# Doppler shift

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## Doppler shift

See Doppler effect.

## 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.

## Doppler shift

Doppler effect in moving receiver.
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.
References in periodicals archive ?
Doppler shift, used as an index of sternal skin stress, was recorded continuously as the subject performed three trials of each lift.
A true self-test must verify both the transmitter's operation and the ability of the sensor to recognize and respond to a Doppler shift.
The second effect is the Doppler shift factors 1/(1 [+ or -] v/c), giving the detected frequencies
The researcher said that they used the Doppler shift for light to tell whether the gas in these quasars is moving away from Earth or toward these distant black holes, which have a mass from millions to billions of times that of the Sun.
Doppler Weather Radar measures not only the location and intensity of precipitation but also the wind speed and direction around radar sensors by analyzing the Doppler shift of radio waves returned from precipitation particles in the wind.
He outlines the basics of Fourier analysis, radar fundamentals, and synthetic aperture radar; basic ISAR concepts; procedures for conventional ISAR imaging; imaging techniques and fine-tuning procedures such as zero-padding and windowing that enhance image quality; ISAR waveforms and receivers, quadrature detection, Doppler shift phenomena, and range-Doppler ISAR imaging algorithms; scattering center representation of ISAR, including algorithms to reconstruct high-fidelity images and field data from the scattering centers; applications of ISAR to solve engineering problems such as antenna scattering and coupling; and motion compensation techniques, including the cross-correlation method, minimum entropy method, and joint-time, frequency-based motion compensation.
The major sources of uncertainty in frequency biases in thermal-beam, cesium frequency standards are second-order Zeeman shift, second-order Doppler shift, end-to-end cavity phase shift and possibly cavity pulling, fluorescence light shift, and line-overlap shift.
Implications will be presented with emphasis on time dilation and the Doppler shift as practical considerations.
The discovery of the quantum detection of gravitational waves, showing correlations between well separated locations, that permitted the absolute determination of the 3-space velocity of some 500 km/s, in agreement with the speed and direction from a number of previous analyses, including in particular the NASA spacecraft Earth-flyby Doppler shift effect.
When a distress beacon is detected, its location can be computed based on the Doppler shift of the beacon signal as the satellite passes overhead.
As a result of the Doppler shift the spaceship would be bombarded by intense X-rays, exerting a pressure strong enough to slow it down.
HARPS finds distant worlds by focusing on wobbly stars pulled in different directions by orbiting bodies, causing a Doppler shift in the color of the starlight.

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