optimum Electrical Performance
		Characteristic impedance is a term borrowed from transmission-line theory and is, at a very academic level, the ratio of the electric-to-magnetic field distribution in a transmission line, where a transmission line is a multi-conductor structure that propagates a signal [1]-[4].
		Although closed form solutions for characteristic impedance exist for certain configurations that are very similar to the designs used in traces in Intel’s packages, these formulas are for aspect ratios of trace width to plane separation that are different from those of Intel’s packages.
		Crosstalk in a package is dependent upon the stack-up, just as is characteristic impedance; however, crosstalk is primarily affected by the distance between traces, by the amount of parallelism between traces, and by the presence of reference plane discontinuities.
	developer.intel.com /technology/itj/q32000/articles/art_3d.htm (1815 words)

	Characteristic Impedance - Transmission Lines
		The impedance (resistance) of this line in ohms is called the characteristic impedance, and it is fixed by the geometry of the two conductors.
		Characteristic impedance is also known as natural impedance, and it refers to the equivalent resistance of a transmission line if it were infinitely long, owing to distributed capacitance and inductance as the voltage and current "waves" propagate along its length at a propagation velocity equal to some large fraction of light speed.
		Characteristic impedance is purely a function of the capacitance and inductance distributed along the line's length, and would exist even if the dielectric were perfect (infinite parallel resistance) and the wires superconducting (zero series resistance).
	www.opamp-electronics.com /tutorials/characteristic_impedance_2_14_03.htm (1093 words)

	Characteristic impedance (Site not responding. Last check: 2007-10-08)
		A uniform line terminated in its characteristic impedance will have no standing wave s, no reflections from the end, and a constant ratio of voltage to current at a given frequency at every point on the line.
		The characteristic impedance of a linear, homogeneous, isotropic, dielectric propagation medium free of electric charge is given by the relation :
		Where the magnetic permeability and electric permittivity of the vacuum are used, this equation defines a fundamental physical constant, the characteristic impedance of free space and turns out to be equal to 120π (about 377) ohm s.
	www.serebella.com /encyclopedia/article-Characteristic_impedance.html (246 words)

	characteristic impedance (Site not responding. Last check: 2007-10-08)
		) of a uniform transmission line is the impedance of a circuit that, when connected to the output terminals of a line of arbitrary length, causes the line to appear infinitely long.
		A uniform line terminated in its characteristic impedance will have no standing waves, no reflections from the end, and a constant ratio of voltage to current at a given frequency at every point on the line.
		Where the magnetic permeability and electric permittivity of the vacuum are used, this equation defines a fundamental physical constant, the characteristic impedance of free space and turns out to be equal to 120π (about 377) ohms.
	www.wapipedia.org /wikipedia/mobiletopic.aspx?cur_title=characteristic_impedance (205 words)

	Method for measuring a characteristic impedance and a propagation constant of a two-port network - Patent 4904927
		In a method for measuring a characteristic impedance and a propagation constant of a two-port network (2), an output port (5) of the two-port network (2) is successively terminated with at least two different finite known impedances (3a, 3b) which are independent of the two-port network (2).
		From the termination impedances (ZA1, ZA2) of the impedances (3a, 3b) and the corresponding input impedances (ZE1, ZE2), the propagation constant and the characteristic impedance are determined.
		The input 22 of the impedance selection circuit 15 is directly connected to the output 21 of the reflection measuring instrument 1 (the switch 6a is now in the position in which it connects the reflection coefficient bridge 9 to the output 21 of the reflection measuring instrument 1).
	www.freepatentsonline.com /4904927.html (3471 words)

	Even and Odd Mode Impedances- Microwave Encyclopedia - Microwaves101.com
		Impedance is a vector quantity that expresses the ratio of electromagnetic voltage (or electric field strength) to current (or magnetic flux density).
		There are three impedances that characterize the structure, characteristic impedance, even mode impedance and odd mode impedance.
		The first is the direct capacitance to ground of each trace, the second is the mutual capacitance between the traces, and the third represents the distortion of each caused by the presence of the coupled element (and a small contribution due the thickness of each).
	www.microwaves101.com /encyclopedia/evenodd.cfm (922 words)

	Cable Impedance.
		This is the input impedance of either an infinite length of the cable, or more practically of a finite length terminated by an impedance equal to the characteristic impedance.
		Cable impedance is generally some sort of logarithmic function of dimensions such as conductor spacing, and so even large changes in dimensions have little effect on impedance, and if some unusual value such as 4 ohms is required, then the dimensions may need to be inconveniently large or small to achieve this.
		The characteristic impedance can be worked out theoretically, the method I once had to learn is called 'conformal transformation', but fortunately there are only a few common arrangements of conductors and the relevant equations are well known.
	www.angelfire.com /ab3/mjramp/golopid/impedance.html (806 words)

	Understanding Impedance
		The output voltage from the source is developed across the input impedance of the destination (often called the load impedance, or simply the load), and therefore the signal voltage is passed from source to destination.
		The impedance of a headphone is determined by the design of its voice coils — the length and size of wire used, the number of turns around the former, and so on.
		The use of the transformer is principally to translate the effective load impedance between that required by the valves, and that of a practical loudspeaker — a typical valve output circuit requires a load of between 5k(omega) and 10k(omega), whereas a practical loudspeaker presents a nominal impedance of between 4(omega) and 15(omega).
	www.soundonsound.com /sos/jan03/articles/impedanceworkshop.asp (5518 words)

	Impedance
		Impedance is defined for mechanical systems as force divided by velocity, while the inverse (velocity/force) is called an admittance.
		In the lossless case (no dashpots, only masses and springs), all driving-point impedances are purely imaginary, and a purely imaginary impedance is called a reactance.
		The wave impedance (also called the characteristic impedance) in open air is the ratio of pressure to particle velocity in a sound wave traveling through air, and it is given by
	www-ccrma.stanford.edu /~jos/book2000/Impedance.html (493 words)

	Characteristic Impedance of Cables at High and Low Frequencies
		The impedance which is due to pure inductance is called inductive reactance (XL) and, in ohms, is equal to 2(3.1416)f L where f is frequency in hertz (cycles per second) and L is inductance in henries.
		The impedance which is due to pure capacitance, called capacitive reactance (Xc), is equal in ohms to 1/(2(3.1416) f C), where f is frequency in hertz and C is capacitance in farads.
		If the magnitude of the impedance (in ohms) is plotted as a function of frequency (in hertz) on log-log graph paper, the result is a straight line having a slope of one decade of ohms for two decades of frequency, extending downward and to the right.
	home.mira.net /~marcop/ciocahalf.htm (2647 words)

	Understanding the Transmission Line Theory (Site not responding. Last check: 2007-10-08)
		The impedance of a capacitor rotates the phase of the current 90° in the negative or direction to generate the voltage across the capacitor.
		A controlled impedance transmission line is a pair of conductors that have a uniform cross section and uniform distribution of dielectric materials down their length.
		The impedance is determined by the speed of the signal and the capacitance per length of the pair of conductors, both intrinsic properties of the line.
	www.ece.uci.edu /docs/hspice/hspice_2001_2-269.html (4463 words)

	U.S. Patent: 5278720 - Printed circuit-mounted surge suppressor matched to characteristic impedance of high frequency ...
		wherein the geometries of said first and second conductor layers are defined so as to match the characteristic impedance of the transmission line with the characteristic impedance represented by the combination of said dielectric layer, said first and second conductor layers, said discharge device and stray capacitance associated with the combination thereof.
		A second of F type coaxial connector is mounted at the other end of the printed circuit board, having its center feed conductor soldered to a second end of the first conductive layer and its outer sheath soldered to the adjacent end of the ground plane layer.
		The geometry of the first conductor strip and the permitivity of the dielectric board, which determine the characteristic impedance of the microstrip section, are such that the resulting characteristic impedance matches that (e.g.
	www.everypatent.com /comp/pat5278720.html (3142 words)

	Definition: characteristic impedance (Site not responding. Last check: 2007-10-08)
		The impedance of a circuit that, when connected to the output terminals of a uniform transmission line of arbitrary length, causes the line to appear infinitely long.
		Note 1: A uniform line terminated in its characteristic impedance will have no standing waves, no reflections from the end, and a constant ratio of voltage to current at a given frequency at every point on the line.
		For Maxwell's equations, the impedance of a linear, homogeneous, isotropic, dielectric propagation medium free of electric charge, given by the relation Z =(
	www.its.bldrdoc.gov /fs-1037/dir-007/_0942.htm (117 words)

	Loudspeaker Cable Characteristic Impedance
		The characteristic impedance of a cable (Zo) is a complex function of the diameter (or dimensions if other than round) of the conductors, their relative spacing, and the insulation material.
		In order to obtain a low characteristic impedance, it is necessary to have very low inductance and relatively high capacitance, and the high capacitance may impose serious constraints on the amplifier.
		For video, the standard impedance is 75 ohms, so the output impedance of a video line driver will be 75 ohms, 75 ohm coaxial cable is used for connections, and the receiving end is also 75 ohms.
	sound.westhost.com /cable-z.htm (5994 words)

	eFunda: Electrical Impedance of Piezo Materials
		The electrical impedance is a distinguishing characteristic for piezoelectric elements.
		Recall that the electrical impedance is defined as the voltage drop across an element divided by the current through the element.
		The impedance for a non-piezoelectric element (of the same shape and dielectrical properties) is also shown in blue.
	www.efunda.com /materials/piezo/electronics/elec_impedance.cfm (154 words)

	Untitled
		Characteristic impedance is one important thing to check, not so much for AC power lines, or even loudspeaker lines, but certainly for video lines and matched impedance lines.
		The characteristic impedance of any transmission line is the impedance that must be connected to the far end of the line in order to make the input impedance of the line equal to the terminating impedance.
		The characteristic impedance depends on the parameters of the line and the applied frequency.
	svconline.com /mag/avinstall_ (256 words)

	Sound - Wikipedia, the free encyclopedia
		In a soundwave, the complementary variable to sound pressure is the acoustic particle velocity.
		For small amplitudes, sound pressure and particle velocity are linearly related and their ratio is the acoustic impedance.
		The acoustic impedance depends on both the characteristics of the wave and the medium.
	en.wikipedia.org /wiki/Sound (944 words)

	Impedance Matching and the Smith Chart: The Fundamentals - Maxim/Dallas (Site not responding. Last check: 2007-10-08)
		The amount of reflected signal from the load is dependent on the degree of mismatch between the source impedance and the load impedance.
		Once the impedance point is plotted (the intersection point of a constant resistance circle and of a constant reactance circle), simply read the rectangular coordinates projection on the horizontal and vertical axis.
		This occurs because the plot is an impedance plot.
	www.maxim-ic.com /appnotes.cfm/appnote_number/742 (3024 words)

	Characteristic Impedance (Site not responding. Last check: 2007-10-08)
		This note presents an alternative to the derivation of the characteristic impedance of a transmission line found in most texts.
		The characteristic impedance is defined as the ratio of the input voltage to the input current of a semi-infinite length of line.
		Hence we can say that the impedance looking into the line on the far left is equal to Zo in parallel with Cdx and Gdx, all of which is in series with Rdx and Ldx.
	www.ee.scu.edu /eefac/healy/char.html (288 words)

	Insight On Rules #40
		However, the input impedance of a short no loss transmission line with a low characteristic impedance is about the same as the load impedance.
		The impedance seen on the generator side of the line (the inside of the phaser cabinet) is about the same as the characteristic impedance of the line, since the line has so much loss.
		It is terminated by the impedance at the input of the transmission line that models the aluminum side of the cabinet (2 milliohms).
	www.broadcast.net /hallikainen/insite40.html (1323 words)

	Transmission Line Zo
		The characteristic impedance of a line is the impedance you would see at one end of a transmission line of infinite length.
		The changes in the impedance plots come about becasue the impedance of a capacitor and inductor are a direct function of frequency.
		The Z Transform measurement of the imaginary part of the cable impedance (open circuit) at 1 Mhz is 81.725 Ohms, or the cable has a capacitance of 1.95 nF.
	www.pacificsites.com /~brooke/Zo.shtml (3759 words)

	CHARACTERISTIC IMPEDANCE (Site not responding. Last check: 2007-10-08)
		Characteristic impedance of cables is square root of ratio of distributed inductance to capacitance of the cable.
		When a cable with 75 W of characteristic impedance is connected between source and load, both source and load impedance should be 75 W. This results in perfect impedance match.
		RL represents input impedance of video receiving unit like a monitor, switcher etc. Since RS = RL = Z0 = 75 W, the video signals get attenuated by a factor of 2 at the receiver.
	www.mtxindia.com /An3.htm (261 words)

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