A new planar multiple-input–multiple-output (MIMO) antenna for ultra wideband (UWB) applications is presented. The proposed antenna operates over the frequency band from 3.1 to 10.6 GHz and it consists of two identical circular monopoles on an FR4 substrate. The wide isolation is achieved through a novel planar decoupling structure that is being inserted between the dual antennas. Moreover, a center slot is etched on the common ground to further increase isolation. The effectiveness of the decoupling structure is analyzed, and performance study has been performed to investigate the mutual coupling reduction. A good isolation of more than 31 dB has been achieved through the entire UWB band (more than 12 dB improvement over the reference antenna). The proposed UWB antenna with and without the wideband decoupling structure has been investigated and verified both numerically and experimentally. The measurement results of the proposed UWB–MIMO antenna are in good agreement with the simulation results. The proposed UWB antenna has been compared with previous works regarding antenna size, geometric complexity, bandwidth, and isolation level. The proposed antenna has some outstanding characteristics such as a geometric simplicity, compact size, broad bandwidth, and low correlation which give the antenna an excellent diversity performance and a good candidate for UWB applications.

This work presents a fully differential wideband and low power 240 GHz multiplier-by-8 chain, manufactured in IHP's 130 nm SiGe:C BiCMOS technology with fT/fmax = 300/500 GHz. A single ended 30 GHz input signal is multiplied by 8 using Gilbert cell-based quadrupler and doubler, and then amplified with a wideband differential 3-stage cascode amplifier. To achieve wide bandwidth and optimize for power consumption, the power budget has been designed in order to operate the frequency multipliers and the output amplifier in saturation. With this architecture the presented circuit achieves a 3 dB bandwidth of 40 GHz, meaning a relative 3 dB bandwidth of 17%, and a peak saturated output power of 0 dBm. Harmonic rejections better than 25 dB were measured for the 5th, 6th, and 7th harmonics. It dissipates 255 mW from 3 V supply which results in drain efficiency of 0.4%, while occupying 1.2 mm2. With these characteristics the presented circuit suits very well as a frequency multiplier chain for driving balanced mixers in 240 GHz transceivers for radar, communication, and sensing applications.

In this paper, an orthogonal crossover artificial bee colony (OCABC) algorithm based on orthogonal experimental design is presented and applied to infer the marine atmospheric duct using the refractivity from clutter technique, and the radar sea clutter power is simulated by the commonly used parabolic equation method. In order to test the accuracy of the OCABC algorithm, the measured data and the simulated clutter power with different noise levels are, respectively, utilized to estimate the evaporation duct and surface duct. The estimation results obtained by the proposed algorithm are also compared with those of the comprehensive learning particle swarm optimizer and the artificial bee colony algorithm combined with opposition-based learning and global best search equation. The comparison results demonstrate that the performance of proposed algorithm is better than those of the compared algorithms for the marine atmospheric duct estimation.

This paper discusses some significant design issues that are faced in resonant inductive system for wireless power transfer ‘on the move’. The targeted system adopts a single AC source to power a sequence of transmitting (Tx) coils, placed along the Rx path, whose geometry is optimized to minimize the variations of coupling for every possible Rx position. To retain a constant coupling coefficient, two nearby Tx coils are series-connected and simultaneously activated, establishing a path without any theoretical bound on its length, by a suitable switching network. This work analyzes the effects of asynchronous switching times, which are rigorously accounted for and minimized by a proper design of the compensating circuit elements, minimizing both the voltage spikes and the over currents on the coils, while keeping the system at resonance. A prototype operating at 6.78 MHz is built and experimental validations are carried out to verify the feasibility of a constant coupling link without experiencing the mentioned effects, but the adopted procedure is general and independent on its size or frequency.

A simple closed-form analytical formula is proposed to compute the probe reactance of an equilateral triangular patch antenna. The variation of the probe reactance with the variation of antenna dimension, substrate electrical parameters, and probe location is examined thoroughly. The computed values employing the present model show excellent agreement with experimental and simulation results.

This paper presents the design of all dielectric non-absorptive phase gradient reflective surfaces that can be used to manipulate the reflected electromagnetic waves at millimeter-wave regime. Compared with a bare perfect electrical conductor reflector which obeys the classical Snell's law of reflection, the presented design can effectively alter both the shape and level of the backscattered energy and thus radar cross section (RCS) reduction is achieved in the specular direction. One- and two-dimensional phase gradient reflective dielectric surfaces of phase change about 72° across their apertures are designed and their ability to manipulate the reflected waves under normal incidence are investigated both by means of full-wave simulations and experimentally tested for validation. More than 6 dB of specular RCS reduction is achieved from about 66.5–78.2 GHz.

This paper investigates a wideband and low axial ratio circularly polarized (CP) antenna, which is composed of a monopole on a novel polarization rotating reflective surface (PRRS) based on a corner-truncated artificial magnetic conductor (AMC) structure. By adjusting the dimensions of truncated corner properly, the PRRS has two polarization rotation (PR) frequency points. Then, a large PR band of 18% (5.55–6.65 GHz) can be achieved with two adjacent PR frequency points coming together. The profile of the newly PRRS is only0.04λ0. With corner-truncated AMC-based PRRS loading, a measured impedance bandwidth of 1.8 GHz (5.4–7.2 GHz) and the 3 dB axial ratio bandwidth of 1 GHz (5.55–6.65 GHz) could be obtained by the monopole antenna and validated by measurements. The values of AR were well below 1 dB at most of the CP region, which show a perfect CP performance. Moreover, the proposed antenna has exhibited a large axial ratio beamwidth in both the xoz- and yoz-planes and a peak gain of 6.1 dBic within the operational bandwidth.

A wideband and high-efficiency polarization conversion metasurface (PCM) is proposed and applied to reduce radar cross section (RCS). The proposed PCM unit is composed of two oblique asymmetry triangle split rings, which generate multiple plasmon resonances. Simulated and measured results demonstrate that it achieves polarization conversion over 90% from 9.24 to 17.64 GHz. Besides square checkerboard, the proposed PCM units and mirror units are arranged in triangle checkerboard. The mechanisms of both checkerboard PCMs are analyzed based on standard array theory, including the relationship between RCS reduction value and polarization conversion ratio value. The derived formulas provide a guideline to design checkerboard structure based on PCM. Simulated results demonstrate that both checkerboard PCMs achieve over 62% relative bandwidth of 10 dB RCS reduction under normal incidence with respect to the equal-sized metallic plate, which also means that the triangle one could be an alternative solution to reduce RCS. To verify the analyzed and simulated results, the fabricated sample and measured results of both checkerboard PCMs are presented. Good agreements are achieved between measurements, simulations and numerical analysis.

This paper presents a broadband hybrid slot-dielectric resonator antenna for radiofrequency (RF) energy-harvesting application. The antenna geometry consists of a simple pentagon-shaped dielectric resonator antenna (PDRA) excited by a microstrip feed underlying rectangular slot with narrow notch. It is investigated that the bandwidth of the proposed PDRA is improved significantly owing to electromagnetic coupling between feeding slot and the dielectric resonator. The measured results demonstrate that the proposed PDRA achieves an impedance bandwidth of 110.8%, covering the frequency range from 0.86 to 3 GHz in addition of stable radiation pattern with peak gain of 6.8 dBi and more than 90% radiation efficiency throughout the band, showing its suitability for RF energy harvesting application. For this to be feasible, the developed antenna is matched with the rectifier at two public telecommunication bands of GSM-900 and GSM-1800 using a compact dual-band hybrid matching network. The measured result demonstrates that the proposed dual-band rectenna system provides the peak efficiency of 63 and 59% for a load impedance of 4.7 kΩ at 0.9 and 1.8 GHz, respectively.

A modified H-shaped metamaterial is imparted in this paper that has a multiple band coverage for reflection and transmission coefficient. The proposed structure exhibits triple band coverage for the permittivity and permeability. Two split ring resonators (SRR) are connected with the substantial H-shaped structure. The 12 × 12 mm2 structure has been printed on FR-4 and a correlation is made between the basic unit-cell and array structures. A comparison is made among 1 × 2, 2 × 2, and 4 × 4 array structures with 1 × 2, 2 × 2, and 4 × 4 unit-cell configurations to validate the performance of the proposed metamaterial. A great transmission coefficient having a band of 13 GHz with a 500 MHz band gap in the middle is demonstrated for all of these configurations. The effective parameters of the resonators cover C, X, and Ku bands independently with double-negative phenomena at X and Ku bands with a frequency range of about 2.5 GHz. The reflection and transmission coefficients of the unit cell are obtained by CST microwave studio. Having an auspicious design and wide range double-negative characteristics, this structure can be applied to satellite communication.

This article presents a compact novel quasi-self-complementary semi-octagonal-shaped antenna for ultra-wideband (UWB) application. The proposed novel structure is fed by a microstrip line where different rectangular truncation is etched to the ground plane as an impedance matching element, which results for much wider impedance bandwidth (VSWR<2) from 2.9 to 20 GHz. In order to obtain band-notched characteristics at 5.5 GHz, an open-ended, quarter wavelength, spiral-shaped stub is introduced in the vicinity of the truncated part of the ground plane. An equivalent circuit model is adopted to investigate the band rejection characteristics of the ground plane stub. Sharpness of the rejection band can be controlled by maintaining the gap between stub resonator and the slotted periphery of ground plane. The proposed antenna design is validated by experimental measurements.

Multipath propagation occurs in many situations of radar measurements in complex environments. The unwanted effects range from interference over the radar channels, which causes amplitude fading and a corrupted direction of arrival (DOA) estimation, to the detection of ghost targets in an angle of arrival of the multipath direction. Due to the different number of reflections, polarimetric radars are capable to separate certain multipaths from direct paths if the target is known in advance. Furthermore, it is possible to separate objects with different polarimetric features in DOA that are located in the same radial distance to the radar. In this paper, a new approach to DOA detection based on the coherent Pauli decomposition is presented. With this approach, important multipath and DOA effects are analyzed and measurement results at 77 GHz on canonical objects in an anechoic chamber are presented. The results prove the feasibility of the approach and demonstrate the occurring effects.

In this paper, theoretical/simulation study of specific absorption rate (SAR) and/or temperature distributions in a bi-layered bio-media (fat and muscle)/realistic tri-layered bio-media (skin, fat, and muscle layers) in direct contact with water-loaded metal diagonal horn (MDH) designed at 915 MHz are investigated. The effects of fat thickness on the input reflection coefficient, reflection coefficient at the interface between the MDH and the bi-layered bio-media, and the SAR distribution in the bi-layered bio-media are also studied through simulation and theoretically at 915 MHz. Further, the SAR parameters such as penetration depth and effective field size inside the bi-layered bio-media due to the MDH are evaluated theoretically and the theoretical results are compared with the corresponding simulation results. Finally, SAR and temperature distributions in tri-layered bio-media without and with embedded irregular/oval-shaped tumor are provided for demonstrating the hyperthermia performance of the MDH applicator.

For a fast scan-phase satellite radio antenna diversity system a noise correction method is presented for a significant improvement of audio availability at low signal-to-noise ratio (SNR) conditions. An error analysis of the level and phase detection within the diversity system in the presence of noise leads to a correction method based on a priori knowledge of the system's noise floor. This method is described and applied in a hardware example of a satellite digital audio radio services antenna diversity circuit for fast fading conditions. Test drives, which have been performed in real fading scenarios, are described and results are analyzed statistically. Simulations of the scan-phase antenna diversity system show higher signal amplitudes and availabilities. Measurement results of dislocated antennas as well as of a diversity antenna set on a single mounting position are presented. A comparison of a diversity system with noise correction, the same system without noise correction, and a single antenna system with each other is performed. Using this new method in fast multipath fading driving scenarios underneath dense foliage with a low SNR of the antenna signals, a reduction in audio mute time by one order of magnitude compared with single antenna systems is achieved with the diversity system.

In this paper, a high gain broadband low profile microstrip antenna with the dual-layered substrate and four parasitic metal elements is presented. The proposed microstrip antenna is mainly composed of four parts: four circular parasitic metal patches with dual arced breaches, a rectangular metal patch sandwiched between substrates, a square ground plane, and two-square substrates. The circular parasitic elements are the main radiation structure and determine the characteristics of the proposed antenna are closely related to the parasitic elements. The proposed antenna has been fabricated for experimental measurement. The reflection coefficient, radiation pattern, radiation efficiency, and gain have been studied in detail. The simulated and measured impedance bandwidth is 27.0% (3.30–4.33 GHz), the maximum realized peak gain reaches up to 6.52 dBi at the frequency of 3.65 GHz. The radiation pattern has a single peak which is perpendicular to the surface of the substrate. The proposed antenna is suitable to be applied in the 5G mobile or WiMAX wireless communication. Dual antenna with a pair of parasitic elements has been investigated numerically to explain the principle of the proposed antenna.

Metamaterial-based energy harvesting structures operating at GSM 900 and GSM 1800 frequency bands have been proposed. The basic structure is composed of four nested U-shaped elements on the front and back side of the dielectric substrate, with a 180° relationship between the front and back resonators. As energy harvesting capability is directly related to the quality of absorption, with the aim being perfect absorption, there is an air gap to allow tuning of the resonance frequency, and copper plate follows the air gap to facilitate the perfect absorption of electromagnetic waves, which is verified by means of simulation and experimental tests. A set of simulations and experimental study were further carried out to demonstrate incident and polarization angle dependency, the effects of Schottky diodes, and the optimal orientation of the U-shapes. Spectrum analysis and DC voltage measurements across the HSMS 2860 Schottky diode are also presented to test the energy harvesting capability: the spectrum analyzer shows a 40 dBm difference, while 81.7 mV maximum DC voltage is observed at 900 MHz. The simulation and experimental study results, while displaying several differences, do suggest that the proposed design can be used for running low-energy consumption devices such as sensors and switches.

In this paper, the first reported waterproof inkjet-printed dual-band monopole antenna on the flexible organic paper substrate is presented. The antenna, which operates at 900 MHz and 2.4 GHz, is inkjet-printed on commercially available photopaper using conductive silver nano-particle ink. To protect it from ambient humidity, a 1 µm thick Parylene-C layer was deposited on top of the antenna. To verify its waterproof capability, the Parylene-C coated antennas were submerged in distilled water for 48 days, and no significant performance degradation was observed in its performance.

A novel radio frequency identification antenna based on log-periodic dipole array (LPDA) antenna at 5.8 GHz is presented. The antenna design approach consists of two major steps. Firstly, the conventional primitive method is used to design a traditional LPDA antenna. The antenna structure is then miniaturized and its overall performance significantly improved. Dynamic scaling factor along with uniformly separated elements are introduced in this class of antenna, resulting in a 51.5% length reduction. To improve front-to-back (F/B) ratio a symmetrical folding technique is employed, leading to 21.5 dB F/B ratio for the fabricated prototype. An excellent level of input impedance matching (S11 = −28 dB) is achieved using a well-designed feeding system through a proximity coupling technique. The measured gain of the fabricated prototype is 6.2 dBi, and the overall dimension of the antenna substrate is only 30 × 45 mm2 (0.58λ0 × 0.87λ0).

A coplanar waveguide slot antenna is herein presented. A rectangular slot is excited by a Y-shaped monopole etched on a single FR4 substrate. This structure exhibits two resonances due to the presence of the slot and the central monopole which can be used to design a dual-band or a wideband antenna. A parametric analysis is presented to describe the impedance matching mechanism for the two impedance bandwidths (BWs), as well as for the wideband antenna. The latter is fabricated and provides a measured impedance BW from 2.28 to 3.6 GHz, and gain larger than 2 dBi, yielding an outstanding BW/size trade-off. Finally, a 60 mm × 60 mm back metallic reflector is used to achieve a directive antenna with 6 dBi of measured gain, and an impedance BW from 2.16 to 3.59 GHz.

A compact printed reconfigurable monopole antenna with switchable band-notches is designed and manufactured. The proposed antenna mainly consists of a disc-like radiator with two pairs of T-shaped strips protruded inside a rectangular aperture. Five PIN diode switches are employed to bridge or open the slots, which allow the antenna to be configured into three different structures functioning as an ultra-wideband (UWB) antenna, or an antenna with notched frequencies at WLAN or WiMAX band. Design and optimization of the antenna are done using CST Microwave Studio. After fabrication on an FR4 substrate with dimensions of 35 mm (width) × 41 mm (length) × 1.5 mm (thickness), numerical and experimental results of the proposed reconfigurable antenna are presented and discussed. The experimental results confirm the design as a good candidate for UWB applications.