Antenna miniaturisation and broadband design via a decomposition of structure into conjugated elemental antennas for natural impedance matching

Abstract

This study introduces a useful technique for an effective antenna design to achieve size miniaturisation or broadband operation. The key idea is the decomposition of the antenna structure into several elemental parts having naturally conjugate input reactance values. Each of the decomposed elemental parts serves as both the matching element and radiator simultaneously, instead of simply being lumped components such as capacitors or inductors. Since the matching element has a reactance conjugate to that of the original antenna, the integrated structure via the connection of these elements in series or parallel will be able to achieve a natural resonance, allowing one to either miniaturise the antenna by using small‐sized elements, or achieve a broadband operation if the impedance variations of these elements are similar.

Miniaturised antenna design with crossed‐field elements to radiate strong electromagnetic fields for near‐field communications

“…A pair of conjugated antenna elements is employed to mutually match the input impedances [11], where the input impedances of each individual antenna are conjugated in their reactive parts. Fig.…”

“…To understand the radiation mechanisms, this paper examines the NF radiations of antennas, and develops the design concepts for antennas to radiate strong NFs with miniaturised antenna sizes. In particular, we use the antenna elements with conjugated input impedances [11] and adjust the radiation orientations of individual electrical and magnetic sources to not only reduce the antenna sizes, but also assemble the EM field characteristics as they have in the FF governed by Poynting theorem. In this case, the RX antenna can be either electric or magnetic without the need to consider the antenna type for a good coupling with the TX antenna at any location, which motivates the works in this paper.…”