Self-complementary antenna

Abstract: The self-complementary antenna structure was originated and its constant-impedance property was discovered by the author in 1948. He pursued investigations of this type of antenna for many years, and he attained many extensions of the principle of self-complementarity, from the simplest planar structure to various other cases. In parallel with these studies, extensive developmental investigations of extremely broadband antennas have been carried out in Japan, based on this principle. This article succinctly describes a long history of these studies on self-complementary antennas, including the background of its origination. In connection with the extremely broadband property of this type of antenna, the non-constant-impedance property of incorrectly arranged log-periodic antennas is clearly shown, based on the results of experiments. This experimental fact indicates that the log-periodic shape in an antenna's structure does not guarantee a broadband property for the antenna. Most of experimental details and all of the theoretical treatments are omitted from this article.

Abstract: A novel and simple ultrawideband (UWB) printed quasi-self-complementary antenna is presented. The proposed antenna, which is fed by a microstrip line, has been demonstrated to provide an ultrawide 10-dB impedance bandwidth with satisfactory radiation properties. It also features both physically and electrically small dimensions, 16 mm times 25 mm in a physical size and 0.24lambda in an electrical size, respectively. The key parameters that affect the performance of the antenna are investigated. A good agreement is achieved between the simulation and the measurement.

Abstract: A compact multiple-input-multiple-output (MIMO) antenna with a very small size of only 21 × 38 mm 2 is proposed for ultra-wideband (UWB) applications. It consists of two quasi-self-complementary antenna (QSCA) elements with an inverted T-shaped common ground plane. The QSCA elements are the mirror images of each other, having a half-circular conductor patch on one side of the substrate and a slot with the complement of the half-circular shape on the other side. To reduce mutual coupling between the two QSCA elements, two rectangular slots are cut symmetrically on the ground plane between the two elements. Simulation and measurement are used to study the performance of the MIMO antenna in terms of reflection coefficient, isolation between the two ports, radiation pattern, realised gain, efficiency and envelope correlation coefficient. The results show that the MIMO antenna has a bandwidth from 3.1 GHz to more than 10.6 GHz with a mutual coupling of less than -15 dB and a correlation of less than 0.1, respectively, making it a good candidate for portable UWB applications.

Abstract: A novel and simple design of a quasi-self-complementary antenna for ultra wideband applications is presented. The proposed antenna, which is fed by a 50 Ω coplanar waveguide without using a matching circuit, can offer an ultra-wide 10 dB impedance bandwidth. It also features a compact and small size, only 0.22 λ at 1.3 GHz, which is the lower end of the bandwidth. Good agreement is achieved between the simulation and the experiment.