**3. Narrowband and dual band antenna design**

The UWB monopole antenna can be reconfigured to others frequency bands by using an inverted L and rectangular shaped slotted structure placed on the ground plane, as shown in **Figure 4**. This inverted L-shaped slot in ground plane generating an additional current path due to the perturbation of the current flow in antenna structure that leads to the filter characteristics, responsible to suppress the frequencies outside the desired frequency band. These ground slots are generating the stop bands in the UWB frequency range [9]. **Figure 5** represents the different filter structures of the proposed design by variation in the inverted L-shaped slot.

**Figure 6** represents the input reflection coefficient S11 (below −10 dB) of the antenna for different filter structures. Structure I and II are creating the dual bands whereas structure III and IV are responsible for obtaining the single bands only.

Moreover, the bandwidth of each filtering structure in **Figure 6**, is controllable with changing the length *l*2 and width *W*2 of parallel vertical arms (in **Figure 4**). By the variations of these arms dimensions impedance bandwidth changes accordingly, as shown in **Figure 7**. While increasing the slot length *l*2 and width *W*2,

**5**

**Figure 6.**

**Figure 5.**

*Filter structures placed on the ground plane.*

*Frequency Reconfigurable UWB Antenna Design for Wireless Applications*

the bandwidth of antenna decreases from 30 to 12% in structure III. The desired resonant band with the input reflection coefficient S11 (below −10 dB) is achieved at

the optimized value *l*2 = 2.5 mm and *W*2 = 1 mm respectively.

*Simulated reflection coefficient S11 of the antenna for filter structures in* **Figure 5***.*

*DOI: http://dx.doi.org/10.5772/intechopen.86035*

**Figure 4.** *Slotted structure on ground plane.*

*Frequency Reconfigurable UWB Antenna Design for Wireless Applications DOI: http://dx.doi.org/10.5772/intechopen.86035*

**Figure 5.**

*UWB Technology - Circuits and Systems*

**3. Narrowband and dual band antenna design**

shown in **Figure 3**.

the inverted L-shaped slot.

From **Figure 2**, it is indicated that at lower frequencies (2–4 GHz) that the impedance matching is improved when the slot dimensions are reduced (either by reducing *l*1 or *W*1). At higher frequencies (above 5 GHz), the impedance matching is enhanced when the slot dimensions are increased. The input reflection coefficient S11 (below −10 dB) of UWB antenna is achieved at the optimized value of *l*1 = 6.1 mm and *W*1 = 1 mm. The impedance bandwidth of 141% (2.87–16.56 GHz) under simulation and 140% (2.85–15.85 GHz) in measurement is obtained as

The UWB monopole antenna can be reconfigured to others frequency bands by using an inverted L and rectangular shaped slotted structure placed on the ground plane, as shown in **Figure 4**. This inverted L-shaped slot in ground plane generating an additional current path due to the perturbation of the current flow in antenna structure that leads to the filter characteristics, responsible to suppress the frequencies outside the desired frequency band. These ground slots are generating the stop bands in the UWB frequency range [9]. **Figure 5** represents the different filter structures of the proposed design by variation in

**Figure 6** represents the input reflection coefficient S11 (below −10 dB) of the antenna for different filter structures. Structure I and II are creating the dual bands whereas structure III and IV are responsible for obtaining the single bands only. Moreover, the bandwidth of each filtering structure in **Figure 6**, is controllable with changing the length *l*2 and width *W*2 of parallel vertical arms (in **Figure 4**). By the variations of these arms dimensions impedance bandwidth changes accordingly, as shown in **Figure 7**. While increasing the slot length *l*2 and width *W*2,

**4**

**Figure 4.**

*Slotted structure on ground plane.*

*Filter structures placed on the ground plane.*

**Figure 6.** *Simulated reflection coefficient S11 of the antenna for filter structures in* **Figure 5***.*

the bandwidth of antenna decreases from 30 to 12% in structure III. The desired resonant band with the input reflection coefficient S11 (below −10 dB) is achieved at the optimized value *l*2 = 2.5 mm and *W*2 = 1 mm respectively.

**Figure 7.** *Simulated reflection coefficient S11 of the antenna for different values of l2 and W2 in structure-III.*
