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In this article, a novel multibranch encoder-decoder-based artificial neural network (ANN) framework is proposed for pattern-reconfigurable nonuniformly spaced linear array synthesis. In the proposed framework, different encoder–decoder branches are devoted to synthesizing different radiation patterns to satisfy the desired radiation patterns. In each encoder–decoder branch, the encoder, and the decoder serve as the array synthesizer and analyzer, respectively. By minimizing a suitably-defined loss function with respect to multiple radiation patterns, element amplitudes, and positions, not only multiple mask-constrained radiation patterns can be successfully achieved, but also the common element amplitudes and positions with minimum inter-element spacing control can be obtained. Thus, different radiation patterns can be switched by phase-only control. In addition, by using different training samples, the proposed method can consider the ideal synthesis of the array factor, as well as the actual synthesis of antenna arrays to consider the mutual coupling effects in the synthesis process. Simulation results are provided to validate the capability, efficiency, and attractiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Previously, the alternating convex optimization (ACO) was used to reduce the number of elements in the single-pattern linear array. This work extends the ACO method to synthesize the unequally spaced sparse linear arrays with reconfigurable multiple patterns. In this extended ACO, the minimum interspacing constraint can be easily incorporated in the sparse array synthesis by performing a set of constrained alternating convex optimizations. Three examples for synthesizing sparse linear array with different multiple-pattern requirements are conducted to validate the effectiveness, robustness, and advantages of the proposed method. The synthesis results show that the proposed method can effectively reduce the number of elements in the reconfigurable multiple-pattern linear arrays with good control of the sidelobe levels and minimum interspacing. The comparisons with other methods are also given in the examples.

A design for single-fed circularly polarized (CP) antennas with broadband operation and high front-to-back ratio is first described. The antenna is mainly composed of a monopole slot, a dipole, and a metallic box. When the monopole slot is operated in its half-wavelength mode, the radiated fields of the slot and dipole have the same amplitudes and 90° phase differences; in addition, the two radiating elements are arranged in an orthogonal configuration. Consequently, a CP radiation is obtained. Then, the CP antenna is adopted as a radiating element of a 3-D array, and a feed network composed of power dividers is used to excite the array. Both the simulated and measured results prove that the CP array can give a nearly omnidirectional pattern, bidirectional patterns with 8 dBi directivity, and scanned beams with a directivity of 11 dBi. Moreover, the half-power beamwidth of the scanned beam can be changed among 48°, 124°, and 240°. The total size of the array is about $1.5\lambda _{0} \times 1.5\lambda _{0} \times 2.5\lambda _{0}$. Details of the designs for the CP element and array are presented. [ABSTRACT FROM AUTHOR]