No abstract

No abstract

Blacksmith and Mack: RCS of Ducks and Chickens 1125 different radar signature effects because of attenuation of the waves propagating within the material. REFERENCES [l] J. R. Mentyer, Scullwing and Difroction of Radio W'oocs. New York: Pergamon. [2] J. E.' Keys and R. I. Primich. "The radar cross section of right circular metal [3] L. Peters, Jr.. End-fire echo area of long, thin bodies," I R E Trans. on Antennas Abstract-The experimental determination of the RCS of some typical birds is described. The results, which are summarized, can have significant implications in the operation of both ground based and aircraft radars. Everybody who tries to determine radar cross sections (RCS's)is m n e r or later confronted with a target that seems to defy all of the theoretical and experimental techniques discussed in other papers n this issue. Birds fall into this category. Although radars have frequently been used to track groups of birds1,* and study their migratory patterns, little information is available concerning the RCS of a single bird. The following describes an attempt at making measurements of this kind. Two ducks and a chicken were chosen as fairly docile examples of small-to-medium-sized birds. At the beginning of the measurements the ducks weighed about 23 and 4 : pounds and the chicken weighed about 1) pounds. An estimate of the duck sizes may be obtained from Fig. 1; the sphere was six inches in diameter and was used as a standard for all of the measurements.The most difficult problem was keeping the birds in the desired attitude long enough for a measurement. Initially, it was planned to record complete scattering patterns by simply placing a duck on a "polyfoam" mount and rotating it very slowly; however, the ducks repeatedly flew off. Kext a cylindrical polyfoam cage was attached to the turntable and the duck placed inside. This, too, was ineffectual, because the duck went into random motion within the cage as soon as the mount was turned. Finally, it was decided to confine the measurements to standing and squatting positions with the ducks' breasts directly toward, or away from, the transmitting antenna. R'ith some training and patience, the ducks could be persuaded to remain still for a short time in these positions and could be made to change from a standing to a squatting position with a light touch on the head.Typical results (for the larger duck standing with its breast towards the transmitter) are shown in Fig. 2. The polarization was vertical and the frequency about 400 MHz. LVith this polarization, the measured values were particularly sensitive to the exact position of the duck's head and neck so that repeated measurements showed considerable variation. For that reason, the results plotted in decibels referred to one square meter vs. the percentage of measurements for which the cross sections were below the indicated value. For example, The authors are with the OiXce of Aerospace Research, Air Force Cambridge Manuscript received May 12, 1965.

No abstract

No abstract