# Doppler shift

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## Doppler shift

See Doppler effect.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

## Doppler shift

[′däp·lər ‚shift]
(physics)
The amount of the change in the observed frequency of a wave due to Doppler effect, usually expressed in hertz. Also known as Doppler frequency.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## Doppler shift

In airborne Doppler radar, a transmitter which, by means of a directional antenna, radiates energy toward the ground. This results in a situation in which both the transmitter and the receiver are moving relative to the ground; consequently the original frequency is changed twice. The difference between transmitted and received frequencies is known as the Doppler shift and is very nearly proportional to the relative motion between the aircraft and the ground along the direction of the radar beam. A moving target will cause the frequency of the echo signal to increase if it is approaching the radar or decrease if it is receding from the radar. Since the Doppler frequency shift is proportional to radial velocity, a radar system that measures such a shift in frequency can also provide the radial velocity of a target. The Doppler frequency shift also is used to separate moving targets from stationary ones even when the undesired clutter power might be much greater than the power of echo from the targets. Also called the Doppler effect.

## Doppler effect

The change in electromagnetic frequency that occurs when the source of the radiation and its observer move toward or away from each other. The faster they come together, the higher the frequency. The faster they move away, the lower the frequency. Discovered by Austrian physicist Christian Doppler (1803-1853), this condition has a great effect on low-earth orbit (LEO) satellites as they weave towards and away from the earth. See Doppler radar.
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References in periodicals archive ?
His high-resolution spectra of 51 Pegasi suggested that the shapes of the star's spectral lines are what change with a 4.2-day period, not their overall Doppler shifts (S&T: May 1997, page 24).This would imply that the photosphere of the star is undergoing a complex, nonradial oscillation of a sort never seen in the Sun nor anticipated theoretically in stars.
And the third influence of Doppler Effect is Doppler Shift which for v = 5 km/h is about -4,261 Hz to 4,261 Hz and for v = 10 km/h is about -8,521 Hz to 8,521 Hz, where the sender frequency signal wave is distorted.
The statistical results based on short-term Doppler shifts are summarized in Table 4.
Electron density profile, virtual heights, polarization, and Doppler shift can be obtained according to the ionogram of 1-30 MHz scanning-frequency results.
The set of the missed dominant paths can be covered through the geometry factor in adjacent WSS time windows, that is, involving the geometry factor in (5) and (6) to calculate the delay and Doppler shifts and then deriving the power by the power model presented in the next section.
In the satellite to ground uplink system, for the Doppler shift signal exists, the uplink signals received at the satellite deviates from its actual frequency which the user terminal transmits.
1 shows the direction of the 3-space flow as determined from NASA satellite Earth-flyby Doppler shifts [6], revealing that the flow direction is close to being South to North, which is relevant to the ESR Darmstadt experiment in which the [Li.sup.+] ions travel also from South to North.
Lu et al (2010) proposed an algorithm known as D-Sync, leverages the Doppler shift in underwater environment to do time synchronization.
To investigate the effect of channel parameter on system performance, in Figure 9, the system performances are investigated with various maximum Doppler shifts at relay branch (source-relay-destination link).
To examine the potential contributions of physical characteristics to Doppler shift, correlations between each of the characteristics and the Doppler shifts recorded during lifting and during transfers were computed (see Table 2).
Over 40 years ago, experiment results showed a significant difference between the co-polarized Doppler shifts at moderate to high incidence angles, with the Doppler shifts of horizontally polarized (HH-polarization) signals being larger than the results corresponding to vertically polarized (VV-polarization) signals [18,19].

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