**2. Ultra wideband (UWB) antenna design**

In this section initially octagonal shape monopole antenna size of 40 × 40 × 0.40 mm3 is designed, as represented in configuration "a" of **Figure 1**. The proposed design is constructed on 0.40 mm thick Roger RT 5880 substrate with the relative permittivity 2.2, fed with 50 ohm microstrip feed line. Octagonal shape radiating element has the dimensions ab = ef = 10 mm, bc = ha = 5.14 mm, cd = gh = 6.0 mm and de = fg = 5.14 mm attached with feedline of dimensions 22 × 1.25 × 0.01 mm3 . On back side of antenna, ground plane

**3**

**Figure 3.**

**Figure 2.**

*Frequency Reconfigurable UWB Antenna Design for Wireless Applications*

istics is achieved at length *l*1 = 6.1 mm and width *W*1 = 1 mm.

*Simulated reflection coefficient S11 of the proposed antenna for different values of l1 and W1.*

*Simulated and measured reflection coefficient S11 of the proposed UWB antenna.*

exist with length of 21.1 mm, width of 40 mm and thickness of 0.01 mm. **Figure 1** shows

The operational performance of the antenna is analyzed with variations in its parameters such as ground slot dimensions (length *l*1 and width *W*1) are known as the parametric study of the proposed design. This study is carried out by variations in slot length *l*1 and width *W*1 while keeping other parameters constant. Slot length *l*1 and width *W*1 is varied from 0 to 7 mm and 0.6 to 1.4 mm respectively, as depicted in **Figure 2**. It is observed that, as variation are done in the value of *l*1 and *W*1, the reflection coefficient (S11) is changes and the respective frequency band is also changes accordingly. The optimized impedance matching for UWB band character-

the configuration of the proposed antenna with a top view and bottom view.

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

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

*UWB Technology - Circuits and Systems*

prototype machine (Caddo-71).

**2. Ultra wideband (UWB) antenna design**

with feedline of dimensions 22 × 1.25 × 0.01 mm3

narrowband mode switching facility. A frequency band reconfigurable antenna with four photoconductive switches is proposed that operating with switching between the three narrowband modes and UWB mode [7]. In [9], antenna has been proposed with narrowband and wideband functionality with reconfigurability characteristics is achieved with the implementation of p-i-n and varactor diodes. Tunable EBG structure are analyzed with active switching devices FET and obtained the transmission characteristics of the structure [12, 13]. Many techniques such as defective ground [14], etching slots [15, 16], metamaterial loading [17–23], dielectric resonator [24], fractal geometry [25, 26], etc., are applied to accomplish

multiband reconfigurable operation to cover various wireless applications. In this chapter, firstly design the octagonal shape patch antenna and implementing the inverted L shaped switchable slotted ground yielded switchable resonant modes such as, two narrowband modes (5.05–5.89 and 8.76–9.80 GHz), two dual band modes (2.21–2.52 GHz and 5.07–5.89 GHz and 2.18–2.52 GHz and 8.78–9.71 GHz) and UWB mode (2.87–16.56 GHz) for wireless applications. As per requirement to design antenna to frequency band reconfigurability introducing the five switching elements p-i-n diodes placed inside the slotted ground. The proposed design is compact in size as compared to antennas are discussed in published literature [6–11]. The simulation work of antenna is done by using CST Microwave Studio (CST MWS) software [27] and measurement is performed with the help of VNA (vector network analyzer-E5071C (300 KHz–20 GHz) ENA series Agilent Technologies). The fabrication of proposed structure is executed by using of PCB

Following sections focused on the antenna designing with parametric study and switchable modes analysis with results in simulated as well as measurement modes.

In this section initially octagonal shape monopole antenna size of 40 × 40 × 0.40 mm3 is designed, as represented in configuration "a" of **Figure 1**. The proposed design is constructed on 0.40 mm thick Roger RT 5880 substrate with the relative permittivity 2.2, fed with 50 ohm microstrip feed line. Octagonal shape radiating element has the dimensions ab = ef = 10 mm, bc = ha = 5.14 mm, cd = gh = 6.0 mm and de = fg = 5.14 mm attached

*Configuration of the UWB antenna: (a) front view of structure and (b) back view of structure.*

. On back side of antenna, ground plane

**2**

**Figure 1.**

exist with length of 21.1 mm, width of 40 mm and thickness of 0.01 mm. **Figure 1** shows the configuration of the proposed antenna with a top view and bottom view.

The operational performance of the antenna is analyzed with variations in its parameters such as ground slot dimensions (length *l*1 and width *W*1) are known as the parametric study of the proposed design. This study is carried out by variations in slot length *l*1 and width *W*1 while keeping other parameters constant. Slot length *l*1 and width *W*1 is varied from 0 to 7 mm and 0.6 to 1.4 mm respectively, as depicted in **Figure 2**. It is observed that, as variation are done in the value of *l*1 and *W*1, the reflection coefficient (S11) is changes and the respective frequency band is also changes accordingly. The optimized impedance matching for UWB band characteristics is achieved at length *l*1 = 6.1 mm and width *W*1 = 1 mm.

**Figure 2.** *Simulated reflection coefficient S11 of the proposed antenna for different values of l1 and W1.*

**Figure 3.** *Simulated and measured reflection coefficient S11 of the proposed UWB antenna.*

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 shown in **Figure 3**.
