**3.3 Simulation and experimental results**

Powerful computer simulation tools are used to drastically reduce the design time. Advanced Design System (from Keysight) is one of the electromagnetic (EM) simulators used to estimate the performance of certain designs in this chapter. Normally, there is small variation between the simulation and measurement results because of the fabrication variation, material variation and connectors mismatch, etc. There is limited effect on frequency below 6 GHz, however, this becomes significant when the frequencies are in millimeter wave. Two antennas are designed based on structure in **Figure 5**. The dimensions of these two examples (called Antenna PCB A and Antenna PCB B) of PIFA shown in **Table 1** and in **Figure 6**.

Antennas in **Figure 6** were simulated on FR4 substrate with a dielectric constant of 4.6 and 0.8 mm thickness. The PCB design mainly contains PIFA, ground plane, transmission line and 3.5 mm SMA connector. The size of PCB, 18.8 mm× 43.2 mm was chosen, which is the normal size of a 2.4 GHz ISM band wireless module. At end of meandering line is 4.2 mm for Antenna PCB A and 2.9 mm for Antenna PCB B. The resonance frequency of Antenna PCB A is expected to be lower due to the longer trace. Antenna PCB C was fabricated to calibrate the transmission line by the port extension measurement. The simulated results of Antenna PCB A and Antenna PCB B are shown in **Figure 7** and the return loss indicates the resonant frequency of the antennas [9]. The input feed point in the simulation is at Port A in **Figure 6(a)** which is without the transmission line and connector but others are the same as in **Figure 6(a)**.

In **Figure 7**, the resonance frequency of Antenna PCB A is lower than that of Antenna PCB B. Antenna PCB A and Antenna PCB B were fabricated with


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**Figure 6.**

matching components.

*Planar Antenna Design for Internet of Things Applications*

the transmission line and connector in **Figure 6(a)**. The width of the transmission line is 1.5 mm so that the characteristic impedance of the line is equal to 50 Ohm. The return losses of antenna were measured by vector network analyzer (VNA). If the return losses are not significant high enough, matching network is needed for maximum power transfer. Antenna PCB C is used for port extension by VNA so that the measurement reference plane is moved to Port A since the VNA can predict the open circuit at end of the transmission line from the connector in Antenna PCB C by the electrical length *L* of the transmission line. The simulated and measured results of Antenna PCB B are plotted in **Figure 8**. It is also shown that the overall performance of antenna at Port B is close to the same at Port A. The radiation patterns and gain measurement are carried out by passive antenna measurement system. The active antenna measurement sometimes is used to indicate the overall transmission and reception of the complete products. The maximum gain of the PIFA is normally around 3 dBi. Antenna PCB B, therefore, is suitable for 2.4 GHz ISM band applications. **Table 2** shows the comparison table of different antennas, which shows that the dielectric antennas have a little size smaller than the PIFA. However, PIFAs were only fabricated on PCB, which is approximately zero in thickness as well as zero cost of antenna and

*PIFA: (a) Antenna PCB A (l2 = 4.2 mm) and Antenna PCB B (l3 = 2.9 mm) (b) and Antenna PCB C.*

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

**Table 1.** *Parameters used in the PIFA.* *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*

area and impedance matching network for maximum power transfer [13].

transmission line and connector but others are the same as in **Figure 6(a)**.

**Parameters Length (mm)** *w1* 0.9 *w2* 0.5 *s1* 2.0 *s2* 1.7 *l1* 2.5 *l2* (Antenna PCB A) 4.2 *l3* (Antenna PCB B) 2.9

In **Figure 7**, the resonance frequency of Antenna PCB A is lower than that of Antenna PCB B. Antenna PCB A and Antenna PCB B were fabricated with

Powerful computer simulation tools are used to drastically reduce the design time. Advanced Design System (from Keysight) is one of the electromagnetic (EM) simulators used to estimate the performance of certain designs in this chapter. Normally, there is small variation between the simulation and measurement results because of the fabrication variation, material variation and connectors mismatch, etc. There is limited effect on frequency below 6 GHz, however, this becomes significant when the frequencies are in millimeter wave. Two antennas are designed based on structure in **Figure 5**. The dimensions of these two examples (called Antenna PCB A and Antenna PCB B) of PIFA shown in **Table 1** and in **Figure 6**. Antennas in **Figure 6** were simulated on FR4 substrate with a dielectric constant of 4.6 and 0.8 mm thickness. The PCB design mainly contains PIFA, ground plane, transmission line and 3.5 mm SMA connector. The size of PCB, 18.8 mm× 43.2 mm was chosen, which is the normal size of a 2.4 GHz ISM band wireless module. At end of meandering line is 4.2 mm for Antenna PCB A and 2.9 mm for Antenna PCB B. The resonance frequency of Antenna PCB A is expected to be lower due to the longer trace. Antenna PCB C was fabricated to calibrate the transmission line by the port extension measurement. The simulated results of Antenna PCB A and Antenna PCB B are shown in **Figure 7** and the return loss indicates the resonant frequency of the antennas [9]. The input feed point in the simulation is at Port A in **Figure 6(a)** which is without the

**3.3 Simulation and experimental results**

High directivity sometimes is considered in certain situation. However, it will not be discussed here since most of planar antennas are omni-directional transmission and reception instead of unidirectional antennas. The basic design rules and antenna performance characterization methods are addressed by case study in 2.4 GHz ISM band. The operation frequency of the antenna is governed by the basic dispersion relation *c = fλ*. The letter *c* represents the speed of electromagnetic wave in the air, which is a constant if only consider the wave traveling in single medium. In previous section, it shows that a dipole antenna resonates when the physical length of antenna equals to the quarter wavelength of incident signal and a sufficiently large ground plane form the mirror image under the plane. The length of the resonant line occupies a considerable area on the PCB, which is around one third of a wireless module. Proper selection of traces' length and width reduces the occupied

**54**

**Table 1.**

*Parameters used in the PIFA.*

the transmission line and connector in **Figure 6(a)**. The width of the transmission line is 1.5 mm so that the characteristic impedance of the line is equal to 50 Ohm. The return losses of antenna were measured by vector network analyzer (VNA). If the return losses are not significant high enough, matching network is needed for maximum power transfer. Antenna PCB C is used for port extension by VNA so that the measurement reference plane is moved to Port A since the VNA can predict the open circuit at end of the transmission line from the connector in Antenna PCB C by the electrical length *L* of the transmission line. The simulated and measured results of Antenna PCB B are plotted in **Figure 8**. It is also shown that the overall performance of antenna at Port B is close to the same at Port A. The radiation patterns and gain measurement are carried out by passive antenna measurement system. The active antenna measurement sometimes is used to indicate the overall transmission and reception of the complete products. The maximum gain of the PIFA is normally around 3 dBi. Antenna PCB B, therefore, is suitable for 2.4 GHz ISM band applications. **Table 2** shows the comparison table of different antennas, which shows that the dielectric antennas have a little size smaller than the PIFA. However, PIFAs were only fabricated on PCB, which is approximately zero in thickness as well as zero cost of antenna and matching components.

**Figure 7.** *Simulated S-parameter, S11 of Antenna PCB A and Antenna PCB B at Port A.*

**Figure 8.** *Antenna PCB B: Simulated (at Port A) and measured (at Port A and B)* S*-parameter,* S11.
