## 5 Applications of DRA
### Biomedical Applications  
The advantages of DRA also make it a suitable candidate for biomedical applications [99; 100; 101; 102; 103]. Various biomedical applications have different requirements in terms of data rate, transmitter power, and link distance in order to ensure that discriminative information is delivered within a satisfactory timeframe for the most serious situations. In [99], a new coil setup for dual-nuclei imaging has been proposed by combining an annular DR filled with a high permittivity material for phosphorous and a traveling-wave antenna for \({}^{1}\)H scout imaging and shimming. However, the DR has a lower sensitivity which is only half that of an equivalently sized birdcage on the phosphorous channel. A dual-polarized (DP) omnidirectional hemisphere DRA for a wireless capsule endoscope system (WCE) is proposed in [100]. The antenna was excited in TM\({}_{015}\) and TE\({}_{015}\) modes to radiate a DP wave by a feeding probe and four arc microstrip line, respectively. The omnidirectional DP wave are realized when the TM\({}_{015}\) and TE\({}_{015}\) modes are equal in amplitude and phase. The hemispherical shape of the DR is easy to be conformal with the end of the capsule. The proposed antenna has a gain between \(-13.5\) and \(-15\)dBi, with an impedance bandwidth from 2.4 to 2.48 GHz. However, the measured reflection coefficient is slightly worse than the simulated one, mainly owing to a machining error. A rectangular DRA operating at 2.45 GHz is proposed in [101] as an implantable antenna with no metallic losses, bio-compatibility, and a varied implant depth performance. The DRA are made up of biocompatible ceramics with \(\varepsilon_{r}\) = 80. The implant DRA is mounted on a PVC substrate and fed by a coplanar waveguide. It is concluded that the reflection coefficient degraded as the depth of the implant antenna increases but still has an acceptable performance for the defined 'depth window'. Moreover, the proposed antenna has acceptable radiation limits for the specific absorption rate (SAR) value. In [102], a singly-fed CP wearable DRA for off-body communications has been proposed. The antenna has been excited using a H-shaped conformal metal strip, as shown in Figure 25. This antenna radiates in circular polarization with an impedance bandwidth of 20.7% from 6.95 to 8.68 GHz. Moreover, this antenna recorded a low SAR value. However, the lossy and high dielectric constant characteristics of human body may affect the frequency and reduce the efficiency of the antenna. Further, the antenna designer should be aware of the antenna's impact on the human body. DRA can also be used for tumor detection [103]. The proposed antenna consists of a cylindrical DR fed by a microstrip line and operated from 2.2 to 2.6 GHz. Circular polarization is realized by aperture coupling using the cross slot. In this work, the breast phantom is placed between two cylindrical CP DRAs for obtaining the simulation results, as shown in Figure 26b. The simulation was carried out for various tumor sizes from 1 to 8 mm in order to test the sensitivity of the system. As the size of the tumor increases, the overall permittivity of the tissue increases and disturbs the phase of orthogonal components of currents; therefore, AR increases from 3.5 dB to 4.8 dB. Table 10 summarizes a comparison between various DRAs for biomedical applications.