Accession Number : AD0804197

Title :   ECM AEROSPACE ANTENNA STUDIES. VOLUME 2.

Descriptive Note : Final technical rept. 1 Aug 65-31 Aug 66,

Corporate Author : SPERRY GYROSCOPE CO GREAT NECK NY RADIATION DIV

Personal Author(s) : Bates, Richard H. ; Freyheit, Paul J. ; Kristal, Richard ; Lustig, Carl D. ; Meltz, Gerald

Report Date : SEP 1966

Pagination or Media Count : 84

Abstract : Measurements have been made of the effects of a conical plasma about an azimuthally slotted cone excited in the first higher order mode. The antenna was tested in the center of its 100-Mc bandwidth at about 750 Mc. Antenna pattern measurements show distortion of the initially omnipattern (+ or - 3 db) into primarily a forward and rear lobed pattern. Implications for actual re-entry conditions are discussed as are recommendations for future work in this area. An expression is derived for the admittance of a circumferential slot in an infinite cylinder covered by a set of coaxial dielectric of plasma layers. The slot is fed by the dominant TEM mode in a narrowly-spaced, parallel-plate, radial waveguide. Numerical computations are presented for a multiple layer model of a lossy inhomogeneous plasma and for a dielectric layer which supports surface waves. These computations are compared with previously obtained admittance measurements of a gap-excited cylinder surrounded by an annular pulsed discharge. The measurements are in fair agreement with calculated values based on a three-layer model of the plasma and the discharge tube. Calculations were made on the pattern distortion of plasma-covered slotted wedges appropriately phased to have forward coverage. The numerical results for the two-dimensional wedge are illustrative of the pattern distortion in the forward hemisphere of a similarly excited cone. Both infinite and finite (two-dimensional) geometries have been considered. The finite wedge is treated by an integral equation technique and the corresponding infinite geometry by a modal expansion method. In the latter analysis, the plasma layer is approximated by a linearly varying impedance sheet.

Descriptors :   *ELECTRONIC COUNTERMEASURES), *PLASMA SHEATHS), (*ANTENNAS, (*SLOT ANTENNAS, ATMOSPHERE ENTRY, DISTORTION, ANTENNA RADIATION PATTERNS, ATTENUATION, ADMITTANCE, DIELECTRICS, WAVEGUIDES, SIMULATION.

Subject Categories : Electrical and Electronic Equipment
      Countermeasures

Distribution Statement : APPROVED FOR PUBLIC RELEASE