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International Journal of Infrared and Millimeter Waves

, Volume 16, Issue 9, pp 1593–1672 | Cite as

Microwave radiometry and applications

  • Jiří Polívka
Article

Summary

The radiometry in general is a method of detecting the radiation of matter. All material bodies and substances radiate energy in the form of electromagnetic waves according to Planck s Law. The frequency spectrum of such thermal radiation is determined, beyond the properties of a blackbody, by the emissivity of surfaces and by the temperature of a particular body. Also, its reflectivity and dispersion take part.

Investigating the intensity of radiation and its spectral distribution, one may determine the temperature and characterize the radiating body as well as the ambient medium, all independently of distance.

With the above possibilities, the radiometry represents a base of scientific method called remote sensing. Utilizing various models, temperature of distant bodies and images of observed scenes can be determined from the spatial distribution of radiation.

In this method, two parameters are of paramount importance:
  • the temperature resolution, which flows out from the detected energy, and

  • the spatial resolution (or, angular resolution), which depends upon antenna size with respect to wavelength.

An instrument usable to conduct radiometric observations thus consists of two basic elements: a detector or radiometer, which determines the temperature resolution, and an antenna which determines the angular or spatial resolution.

For example, a photographic camera consists of an objective lens (antenna) and of a sensitive element (a film or a CCD).

In remote sensing, different lenses and reflectors and different sensors are employed, both adjusted to a particular spectrum region in which certain important features of observed bodies and scenes are present: frequently, UV and IR bands are used.

The microwave radiometry utilizes various types of antennas and detectors and provides some advantages in observing various scenes: the temperature resolution is recently being given in milikelvins, while the range extends from zero to millions of Kelvins. Microwaves also offer a chance to penetrate surfaces of non-metallic objects down to some wavelengths, by which it is advantageous in certain applications over e.g. IR waves.

An extreme example of capabilities of the microwave radiometry is found in radio astronomy, where it determines temperatures and spectral features of bodies so remote that their distance from us is measured in millions of light years. Other apparatus serve in remote observation of Earth s resources: soils, water regions and atmosphere. Similar systems also have found applications in medical studies of human body, e.g. in cancer and inflammation diagnostics.

The paper presents a background of the radiometric method, comments to equipment design and outlines some of the applications.

Keywords

Emissivity Thermal Radiation Temperature Resolution Angular Resolution Spectral Distribution 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. (1).
    Evans, G., McLeish, C.W.: RF Radiometer Handbook, Artech House, 1977Google Scholar
  2. (2).
    Kraus, J.D.: Radio Astronomy, McGraw-Hill, New York, 1967Google Scholar
  3. (3).
    Loele, H., Polivka, J., Český, T.: Mikrowellen-Radiometer und Ihre Anwendungen, VEB Verlag Technik, Berlin (unpublished monograph)Google Scholar
  4. (4).
    Carr, K.L.: Radiometric Methods in Detection of Cancer, IEEE Trans. MTT-37, 12, 1989,p. 1862–1868Google Scholar
  5. (5).
    Schanda, E.: Application of Microwaves to Remote Sensing, Mikrowellen-Magazin, 14, 2, 1988, p. 124–132Google Scholar
  6. (6).
    Schmugge, T. et al.: Passive Microwave Soil-Moisture Research, IEEE Trans. GE-24, 1, 1986, p. 12–22Google Scholar
  7. (7).
    Askne, J.I., Westwater, E.R.: Review of Ground-Based Remote Sensing of Temperature and Moisture by Microwave Radiometers, IEEE Trans. GE-24, 3, 1986, p. 340–352Google Scholar
  8. (8).
    Brunfeldt, D.R., Ulaby, F.T.: Microwave Emission from Row Crops, IEEE Trans. GE-24, 3, 1986, p. 353–359Google Scholar
  9. (9).
    Newton, R.W., Rouse, J.: Microwave Radiometer Measurements of Moisture Content, IEEE Trans. AP-28,p. 680–686Google Scholar
  10. (10).
    Newton, R.W. et al.: Soil Moisture Information and Microwave Thermal Emission, IEEE Trans. GE-20, 1982, p.275–281Google Scholar
  11. (11).
    Njoku, E.G., Oneill, P.E.: IEEE Trans. GE-20, 4, 1982, p. 468–475Google Scholar
  12. (12).
    Eom, H.J., Fung, A.K.: A Scatter Model for Vegetation Up to Ku Band, Remote Sensing of Environment, 15, 1984, p. 185–200CrossRefGoogle Scholar
  13. (13).
    Ulaby, F.T. et al.: Relating the Microwave Backscattering to Leaf Area Index, Rem. Sensing of Environ. 14, 1984, p. 113–133CrossRefGoogle Scholar
  14. (14).
    Pampaloni, P., Paloscia, S.: Microwave Emission and Plant Water Content, IEEE Trans. GE-24, 1986, p. 900–905Google Scholar
  15. (15).
    Hüppi, R., Schanda, E.: L to X Band Scatter and Emission Measurements of Vegetation, Proc. Int. Geoscience and Remote Sensing Symposium, Zürich, ESA-SP-254, 1986,p.1113Google Scholar
  16. (16).
    Melnik, J.A.: Remote Sensing of Earth (in Russian), Nauka, Moscow 1980Google Scholar
  17. (17).
    Polívka, J.: Prospects of Microwave Radiometry (in Czech), Slaboproudý Obzor, 43, 11, 1982, p. 532–536Google Scholar
  18. (18).
    Polivka, J.: Radiometric Measurement of Atmospheric Attenuation at 12 GHz,(in Czech), Slaboproudý Obzor, 48, 7, 1987, p. 327–332Google Scholar
  19. (19).
    —"—: A Variable-Pulse Width Radiometer, Acta Polytechnics, III, 1974, 2, p.61–81Google Scholar
  20. (20).
    —"—: Microwave Radiometry, (in Spanish), invited lecture, CICESE Research Center, Ensenada, B.C., Mexico, 5.Dec. 1989Google Scholar
  21. (21).
    -"-: Radiometry Equipment for Clinical Use, VYFO-85 National Conference on Thermal Effects of Microwaves, Lipt.Mikuláš, Slovakia, May 1985Google Scholar
  22. (22).
    Polívka, J.: Active Microwave Radiometry, ELECTRO 89, Technology Institute, Chihuahua, Mexico, 25 Oct. 1989Google Scholar
  23. (23).
    —"—: Active Microwave Radiometry and Its Applications, Internat.Journal of IR and MM Waves, 16, No.3, 1995, p.483CrossRefGoogle Scholar
  24. (24).
    -"-: Determining Atmospheric Attenuation in 12 GHz Band (in Spanish), 1st Int'l Symposium on Metrology, Ixtapa, Mexico, May 12–16, 1990Google Scholar
  25. (25).
    —"—: Experimental “Active” Radiometry, Invited Lecture, Comm.Res.Laboratory, Tokyo, Japan, July 14th, 1992Google Scholar
  26. (26).
    Karhu, S.I. et al.: Atmospheric Attenuation Statistics by a 12 GHz Radiometer in Finland, 21st Eur.Microwave Conf., 9–12 Sep.,1991, Stuttgart, Germany, p. 1229–1234Google Scholar
  27. (27).
    Polívka, J.: Related Czechoslovak Patents: AO 260205, 1988, A Non-Contact System for Measuring Attenuation and Reflectivity of Objects and Media AO 223788, 1983 A circuit for fixing a reference level, with memory AO 237079, 1985 A Microwave Matrix Applicator for Mapping Human Body Temperature by Microwave Radiometry AO 168309, 1977 A Method of Radiation Measurement by a RadiometerGoogle Scholar

Copyright information

© Plenum Publishing Corporation 1995

Authors and Affiliations

  • Jiří Polívka
    • 1
  1. 1.Spacek Labs, IncSanta Barbara

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