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Topic: Phase velocity


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In the News (Sat 15 Jun 19)

  
  Phase Velocity - Microwave Encyclopedia - Microwaves101.com
Phase velocity is the speed at which microwave energy travels along a transmission line.
Velocity for a traveling wave is equal to the speed of light divided by the square root of the effective relative permittivity.
Phase velocity can also be devived from the inductance and capacitance per unit length of a transmission line.
www.microwaves101.com /encyclopedia/phasevelocity.cfm   (150 words)

  
  Phase velocity - Wikipedia, the free encyclopedia
The phase velocity of a wave is the rate at which the phase of the wave propagates in space.
Note that the phase velocity is not necessarily the same as the group velocity of the wave, which is the rate that changes in amplitude (known as the envelope of the wave) will propagate.
The phase velocity of electromagnetic radiation may under certain circumstances exceed the speed of light in a vacuum, but this does not indicate any superluminal information or energy transfer.
en.wikipedia.org /wiki/Phase_velocity   (305 words)

  
 Ferroelectric Phase Shifters- Microwave Encyclopedia - Microwaves101.com
Phase shifters are used to change the transmission phase angle (phase of S21) of a network.
MEMS (micro-electro-mechanical systems) phase shifters have much faster response speeds (measure in milliseconds), however their major drawback is that they have high losses at microwave and millimeter-wave frequencies.
A distributed phase shifter with BST tunable capacitors combines the advantages of both BST low-loss properties in the microwave or millimeter-wave region and the easy design and wide bandwidth of MEMS distributed phase shifter and is the state of the art today.
www.microwaves101.com /encyclopedia/phaseshifters_ferro.cfm   (1803 words)

  
 Phase Velocity
Phase velocity is usually measured using the one or two-station method.
The propagation phase term depends on the phase velocity of the structure.
N term represents the periodicity of the harmonic term in the phase velocities and is estimated using long-period observations, which should converge to globally averaged values at long-periods.
www.uwm.edu /~bketter/Research/Surface_Theory/Phase_Velocity/phase_index.html   (215 words)

  
 Group Velocity Demonstration
The difference between group velocity and phase velocity can be quite difficult to grasp, but at the most basic descriptive level the difference is quite simple.
The quantity we commonly refer to as the "speed-of-light" is its phase velocity: the speed at which the wavefronts of a pure frequency tone travel.
The group velocity and phase velocity are the same in a vacuum, but in any other medium this is not, in general, the case.
www2.ee.mu.oz.au /staff/summer/applets/group_velocity.html   (524 words)

  
 A validity study of phase velocity measurements in spinal cord injury   (Site not responding. Last check: 2007-10-21)
The phase velocity of bending waves was calculated from signals derived from two accelerometers, with a defined distance between them, attached to the wave-conducting structure.
Phase velocity of flexural waves passing through the tibia is a mean to assess the mechanical properties of this bone [20].
Phase velocity measurement of tibia bone evaluates bone mechanical characteristics that are influenced, at least partially, by health status, tibia length, and age.
www.vard.org /jour/05/42/1/debruin.html   (4401 words)

  
 Ozalaybey et al
Thus, a pair of phase velocity data sampling different regions of the model space (corresponding to different periods of phase velocity measurements) is sufficient to provide the information needed to remove the non-uniqueness in the solutions.
The main features of the velocity model are a sharp velocity increase in the upper 5 km (1.8 to 3.5 km/s) followed by a 2 km thick low-velocity layer between 6 and 8 km depth, a nearly constant velocity crust (3.5 km/s), and a crust-mantle transition between depths of 32 and 34 km.
In the velocity model of Catchings and Mooney (1991), this increase is due to the thickening of upper crustal and consequent deepening of middle and lower crustal layers.
www.seismo.unr.edu /ftp/web/htdocs/students/OZALAYBEY/BSSA/manu.html   (11711 words)

  
 CUB model main page
Phase velocities in period range between 40 an 150 s are generously donated by Harvard University and Utrecht University.
The group velocity measurements at periods between 16 and 200s are performed at the Center for Imaging the Earth's Interior in the University of Colorado at Boulder.
The group velocities are measured with the frequency-time analysis (Levshin et al., 1989) in which for every waveform a human analyst defines the frequency range of measurements and separate the signal form a variety of noise sources (e.g., overtones, fundamental modes of different types, other earthquakes, multipaths, scattered arrivals).
ciei.colorado.edu /~nshapiro/MODEL/index.html   (1362 words)

  
 Faster-than-Light Laser Pulses? - UFO Evidence   (Site not responding. Last check: 2007-10-21)
The phase velocity is the speed with which the maxima and minima of the light wave move forward.
In the limited frequency region occupied by the pulse, the phase velocity and frequency decrease as the reciprocal wavelength increases, so that the value of group velocity is a negative number.
The observed group velocity that the NEC group reports is vg = -c/310, i.e., the group velocity is a small negative fraction of the speed of light.
www.ufoevidence.org /documents/doc1096.htm   (2114 words)

  
 Phase versus Group Velocity   (Site not responding. Last check: 2007-10-21)
This animation shows the difference between phase velocity and group velocity in a traveling wave packet.
The phase velocity is the speed of the individual wave crests, whereas the group velocity is the speed of the wave packet as a whole (the envelope).
In this case, the phase velocity is greater than the group velocity.
www.geneseo.edu /~freeman/animations/phase_versus_group_velocity.htm   (55 words)

  
 Electromagnetic Field Propagation Velocity   (Site not responding. Last check: 2007-10-21)
, the equation (2) of the velocity is undefined.
In one parallel time line, the velocity v of electromagnetic wave may be undefined, while in another parallel time line the velocity v of the speed of the electromagnetic wave from the same light source is at c a finite velocity.
If the air radio waves velocity or electric voltage induction in antenna 4 or 5 was instantaneous, the amplitude of the radio waves from the wire antenna 6 would be steady along the wire 6 length x as shown in fiugre 3(c).
www.spots.ab.ca /~belfroy/electromagneticvelocity/electromagneticvelocity.html   (1414 words)

  
 Surface Wave Theory Page
Velocity normally increases with depth so longer period waves are faster because they sample deeper into the Earth where the velocities are higher.
Phase velocity is the culmination of a continuous spectrum of frequencies where each harmonic component has its own velocity (Lay and Wallace, 1995).
Phase velocity is dependent on the source of the earthquake and requires a good knowledge of the moment tensor and depth for accurate measurement.
www.uwm.edu /~bketter/Research/Surface_Theory/Surface.html   (444 words)

  
 A validity study of phase velocity measurements in spinal cord injury
Phase velocity of flexural waves passing through the tibia is a mean to assess the mechanical properties of this bone [20].
Phase velocity measurement of tibia bone evaluates bone mechanical characteristics that are influenced, at least partially, by health status, tibia length, and age.
Measurements of phase velocity in tibia bone of someone with SCI, therefore, are potentially of diagnostic value in the estimation of pathologic fracture risk in lower-limb bones in SCI.
www.rehab.research.va.gov /jour/05/42/1/debruin.html   (4401 words)

  
 Wave Mechanics; Animated de Broglie phase wave   (Site not responding. Last check: 2007-10-21)
Note that this is for the purpose of illustrating the instantaneous phase of the internal periodic phenomenon only; it is not intended to convey that the particle is literally moving up-and-down.
Note that, in accordance with the de Broglie theory, the phase of the phase wave at the position of the particle always exactly matches the instantaneous phase of the internal periodic phenomenon associated with the particle, though (except for massless particles) the particle and the phase wave move, or propagate, with different velocities.
The constant match between the phase of the phase wave and the phase of the internal periodic phenomenon at the position of the particle is illustrated above by the invariable coincidence of the
www.davis-inc.com /physics/wavegrph.html   (398 words)

  
 StockerYale Inc. - Optical Components - Phase Masks FAQs
Phase quantities pertain to the movement of the peaks and valleys of the electric and magnetic fields of the carrier wave.
Phase velocity expresses the speed of the movement of the peaks and valleys of the electric and magnetic fields.
The period of a phase mask is known to within ± 0.02 nm on a typical period of 1060 nm.
www.stockeryale.com /o/lasiris_pm/faqs.htm   (4886 words)

  
 The Backward Wave
In that case, the phase velocity, the energy velocity, and the group velocity are all equal to one another and are constants.
The phase velocity is given by the slope of the line from the origin to a point on the dispersion curve, while the group velocity is given by the slope of a tangent to the dispersion curve.
Phase velocity that decreases with increasing propagation constant is called anomalous dispersion, and backward waves are just one of the interesting phenomena that occur in such regions.
www.du.edu /~jcalvert/tech/back.htm   (2308 words)

  
 Faster-than-light - Wikipedia, the free encyclopedia
The phase velocity of a wave can easily exceed c, the vacuum velocity of light.
However, in general relativity, velocity is a local notion, so velocity calculated using comoving coordinates does not have any simple relation to velocity calculated locally.
Usually, such reports deal with a phase velocity or group velocity faster than the vacuum velocity of light.
en.wikipedia.org /wiki/Faster_than_light   (4300 words)

  
 Product Review
Phase Technology is a brand I have been interested in for quite some time due to their reputation for high value and performance.
The Velocities gave me an early indication of their performance when I was tuning in the system and I decided that it might be fun to watch the U2: Elevation Tour concert DVD.
The Velocities' sound quality on both movies and music was hard to fault, and while it may not be the best at any one aspect of speaker performance, their balanced qualities make their overall sound very enjoyable.
www.hometheaterhifi.com /volume_11_2/phase-tech-velocity-speakers-4-2004.html   (1987 words)

  
 Higher-Order Wave Equations and Matter Waves   (Site not responding. Last check: 2007-10-21)
This suggests that we might regard a particle of mass m and velocity V as a "matter wave" with the frequency w and wave number k proportional to the energy and momentum respectively, in accord with the above equations for E and p.
However, for a massive particle with v less than c, this formula may seem surprising at first, because it implies that the phase velocity of a matter wave exceeds c, and in fact goes to infinity as the speed v of the particle goes to zero.
We saw in equation (9) that the phase velocity V of the total energy of a particle moving at the speed v is c
www.mathpages.com /home/kmath415/kmath415.htm   (1570 words)

  
 RFS
The accuracy of these phase velocities is estimated to be within pm 0.1 km/s, which is nearly equal to the scatter in the measured phase velocities between different station pairs.
The latter model is found by the constrained inversion of the receiver function and the true-model phase velocity pair (3.06 km/s at 10 s and 3.51 km/s at 20 s) (Figure 7b) and is nearly identical to the true-model velocity structure.
The main features of the velocity model are a sharp velocity increase in the upper 5 km (1.8 to 3.5 km/s) followed by a 2 km thick low-velocity layer between 6 and 8 km depth, a nearly constant velocity crust (3.5 km/s),and a crust-mantle transition between depths of 32 and 34 km.
www.seismo.unr.edu /htdocs/students/OZALAYBEY/BSSA/rfs.html   (7889 words)

  
 Phase, Group, and Signal Velocity
On this basis we might say that the velocity of the signal is unambiguously equal to the "phase velocity", but in this context the phase velocity could only be defined as the speed of the leading (or trailing) edge of the overall signal.
The "phase velocity" of the internal oscillations is
It is quite possible for the phase velocity of a perfectly monochromatic wave of light, assuming such a thing exists, to exceed the value of c, because it conveys no information.
www.mathpages.com /home/kmath210/kmath210.htm   (1990 words)

  
 Wave velocity: Facts and details from Encyclopedia Topic   (Site not responding. Last check: 2007-10-21)
Phase, from the greek phasis, meaning appearance, has a number of related meanings in english....
The group velocity of a wave is the velocity with which the overall shape of the waves amplitude (known as the envelope of the wave) propagates through...
A transverse wave is a wave that oscillates perpendicular to the direction it advances....
www.absoluteastronomy.com /encyclopedia/w/wa/wave_velocity.htm   (634 words)

  
 Surface Waves
Then, the time derivative of the velocity potential is equal to the potential of the external forces, here gravitation, when evaluated at the free surface, where the pressure is constant regardless of displacement, and may be taken as zero.
The energy in the wave is moving at the speed of the group, not at the phase velocity of the waves.
If the phase velocity is plotted as a function of wavelength, a tangent from any point intercepts the velocity axis at the group velocity U, as shown on the left in the figure.
www.du.edu /~jcalvert/waves/surfwave.htm   (1857 words)

  
 Jascha Polet's TERRAscope paper   (Site not responding. Last check: 2007-10-21)
In essence, in this method a velocity model is perturbed in such a way that its dispersion curve is modified to the measured phase velocity values, according to the known partial derivatives.
The relatively high velocities at the surface are a result of the greater sensitivity of Love wave phase velocity for shallower layers whereas the low velocity zone at greater depths is caused by the slower Rayleigh wave velocity.
The resulting velocity models (SV velocity for Rayleigh, SH velocity for Love) are shown in Figure 6, the dispersion curves in Figure 8.
www.gps.caltech.edu /~polet/paper2.html   (2311 words)

  
 [No title]
In a negative phase velocity medium, the phase velocity is directed opposite to the direction of energy flow (and attenuation).
But double negativity is not a necessary condition for the phase velocity to be negative (in a passive material).
The term negative phase velocity (NPV) medium is unambiguous and is not in conflict with any physical scenario to which it is applicable.
www.esm.psu.edu /~axl4/lakhtakia/ALNPV.html   (1472 words)

  
 Differential phase velocity determining delay measurement apparatus and associated method - Patent 5698786   (Site not responding. Last check: 2007-10-21)
differential phase velocity output means for generating an output signal related to delay in said at least one ultrasonic delay sensor based upon a difference in phase velocity between the pulse repetition signal and the time base signal.
differential phase velocity output means for generating an output signal related to delay in the at least one ultrasonic delay device based upon a difference in phase velocity between the pulse repetition signal and the time base signal.
The reflection suppression means may be provided by random phase switching means, such as the illustrated pseudorandom sequence generator 25 cooperating with the pulse generator means 22, for randomly switching phases of the series of input pulses to the ultrasonic delay sensor 21 to thereby reduce undesired reflections.
www.freepatentsonline.com /5698786.html   (9591 words)

  
 Phase and Group Velocity   (Site not responding. Last check: 2007-10-21)
PURPOSE: To demonstrate the relationship between the phase velocity and the group velocity of a wavepacket.
The group velocity is seen to move rapidly across the picture, as shown in the photo at right.
The movement of the phase velocity (motion of each transparency) is much slower than the fast moving group velocity.
www.physics.brown.edu /physics/demopages/Demo/waves/demo/3b3320.htm   (272 words)

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