Based on a substrate integrated lens (SIL), a compact line source generator (LSG) for feeding continuous transverse stub (CTS) arrays with linear-polarized (LP) beam scanning and dual-polarized (DP) operations is presented in this paper. The SIL consists of metamaterial cells with different sizes being arranged as concentric annulus and is printed on the center surface of two substrate layers. The SIL can convert the cylindrical wave generated by the feed probe of SIW-horn to the planar wave for feeding the CTS array. This rotationally symmetric SIL can be used conveniently to design LSG for feeding CTS arrays with the continuous beam scanning and DP operations, which has been verified by the fabrications and measurements. By simply rotating the SIW-horn along the edge of SIL, the 10-element LP-CTS array obtains a measured beam scanning range of ±35° with the highest gain of 20.6 dBi. By setting two orthogonal SIW-horns at the edge of the proposed SIL, the nine-element DP-CTS array with orthogonal radiation stubs is excited. The DP array obtains the gain of 20.3 dBi at the center frequency with the isolation of 28 dB and the cross-polarization level <−25 dB.

In this paper, an antenna with 8 GHz (7–15 GHz) bandwidth is designed, simulated, fabricated, and measured. Commonly, for the effective use of electromagnetic sources, mode converters are used to transform donut-shaped patterns to directive patterns. This paper introduces a novel antenna called the pattern director antenna (PDA) that solves most problems associated with the azimuthally symmetric output modes of high-power microwave sources. The PDA accepts directly (without the need for mode conversion) an azimuthally symmetric generated mode of an electromagnetic source and converts it to radiate a directive pattern. For the proof of concept and validation of the design by simulations, the 3D printing technology [using polylactic acid (PLA)] is used to fabricate the PDA and measure its radiation patterns and return loss. The selected material is cheap and also environmentally friendly. The antenna was coated with aluminum to become a conductor. The gain is from 16.8 to 21.8 dB in the frequency range. The S11, main lobe deviation (MLD), and sidelobe level (SLL) are less than −15 dB, 2°, and −7 dB, in all frequency range, respectively. The simulation results are in good agreement with the measurement.

In this paper, the design of frequency reconfigurable planar antenna by incorporation of metasurface superstrate (FRPA-MSS) is presented using an artificial neural network. The dual-layer radiating structure is created on a 1.524 mm thick Rogers RO4350B substrate board (εr = 3.48, tan δ = 0.0037). The candidate antenna is designed and analyzed using a high-frequency structure simulator (HFSS) tool. The transfer matrix method is employed for the successful retrieval of electromagnetic properties of the metamaterial. Frequency reconfiguration is achieved by placing the metasurface superstrate onto the rectangular patch antenna. A simplified ANN approach has been employed for the design of metasurface incorporated proposed antenna. Presented prototypes are characterized through experimental measurements. It is found from the practical observations that the proposed antenna effectively reconfigures the tuning range from 5.03 to 6.13 GHz. Moreover, the presented antenna operates efficiently with agreeable gain, good impedance matching, and stable pattern characteristics across the entire operational bandwidth. The experimental results obtained validate the simulated performance.

In this paper, a dual-band 8 × 8 multi-input multi-output (MIMO) array antenna operating in 3.5 GHz band (3400–3600 MHz) and 5.5 GHz band (5150–5925 MHz) for 5G mobile handset is presented. The proposed hybrid antenna includes a comb-shaped monopole and an L-shaped open slot antenna which are symmetrically located on the inner surface of the side-edge frame of smartphone. Pattern diversity is achieved that can mitigate envelope correlation coefficients (ECCs) and improve the MIMO system performances. The prototype of proposed dual-band eight-element MIMO antenna is fabricated and experimentally measured. The results show that isolation <−10 and <−15 dB, respectively in the lower band and high band without any additional decoupling element are achieved and the desired bands are satisfied under the condition of −6 dB impedance matching. Moreover, the essential parameters for evaluation of the MIMO system performance such as the ECC, mean effective gain (MEG), and ergodic channel capacity are calculated. Furthermore, the influence of user's hand on the radiation characteristics of proposed MIMO antenna are also investigated and discussed. Based on the result, the proposed MIMO antenna is a good candidate for use in future 5G applications.

This article presents a highly miniaturized dual-band electrically small antenna (ESA) for on-demand 3.6 and 5.8 GHz wireless applications. A partial rectangle-shaped structure is printed on the back face of the dielectric material, forming the antenna's ground (GND) plane. The radiating structure of the antenna consists of a C-shaped structure and a U-shaped ring connected to it, which is printed on the dielectric material's front face. The overall dimensions of the designed antenna are 0.160λo × 0.160λo × 0.02λo at the lowest operating frequency. The proposed antenna has a ka value of 0.56 at the lowest operating frequency, which is 3.59 GHz. Thus, the proposed antenna is considered as electrically small. The characteristic mode analysis is adopted to provide a clear understanding of the antenna's resonance behavior. The antenna has been fabricated and the simulation results were validated through measurements. Good agreement between simulated and measured results was obtained. Dual-band operation at 3.62 and 5.75 GHz was achieved, according to the measured reflection coefficient. The proposed antenna offers an adequate performance in terms of gain and efficiency, based on simulation and measurement results. Because of these characteristics, the antenna is well-suited to new wireless applications.

In this work, a printed ultra-wideband (UWB) antenna has been proposed exhibiting band notch characteristics. The proposed design covers the entire UWB band except for the 3.5 GHz band providing the band notch for the WiMAX band. This design consists of two-quarter elliptical patches placed symmetrically over the FR4 substrate. The elliptical shape of the patch is responsible for the UWB band achieved. The slot has been created on the optimized patch area to achieve the desired characteristics providing a notch for the WiMAX band. The slot in the patch is so perfectly designed that it gives the patch a perfect shape of butterfly wings. After designing, the proposed antenna was simulated and then fabricated. The fabricated and simulated results are in close agreement with each other which shows, the proposed UWB antenna is good enough for biomedical applications.

A circularly polarized ring cylindrical dielectric resonator antenna (ring-CDRA) of wideband impedance bandwidth is presented in this article. The proposed ring CDRA consist of an inverted rectangular (tilted rectangular) shaped aperture and inverted L-shaped slotted microstrip feed line. The tilted rectangular shaped aperture and inverted L-shaped microstrip feed line generate two-hybrid mode HEM11δ and HEM12δ while ring CDRA and slotted microstrip feed line are used for the enhancement of impedance bandwidth. The proposed ring CDRA is resonating between 6.08 and 12.2 GHz with 66.95% (6120 MHz) impedance bandwidth. The axial ratio (AR) bandwidth of 6.99% (780 MHz) is obtained between 10.76 and 11.54 GHz with a minimum AR value of 0.2 dB at a frequency of 11 GHz. The proposed geometry of ring CDRA has been validated with measurement performed by VNA and anechoic chamber. The operating range of the proposed radiator is useful for different applications in X-band.

This paper presents a dual-band 1 × 4 antipodal Vivaldi antenna (AVA) array with high gain to operate over a dual-frequency band that covers the 5G frequency spectrum. The gain is enhanced by employing a dielectric lens (DL). The AVA array consists of four radiating patch elements, corrugations, DL, and array feeding network on the top side. The bottom side contains four radiating patches which are the mirror images of top radiating patches. The designed AVA contains 1 × 4 array antenna elements with a DL that is operating in the ranges of 24.59–24.98 and 27.06–29 GHz. The dimensions of the designed antenna are 97.2 mm × 71.2 mm × 0.8 mm. For the improvement in gain and impedance matching at the dual-band frequency, corrugation and feeding network techniques are used. The gain obtained is about 8–12 dBi. AVA array is tested after fabrication and the measured results are reliable with the simulation results.

Electromagnetic inverse-scattering problems (ISPs) are concerned with determining the properties of an unknown object using measured scattered fields. ISPs are often highly nonlinear, causing the problem to be very difficult to address. In addition, the reconstruction images of different optimization methods are distorted which leads to inaccurate reconstruction results. To alleviate these issues, we propose a new linear model solution of generative adversarial network-based (LM-GAN) inspired by generative adversarial networks (GAN). Two sub-networks are trained alternately in the adversarial framework. A linear deep iterative network as a generative network captures the spatial distribution of the data, and a discriminative network estimates the probability of a sample from the training data. Numerical results validate that LM-GAN has admirable fidelity and accuracy when reconstructing complex scatterers.

Low probability of intercept (LPI) radars utilize specially designed waveforms for intra-pulse modulation and hence LPI radars cannot be easily intercepted by passive receivers. The waveforms include linear frequency modulation, nonlinear frequency modulation, polyphase, and polytime codes. The advantages of LPI radar are wide bandwidth, frequency variability, low power, and the ability to hide their emissions. On the other hand, the main purpose of intercept receiver is to classify and estimate the parameters of the waveforms even when the signals are contaminated with noise. Precise measurement of the parameters will provide necessary information about a threat to the radar so that the electronic attack or electronic warfare support system could take instantaneous counter action against the enemy. In this work, noisy polyphase and polytime coded waveforms are analyzed using cyclostationary (CS) algorithm. To improve the signal quality, the noisy signal is pre-processed using two types of denoising filters. The denoised signal is analyzed using CS techniques and the coefficients of spectral correlation density are computed. With this method, modulation parameters of nine types of waveforms up to −12 dB signal-to-noise ratio with an accuracy of better than 95% are extracted. When compared with literature values, it is found that the results are superior.

This review paper explores the potential use of the planar miniaturized antenna for wireless capsule endoscopy application: one of the promising fields in the current era. The paper highlights the design strategy, various optimization techniques with respect to system realization, material compatibility issues and finally the mandatory EM radiation effect analysis for the said application. It compares amongst various currently reported structures in context with different performance metrics. Inherent challenges of this emerging field of bio-medical engineering have also been detailed here along with futuristic approaches for enhancing the throughput.

All textile integrated dual-band monopole antenna with an artificial magnetic conductor (AMC) is proposed. The proposed design operates at 2.4 and 5.8 GHz for wearable medical applications to monitor the heartbeat. A flexible and low-profile E- shaped CPW dual-band textile antenna is integrated with a 4 × 4 dual-band textile AMC reflector to enhance the gain and specific absorption rate (SAR). The SAR is reduced by nearly 95% at both 1 and 10 g. The design was measured on the body with a 2 mm separation. The simulated and measured results appear in high agreement in the case of with and without AMC array integration. The measurement was performed in the indoor environment and in an anechoic chamber to validate the design based on reflection coefficient and radiation pattern measurements.

Propagation modeling of small/big pebbles and air-dry/wet sand environments for wireless sensor networks has not been extensively studied in the 5G frequency band. This study is necessary for the proper coverage planning and efficient operation of wireless sensors in various applications such as monitoring summer sporting activities, and environmental/ground surveillance on coastal pebble/sand environments, or tracking pebble mobility and including the rescue of the flood-type avalanche in Gravel-Bed Rivers. In this study, empirical path loss models are proposed for wireless sensor networks in pebble/sand environments at two discrete frequencies, namely 3.5 and 4.2 GHz. The theoretical models and proposed models are compared to indicate the accuracy of proposed models in predicting the path loss in these environments. Additionally, R-squared and RMSE values of eight different generated models are calculated in the range of 0.931–0.877 and 2.284–2.837, respectively. These comparisons indicate that empirical model parameters have a significant effect on the path loss model.