**3. Design of general printed-F antenna (PIFA)**

## **3.1 Printed inverted-F antenna (PIFA)**

The printed inverted-F antenna (PIFA) is one of common planar antennas used in the commercial and medical devices because of its small size, low profile and low cost [13–20]. The typical PIFA structure is shown in **Figure 4**. Its working principle is same as monopole antenna with quarter-wave long along the main resonant line in **Figure 4**, therefore, the size of the ground plane is also an important part of antenna. It has a shorting feed point at the end of the main resonant line. This folded part introduces capacitance to the input impedance of the PIFA which is canceled by the shorting feed point. This foldable part, therefore, reduces the antenna size.

**53**

**Figure 5.**

*Planar Antenna Design for Internet of Things Applications*

horizontal and vertical lines to form multiple turns.

antenna since PIFA fulfills the requirements of IoT applications.

The matching network in **Figure 4** is used for maximum power transfer and, hence, efficient radiation [10]. Lump elements are normally used in matching network to minimize the size. In this section, PIFA is used as example of planar

**Figure 4** shows a typical PIFA structure on a printed circuit board (PCB) which is indicated with the dotted area at the PCB upper layer. Meandering line is commonly used to increase the total length in antenna design. The meandering line in **Figure 5** is used to replace the main resonant line in PIFA shown by combination of

The requirements of the PIFA are the operation frequency, power transmission efficiency, size and even cost. Simulation, fabrication and measurement are conducted until the antenna fulfills the defined application requirements. In general, a well-designed PIFA has the feature of having resonance at the operation frequency and good return loss, i.e., effective power transmission to antenna and compact

*DOI: http://dx.doi.org/10.5772/intechopen.92456*

**3.2 Meandered PIFA design**

in size.

**Figure 4.**

*Typical PIFA structure [13].*

*PIFA with meandering line.*

The matching network in **Figure 4** is used for maximum power transfer and, hence, efficient radiation [10]. Lump elements are normally used in matching network to minimize the size. In this section, PIFA is used as example of planar antenna since PIFA fulfills the requirements of IoT applications.
