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Topic: Wave impedance

	Wave impedance - Wikipedia, the free encyclopedia
		Wave impedance: At a point in an electromagnetic wave, the ratio of the electric field strength to the magnetic field strength!
		The wave impedance, Z, of an electromagnetic wave is given by the equation:
		In the equation, i is the imaginary unit, and ω is the angular frequency of the wave.
	en.wikipedia.org /wiki/Wave_impedance (284 words)

	Electrical impedance - Wikipedia, the free encyclopedia
		A resistor's impedance is R (its resistance) and its reactance is 0.
		It is important to note that the impedance of a capacitor or an inductor is a function of the frequency f and is an imaginary quantity - however is certainly a real physical phenomenon relating the shift in phases between the voltage and current phasors due to the existence of the capacitor or inductor.
		Impedance is defined by the ratio of two phasors where a phasor is the complex peak amplitude of a sinusoidal function of time.
	en.wikipedia.org /wiki/Impedance (1980 words)

	EJGE Paper
		Impedance functions for a rigid massless circular foundation resting on layered soil subjected to vertical harmonic excitation are found using one-dimensional wave propagation in cones with reflection and refraction occurring at layer interface and free surface.
		For vertical degree of freedom the one-dimensional wave pattern in cones governed by the theory of strength of material of layered half-space with reflections and refractions occurring at the interfaces and free surface is shown in the Figure 3.
		The displacement of wave at a particular depth is directly proportional to the height of its cone and inversely proportional to the height of the apex of cone from the depth considered (one dimensional wave propagation in rods).
	www.ejge.com /2003/Ppr0323/Ppr0323.htm (3047 words)

	Definition: wave impedance (Site not responding. Last check: 2007-10-09)
		Note 1: If the electric field strength is expressed in volts per meter and the magnetic field strength is expressed in ampere-turns per meter, the wave impedance will have the units of ohms.
		The wave impedance, Z, of an electromagnetic wave is given by
		In dielectric materials, the wave impedance is 377/n, where n is the refractive index.
	www.atis.org /tg2k/_wave_impedance.html (127 words)

	Near and Far Fields - From Statics to Radiation (Site not responding. Last check: 2007-10-09)
		Wave impedance is the ratio of the electric field magnitude, E, to that of the magnetic field magnitude, H.
		The concept of wave impedance isn’t useful in electrostatics because the ratio of E to H is infinite.
		Their ratio, which is the wave impedance, is the characteristic impedance of the surrounding medium, just as it is for the Hertzian dipole.
	www.conformity.com /0102reflections.html (1388 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		A transducer with a backing block impedance that is a function of frequency may operate in quarter wave mode at frequencies where the transformed backing block impedance is high and in half wave mode at frequencies where the transformed backing block impedance is low.
		Analogously, an acoustic impedance transformer in accordance with the invention may be designed and constructed using the same method and design equations as used for designing and constructing impedance transformers used in microwave electronics.
		impedance transformer in accordance with the invention in that for example, one or more layers may need to be made of a specific material or have a specified minimum or maximum thickness.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=04/109656.041216&ELEMENT_SET=DECL (6538 words)

	EJGE Paper
		Horizontal impedance in particular was studied by Ahmad and Bharadwaj (1991) for strip foundations and Ahmad and Rupani (1999) for square foundations by using boundary element formulation.
		The impedance functions normalized by the static stiffness of homogeneous half-space with material properties of the top layer are found using the model and compared with the rigorous analytical results of Luco (1974), as shown in Figure 4.
		In summary, it is clearly shown that the horizontal impedance of a circular foundation resting on a layered soil is affected by a number of key geometrical and material parameters, the details of which are presented as dimensionless graphs.
	www.ejge.com /2003/Ppr0340/Ppr0340.htm (3934 words)

	ESTIMATION OF ELECTRON DENSITY OF IONOSPHERIC PLASMA USING WAVE, IMPEDANCE AND TOPSIDE SOUNDER DATA
		The processor-controlled HF wave instrument PRS4 was able to measure wave spectra in the frequency range.1-30MHz, monopole self impedance in frequency range.1-10MHz and to operate as a topside sounder in the frequency range.3-16MHz.
		The notions of susceptibility of the plasma to radiate in this band and the high input impedance of wave instrument resulted in the assumption that the voltage spectrum inside the instrument is directly related to the spectrum of the voltage which drives the circuit.
		It was the successful simulation of the discrepancy between wave and topside sounder data which resulted in the systematic development and understanding of equivalent circuit applicable to HF wave receivers in the ionosphere.
	www-ssc.igpp.ucla.edu /IASTP/93 (5872 words)

	British Journal of Pharmacology - Aminoguanidine prevents age-related aortic stiffening in Fisher 344 rats: aortic ... (Site not responding. Last check: 2007-10-09)
		Wave transit time was determined using the impulse response function of the filtered aortic input impedance spectra.
		The input impedance modulus of aging was displaced upward because of the impaired wall elastic properties and to the right owing to diminished aortic distensibility.
		Since the aortic input impedance cannot be measured in conscious animals, it is difficult to evaluate the effects of pentobarbital anesthesia on rats at different ages and on rats treated with AG.
	www.nature.com /bjp/journal/v140/n1/full/0705410a.html (4560 words)

	Impedance Matching (Site not responding. Last check: 2007-10-09)
		When a traveling wave pulse is started by hand at one end of one machine it will show a partial reflection and a partial transmission when it meets the boundary of the two machines.
		The impedance matching machine has a smooth gradient of progressively longer rods, with short rods at one end that match the short rod machine and long rods at the opposite end that match the long rod machine.
		With the impedance matcher acting as a smooth buffer the abrupt boundary is smoothed between the two different wavelength machines.
	www.physics.brown.edu /physics/demopages/Demo/waves/demo/3b2510.htm (235 words)

	Microwave option paper 99-00 (DJJ questions)
		It is the ratio of voltage to current in a forward travelling wave on the line; it is equal to the input impedance of a very long length of line for times shorter than the time it takes the reflections to return from the far end.
		The wave velocity is therefore either the phase velocity or the group velocity; it is the speed (and direction) with which the wave crests travel along the coaxial cable, and it is also the speed with which the energy and the modulations travel.
		Dispersion: this is a technical term for the case where the phase velocity of waves depends on frequency or wavelength, and a superposition (Fourier) of waves "disperses" in distance as it travels along the line.
	www.ee.surrey.ac.uk /Personal/D.Jefferies/solns9900.html (2095 words)

	Lecture 15
		wave impedance of the total field at any plane parallel to the plane boundary as the ratio of the total electric field intensity to the total magnetic field intensity.
		In the case of a uniform plane wave incident from medium 1 normally on a plane boundary with an infinite medium 2, the magnitudes of the total electric and magnetic field intensities in medium 1 are,
		The wave impedance of the total field in medium 1 at a distance z from the boundary plane:
	www.ee.umd.edu /class/enee381-1.F2004/lectures/lecture15.htm (319 words)

	Shielding Methods
		The importance of wave impedance is shown by an electromagnetic wave encountering an obstacle such as a metal shield (see Figure 3).
		If the impedance of the wave differs greatly from the natural impedance of the shield, much of the energy is reflected and the rest is transmitted across the surface boundary, where absorption in the shield further attenuates it.
		All values are expressed in dB (decibels) Reflection loss (R) includes reflections at both surfaces of the shield, and is dependent upon the relative mismatch between the incoming wave impedance and the frequency of the impinging wave, as well as upon the electrical parameters of the shielding material itself.
	www.parker.com /chomerics/tech/shielding_methods.htm (2585 words)

	Carmel Presents Some Wave Questions
		The motion of the medium is perpendicular to the wave motion.
		The wave and medium motion are along the same line.
		In this the speed of a wave depends on frequency.
	id.mind.net /~zona/mstm/physics/waves/problems/carmelPresentsSomeWaveQuestions/carmelPresentsSomeWaveProblems.html (82 words)

	Transmission Lines/Gate Delay
		From it we may directly derive the voltage/current ratio (that is, the input impedance) at the input to the line.
		When we have a wave traveling in one direction only, the ratio of voltage to current (i.e., the wave impedance) is constant, and equal to the characteristic impedance of the transmission line.
		Generally speaking, if the far-end load has an impedance greater than Z0, the initial effect (when the reflected wave hits the driver) is to raise the effective input impedance of the line.
	www.sigcon.com /Pubs/news/1_19.htm (948 words)

	Nat' Academies Press, Microwave Processing of Materials (1994)
		The wave impedance is thus a real quantity and has the same value anywhere along the z axis.
		The two remarkable properties of wave propagation stated earlier are that the wave carries an equal amount of the electric and magnetic energy and that the wave impedance stays constant in the propagation direction.
		Both the electric and magnetic fields are in the form of a standing wave in the sense that all the energy carried by the wave forward is reflected back and that the wave is neither moving the energy forward nor backward.
	www.nap.edu /openbook.php?record_id=2266&page=21 (476 words)

	Microwave Theory
		The amplitude of the reflected voltage wave normalized to the amplitude of the incident voltage wave is known as the voltage reflection coefficient,
		To match the impedances of the arms of the T to the impedance of the base, the arms must have twice the impedance of the base.
		To launch a wave, on the microstrip transmission line the microwave signal is brought from the generator on a coaxial cable which connects to an on-board PCB mounted jack which is soldered directly to the groundplane and feedlines.
	www.madmadscientist.com /html/Theory.htm (1720 words)

	Comparative analysis of aortic impedance and wave reflection in ferrets and dogs -- Burattini and Campbell 282 (1): 244 ...
		the ascending aortic input impedance is determined by the parallel of the head-end (i = h) and the body-end (i = b) input
		Average (±SE) ascending aortic impedance data computed over five dogs (solid circles with SE bars) are compared with predictions for the ascending aorta (solid line) and for the head-end (dashed line) and body-end (dash-dot line) portions of the arterial system as provided by our modified T-tube model filled with average parameters of Table 2.
		to the reflected wave and the composite wave in the ascending
	ajpheart.physiology.org /cgi/content/full/282/1/H244?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=Millar&searchid=1041608314673_508&stored_search=&FIRSTINDEX=0&volume=282&issue=1&journalcode=ajpheart (5945 words)

	Microwave option paper 98-99 (DJJ questions)
		Define the terms "characteristic impedance", "wave velocity", "velocity factor", "reflection coefficient" and "voltage standing wave ratio VSWR" for waves on a coaxial transmission line.
		Using the SMITH chart, or otherwise, determine the driving point impedance at the input to a 50 ohm feeder of length 21.67 lambda which is connected to this antenna.
		We relate the incoming wave amplitudes ai to the outgoing wave amplitudes bi by the matrix equation bi = sij aj where the sij are the (complex dimensionless) scattering parameters, which can be assembled into a matrix called the scattering matrix.
	www.ee.surrey.ac.uk /Personal/D.Jefferies/solns9899.html (1893 words)

	Reflection coefficient question. (Site not responding. Last check: 2007-10-09)
		A wave generated in a medium and incident in other medium sees a different wave impedance, and therefore part of the energy is reflected and part is transmitted.
		When the wave hits impedance discontinuity some travels ahead but some travels back (this is the reflected wave) and at begining of the structure when original wave entered the reflected wave occurs another impedance dicontinuity and then some gets out and some gets reflected back and so forth and everything becomes a geometrical series.
		Actually there are many reflections between the two ends and the total reflection wave at the input is the summation of all the waves.
	www.edaboard.com /ftopic90050.html (927 words)

	Effects of Diabetes and Gender on Mechanical Properties of the Arterial System in Rats: Aortic Impedance Analysis -- ...
		Modulus (A) and phase (B) of the aortic input impedance, and impulse response function of the filtered impedance spectra (C) in one control rat with female gender.
		The aortic input impedance spectra were computed from the aortic pressure and flow signals using a standard Fourier series expansion technique shown in Appendix 1.
		of pulse wave reflection from the peripheral circulation.
	www.ebmonline.org /cgi/content/full/228/1/70 (4125 words)

	2-D Impedance Estimation
		The 2-D impedance inversion is performed on the preprocessed, migrated, and amplitude-calibrated gathers and reflection angles described in Chapter 2.
		Since the transition from water to sediments is characterized by an increase in P-wave velocity, S-wave velocity and density, both a positive P-wave impedance contrast and a positive S-wave impedance contrast can be expected.
		The velocity analysis in Chapter 2 has shown that the BSR is characterized by a significant decrease in velocity, and thus a negative P-impedance contrast.
	sepwww.stanford.edu /public/docs/sep96/paper_html/node38.html (731 words)

	Speakers
		It is divided into two parts, the blocked impedance that can be measured with the coil immobilized (in which case C' becomes infinite, or effectively a short circuit), and the motional impedance.
		It is instructive to plot the resistance R and the reactance X of the speaker as a function of frequency, with R the abscissa and X the ordinate.
		This is the wave impedance, or the specific acoustic impedance, z, of the horn.
	www.du.edu /~jcalvert/tech/speak.htm (4825 words)

	Minimum-length cascades of short transmission lines
		If conversion is made to a fixed-wave-impedances cascade, the wave impedances are always at the limits, so that the d values for smaller L and C values will be less than the maximum.
		To find a design in which the wave impedances are between 15Ω and 100Ω, it was necessary to choose the electrical length as 35°.
		As with the filter example, this effect determines the minimum length of the network, which is required to have a minimum wave impedance of at least 15Ω.
	rfdesign.com /mag/radio_minimumlength_cascades_short/index.html (4034 words)

	Effects of pulmonary embolism on pulmonary vascular impedance in dogs and minipigs -- Maggiorini et al. 84 (3): 815 -- ...
		To quantify wave reflection, the recorded instantaneous pressure waves were separated into their forward and backward components
		the peak of the wave, and the downward zero crossing of the wave
		of wave reflection were not different in the dogs and in the minipigs.
	jap.physiology.org /cgi/content/full/84/3/815 (3528 words)

	Electromagnetic Field Theory Group at IFH - Lectures
		Electromagnetic waves: wave equation and its solution, wave propagation in layered media, oblique incidence on dielectric interface, incidence on good conductors and good dielectrics, propagation constant, wave impedance, phase velocity, group velocity, polarization, standing waves
		Wave propagation: free-space propagation, reflection, ground effects, ground waves, diffraction, scattering, absorption, refraction, path loss, multipath propagation, propagation models for macro, micro and pico cells, Friis transmission equation, Radar range equation
		Overview of the concepts of the main numerical methods for the simulation of electromagnetic fields: finite difference method, finite element method, transmission line matrix method, matrix methods, multipole methods, image methods, method of moments, integral equation methods, beam propagation method, mode matching technique, spectral domain analysis, method of lines.
	www.ifh.ee.ethz.ch /Field/teaching.html (598 words)

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