CHARACTERISTIC IMPEDANCE OF A WIDE SLOTLINE ON LOW-PERMITTIVITY SUBSTRATES

Computed results on the characteristics impedance of wide slots etched on an electrically thin substrate of low dielectric constant epsilon sub r are presented. These results are used to help provide design data for slotlines. Curves are presented for epsilon sub r = 2.22, 3.0, 3.8, and 9.8. Comparison is shown for the characteristic impedance between the present calculations and those available in the literature for high-epsilon sub r substrates. Empirical formulas, based on least square curve fitting, are presented for the normalized slot wavelength lambda prime/lambda sub 0 and the characteristic impedance Z sub 0 over the range: 0.0015 is equal to or less than W/lambda sub 0 equal to or less than 1.0, 0.006 is equal to or less than d/lambda sub 0 equal to or less than 0.06, 2.22 is equal to or less than epsilon sub 0 equal to or less than 9.8

An efficient MoM formulation for finite-by-infinite arrays of two-dimensional antennas arranged in a three-dimensional structure

In strongly coupled antenna arrays, the behavior of the elements near the edge can exhibit very large deviations with respect to the infinite periodic array solution. Insight into these truncation effects can be obtained by simulating finite-by-infinite arrays. This paper describes an efficient method-of-moments (MoM) scheme for simulating such arrays. This scheme is capable of handling arrays of two-dimensional metallic antennas placed perpendicularly to the array plane, in lossless media. This formulation relies on the free-space Green's function related to arrays infinite in one direction only, with linear phase excitation. After extraction of its singular part,, this function is tabulated. Then, the elements of the MoM impedance matrix are computed in the space domain, with the help of a limited number of integration points. The computation time needed for establishing the MoM system of equations and for solving it is comparable to the time needed in the linear array case. An extension of this formulation is also developed to study infinite-by-infinite arrays and semi-infinite arrays. The latter solutions also provide standard current distributions, which are used to obtain a fast approximate solution of the MoM system of equations. Simulation results are shown for broadband arrays, made of tapered slot antennas consisting of metallic plates

An efficient computation scheme for the free space Green's function of a two-dimensional semiinfinite phased array

A simple scheme is developed to compute the Green's function of a periodic semiinfinite array in free space. It is based on the spectral representation of the fields radiated by an infinite linear array of dipoles. Results related to successive linear arrays are added in the space domain. This summation can be accelerated tremendously by using an elementary extrapolation technique. The resulting formulation converges everywhere in the plane containing the array, and the number of terms required to achieve a given precision increases slowly away from this plane