Radiation distortions in fast frequency-scanned antenna arrays

Abstract

COYhWNICATIONS 537the loop provides an accurate description of the actual field only when lkbl is very small. Note that the electric field is maintained by both the real and imaginary components of the current. The imaginary current can be the largest component on an electrically small loop, and, therefore, the dominant factor determining the behavior of the electric field. N. CONCLUSIONThe approximation of the current on the circular loop by a uniform function (I,) or the first two terms of a Fourier series ( I , f 21, cos 4) is adequate for calculating the input conductance only when the loop is immersed in a medium with very low dissipation (alp A 0). For higher dissipation, the conductance calculated using either of the approximate currents is in poor agreement with that determined from the twenty-term Fourier series analysis.A simple expression for the input admittance of the loop was obtained by examining the Fourier series coefficients. This formula is accurate for loops with pb I 0.2 and media with a/b in the range 0 I cr/b I 1.0 and is much simpler to use than the full Fourier series computation for the circular loop.The nonuniform current on the electrically small loop can maintain a significant far-zone electric field. For loops with lkbi 2 0.05 and 0 I a:'p I 1.0 the maximum field maintained by the nonuniform current is at least 10 percent of the maximum field maintained by the total current.The electrically small bare loop antenna is an infinite homogeneous medium has been discussed here. The results obtained do not apply to loops in an insulating dielectric cavity, this problem is discussed in detail in the literature [7], [8]. loop antenna in a dissipative medium," Radio Science, vol. 8, pp. 71 1-725, Julv 197?.