**3. Compact wearable dual polarized antenna for IoT and medical applications**

The antenna with CSRR and metallic strips is presented in **Figure 3a**. The printed dipole matching network and the metallic strips are etched on the first layer with thickness of 0.16 cm. The radiating element with CSRR is printed on the second layer with thickness of 0.16 cm. The size of the antenna network with the energy harvesting module is 21.54.5 cm. The printed slot antenna is vertically polarized. The printed


#### **Table 1.**

*Comparison of cellular phone technologies.*

#### **Figure 3.**

*(a). Antenna with CSRR and with energy harvesting unit, (b). optimized sensor with CSSR and metallic strips.*

dipole is horizontally polarized. The resonant frequency of the dipole with CSRR is around 0.33GHz, which is lower by 15% than the resonant frequency of the printed dipole without CSRR. Many communications, IoT and healthcare systems operate in the frequency range between 0.1 and 0.55 GHz. The computed S11 and antenna gain are shown in **Figure 4**. The measured antenna bandwidth is around 45% for S11 lower

*Green Wearable Sensors for Medical, Energy Harvesting, Communication, and IoT Systems DOI: http://dx.doi.org/10.5772/intechopen.112352*

**Figure 5.** *Radiation pattern and gain of the antenna with metallic strips and CSRR.*

than -6 dB. The dipole and the slot radiate in the z axis direction. The measured directivity and gain of the antenna with CSRR are around 5.5 dBi, as presented in **Figure 5**. The feed network of the antenna in **Figure 3a** was optimized, see **Figure 3b**, to yield S11 lower than -6 dB in the frequency range from 0.18 to 0.4 GHz, around 60% bandwidth, as presented in **Figure 6**. The dimensions of the antennas presented in this chapter are given in **Table 2**.

**Figure 6.** *S11 of the optimized dual-polarized antenna with metallic strips and CSRR on human body.*



**Table 2.**

*Electrical performance comparison between wearable antennas without and with CSRR.*

The sensors electrical parameters, presented in this chapter, on and near the human body were evaluated, see [2–7], by employing RF CAD software [42, 43]. The theoretical and equations used to design the sensors presented in this chapter are given in previous publications, see [2–7]. The energy harvesting module is connected to the antenna network feed line, as presented in **Figure 3**. The energy harvesting module can charge the battery when the switch is connected to the harvesting unit. Electromagnetic AC power is converted to DC power by employing a rectifying diode. The rectifier may be a half-wave rectifier or a full-wave rectifier. As shown in **Figure 3**, the harvesting module has an antenna, a rectifying circuit, and may recharge the device battery.

## **4. Wearable self-powered active sensor**

A receiving self-powered active sensor is presented in **Figure 7**. The energy harvesting module acts as a dual-mode electromagnetic harvesting module. A switch may connect the LNA to the energy harvesting module. The energy harvesting module charges the battery. The Low Noise Amplifier is matched to the receiving antenna via a matching network. The LNA TAV541 is a linear PHMET amplifier. At 2 GHz, the amplifier has 0.45 dB Noise Figure and 18.5 dB gain. The LNA P1dB, at 2 GHz, is 19 dBm at the output port. The LNA specifications are listed in **Table 3**. A DC bias network supplies the required voltages to the amplifiers. The Low Noise Amplifier is matched to the receiver via an output-matching network. The sensor dimensions are around 21.551.9 cm. Gain and reflection coefficient of the metamaterial sensor is presented in **Figure 8**. The receiving active sensor gain as presented in **Figure 9** is 12 3 dB, and the noise figure is better than 1 dB, for frequencies from 0.1GHz to 1GHz. The active metamaterial antenna was evaluated with Triquint LNA TQP3M9028. The amplifier specifications are given in **Table 3**. The active antenna gain with TQP3M9028 LNA is 11.1 2.5 dB from 0.15 to 0.9GHz, as presented in **Figure 10**. The sensor noise figure, with TQP3M9028 LNA, for frequencies from 0.15GHz to 1GHz is better than 1.9 dB. The measured performance of the sensors with different LNAs is listed in **Table 4**. The active antennas with LNA TAV541 has better noise figure and higher gain. The sensor with LNA TQP3M9028 has a better 1dBc compression point and gain flatness.

## **5. Wearable self-powered active transmitting antenna**

A transmitting self-powered active sensor is presented in **Figure 11**. The energy harvesting module acts as a dual-mode electromagnetic harvesting module.

*Green Wearable Sensors for Medical, Energy Harvesting, Communication, and IoT Systems DOI: http://dx.doi.org/10.5772/intechopen.112352*

#### **Figure 7.**

*Dual polarized receiving sensor with CSRR and with energy harvesting unit.*

**Figure 8.** *S11 and gain of the dual-polarized antenna with CSRR and matching network.*


#### **Table 3.**

*Comparison of the specification of the S-band low noise amplifiers.*

**Figure 9.** *Active receiving dual polarized receiving sensor gain, with LNA.*

**Figure 10.** *Active receiving dual polarized receiving sensor gain, with TQP3M9028 LNA.*

*Green Wearable Sensors for Medical, Energy Harvesting, Communication, and IoT Systems DOI: http://dx.doi.org/10.5772/intechopen.112352*


#### **Table 4.**

*Comparison of the sensors measured performance with different LNA Amplifiers.*

#### **Figure 11.**

*Dual polarized transmitting sensor with CSRR and with energy harvesting unit.*

The harvesting module can be part of a healthcare, IOT, and cellular phone. A switch may connect the transmitter battery to the energy harvesting module. The energy harvesting module charges the battery. Two power amplifiers were used to develop the metamaterial active sensor. The first amplifier is an MMIC GaAs MESFET VNA25, the second amplifier is an MMIC GaAs PHEMT HMC459. The amplifier specification is listed in **Table 5**. A DC bias network supplies the required voltages to the amplifiers. The sensor dimensions are around 21.551.9 cm. The active transmitting sensor


#### **Table 5.**

*Electrical Specification of the HPA Amplifiers.*

**Figure 12.** *Radiation pattern and gain of the dual-polarized antenna with metallic strips and CSRR.*

VSWR, computed and measured, is better than 3:1 for frequencies from 0.25 to 0.45GHz. The computed and measured antenna gain are around 5.8 dBi, as presented in **Figure 12**. The active computed and measured antenna gain with HPA VNA25 is 13 3 dB 1 for frequencies from 0.1 to 0.8 GHz. The transmitting sensor S21 parameter is shown in **Figure 13**. The active computed and measured antenna gain with the HMC459 HPA is 12 4 dB for frequencies from 0.1 to 1 GHz, as shown in **Figure 14**. The transmitting sensor output power is around 19.5 dBm. The measured electrical performance of the sensors with the HPAs is listed in **Table 6**. The active antenna with VNA25 HPA has better gain flatness, higher gain, and lower DC power consumption. The transmitting antenna with HMC459 HPA has higher input and output power, and higher 1 dBC compression point. The HPA HMC459 has wider bandwidth from 1 to 18GHz. Photos of the metamaterial sensors, with CSSR and metallic strips, are shown in **Figure 15**.

*Green Wearable Sensors for Medical, Energy Harvesting, Communication, and IoT Systems DOI: http://dx.doi.org/10.5772/intechopen.112352*

#### **Figure 13.**

*Active transmitting dual polarized sensor gain, with HPA VNA25.*

#### **Figure 14.**

*Active transmitting dual polarized sensor gain, with HPA HMC459.*


#### **Table 6.**

*Comparison of the sensors performance with different HPA amplifiers.*

**Figure 15.** *Photos of the metamaterial antenna. a. Feed layer b. antenna with CSSRs c. CSSR.*
