**Abstract**

Planar antenna plays an important role in Internet of Things (IoT) applications because of its small size, low profile and low cost. In IoT wireless module, antenna is typically occupied one-third size of overall circuit; therefore, planar antenna, i.e., integrated on printed circuit board (PCB) is one of attractive design. In this chapter, the fundamental of antenna is firstly discussed. Printed Inverted-F Antenna (PIFA) is taken as an example to explain the design process of simple planar antenna and a size-reduced 2.4 GHz ISM band PIFA is used for experimental explanation for the short-range IoT applications. Finally, a wideband antenna is shown as wideband planar antenna for short-range and long-range IoT applications.

**Keywords:** bluetooth low energy (BLE), industrial scientific and medical (ISM), printed circuit board (PCB), Internet of Things (IoT), planar antenna, printed inverted-F antenna (PIFA), wideband antenna

#### **1. Introduction**

Internet of Things (IoT) aims to connect existing sensors and devices to the internet in real time. Constantly collecting the information from surrounding help users making wiser decision, leading to higher quality in daily life and higher efficiency in industries [1–5]. Short-range and long-range wireless techniques are suitable used in different IoT applications. One of the wireless techniques for short-range IoT applications is bluetooth low energy (BLE) under 2.4 GHz industrial, scientific, and medical (ISM) band because of its low power consumption [6, 7]. On the other hand, cellular communications provide larger coverage in long-range IoT applications but they have high power consumption [8]. In RF/microwave modules, the size reduction and performance enhancement of the antenna are key design parameters, therefore, planar antenna, i.e., integrated on printed circuit board (PCB) is a suitable antenna for IoT applications.

In this chapter, the fundamental of antenna is firstly discussed. Printed Inverted-F Antenna (PIFA) is taken as an example to explain the design process of simple planar antenna and a size-reduced 2.4 GHz ISM band PIFA is used for experimental explanation for the short-range applications. Finally, a wideband antenna is shown as another approach on wideband planar antenna for short-range and long-range IoT applications.
