3. Practical antenna design

There have been many practical antennas which are designed for the integrated antenna. Through some practical antennas, we can see that the integrated antenna may be implemented for the wireless communication. Design of the integrated antenna is dependent on the system requirement such as array structure and channel environment. In this section, we introduce various practical integrated antennas for several cases.

## 3.1 Practical integrated antenna

It is important to integrate multiple antennas with compact size, which have orthogonal radiation patterns of each other. There are practical integrated antennas without considering array structure as shown in Figure 4. It is found that the integrated antenna has two types of antenna elements which have radiation patterns of electric dipole antenna and magnetic loop antenna. Planer inverted-F antennas (PIFA) are used for the electric dipole antenna, and quarter-wavelength slot antennas are used for the magnetic loop antenna [16, 17]. It is also seen that the integrated antennas have three-dimensional structures because the array structure was not considered. Therefore, it is noted that the integrated antenna may consist of more than two antenna elements practically.

#### 3.2 Practical integrated antenna array

The integrated antenna array may be implemented as shown in Figure 5. It is found that the practical integrated antenna array is composed of Lt array elements. Each array element consists of Bt antenna elements, which are designed by utilizing a planer Yagi-Uda antenna [18].

To reduce the antenna size, we eliminated a conduct strip in front of the antenna element and designed that l<sup>3</sup> is larger than w<sup>2</sup> as shown in Figure 5a. The radiation
