## 3 Proposed Antenna for On- and Off-Body Conditions  
As aforementioned, one of the techniques that degrade the SAR values and its negative effects on body is using a full ground in the antenna structure during the design procedure. However, using a full ground makes the working bandwidth work as a narrowband, since the ground length is much greater than \(\lambda/8\) mm. Therefore, the antenna structure should be improved in a way to widen the BW. To design the antenna, a conventional rectangular patch using the equations presented in [14; 20] is designed. The proposed antenna is fed by a coplanar waveguide (CPW)-fed rectangular slot and SIW transition. Then it is fed from behind through a SubMiniature version A (SMA) port and coaxial cable as depicted in Figure 1.  
The proposed antenna is the first design using the equation presented in [14; 20] and using the transmission technique. The feeding technique is changed to CPW and feeding is done from behind due to the concept of full ground. Feeding from behind is more profitable when using a full ground and wideband or UWB. The conventional rectangular slot uses CPW-fed feeding from behind. In addition, the materials used to design the antenna are flexible textile materials: denim (with a 1.7 dielectric constant and thickness of 0.7 mm) as substrate and ShieldIt conducting (0.17 mm) flexible material as the conductor and/or resonator. After obtaining results from the conventional antenna, some stopbands were noticed in the working BW, especially at the higher band above the centre frequency of the antenna. Therefore, the rectangular patch and the CPW ground's edges were curved to reduce the undesired surface waves and improve the stopbands at bands above 15 GHz and convert them to passbands. It also widens the BW at higher bands. The edge and the angle of chamfering are optimized in each step to obtain the best results. After checking the results obtained from chamfering the edges of the CPW ground and the rectangular patch, the antenna transition feeding from the ground coplanar waveguide (GCPW) to the SIW is started. This new transition using SIW for the feeding broadens the BW and the impedance matching results of the antenna at the lower bands below the centre frequency. Furthermore, the rectangular slot and latter arc slot act as a coupling slot, which leads to a smooth transition (Figure 1c) [45; 46]. The higher band above 15 GHz is achieved well and is within the working BW. However, the lower band below the centre frequency has yet to be reached. Two sets of shorting pins are located as EBGs to shift the whole BW to the lower band and increase the BW towards the lower band. In addition, these EBG pins are driving the current to the patch and distributing it to all parts of the antenna (Figure 1d). After expanding and widening the BW and meeting the UWB requirements, the remaining stopbands can be removed by loading the antenna with shorting pins and arc slots cut from each pin based on the surface current distribution at each associated frequency. These shorting pins are located at locations where the electric field is zero or surface current distribution is high. Thus, the electric field and surface current distributions should be considered in order to convert the stopband to a passband at each desired frequency. Moreover, the capacitive and conductive loading of the antenna using the sorting pins changes the flow of the surface current to increase the radiation efficiency of the antenna. In addition, utilizing the shorting pins and arc slots produces additional resonances at 3.8 and 5.7 GHz for both ISM and 5G applications, respectively. Figure 4 depicts the reflection coefficient result of the proposed antenna for both on-body and off-body conditions. Off-body means in free space. The off-body condition should be considered to see how much the results change between when the antenna is in free space  
and when it encounters the body. Air's dielectric constant is one, which is significantly different than those of breast, skin, and tumour tissue.