*2.3.1 The return loss S11*

**Figure 2** shows the return loss or more known as the parameter S11 of the antenna, the spectrum of **Figure 2** contains the UWB frequency band spectrum. The spectrum's antenna range is form 2.8 GHz to 10.9 GHz and contains tow resonate frequencies

**Figure 1.** *Geometry of the antenna proposed.*

**Figure 2.** *The return loss S11 as a function of frequency.*

6.1 GHz and 9.8 GHz with their S11 parameters −46 dB and −35 dB respectively. The antenna can be easily used in the UWB (3.1 GHz – 10.6 GHz) applications [4].

#### *2.3.2 Voltage standing wave ratio (VSWR)*

VSWR is a parameter that describes the power that is reflected by the antenna. It is a function of the reflection parameter.

**Figure 3** shows the graph of the VSWR of the antenna proposed, we can tell from the graph that the VSWR is under tow in all the bandwidth so the VSWR can be considered as good.

#### *2.3.3 Radiation pattern*

The main focus of the chapter is to design a UWB antenna that can be easily implemented in UWB application with a small dimension and a larger frequency spectrum. **Figure 4** shows the radiation pattern of the antenna proposed for the frequency of 9.8 GHz, the color red defined the higher range of the gain and the green refers to the lower part [7].

#### **2.4 Paramertic study**

The parametric study is done in two parts the first part was to choose the laminate and then the value of the radius of the patch.

#### **2.5 Comparison with others UWB antennas**

The antennas that was compared to the antenna proposed in the chapter is: a coplanar microstrip antenna with defected ground structure for UWB applications [7]. A printed UWB antenna with full ground plane also for WBAN applications and CPW-fed slot patch antenna [8–10]. The study is to compare the proposed geometry on tree different Rogers laminates. **Table 1** shows the characteristics of the tree laminates.

**Figure 5** presents the return loss of the antenna with the different laminates, according to the results of **Figure 5**, the laminate Rogers with a thickness of 3.175 mm was chosen to complete the parametric study. The variation of the radius is

**81**

around 5.6 dBi.

*Design of a UWB Coplanar Fed Antenna and Circular Miniature Printed Antenna for Medical…*

altered around the theoretical radius to optimize the performance of the antenna. The patch of the antenna is separated into two parts, first where the cutouts are and the second part is the ring that contour the cutouts, this parametric study consisted on varying the inner radius of the patch, the radius of the circle that contain the cutouts. **Figure 6** shows a relation between the radius and the depth of the return

**Standard thickness Standard copper cladding**

**Laminates Laminate characteristics**

Laminate 1 0.787 mm 35 μm Laminate 2 1.57 mm 35 μm Laminate 3 3.175 mm 35 μm

**Table 2** shows the difference between four UWB antennas, the proposed antenna has a wider band, includes all UWB frequencies, the highest gain is

loss, *R* = 4.8 mm shows a better S11 parameter.

*DOI: http://dx.doi.org/10.5772/intechopen.93205*

**Figure 3.**

**Figure 4.**

**Table 1***.*

*Radiation pattern of the proposed antenna.*

*Standard laminales characteristics.*

*VSWR as a function of frequency.*

*Design of a UWB Coplanar Fed Antenna and Circular Miniature Printed Antenna for Medical… DOI: http://dx.doi.org/10.5772/intechopen.93205*

**Figure 3.** *VSWR as a function of frequency.*

*Advanced Radio Frequency Antennas for Modern Communication and Medical Systems*

6.1 GHz and 9.8 GHz with their S11 parameters −46 dB and −35 dB respectively. The antenna can be easily used in the UWB (3.1 GHz – 10.6 GHz) applications [4].

VSWR is a parameter that describes the power that is reflected by the antenna. It

**Figure 3** shows the graph of the VSWR of the antenna proposed, we can tell from the graph that the VSWR is under tow in all the bandwidth so the VSWR can

The main focus of the chapter is to design a UWB antenna that can be easily implemented in UWB application with a small dimension and a larger frequency spectrum. **Figure 4** shows the radiation pattern of the antenna proposed for the frequency of 9.8 GHz, the color red defined the higher range of the gain and the

The parametric study is done in two parts the first part was to choose the lami-

The antennas that was compared to the antenna proposed in the chapter is: a coplanar microstrip antenna with defected ground structure for UWB applications [7]. A printed UWB antenna with full ground plane also for WBAN applications and CPW-fed slot patch antenna [8–10]. The study is to compare the proposed geometry on tree different Rogers laminates. **Table 1** shows the characteristics of

**Figure 5** presents the return loss of the antenna with the different laminates, according to the results of **Figure 5**, the laminate Rogers with a thickness of 3.175 mm was chosen to complete the parametric study. The variation of the radius is

*2.3.2 Voltage standing wave ratio (VSWR)*

*The return loss S11 as a function of frequency.*

is a function of the reflection parameter.

be considered as good.

**Figure 2.**

*2.3.3 Radiation pattern*

**2.4 Paramertic study**

the tree laminates.

green refers to the lower part [7].

nate and then the value of the radius of the patch.

**2.5 Comparison with others UWB antennas**

**80**

#### **Figure 4.**

*Radiation pattern of the proposed antenna.*


#### **Table 1***.*

*Standard laminales characteristics.*

altered around the theoretical radius to optimize the performance of the antenna. The patch of the antenna is separated into two parts, first where the cutouts are and the second part is the ring that contour the cutouts, this parametric study consisted on varying the inner radius of the patch, the radius of the circle that contain the cutouts. **Figure 6** shows a relation between the radius and the depth of the return loss, *R* = 4.8 mm shows a better S11 parameter.

**Table 2** shows the difference between four UWB antennas, the proposed antenna has a wider band, includes all UWB frequencies, the highest gain is around 5.6 dBi.

**Figure 5.** *Effect of the thickness of the substrate.*

**Figure 6.** *Effect of the inner radius on the antenna.*


**83**

**Figure 7.** *Antenna geometry.*

**Table 3.**

*The dimensions of the circular miniature printed antenna.*

*Design of a UWB Coplanar Fed Antenna and Circular Miniature Printed Antenna for Medical…*

The patch of radius (r) is produced on a substrate of the FR-4 type (dielectric

permittivity εr = 4.3, thickness h = 1.575 mm) and of dimensions ls = 25 mm and ws = 25 mm. A rectangular slot is inserted on the radiating element (u × s) ensuring its miniaturization. The latter is supplied by microstrip line of wm east width in order to adapt it to a 50 Ω supply [11, 12]. **Figure 7** shows the proposed

From **Table 3** values, we perform a simulation on the CST software [13].

The parameter S11 is the coefficient that most concerns designers of printed antennas because it represents the reflection coefficient which plays the role of

We see that the coefficient S is around −22.35 dB for a resonant frequency of

**Parameters r lm wm tm lg u s v g k** mm 8 9 2.25 0.035 8 1 10 4 0.27 5

3.8 GHz, the bandwidth is 3.17–15 GHz, as shown in **Figure 8** [15].

**3. Design of a UWB circular miniature printed antenna**

*DOI: http://dx.doi.org/10.5772/intechopen.93205*

*3.1.1 Antenna geometry*

*3.1.2 Simulation results*

disturbance on data transmission [14]:

*3.1.2.1 S11 parameter*

antenna.

**3.1 Design of circular miniature printed antenna**

**Table 2.** *Performance comparison.* *Design of a UWB Coplanar Fed Antenna and Circular Miniature Printed Antenna for Medical… DOI: http://dx.doi.org/10.5772/intechopen.93205*
