Designing Antennas With Quasi-Isotropic Radiation Patterns Using Pixel Structures

In this article, a systematic method for designing antennas with quasi-isotropic patterns is proposed based on pixel structures and
${N}$
-port networks. Multilayered pixel structures are employed to provide more design freedoms. The initial pixel structure is first described as an
${N}$
-port network, with the impedance matrices and the radiation pattern at each terminal calculated across the frequency band. With different combinations of the port status, different radiation patterns and port impedances can be synthesized through numerical calculation without extra full wave simulations. After optimization, a multiobjective function is then established, considering gain variations, port isolations, and input impedances. Balanced results can be selected from the Pareto front, leading to the optimized structure. A compact planar single antenna and an in-band full duplexing (IBFD) antenna system with isotropic patterns are designed at 2.4 GHz WLAN/bluetooth (BT) band, providing gain variations of 0.7 and 4.2/3.8 dB, respectively. The 6 dB gain variation bandwidths of the proposed antennas are all above 10%. The optimized IBFD antennas were validated experimentally, with the measured results agreeing well with the simulated ones. The proposed method provides a promising solution for designing quasi-isotropic antennas for various electronic devices.