**4. Wideband planar antenna: foldable and non-foldable**

#### **4.1 Wideband planar antenna for IoT applications**

Various IoT applications use different solutions to connect devices and sensors. Low power technologies such as Bluetooth and Zigbee are preferred for short-range applications because of their low power usage. Cellular communication technologies sometimes are required used for large coverage and high data rate applications

**57**

**Figure 9.**

*Planar Antenna Design for Internet of Things Applications*

despite its large power consumption. Multiple narrowband antennas are needed when different technologies are used in IoT applications. One wideband antenna, therefore, is an attractive approach to replace multiple narrowband antennas. Different wideband structures were proposed to combine different frequency bands into one individual wideband antenna to serve different technologies in order to reduce the size and simplicity [21–23]. The wideband antenna is still large to be used in portable devices, therefore, foldable design [21] provides flexibility of IoT

*Gain between dielectric and PCB antennas [10] (includes the area of matching network, but not the ground* 

**Antenna Plane Total average (dBi) Area (mm2**

PIFA (Antenna PCB B) Y-Z 1.60 16 × 7.0

Miniaturized PIFA [13] Y-Z −0.70 15 × 6.0

Capacitive-loaded antenna Y-Z — 12 × 5.0

Dielectric antenna (3 mm length) Y-Z 0.89 12 × 5.0

Dielectric antenna (5 mm length) Y-Z −3.22 18 × 11

X-Z 3.30 X-Y 1.10

X-Z −1.98 X-Y −1.26

X-Z −1.76 X-Y −3.32

X-Z −1.85 X-Y −2.56

X-Z −3.24 X-Y −3.12

**)**

Dipole antenna in **Figure 1** could be extended to be a wideband antenna. Two conductive arms are replaced by thicker wire or even a plane to extend the bandwidth. One of example for wideband planar foldable and non-foldable antennas is

*DOI: http://dx.doi.org/10.5772/intechopen.92456*

products as well as further size reduction.

*Wideband planar foldable and non-foldable antennas [21].*

**4.2 Wideband planar antenna design**

shown in **Figure 9**.

**Table 2.**

*plane).*


*Planar Antenna Design for Internet of Things Applications DOI: http://dx.doi.org/10.5772/intechopen.92456*

#### **Table 2.**

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

**4. Wideband planar antenna: foldable and non-foldable**

*Antenna PCB B: Simulated (at Port A) and measured (at Port A and B)* S*-parameter,* S11.

*Simulated S-parameter, S11 of Antenna PCB A and Antenna PCB B at Port A.*

Various IoT applications use different solutions to connect devices and sensors. Low power technologies such as Bluetooth and Zigbee are preferred for short-range applications because of their low power usage. Cellular communication technologies sometimes are required used for large coverage and high data rate applications

**4.1 Wideband planar antenna for IoT applications**

**56**

**Figure 8.**

**Figure 7.**

*Gain between dielectric and PCB antennas [10] (includes the area of matching network, but not the ground plane).*

despite its large power consumption. Multiple narrowband antennas are needed when different technologies are used in IoT applications. One wideband antenna, therefore, is an attractive approach to replace multiple narrowband antennas. Different wideband structures were proposed to combine different frequency bands into one individual wideband antenna to serve different technologies in order to reduce the size and simplicity [21–23]. The wideband antenna is still large to be used in portable devices, therefore, foldable design [21] provides flexibility of IoT products as well as further size reduction.

#### **4.2 Wideband planar antenna design**

Dipole antenna in **Figure 1** could be extended to be a wideband antenna. Two conductive arms are replaced by thicker wire or even a plane to extend the bandwidth. One of example for wideband planar foldable and non-foldable antennas is shown in **Figure 9**.

**Figure 9.** *Wideband planar foldable and non-foldable antennas [21].*

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


#### **Table 3.**

*Parameters used in the wideband planar foldable and non-foldable antennas.*

**Figure 10.**

**59**

**Figure 11.**

*(b) non-foldable.*

*Planar Antenna Design for Internet of Things Applications*

This planar antenna consists of two rectangular metal planes. The important parameters could be tuned in this design are width W, length L and gap G. The length is used for tuning in this example as it has significant impact on the performance of antenna. All parameters are fixed in **Table 3** except the length L which is the parameter chosen to be tuned for foldable and non-foldable antennas. The foldable design was fabricated in the metal sheet and the non-foldable design was fabricated on the FR4 substrate with a dielectric constant of 4.6 and thickness of 0.8 mm. The simulated results of return loss are shown in **Figure 10** with different lengths of sheet L. In **Figure 10**, the frequency range is shifted to the lower side with a longer length L

because the length L is closer to the quarter-wavelength of a lower frequency.

*Comparison between simulated and measured results of wideband planar antennas [21]: (a) foldable and* 

*DOI: http://dx.doi.org/10.5772/intechopen.92456*

*Planar Antenna Design for Internet of Things Applications DOI: http://dx.doi.org/10.5772/intechopen.92456*

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

**Parameters Length (mm)** *G* 0.9 *W* (foldable design) 29 *W* (non-foldable design) 25

*Parameters used in the wideband planar foldable and non-foldable antennas.*

*Simulated results of wideband planar antennas [21]: (a) foldable and (b) non-foldable.*

**58**

**Figure 10.**

**Table 3.**

This planar antenna consists of two rectangular metal planes. The important parameters could be tuned in this design are width W, length L and gap G. The length is used for tuning in this example as it has significant impact on the performance of antenna. All parameters are fixed in **Table 3** except the length L which is the parameter chosen to be tuned for foldable and non-foldable antennas. The foldable design was fabricated in the metal sheet and the non-foldable design was fabricated on the FR4 substrate with a dielectric constant of 4.6 and thickness of 0.8 mm. The simulated results of return loss are shown in **Figure 10** with different lengths of sheet L. In **Figure 10**, the frequency range is shifted to the lower side with a longer length L because the length L is closer to the quarter-wavelength of a lower frequency.

#### **Figure 11.**

*Comparison between simulated and measured results of wideband planar antennas [21]: (a) foldable and (b) non-foldable.*

**Figure 11** shows the comparison between simulated and measured results of wideband planar foldable and non-foldable antennas. **Figure 11(a)** shows the simulated and measured results of the fabricated foldable antenna which shows that the simulated and measured results are close to each other with the bandwidth of 76% from 1.3 to 2.9 GHz. This range covers the applications in GPS, the 2.4 GHz ISM band, and the general 3GPP WCDMA bands and LTE bands. **Figure 11(b)** shows the simulated and measured results with L equal to 36 and 41 mm (same width of W = 25 mm). Simulated and measured results show that they are close to each other with the bandwidth of 76% from 1.35 to 2.75 GHz, which is little worse than the foldable design in **Figure 11(a)**. The maximum gain of the non-foldable is between 2.5 and 3.5 dBi.
