|2.1 Radar Detection Theory
By: Dr. Harry Urkowitz
Lockheed Martin, MS2
and: Dr. Thomas F Halpin
Lockheed Martin MS2
At its base, radar detection theory is an application of a statistical test of two hypotheses: 1) Noise (and clutter) present; 2) Noise plus signal present. The Neyman Pearson test is appropriate here. In such a test, there are two types of error may occur: 1) Noise alone may be present, but signal may be declared (false alarm); 2) Signal may be present, but not detected (false dismissal). The probability of false alarm is held fixed at an acceptable values and the probability of correct detection is maximized. The appropriate quantity to be obtained is the likelihood ratio. The radar receiver obtains an equivalent to the likelihood ratio, by means of matched filtering, followed by envelope or squared envelope extraction. The resulting sequence of envelopes may undergo further processing.
The radar detection framework is a combination of so-called coherent processing and pulse to pulse noncoherent processing. Coherent processing involves exploiting the phase characteristics of as radar echo by means of matched filtering that exploits not only the phase characteristic of each radar pulse by means of “matched filtering’, but also the pulse to pulse phase variation arising from Doppler shift caused by target closing speed. The pulse to pulse coherent processing, if multiple pulses are received, involves a bank of Doppler filters followed by envelope detectors, and, often, further noncoherent sample to sample (or pulse to pulse) integration, i.e., addition of envelopes or squared envelopes. The results of such processing depend the pulse to pulse target fluctuation. The detection characteristics of various pulse to pulse fluctuation of models, including the Swerling models, will be explained. Various forms of constant false alarm rate (CFAR) will be explained, including so-called distribution free CFAR.
|2.2 A Polarimetric Doppler Weather Radar
By: Dr. Richard J. Doviak
National Severe Storms Laboratory
This tutorial reviews the principles of Polarimetric Doppler weather
radar and its application to the observation of weather and the
quantitative radar measurement of meteorological parameters. It
highlights the engineering and scientific research to remotely probe
and show the structure of many atmospheric phenomena (tornadoes,
microbursts, solitary waves, etc.) not available by any other
practical means. The quantitative measurement of rainfall provided
by polarimetry will also be discussed. Doppler techniques have found
application in the network of weather radars (NEXRAD/WSR-88D)
presently operated by the USA National Weather Service (NWS), as well
as in other nations, and now the NWS plans to upgrade its operational
radars to have polarimetric capability.
The use of phase coded signals and staggered PRF techniques to resolve
range ambiguities will also be discussed. Radar observations will be
related to atmospheric phenomena observed by eye, and radar data
fields are correlated with photographs and/or satellite images of the
The attendees will benefit by gaining an understanding of the theory,
design, operation, and applications of Polarimetric Doppler weather
radar. The focus will be on meteorological phenomena, their radar
signatures, and quantitative measurement of weather parameters.
This Tutorial has a recommended book:
“Doppler Radar and Weather Observations”, Richard J. Doviak and Dusan
S. Zrnic, Academic Press, 2nd edition, 1993.
You may order this book at a 30% discount by contacting Heather Hall
at Elsevier Science & Technology Books, 800-894-3434, or 619-699-6760
, extension 6760, or email email@example.com. Please order the book
no later than April 12, 2004 in order to receive it before leaving
for the conference (before April 23rd).