Strip Antenna Figure Errors due to Support Truss Member Length Imperfections

Abstract

The dependence of strip antenna steady state geometric errors on member length uncertainties in the supporting truss beam is studied with the Monte Carlo analysis of a representative truss design. The results, presented in a format streamlined for practical use, can guide the specification for hardware fabrication of required error tolerances (for structural properties as well as member lengths), or they can aid the prediction of antenna performance if component statistics are available. The standard rms error and locally defined errors are both considered. (The latter quantify surface and slope discontinuities between trusdantenna bays- discontinuities that may limit the effec-tiveness of some electronic error compensation schemes.) Second order global error compensation along the antenna length is also simulated. The judicious definition of normalized variables leads to a straightforward set of scaling laws that easily relate the results to various truss dimensions and member length error magnitudes for trusses up to 100 bays long. The data pools on which quantitative observations are based are each populated by 35,000 (thirty-five thousand) to 3,465,000 (nearly three and a half million) elements. NOM EN c L ATU RE number of bays in the entire truss and in a segment (subtruss) truss cross section edge (batten length) truss, bay, and subtruss lengths number of subtrusses generic error symbol and rms surface error RF wavelength, antenna gain scaling coefficients for global dimensions and member length errors probability density function maximum member length error magnitude vector of reference surface parameters a, vector and matrix quantities for rms surface error assessment elements of A and b, evaluated via integration over the antenna aperture additional parameter for rms surface error assessment bay sag, bay twist, and panel twist