Fung-I Tseng

Optimum scannable planar arrays with an invariant sidelobe level

This paper presents two alternative methods for determining the current distribution in the elements of a scanning rectangular array which is optimum in the sense that its radiation pattern has a constant sidelobe level and a narrowest beamwidth in all directions. Exact formulas for both even and odd numbers of elements are given. The dependence of the main-lobe beamwidth on the total number of elements, the element spacing, the sidelobe level, and the scan angle is studied in detail. The minimum required number of controlled elements in a square array with electronic beam scanning over a specified sector for a guaranteed upper limit on beamwidth without grating lobes is determined. Numerical results are included, which illustrate many interesting features of the new design technique.

Optimum spatial processing in a noisy environment for arbitrary antenna arrays subject to random errors

A procedure is presented for the maximization of the expected signal-to-noise ratio improvement factor for arbitrary antenna arrays whose excitation amplitudes and phases, as well as element positions, are subject to random errors. In its general form, the formulation imposes no restrictions on either the probability distribution or the variance of the random errors. Correlations are allowed to exist between the random variations in array parameters, and the effect of system internal noise is considered. Computed results for a linear endfire array in a typical noise environment are given, illustrating the dependence of the signal-to-noise ratio improvement factor on the system internal noise; the system bandwidth; the amplitude, phase, and position errors; and the error correlation intervals. Typical expected power pattern functions are also plotted.

Pattern synthesis of circular arrays with many directive elements

A method for synthesizing the radiation pattern of a circular array with directive elements is presented. The required excitations are determined from an explicit formula which requires no reduction or inversion of matrices. It is particularly useful for designing large circular arrays with many elements.

Pattern synthesis of circular arrays in a moving medium

Based on a modified expression for the radiation field of a circular array in a moving medium, pattern synthesis is performed for medium motion both in the direction of and parallel to the main beam. It is shown that medium motion, even considering only first-order effects, changes the synthesized patterns significantly. The required excitation amplitudes and phases for the proper synthesis of a 21-element circular array to yield a cosine-square pattern in a moving medium are given.