**4.2. Multisegment DRA**

40 Dielectric Material

application.

miniaturize a DRA.

h

**Figure 16.** Integration of a metallic plate

frequency and impedance bandwidth.

The dielectric material choice is one of the most important degree of freedom in the DRA design. It is necessary to highlight the best tradeoff, keeping in mind the targeted

Thus, using high dielectric permittivity values is one method for achieving a compact design, but it is not the only one. The next section will deal with different techniques to

This part examines techniques to design compact DRAs. Targeted applications are mobile handsets or wireless tablet. There are several techniques to make DRAs more compact. By adding metal plates, inserting a high permittivity layer (multisegment DRA) or removing

The rectangular DRA shape has been studied in the first part. The perfect metallic wall implies that electric fields are normal to this conductor, while magnetic fields are tangential. E and H fields presented Figure 11 assume that a metallic plate can be inserted in the middle of the DRA according to the y-component. The principle is detailed and explained by the

> H field E field

By applying the image theory, it is possible to insert a metal plate in the y=w/2 plane. The Table 1 extracted from [12] shows the influence of the metallic plate insertion on resonant

εr w (cm) d (cm) h (cm) Metallization f0(GHz) Bandwidth

**Table 1.** Influence of the metallic plate insertion on both resonant frequency and impedance bandwidth

12 2.75 2.75 2.95 No 1.98 10% 12 2.75 2.75 2.95 Yes 1.24 5.6%

Ground plane

z y w w/2

Metallization

**4. Overview of techniques to miniaturize DRAs** 

portions of the DRA, a significant size reduction can be achieved.

**4.1. Addition of a metallic plate on a DRA face** 

Figure 16. It also shows the E and H fields of the TE111 mode.

Another way to decrease the DRA size is to insert different substrate layers as illustrated Figure 17.

**Figure 17.** Multisegment DRA

It allows achieving strong coupling when the first insertion has a relatively high dielectric permittivity. This technique is detailed in [12] and [31]. The Table 2 summarizes a parametrical study done in [31] for one layer inserted (Figure 17) with w=7.875 mm, d=2 mm, h=3.175 and εr=10. It is mounted on a 0.762 mm height substrate of permittivity εs=3. The TE111 mode of the DRA is excited with a 50Ω microstrop line.


**Table 2.** A parametrical study done in [31] for one layer inserted

Thus, a thin layer insertion allows improving the coupling of modes inside the DRA while decreasing the resonant frequency thanks to the decrease of the effective dielectric permittivity of the DRA. As the previous technique, the downside is the decrease of the impedance bandwidth.
