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Doppler Radar Tracking Using Moments
Mohammad Hossein Gholizadeh and Hamidreza Amindavar
Amirkabir University of Technology, Tehran
Iran
1. Introduction
A Doppler radar is a specialized radar that makes use of the Doppler effect to estimate targets
velocity. It does this by beaming a microwave signal towards a desired target and listening for
its reflection, then analyzing how the frequency of the returned signal has been altered by the
object's motion. This variation gives direct and highly accurate measurements of the radial
component of a target's velocity relative to the radar. Doppler radars are used in aviation,
sounding satellites, meteorology, police speed guns, radiology, and bistatic radar (surface to
air missile).
Partly because of its common use by television meteorologists in on-air weather reporting, the
specific term "Doppler Radar" has erroneously become popularly synonymous with the type
of radar used in meteorology.
The Doppler effect is the difference between the observed frequency and the emitted
frequency of a wave for an observer moving relative to the source of the waves. It is commonly
heard when a vehicle sounding a siren approaches, passes and recedes from an observer. The
received frequency is higher (compared to the emitted frequency) during the approach, it
is identical at the instant of passing by, and it is lower during the recession. This variation
of frequency also depends on the direction the wave source is moving with respect to the
observer; it is maximum when the source is moving directly toward or away from the observer
and diminishes with increasing angle between the direction of motion and the direction of
the waves, until when the source is moving at right angles to the observer, there is no shift.
Since with electromagnetic radiation like microwaves frequency is inversely proportional to
wavelength, the wavelength of the waves is also affected. Thus, the relative difference in
velocity between a source and an observer is what gives rise to the Doppler effect.
Now, suppose that we have received an unknown waveform from the target. This waveform
is a result of reflection from a fluctuating target in presence of clutter and noise. The received
signal is often modeled as delayed and Doppler-shifted version of the transmitted signal. So
not only the Doppler estimation, but the joint estimation of the time delay and Doppler shift
provides information about the position and velocity of the target. So we should focus on
the joint estimation of both parameters. There are many works for estimating the joint time
delay and Doppler shift, with advantages and disadvantages apiece. Among these methods,
Wigner Ville (WV) method has proven to be a valuable tool in estimating the time delay and
Doppler shift. WV method is a time-frequency processing. It possesses a high resolution
in the time-frequency plane and satisfies a large number of desirable theoretical properties
[Chassande-Mottin & Pai, 2005].
In fact, these properties are the fundamental motivation
