Miniature Meander-Line Dipole Antenna Arrays, Designed via an Orthogonal-Array-Initialized Hybrid Particle-Swarm Optimizer

This paper introduces a powerful technique that utilizes a hybrid Particle-Swarm Optimization (PSO) method for the design optimization of aperiodic linear phased arrays of tightly packed miniature meander-line dipole elements. Miniaturization is achieved by first introducing a fixed grid of reduced length, and then employing a hybrid PSO to determine the optimum meander-wire shape on the grid and the optimal element spacing. The purpose was to achieve comparable performance in terms of voltage standing-wave ratio (VSWR) and sidelobe levels during scanning to conventional full-size periodic phased arrays of linear half-wave dipoles. This design technique is applicable in cases where the desire for aperture miniaturization takes precedence over the reduction in gain that comes as a consequence. As one of the design criteria, the same number of antenna elements was maintained and tightly packed into a smaller aperture area. This allowed the antenna elements to be driven by lower-power transmitting modules for a given effective radiated power (ERP), compared to a thinned array with the same aperture size. This method also provides flexibility in controlling the self impedance of individual elements and the mutual coupling among array elements. It is hence capable of evolving compact array configurations with meander-line dipole elements that have well-behaved driving-point impedances and low sidelobe levels over a prescribed scan range. In order to overcome the optimization difficulty of arrays with a large number of antenna elements, orthogonal design with quantization (OD/Q) was employed for this mixed-valued optimization problem to generate relatively fit particles at the initialization stage. Several design examples were considered with parallel or planar grids, and with identical or different element configurations. Included among these examples was a design with 32 identical elements that achieved a 42% array-length reduction and a 16% element-size reduction, while providing a relative sidelobe level less than -10 dB and a VSWR less than 2: 1 for each element over the scan range of +/- 30 degrees from broadside.