An Optimization Method for the Synthesis of Flat-Top Radiation Patterns in the Near- and Far-Field Regions

This paper presents an optimization method for the design of array antennas with flat-top radiation patterns in the far-field and near-field regions, in which the synthesis of flat-top radiation patterns is formulated as a quadratically constrained quadratic programing (QCQP) problem with equality constraints. It is shown that the notoriously difficult QCQP problem can be linearized and simplified for the synthesis of flat-top radiation patterns in the far-field region and can be extended to the near-field region by introducing a weighted diagonal matrix. To validate the optimization theory, a flat-top sector beam antenna for base station applications and an RFID bookshelf reader antenna are designed and fabricated. Simulation and measurement results show that the base station antenna operating at 5.4 GHz provides a flat-top radiation pattern with less than 1 dB fluctuation in the desired covering range of the main beam. The five-element RFID reader antenna working in the UHF band for library applications is demonstrated to generate uniform electric field intensity with less than 3 dB fluctuation across the whole bookshelf.