Fourth generation mobiles require multi-standard operating handsets with small physical size as well as increasing demand for higher data rates. Compact multi-band printed inverted-F antennas (IFA) for available wireless communications are proposed in this paper. New design of printed IFA based on uniplanar compact electromagnetic band-gap (EBG) structure concept is proposed. A printed-IFA with L-load shaped over an artificial ground plane is designed as the main antenna to cover most wireless applications such as GSM, LTE, UMTS, Bluetooth, Wimax, and WLAN. The multi-band is created by means of an EBG structure that is used as a ground plane. Different shapes of uniplanar EBG such as ring, split ring resonator, and spiral rather than mushroom-like structure are investigated. The proposed antenna is built on the uniplanar EBG ground plane with size of 35 × 45 mm2, which is suitable for most of the mobile devices.

This paper reports the test results of a small-scale prototype that implements a digitally beam-formed phased antenna array in the E-band. A four-channel dual-conversion receive RF module for 71–76 GHz frequency band has been developed and integrated with a linear end-fire antenna array. Wideband frequency-domain angle-of-arrival estimation and beam-forming algorithms were developed and implemented using Orthogonal Frequency Division Multiplexing (OFDM) with Quadrature Phase-Shift Keying (QPSK) at 1 Gbps. Measured performance is very close to the simulated results and experimental data for an analogue-beam-formed array. This work is a stepping stone toward practical realization of larger hybrid arrays in the E-band.

A triple-frequency operated concentric annular ring microstrip antenna which is single fed is presented. The proposed antenna with three concentric annular rings and two symmetrical notches on its outer ring and having a cross slot in its ground surface shows triple band at resonance frequency 1.22760, 1.57542, and 2.18 GHz, respectively. At the first two bands (GPS L2 and GPS L1), circular polarization characteristic is observed and the third band observes linear polarization finding its application in Universal Mobile Telecommunication System (UMTS). The complete dimension of the antenna designed and fabricated is only 51.6 × 51.6 × 1.6 mm3. Experimental results depict the proposed antenna gain of 3.31, 3.55, and 3.50 dBi in three bands, respectively, and closely matches with the theoretical results.

A small and compact ultra-wideband (UWB) aperture antenna with extended band-notched design is proposed. The antenna is composed of a rectangular aperture on ground plane of a printed circuit board and a fork-like exciting stub. The presented co-planar wave guide triple-fed antenna is easy to be applied with RF and microwave circuitry for low manufacturing cost. The antenna is successfully designed, implemented, and measured. A compact aperture area of 12.5 × 23 mm2 is acquired with promising performances, including broadband matched impedance and stable radiation patterns. The correlation between the mode-based field distributions and radiation patterns is discussed. Extended from the proposed antenna, one advanced band-notched (5–6 GHz) designs are also presented as a desirable feature for UWB applications.

This paper details the design and development of a planar switched beam network using 4 × 4 Butler matrix (BM) over a thin and flexible type biocompatible substrate. Four mils thick liquid crystal polymer (LCP) is used as a substrate here (ϵr = 2.92, tanδ = 0.002). The proposed design is centered at 28 GHz, targeting commercial millimeter-wave applications. Floral-shaped antenna with defective ground structures has been implemented as basic radiating elements. The whole structure is based on microstrip line configuration. The architecture occupies an area of 23.85 × 19.20 mm2 over the LCP substrate. Individual components of the BM are detailed here, followed by a system analysis of the whole integrated structure. The present work also covers the electrical equivalent circuit modeling of the whole beam-forming network. The fabricated prototype offers better than 18 dB return losses at each input port for the desired frequency band with 6 dBi (max.) peak gain and 500 MHz bandwidth around the center frequency. Port-to-port isolation of better than 15 dB is achieved with this topology. Experimental and simulated results are in good agreement in all aspects. A comparative study is also chalked out to highlight the significance of the current research work with respect to alike earlier reported structures.

Structures of tunneling nanotubes (TNTs) of the circular cross-section of 50 and 200 nm and length up to 1 mm form a communication system between cells. While transport of material such as endocytic vesicles, mitochondria, proteins, cytoplasmic molecules, etc., is experimentally proven, a possible transfer of electric and electromagnetic energy across TNTs corresponding to electrotechnical processes of excitation, propagation, and amplification in cavity systems is yet in a beginning stage of research. The ideas presented in this paper are based on technical mechanisms applied to submicroscopic systems. Main features of corrugated periodic structures, electromagnetic circular waveguides, the Manley–Rowe amplification, the Fröhlich non-linear interaction of coherent electric polar vibrations, and description of cut-off frequency propagating limits in the waveguide and cavities and along periodic structures are discussed. We suggest that cell-to-cell connection with TNTs may form a unified coherent cavity system which enables simultaneity and mutual cooperation in multicellular organisms.

This paper presents the design fabrication and measurement of a nanogap radio frequency microelectromechanical system (RF MEMS) metal-contact switch. The prosed device generates a relatively high contact force with a low actuation voltage using a dielectric layer between the actuation electrode and the moveable beam. The actuation voltage is decreased with good reliability of the device by scaling down the gap. Beam geometry optimization allowed reaching 126 micronewtons contact force with only 10 V bias voltage. The fabricated miniature switch (80 × 50 × 0.95 µm) has indeed a pull-down voltage of 6 V and a contact resistance <2 Ω with 10 V bias applied. By measuring the S-parameters, the up-state capacitance has been fitted to 22 fF. The remarkable figure-of-merit Ron × Cup = 44 fs reflects the good performance of the device. A cycling test showed the device operated for 90 min without any charging problem noted.

Coupled-mode theory is applied to obtain an analytic form of scattering parameters for a class of transmission line metamaterials with antisymmetric split-rings. The same structure is modeled with equivalent circuit, which includes electric and magnetic coupling with the line and inter-resonator coupling. Modified even/odd analysis is used to obtain scattering parameters from the equivalent circuit. These two methods are shown to be equivalent in a narrow band, and their constants related. The obtained results are compared with full-wave simulations and measurements, and it is shown that both methods give accurate approximation in one octave frequency band. The derived analytic expressions are suitable for study of resonant phenomena, with potential practical applications for filters, phase shifters, delay lines, and sensors.

We present the design, fabrication, and measurement of a 2-way modified Wilkinson divider constructed in a coplanar geometry exhibiting ultra wideband isolation, transmission, and port matching in the millimeter-wave frequency range. The proposed divider replaces the lumped resistor in the conventional Wilkinson divider with two quarter-wave length transmission lines, a phase inverter, and two 2Z0 resistors. Except for the three ports that are coplanar waveguides (CPWs), the main body of the divider uses coplanar striplines (CPS). The phase inverter is realized using a simple airbridge-based crossover which is compatible with a modern monolithic microwave integrated circuit process. The divider has a ring-like configuration fabricated on a 620 µm thick semi-insulating GaAs wafer using electron beam lithography (EBL) technology. Three-dimensional (3D) full-wave electromagnetic simulations have been carried out to optimize the design and investigate the possible effect of fabrication tolerance on the performance of the crossover and the divider. Two dividers working at center frequencies of 25 and 80 GHz have been designed, fabricated, and tested. They all show consistent performance in terms of bandwidth, isolation, and port matching. Experimental and simulation results are in excellent agreement.

This paper presents a 31 GHz integrated power amplifier (PA) in 28 nm Fully Depleted Silicon-On-Insulator Complementary Metal Oxide Semiconductor (FD-SOI CMOS) technology and targeting SoC implementation for 5 G applications. Fine-grain wide range power control with more than 10 dB tuning range is enabled by body biasing feature while the design improves voltage standing wave ratio (VSWR) robustness, stability and reverse isolation by using optimized 90° hybrid couplers and capacitive neutralization on both stages. Maximum power gain of 32.6 dB, PAEmax of 25.5% and Psat of 17.9 dBm are measured while robustness to industrial temperature range and process spread is demonstrated. Temperature-induced performance variation compensation, as well as amplitude-to-phase modulation (AM-PM) optimization regarding output power back-off, are achieved through body-bias node. This PA exhibits an International Technology Roadmap for Semiconductors figure of merit (ITRS FOM) of 26 925, the highest reported around 30 GHz to authors' knowledge.

A new class of 3-dB impedance transforming directional couplers has been proposed in which the recently published coupled-line couplers, consisting of coupled-line sections having different electrical lengths, have been utilized. The main advantage of the proposed directional couplers is the possibility of obtaining high impedance transformation ratio, thus the known limiting condition of realizable impedance transformation in 3-dB couplers is overcome. Moreover, the proposed directional couplers feature significantly wider operational bandwidths. The theoretical analysis of the proposed impedance-transforming directional couplers has been shown and is fully supported by the measurements of the manufactured model operating in 0.5–1.5 GHz frequency range.

A novel reconfigurable circular microstrip G-slotted antenna having a circularly defected ground structure (DGS) capable of switching its resonance frequency for several microwave applications is presented in this paper. Reconfigurability of the proposed G-slot antenna is obtained by incorporating three PIN diodes. One diode is embedded in the patch and two diodes are integrated into the DGS structure at appropriate places in the slot to achieve four different wireless applications such as aeronautical radio navigation (4.3 GHz with gain 3.6 dB), satellite communication (3.78 GHz with gain 3.7 dB), mobile communication (4.55 GHz with gain 4.0 dB), and WiMAX (3.35 GHz with gain 3.3 dB). These four bands are achieved depending on the different biasing conditions of the three PIN switches used. Antenna performance has been analyzed in ANSYS Electronics Desktop 2018.2 software. The equivalent circuit component of the switching element (PIN diode) has been considered and designed during the simulation. The creative structure lies in the way that it exhibits higher gain with compact size than the previously reported similar antenna. A prototype of the proposed patch antenna has been fabricated on a Roger substrate and its testing and measurement have been performed to demonstrate its desirable characteristics and features.

In this article, the development of a high-efficiency power amplifier (PA) with the inverse class-F configuration and a novel 3/4 spiral defected ground structure (DGS) is presented. The proposed DGS structure has improved rejection characteristic and its resonance frequencies are more convenient to adjust than conventional symmetric and asymmetric spiral structure. The electromagnetic-simulated result shows that the proposed circuit has improved harmonic control performance with simplified structure and less return loss than the conventional microstrip harmonic control circuit. The 3/4 spiral harmonics control circuit (HCC) can be modeled by three parallel RLC resonators. Using the proposed structure a high-performance harmonic control circuit is designed for implementing an inverse class-F PA. For comparison, two inverse class-F PAs operating at 2.4 GHz have been implemented by the microstrip HCC and the proposed HCC, respectively. According to the experiment results, the size of the proposed inverse class-F PA is reduced by 20%, the power-added efficiency and the gain are increased by 4.8% and 1.5 dB, respectively.

This paper proposes a lightweight frequency selective surface polarization-insensitive wideband metamaterial absorber in C band and X band that employs only a few resistive elements. The proposed absorber is embodied with four quadrature slotted inner circular patch, which is horizontally and vertically bisected, and outer concentric copper rings of 0.035 mm thickness are attached with four lumped resistors placed at 90° apart. A slotted inner circular patch provides significant inductive and capacitive loading. The absorption bandwidth of 8.02 GHz with more than 90% absorption is observed from 5.69 to 13.71 GHz under normal incidence and maintains almost same absorptivity range under oblique incidence up to 45° in both transverse electric mode and transverse magnetic mode. The designed metamaterial absorber is fabricated and measured using free space measurement technique. The actual experiments and the simulated ones are in good agreement.

This paper presents a pattern diversity UWB antenna for Wireless Body Area Network (WBAN) communications. Pattern diversity antenna comprises two antenna elements with directional and omnidirectional patterns suitable for off-body and on-body communications respectively. Several broad-banding techniques such as Co-Planar waveguide, parasitic patches, and cavity resonant techniques are incorporated in microstrip antenna to achieve an ultra-wideband of 7.5 GHz (3.1 to 10.6 GHz) with a directional pattern. Monopole radiator topology is utilized to achieve a UWB frequency range of 2.6–10.6 GHz with an omnidirectional pattern. Pattern diversity is achieved using an orthogonal arrangement of the antenna elements in a compact size of 40 mm × 34 mm, maintaining the isolation >20 dB between the antennas. Gain varies from 2.2 to 4.6 dBi and 2.5 to 7.5 dBi for omnidirectional and directional antenna respectively. The simulated radiation efficiency for the directional antenna and the omnidirectional antenna are 74–86% and 52–66.5% respectively. The proposed design provides a good diversity performance in the entire UWB bandwidth with ECC<0.1 and a diversity gain of approximately 10 dB. SAR impact evaluated under various conditions is found to be <1.6 W/Kg for 1 gram of tissue.

In this paper, we present a near-field microwave microscopy method for the characterization of dielectric materials samples in the Industrial, Scientific and Medical (ISM) band. The system proposed is composed of a probe coupled to a dielectric resonator (DR) operating in the TE011 mode. Latter this is used to fix the resonance frequency of the resonator at 2.45 GHz. This system is used for the characterization of dielectric samples with accuracy and high spatial resolution, knowing that they do not have predetermined forms, but a small plane surface.The same device is used for a multi-frequency characterization (4–20 GHz) using resonance frequencies of the cavity instead of one resonance frequency of the DR.

This paper presents a new artificial neural network (ANN)-based radar data processing approach for the detection of breast cancers located inside fibro-glandular tissues. The aim is not the breast imaging but detecting tumors through ANN processing of data extracted from the radar signals measured around the breast. The proposed approach has been assessed using several realistic two-dimensional breast geometries derived from the models provided by the numerical breast phantom repository of the University of Wisconsin Cross-Disciplinary Electromagnetic Laboratory (UWCEM). The pulsed radar system was assumed to operate in the mono-static configuration. The obtained results showed the abilities of the proposed approach to detect, for any single radar trace, tumors located inside the fibro-glandular tissues with a sensitivity of 93%, a specificity of 90%, and an overall accuracy of 92%.

Frequency-modulated continuous-wave radar systems profit from increasing the absolute bandwidths of the generated frequency chirps to improve range resolution. As the relative bandwidth of SiGe-voltage-controlled oscillators (VCOs) is limited to about 80%, increasing the center frequency fundamentally or via frequency multiplication is the most direct way to increase that absolute bandwidth. However, as some applications require penetration depth, which dramatically decreases with frequency, other solutions are necessary. Therefore, state-of-the-art concepts rely on the down-conversion of generated frequency chirps via two separately stabilized frequency sources. This article implements a novel architecture, offering relative bandwidths of >100% within a single phase-locked loop (PLL). Therefore, two VCOs at different center frequencies are fed into a down-conversion mixer, whose output is directly stabilized via that PLL with one loop filter generating both tuning voltages. Those circuit blocks can be summarized as one equivalent VCO, offering a higher relative bandwidth and a significantly more linear tuning curve. Thereby, a solution to limited relative bandwidths with high VCO gain variation of single VCO synthesizers is offered while substantially reducing the hardware and implementation effort compared to the state-of-the-art.

This work presents a study where a sinusoidal corrugated antipodal Vivaldi antenna (SC-AVA) operating in the ultra-wideband (UWB) region is employed as a transducer for microwave imaging (MWI) of a cancerous breast. The functionality of the antenna within the UWB range is confirmed based on performance parameters like return loss, gain, radiation pattern, fidelity factor, and group delay. E-field distribution, H-field distribution, and near field directivity simulations in the presence of the breast phantom have also been carried out and reported. The practical application of the developed antenna for biomedical imaging is evaluated by measuring the specific absorption rate (SAR) readings at multiple frequencies within its operating range. The SAR readings are obtained from an electromagnetic simulator by modelling a realistic heterogeneous breast phantom with multiple embedded tumors, and placing them in close proximity to the transducer. The modelled SC-AVA is further utilized for imaging multiple tumors hidden inside the gland layer of the heterogeneous breast phantom developed in-house. The fabricated breast phantom is scanned using the in-house developed multistatic MWI setup. Based on the data obtained from the scanning setup the images are reconstructed using both the delay multiply and sum (DMAS) and iterative DMAS imaging algorithms. Furthermore, a comparison of the reconstructed images is done to check in which case the obtained images are closer to the fabricated breast phantom.