A novel CPW-fed broadband circularly polarised square slot antenna is proposed and fabricated. The proposed antenna is fed by a CPW with a widened L-type strip along the diagonal line of the square slot. Measured results show that the 3 dB axial-ratio bandwidth of the proposed antenna can reach 17%. The proposed antenna has simple coplanar geometry which can be easily fabricated on inexpensive substrate.

A folded slot with open end is introduced to achieve a dual-band coplanar waveguide (CPW)-fed monopole antenna for radio frequency identification (RFID) applications. The designed antenna, which, including the substrate, is only 32 mm in height and 20 mm in width, can operate simultaneously at the 2.45 and 5.8 GHz bands with -1.8 and 2.3 dBi gains, respectively. Its properties make the antenna suitable for RFID tags.

A novel small CPW-fed T-shaped antenna for MIMO application is presented. The size of the antenna is only 35% of that of conventional CPW-fed T-shaped antenna, which has satisfied return loss bandwidth and omnidirectional radiation characteristics. A multifeed 8-element planar array is fabricated and measured. It shows that the features of small size, uniplanar structure, good radiation characteristics and small mutual coupling are promising for MIMO applications in compact portable devices.

In this paper, a hybrid genetic algorithm for solving constrained optimization problems is addressed. First, a real-coded genetic algorithm is presented. The simplified quadratic interpolation method is then integrated into the genetic algorithm to improve its local search ability and the accuracy of the minimum function value. Simulation results on 13 benchmark problems show that the proposed hybrid algorithm is able to avoid the premature convergence and find much better solutions with high speed compared to other existing algorithms.

The particle swarm optimization algorithm presents a new way for finding an optimal solution of complex optimization problems, where each particle represents a solution to the problem. In this paper a modified particle swarm optimization algorithm is applied to the optimization of the antenna array. Adding an item of integral control and the contractive factor in the modified algorithm can improve its global search ability. Simulation results show that the optimal pattern of the antenna array is able to approach the desired pattern. The results also demonstrate that the modified algorithm is superior to the original algorithm and the nonlinear least-square method.