Abstract Sub-terahertz (THz) technology is expected to deliver exceptional data rates for future sixth generation wireless communication systems especially for intelligent communication among devices falling under the Internet of Things (IoT) category. Moving from current 5G millimeter wave (mmW) technology towards THz spectrum will eventually provide unprecedented solutions that will guarantee higher transmission rates and channel capacity for any wireless communication system. With various electronic and wireless components working together to fulfill this promise, high gain antennas having compact profile is one such technology that will aid in achieving sub-THz communication while offering low path and power losses with reliable and fast data transfers. In this context, this work proposes a novel deformed patch antenna operating in the sub-THz spectrum i.e. at 300 GHz band. The proposed antenna is fed via a microstrip line following the proximity coupled feeding technique. Utilizing this technique provides a wide impedance bandwidth with a broadside radiation pattern having minimum side lobe levels of around −12 dB and a directivity of 10–15 dBi for the single and array elements respectively. The proposed design has a small footprint of 1.5 × 1.5 × 0.06 mm3for the single element while the array element has dimensions of 6 × 5 × 0.06 mm3. Both the designs have been simulated in Computer Simulation Technology-Microwave Studio (CST-MWS) and the results verified via high-frequency structure simulator (HFSS) simulator. The results confirm the viability of the proposed designs to be potential candidates for future sixth generation and IoT based applications.

Abstract A compact rat-race ring coupler with modified T type capacitor loading is presented in this paper. Two variable parameters are added to the conventional T type capacitor loading structure, and adjusting these two parameters can control the position and width of harmonic suppression stop-band. The new coupler effective reduces the occupied area to 14.1% of the conventional one. The design is validated both by simulation and measurement.

Abstract Radio Frequency (RF) plays a vital role nowadays in harvesting RF Energy from the ambient source. An antenna is required to harvest RF energy and solve the spectrum underutilization problem for the Cognitive Radio (CR) system. This paper presents an optimization of a reconfigurable Coplanar Waveguide Antenna (CPW), which harvests RF energy and is also used for sensing and communication purposes. The performance metrics of the proposed antenna are gain, radiation efficiency, front-back ratio (FBR) and group delay. First, the optimized CPW antenna (sensing antenna) is designed and fabricated in the FR4 substrate for the wideband frequency range of (0.25–3 GHz) with the fractional bandwidth percentage of 175%. The gain of the proposed optimized CPW antenna for different frequency band is: DTV band (UHF-0.47 GHz)-3.327 dBi, GSM 900-2.39 dBi, GSM 1800-3.42 dBi, 3G-3.227 dBi, and Wi-Fi-3.21 dBi. The average gain of the optimized CPW antenna for the frequency range of (0.25–3 GHz) is 3.11 dBi, and the maximum radiation efficiency of the antenna is 91.05%. Next, the optimized CPW antenna is reconfigurable, and it can be reconfigured for a specific frequency band using a PIN diode switch. When the PIN diode switch is in ON state, the antenna acts as a reconfigurable antenna (communicating antenna), and it is operated for the specific frequency band of (0.47 GHz-DTV [UHF] band), (0.9, 1.8, and 2.1 GHz-mobile bands), and (2.4 GHz-Wi-Fi bands). The maximum gain of the optimized frequency reconfigurable CPW antenna is 3.61 dBi, and the radiation efficiency is 92.5%. In the OFF state, the antenna acts as a sensing antenna, and it operates at a wideband frequency range of (0.25–3 GHz). Finally, the prototype of a four-stage Villard voltage multiplier RF-dc conversion circuit using an adjustable impedance matching network is proposed for powering the cognitive radio applications.

Abstract In this paper, an efficient high-frequency method combining physical optics and shooting and bouncing rays is proposed to calculate the electromagnetic near-field scattering from the electrically large target (such as ship) in the near zone. In order to solve the mono-static and bi-static scattering problems, the local expansion technique based on the facets of target is presented to account for the near-field scattering, which has a singularity-free characteristic. And then the near-field contour-integral representation is introduced by refining the formulations in traditional far-field calculation to reduce the computational complexity. Therefore, this method is more straightforward to deal with the near-field scattering problem. Finally, some analyses on the near-field scattering characteristics and Doppler spectra of a surveillance ship in near zone are investigated by using the proposed method.

Abstract A Triple-band Multiple-Input-Multiple-Output (MIMO) antenna for 5G mobile terminal applications is proposed in this paper. The design comprises four-port/two resonators, each having two concentric circular slot ring radiators etched on a ground plane of size 50 mm × ${\times}$ 50 mm. The antenna is fed by perpendicularly arranged 50 Ω microstrip line feeds on the top layer. Decoupling techniques were used to suppress mutual coupling between the two resonators. The perpendicular arrangement of the feed lines and port reduces mutual coupling between the two ports and increases isolation. The antenna operates in multiple bands: 3.35–3.69 GHz, 24–28 GHz, and 37–40 GHz frequency range with central frequencies at 3.5 GHz, 26 GHz, and 38 GHz, respectively allocated for 5G. The antenna provides a gain of 2.7–7.8 dB and a radiation efficiency of 0.49–0.85 in the operating bands. Diversity performance is studied in terms of the Envelop Correlation Coefficient (ECC), Diversity Gain (DG), and Total Active Reflection Coefficient (TARC) were found to be less than 0.01, greater than 9.99 dB, and less than −10 dB respectively. The proposed antenna offers good S-parameters, voltage standing wave ratio (VSWR), TARC, radiation pattern, high gain, and low ECC. The antenna was fabricated and tested. The measured results and simulated results are in good agreement. It possesses sufficient potential for 5G mobile terminal and smart wearable applications.

Abstract In this paper, a methodical approach for the in-situ monitoring of the mechanical wear of electrical conductors is presented. The state of life can be assessed by means of the characteristic attenuation of an applied high-frequency alternating current. The advantages of this approach include its non-destructive nature and the applicability to installed and otherwise inaccessible conductors.

Abstract A multi spiral split ring resonator based sensor is proposed for the characterization of the dielectric properties of a water ethanol mixture. The use of a narrowed microstrip line to excite the multi spiral resonator allows enhancement of excitation current and increase the sensitivity of the sensing area. Good agreement will be presented between theoretical and measured electrical parameters of the resonator in a wide frequency range from 2 to 5 GHz. The proposed sensor shows high sensitivity, miniature size, and affordable cost and above all laboratory-on-chip compatibility important for a large-scale production.

Abstract In this paper a Quad-band diversity antenna with a small size of 48 × 28 × 0.8 mm3 printed on FR4 substrate is presented that consists of two same pentagonal-shaped patch elements. Four arc-shaped slots in the radiating elements are introduced to obtain the quad-band operation with good return loss. The antenna is designed for covering 5.91 GHz in IEEE 802.11 b/g/n standards, 7.40 GHz in C-Band, 9.18 and 10.72 GHz in X-Band. To achieve the lowest coupling between two elements, three structures for embedding elements are investigated. The prototype is fabricated, and measured results are in good agreement with simulated results. The final antenna accomplishes a weak mutual coupling below −29.2 dB in the all operational bands. Radiation characteristics, radiation efficiency and diversity performance such as diversity gain and envelope correlation coefficient of the final structure, are presented.

Abstract Smartdielectric resonator antenna (DRA) having beam control mechanism is anew area to be explored by antenna researchers. Proposed new geometry DRA has low loss, design flexibility, high efficiency, compact size and desired radiated beam control. Developing beam control in new geometry DRAs is investigated for the first time in this letter. Unique technique for beam control and beam width control is proposed using pit top and mount top DRA. Gain is controlled from 5.0 to 9.98 dBi and beam is controlled from ±30° to ±70° in broadside radiation pattern. U shape pit DRA has maximum directive gain of 9.98 dBi and efficiency 98% at 5.8 GHz frequency. Measured and simulated results of radiation pattern and reflection coefficient are found to be in close proximity. Hardware of U shape pit top DRA, mount top DRA, left side arc top DRA, right side arc shape top DRA is developed and investigated. Mobile and cellular communication network need wide coverage, hence large beam width is required. Narrowing of beam width at higher order mode is also achieved.

Abstract In this paper, a new Wilkinson Power Divider ‎‎(WPD) using open and short stubs is proposed. ‎Open and short stubs are utilized instead of 1/4 wave transmission lines in initial ‎structure to achieve harmonics suppression. The proposed WPD is designed for ‎operational frequency of 0.9 GHz and creates 3 transmission ‎zeros at 1.8 GHz, 2.7 GHz and 3.6 GHz, for suppressing second, third and fourth harmonics. The proposed WPD has been fabricated and the ‎measurement results are in good accordance with simulation results. The designed ‎WPD has a 22 % fractional bandwidth with 0.1 dB insertion loss.‎