Hyperthermia (HT) is an adjuvant treatment method aimed at elevating the temperature in target tissues while minimizing the impact on surrounding non-target tissues. Microwave hyperthermia is particularly notable due to the strong interactions between microwaves and biological tissues. The design of a microwave hyperthermia applicator is a critical component of the treatment system, making various antenna designs and arrays a focal point of research in this field. The operating parameters of the designed antenna significantly influence metrics that indicate the efficiency of hyperthermia treatment, such as target-to-body Specific Absorption Rate (SAR) and temperature ratios. In this study, a two-layer hyperthermia applicator utilizing eight microstrip dipole-type antennas with broadside radiation characteristics was proposed. Hyperthermia performance across four different target regions of tissue at 20 frequencies was analyzed. Although this study implemented a simple fat cylinder as a body part, the target-to-body Specific Absorption Rate (SAR) ratios showed that for each target position, a different frequency provided the best performance. Adding the complexity of a real-life problem of an inhomogeneous body with complex geometries, using broadband antennas to perform hyperthermia on different frequencies will provide a significant advantage for focused hyperthermia. The results demonstrate that different frequencies yield varying hyperthermia performance depending on the target position, with mid-range frequencies (2800-3200 MHz) generally providing better SAR distribution and thermal efficiency. Notably, 3000 MHz exhibited the best balance between targeted heating and minimal impact on healthy tissues, while higher frequencies, such as 4000 MHz, resulted in suboptimal performance due to lower realized gain.

An antenna array with dual-functionality - electromagnetic radiation and thermal cooling - is proposed. An iterative array design procedure is developed to improve cooling, mutual coupling, side lobe levels, and gain levels in dual-functional antenna arrays with adaptive beam steering. Heatsink-attached patch elements are combined with complementary split ring resonator (CSRR) structures in between the elements, resulting in a novel modular heatsink antenna array. Based on the proposed design, the beam scanning performances of four-element and eight-element linear arrays at 26 GHz are studied. A conventional shorted patch antenna array is used for benchmarking. Through thermal and electromagnetic simulations, it is demonstrated that the proposed antenna array decreases the maximal array temperature by more than 40°C as compared to the benchmark. Moreover, the new design resolves the pattern performance degradation problems in heatsink arrays, while approaching to the electromagnetic performance of the benchmarked array.

Both thermal and electromagnetic performance of substrate-integrated waveguide (SIW) and microstrip line-fed shaped-beam arrays with slot and patch radiating elements are conducted. Three array types operating at 26 GHz band, namely SIW slot array, SIW array with patches, and proximity coupled patch array, are considered. The array performances regarding shaped radiation pattern stability with frequency and maximal temperature at the power amplifier chips are discussed. The study highlights intriguing trade-offs between radiation pattern performance and cooling ability in phased arrays.

The present study proposes a dual-polarized bandwidth-enhanced filtering specialized dipole antenna design for 5G by employing a wide printed dipole, filtering resonators, a reflector surface, and specially designed balun structures. Such a configuration is commonly deployed in conventional base stations. To increase the antenna impedance and radiation bandwidth, a specifically designed, wide-printed flared dipole antenna structure is used as the main radiator element. Transmission zeros are introduced at both pass band edges to create a filtering response by engaging parasitic elements. The parasitic element for the higher frequency edge of the filtering is placed close to the maximum amount of the induced current on the radiator at the operating frequency, whereas the parasitic element for the lower frequency edge of the filtering is located close to the perpendicularly polarized structure. The antenna aims to create radiation nulls at the impedance bandwidth limits; therefore, the parasitic arcs are used to create surface currents that cancel the broadside radiation at the limits of the impedance bandwidth. The study illustrates a complete analysis of the broadband printed patch antenna having a filtering effect by parametric investigations on the dimensions and resulting physical phenomenon in detail. To demonstrate the approach, a prototype of the antenna is fabricated and measured. According to the measurement results, the antenna performs 76% impedance bandwidth between 2.49 GHz and 5.59 GHz with |S11| and |S22| < -10 dB by providing exceptional isolation values of |S21| < -20 dB in entire operating band. The fabricated antenna has a stable radiation beamwidth with less than ± 50 variation and the measured gain in the operating frequency is almost constant and equal to 8.2 dBi.

A novel electromagnetic-thermal codesign and optimization methodology is proposed for thermal management in active finned-heatsink antenna arrays. An innovative complementary split-ring resonator embedded dual-functional (i.e., heat-dissipating electromagnetic-isolation) wall is introduced. For concept demonstration, a two-element unit cell is designed at 26 GHz with the wall in between the antenna elements. It is shown via simulations that the proposed design decreases the junction temperature of the chip driving the elements by almost 40 $^{\circ }$C and 15 $^{\circ }$C as compared with the conventional and finned-heatsink antennas, respectively. Moreover, the port coupling level is reduced to below -25 dB near the operating frequency and a low-complexity beam- switching and nulling function is achieved.

In this study, a dual-band Quasi-Yagi reconfigurable binomial weighed phased array design is proposed for the unlicensed Wi-Fi and planned 5G band for European Zone. The analytical calculations, numerical simulations, and experimental analysis are done. The antenna array operates at 2.45 and 3.6 GHz. By analog beamforming and the binominal weighting, the antenna has three distinct main lobes for each corresponding phased configuration with reduced sidelobes. The simulations are done on the High-Frequency Structure Simulator (HFSS), and experimental measurements are carried out on the fabricated prototype. The numerical and experimental results are presented.