Internet of Things (IoT) will play an important role in modern communication systems. Thousands of devices will talk to each other at the same time. Clearly, smart and efficient hardware will play a vital role in the development of IoT. In this context, the importance of antennas increases due to them being essential parts of communication networks. For IoT applications, a small size with good matching and over a wide frequency range is preferred to ensure reduced size of communication devices. In this paper, we propose a structure and discuss design optimization of a wideband antenna for IoT applications. The antenna consists of a stepped-impedance feed line, a rectangular radiator and a ground plane. The objective is to minimize the antenna footprint by simultaneously adjusting all geometry parameters and to maintain the electrical characteristic of antenna at an acceptable level. The obtained design exhibits dimensions of only 3.7 mm × 11.8 mm and a footprint of 44 mm2, an omnidirectional radiation pattern, and an excellent pattern stability. The proposed antenna can be easily handled within compact communication devices. The simulation results are validated through measurements of the fabricated antenna prototype.

In this paper, a novel structure of a compact UWB slot antenna and its design optimization procedure has been presented. In order to achieve a sufficient number of degrees of freedom necessary to obtain a considerable size reduction rate, the slot is parameterized using spline curves. All antenna dimensions are simultaneously adjusted using numerical optimization procedures. The fundamental bottleneck here is a high cost of the electromagnetic (EM) simulation model of the structure that includes (for reliability) an SMA connector. Another problem is a large number of geometry parameters (nineteen). For the sake of computational efficiency, the optimization process is therefore performed using variable-fidelity EM simulations and surrogate-assisted algorithms. The optimization process is oriented towards explicit reduction of the antenna size and leads to a compact footprint of 199 mm2 as well as acceptable matching within the entire UWB band. The simulation results are validated using physical measurements of the fabricated antenna prototype.