Depolarization over a link due to rain: Measurements of the parameters

McCormick, G.; Hendry, A.W.; Allan, L.

doi:10.1029/rs011i008p00741

Cited by 10 publications

(1 citation statement)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several workers have carried out measurements in snow relevant to terrestrial paths [e.g., Hendry et al, 1976;Watson, 1976;Zufferey, 1976;Delogne and Sobieski, 1977;Watson et al, 1977;Dilworth andEvans, 1978, 1980]. The most important conclusion for systems designers is that snow would appear to be a less serious cause of cross polarization than rain for the small percentages of time of greatest interest.…”

Section: Snow Depolarizationmentioning

confidence: 99%

Cross polarization during precipitation on terrestrial links: A review

Olsen¹

1981

Radio Science

View full text Add to dashboard Cite

This paper reviews recent theoretical and experimental research on cross polarization that occurs during precipitation on terrestrial microwave links. Consideration is first given to the physical mechanisms, such as raindrop canting, that cause precipitation depolarization. Coherent rain depolarization models are then discussed and recent investigations of incoherent depolarization effects summarized. Particular attention is given to semi-empirical models since they can be used most readily for statistical predictions in design applications. 'Model oriented' cross polarization measurements aimed at characterizing the physical properties of the depolarizing medium for use in model development are also given particular attention. Effective parameters of the raindrop canting angle distribution derived from these measurements are tabulated. Finally, some mention is made of the relative importance of rain depolarization and attenuation in causing outages on digital radio systems. INTRODUCTIONMany terrestrial analog radio systems now employ orthogonal linear polarizations on adjacent channels in order to minimize frequency separation and therefore increase capacity. Furthermore, an increasing number of digital radio systems that use orthogonal polarizations in the same frequency band are coming into operation. In both systems an adequate cross-polarization isolation (XPI) between these orthogonally polarized channels must be maintained. A major limiting factor to the reliability of operation, however, is the deterioration in XPI and consequent cross-polarization interference caused by propagation effects along the path. Some of these effects are now reasonably well understood, and practical propagation models for use in statistical predictions are being developed. This paper reviews recent theoretical and experimental research on the cross polarization that occurs on terrestrial paths as a result of precipitation. A companion paper [Olsen, 198 la] reviews corresponding research on cross polarization during clear-air conditions. It has long been recognized from theory [Oguchi, 1960] and experiment [Okamura et al., 1961] that rain attenuation is polarization dependent. Interest in precipitation-induced cross polarization was stimulated in the late 1960's by the realization thatthis could impose a limitation to systems utilizing dual polarizations. Since that time there has been an increasing effort, both theoretically and experimentally, to characterize the problem.Much of the emphasis in this review is on theoretical and experimental work that has contributed to a better understanding of the precipitation depolarization mechanisms and the development of propagation models. Particular emphasis is placed on semi-empirical models that can be readily used for statistical predictions in design applications. Although some consideration is given to the effects of cross polarization on particular types of radio systems, the review is less complete on this aspect.Since an extensive overall review of the most significant phenomen...

show abstract

Section: Snow Depolarizationmentioning

confidence: 99%

Cross polarization during precipitation on terrestrial links: A review

Olsen¹

1981

Radio Science

View full text Add to dashboard Cite

show abstract

Affaiblissements différentiels a 13 GHz sur 53 km comparaison a des mesures simultanées a 20,5 GHz

Fimbel¹,

Juy²

1977

Ann. Télécommunic.

View full text Add to dashboard Cite

Techniques for the determination of the polarization properties of precipitation

McCormick¹,

Hendry²

1979

Radio Science

Self Cite

View full text Add to dashboard Cite

Experimental techniques related to the use of a polarization diversity radar and a short transmission link are discussed. The equipment, operated at 16.5 GHz, located at Ottawa, Ontario, is for the observation of rain and other hydrometeors. Components related to the radar's polarization capability include the antenna and polarizer, a dual-channel receiving system with power and correlation detection, and a 12-gate video processor. There is a discussion of calibrations, errors, and extraneous effects. INTRODUCTIONThe principles for determining precipitation parameters by means of polarization techniques over a transmission link or by using a polarization diversity radar have been discussed in previous papers [McCormick and Hendry, 1973, 1975]. Many of the techniques are standard and require no further comment. We deal here with equipment and methods including calibrations which are peculiar to the use of orthogonal polarizations and the handling of two-channel stochastic signals. It is common to all of our determinations that RF signals, R l and R 2, from two channels are available and that processing is done on the products R l R•, R2R • , and RiR •. They lead to the mean powers in the two channels and the complex correlation between the channels.The properties of precipitation as a scattering assembly or as a transmission medium depend on the distribution of particle orientations. Hence a formulation based on circular polarization has a particular appropriateness on account of the direct correspondence between the mean orientation angle and the relative phase of received circular polarization components. Circular polarization has, in fact, been used in most of our experimental program; but other polarizations can be advantageous. Thus linear polarization is optimum for suppressing cross polarization in a communications system, and at higher microwave frequencies, radar clutter due to precipitation is minimized by the use of elliptical rather than circular polarization [Hendry and Mc-Cormick, 1974a]. •'herefore the equipment to be described, the calibrations, and other discussion imply the use of any pair of orthogonal polarizations. Antenna errors are of prime importance in the measurement of polarization parameters. Formulas are derived for the circular polarization case, and measurement methods are discussed. A more extensive theoretical treatment is given separately [McCormick, 1979]. This paper is based on experience with the 16.5-GHz radar situated at the National Research Council, Ottawa, Ontario, where it is used for year-round observation. It has been in full operation since 1971 with limited operation dating from 1968. Observations on the link began in 1972. Some results of these observations, in addition to those referred to above, have appeared in previous publications [McCormick et al., 1972, 1976; Hendry and McCormick, 1974b, 1976; McCormick and Hendry, 1974, 1976, 1977; Hendry et al., 1976a, b]. 2. DISCUSSION OF EQUIPMENT The essential features of the radar apparatus are shown in Figure 1. Antenna...

show abstract

Depolarization over a link due to rain: Measurements of the parameters

Abstract: Observations of depolarization caused by rain at 16.5 GHz taken over a short link during parts of four seasons, 1972–1975, at Ottawa, Canada, are presented. They include determinations of the mean canting angle and the real and imaginary parts of the differential propagation constant.

Cited by 10 publications

References 23 publications

Cross polarization during precipitation on terrestrial links: A review

Cross polarization during precipitation on terrestrial links: A review

Affaiblissements différentiels a 13 GHz sur 53 km comparaison a des mesures simultanées a 20,5 GHz

Techniques for the determination of the polarization properties of precipitation

Contact Info

Product

Resources

About