Difference between revisions of "Cancellation ratio"
Revision as of 14:47, 20 February 2012
- Broadly, a power ratio used in certain applications of radar that describes the degree to which the backscattered power from unwanted targets (clutter) is suppressed or canceled in one mode of measurement relative to another mode of measurement.
It is defined to yield a value greater than unity or, equivalently, a positive decibel quantity. For example, in some applications it is defined as the ratio of signal intensity backscattered from rain observed with linear polarization to the signal intensity backscattered from rain observed with circular polarization. Values of 25–30 dB are typical of light rain observed at wavelengths of 3– 10 cm.
- For a dual-channel radar, the ratio of the power received in the orthogonal channel to that received in the transmission channel for transmitted circular polarization. The stronger component of the target signal from precipitation is the component in the orthogonal channel because the sense of the circular polarization is reversed as its direction of propagation changes when it is scattered back toward the radar.
- A ratio that describes the degree to which radar clutter is suppressed by a clutter filter. This usage applies particularly to moving-target indication (MTI) radars. Shrader and Gregers-Hansen recommend that the term "improvement factor" be used in place of "cancellation ratio" because the latter term has been used inconsistently.
Compare circular depolarization ratio.
Shrader, W. W., and V. Gregers-Hansen 1990. Radar Handbook. 2d ed., M. I. Skolnik, ed., McGraw-Hill, . MTI Radar, chapter 15, . 15.1–15.72.
Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact firstname.lastname@example.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.