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In an autonomous robotic space debris removal mission, an essential sensor used for navigation is an FMCW radar designed for close-range relative navigation. To achieve the required range performance, minimizing RF leakage between the transmitter (Tx) and receiver (Rx) antennas is essential for the accurate detection of the range and velocity of the targeted space debris. Antennas positioned above the metallic satellite front face are highly susceptible to RF leakage, primarily caused by surface current propagation and lateral waves traveling parallel to the platform. This study presents two lightweight, single-layer planar metamaterials—a novel compact electromagnetic bandgap (EBG) and a non-uniform high-impedance surface (HIS)—optimized to suppress both surface waves and interact with space waves within the 9.3–9.8 GHz frequency range. These designs address strict size, weight, and power (SWaP) constraints while ensuring compatibility with extreme space conditions and resistance to mechanical shocks. Experimental validation indicates that a minimum Tx/Rx isolation improvement of 10 dB is achieved using the HIS, and 20 dB is achieved using the EBG across the radar's operational bandwidth (5%). [ABSTRACT FROM AUTHOR]

A rectangular waveguide antenna was tested for eucalyptus wood moisture content (MC) measurement before being used. To improve the moisture content measurement of the rectangular waveguide antenna, a woodpile-shaped Electromagnetic Band Gap (EBG) was installed by Transverse Electric (TE) arrangement. This antenna is responsible for receiving and transmitting signals which are converted from electrical energy into radio frequency energy transmitted through the air. In this research, we take advantage of the wave propagation of antennas in the air and use them to propagate waves through wood materials. To compare signal transmission power to determine moisture content in wood and the benefit of the EBG is that it acts like a convex lens to increase the strength of the waves so that they can penetrate the wood more efficiently. The results showed that woodpile-shaped EBG could increase the efficiency of receiving and transmitting signals, reduce working hours for farmers and reduce costs by about 90 %. When this antenna was tested and actually used, it was found that the frequency band that responded best to the moisture content value was 2.20 GHz. This antenna was built with an aluminum material of size 9×4×15 cm3 and 2×6 units woodpile EBG on a 9.54×4 cm2 Polyester Mylar base plate. There was a gain of 7.81 dBi from the original structure, or by 20 %. At a radius of 4 cm, the values of moisture content ranged from -9.46 to -42.19 dBm. At a radius of 6 cm, the values were -9.41 to -42.89 dBm. At a radius of 8 cm, the values ranged from -9.39 to -43.01 dBm, respectively. All 3 values were found to be efficient. The size was not less than 84 % compared to the general standard meter. [ABSTRACT FROM AUTHOR]

In this paper, a novel tri-band low-cost antenna covering the desired frequencies is presented. The architecture is formed by a printed dipole coupled by a split-ring within an electromagnetic bandgap (EBG) structure for high radiation gains. The printed dipole is placed beneath two dielectric superstrates, and the coupling split-ring is placed on its top. The proposed antenna is excited by the printed dipole with a coaxial connector. It is placed in the middle cavity formed by two dielectric superstrates and a metal reflector as the simple EBG structure. The simulation results show three resonant frequencies at 1.42, 2.39 and 5.40 GHz respectively, with uni-directional radiation patterns and high gains enhanced by the EBG structure. Experimental measurements over an antenna prototype validate the results of reflection coefficients and radiation patterns. It is found that the gains are 8.50, 6.00 and 8.10 dBi at 1.42, 2.39 and 5.00 GHz respectively, which are sufficient for L-band and WiFi applications. In addition, simulation and measurement results are in good agreement.

In an autonomous robotic space debris removal mission, an essential sensor used for navigation is an FMCW radar designed for close-range relative navigation. To achieve the required range performance, minimizing RF leakage between the transmitter (Tx) and receiver (Rx) antennas is essential for the accurate detection of the range and velocity of the targeted space debris. Antennas positioned above the metallic satellite front face are highly susceptible to RF leakage, primarily caused by surface current propagation and lateral waves traveling parallel to the platform. This study presents two lightweight, single-layer planar metamaterials—a novel compact electromagnetic bandgap (EBG) and a non-uniform high-impedance surface (HIS)—optimized to suppress both surface waves and interact with space waves within the 9.3–9.8 GHz frequency range. These designs address strict size, weight, and power (SWaP) constraints while ensuring compatibility with extreme space conditions and resistance to mechanical shocks. Experimental validation indicates that a minimum Tx/Rx isolation improvement of 10 dB is achieved using the HIS, and 20 dB is achieved using the EBG across the radar’s operational bandwidth (5%).

In this paper, a novel tri-band low-cost antenna covering the desired frequencies is presented. The architecture is formed by a printed dipole coupled by a splitring within an electromagnetic bandgap (EBG) structure for high radiation gains. The printed dipole is placed beneath two dielectric superstrates, and the coupling splitring is placed on its top. The proposed antenna is excited by the printed dipole with a coaxial connector. It is placed in the middle cavity formed by two dielectric superstrates and a metal reflector as the simple EBG structure. The simulation results show three resonant frequencies at 1.42, 2.39 and 5.40 GHz respectively, with uni-directional radiation patterns and high gains enhanced by the EBG structure. Experimental measurements over an antenna prototype validate the results of reflection coefficients and radiation patterns. It is found that the gains are 8.50, 6.00 and 8.10 dBi at 1.42, 2.39 and 5.00 GHz respectively, which are sufficient for L-band and WiFi applications. In addition, simulation and measurement results are in good agreement. [ABSTRACT FROM AUTHOR]

Concept of ringed stacked patch antenna with low side lobe level and enhanced bandwidth is introduced for radio altimeter avionics applications. One dimensional electromagnetic band gap is designed using metallic vias with circular rings along the radiating patches on multilayered substrate for providing high isolation in H-plane and reducing lateral surface currents. A stacked patch antenna configuration is used for enhancing the bandwidth of the antenna. Simulation and analysis are performed for the optimization of the frequency response and sidelobe levels of the proposed antenna. Gain of more than 12 dB with sidelobe levels less than −42 dB were measured for a fabricated prototype. Signal to interference ratio of 85 dB is achieved between two adjacent antennas, which is 5dB better than commercial antennas due to increased gain and reduced sidelobe levels. The antenna is designed for enhanced frequency bandwidth from 4.06 GHz to 4.53 GHz. Computed drag coefficient of the antenna mounted on the fuselage of Cessna 210 aircraft show that the drag is essentially negligible.

Repeaters have been widely used to improve communication quality and extend the coverage areas of wireless communication systems. However, mutual coupling between the Tx and Rx antennas significantly deteriorates the performance of repeater systems. This work presents a high-isolation repeater antenna operating in a frequency range of 3.6–3.7 GHz in a 5G communication system. Perpendicularly arranged microstrip patch antennas are used because this arrangement can lead to greater isolation than a parallel arrangement. However, the perpendicular arrangement results in radiation pattern distortion due to the ground mode. A novel defected ground structure (DGS) is developed to suppress the ground mode and simultaneously reduce the mutual coupling between the Tx and Rx antennas. An electromagnetic bandgap (EBG) is additionally employed to further increase isolation. The measurement results of a fabricated repeater antenna show no radiation pattern deformation and an isolation improvement of 28 dB over the repeater antenna without the DGS and EBG.

Abstract High isolation between massive MIMO antenna elements is one of the important parameters that improves antenna performance, especially for 5G communication applications. In this study, we propose a design to improve isolation between elements to enhance the antenna performance. The proposed solution to improve the performance of massive MIMO antennas is to use a combination of dielectric resonator, electromagnetic bandgap (EBG) and defected ground structure (DGS) techniques at the frequency band 3.5 GHz as the 5G frequency band under 6 GHz. The material used is FR-4 which has a dielectric constant ( $${\varepsilon }_{r}$$ ε r ) of 4.3. Simulation results and measurements between antenna elements show an improvement in mutual coupling, widening the bandwidth and increasing the gain of the antenna. The proposed design using the dielectric resonator antenna (DRA) by MIMO 8 × 8 16 port—64 elements and the addition of EBG and DGS structures on the ground plane—has shown to suppress mutual coupling parameter lower than without using DRA-EBG-DGS design by 15 dB, increase bandwidth to 246 MHz, increase gain to 24.7 dB and improve the overall envelope correlation coefficient (ECC) parameter.

We present a novel paradigm for dispersion engineering in coupled transmission lines (CTLs) based on exceptional points of degeneracy (EPDs). We also develop a theory for fourth-order EPDs consisting of four Floquet-Bloch eigenmodes coalescing into one degenerate eigenmode; present unique wave propagation properties associated with the EPD; develop a figure of merit (FOM) to assess the practical occurrence of the fourth-order EPDs in CTLs with tolerances and losses; and experimentally verify for the first time the existence of a fourth EPD (the degenerate band edge), through dispersion and transmission measurements in microstrip-based CTLs at microwave frequencies. In addition, we report that based on experimental observation and the developed FOM, the EPD features are still observable in structures that radiate (leak energy away), even in the presence of fabrication tolerances and dissipative losses. We investigate the 'gain and loss balance' regime in CTLs as a means of recovering an EPD in the presence of radiation and/or dissipative losses, without necessarily resorting to parity-time (PT)-symmetry regimes. The versatile EPD concept is promising in applications such as high-intensity and power-efficiency oscillators, spatial power combiners, or low-threshold oscillators and opens new frontiers for boosting the performance of large coherent sources.

In ultra-wideband (UWB) communications, highly selective notch bands are required to avoid interference with other licensed bands. This study presents a highly selective triple-notch UWB-MIMO antenna, which consists of a four-radiating patch antenna and an isolator. The single-element antenna consists of a radiating patch, substrate, ground plane, electromagnetic bandgap (EBG) structures, and split ring resonators (SRR). To achieve the designated UWB bandwidth, the lower edges of the antenna patch are cut by a quarter-circle radius. The three sharp notches are achieved by utilizing four EBGs and two SRRs at the back of the antenna. The notch bandwidth can also be controlled by changing the parameters such as the width and length of the EBG structure and SRR. The single antenna is then translated into 4-port MIMO systems. The high correlation between elements is reduced by inserting a unique parasitic decoupling structure. The decoupling structure is designed in a way that reduces the mutual coupling in all passbands. The proposed antenna offers a (|S11| < –10 dB) of 3.1 – 11.8 GHz impedance bandwidth. The proposed MIMO antenna having an overall size of 54 × 54 × 1.52 mm3 is fabricated to verify the simulation results. The MIMO antenna shows exceptional diversity properties, including better isolation between unit elements of MIMO antenna (>20 dB), a diversity gain (DG) very close to 10 dB (>9.99 dB), an envelope correlation coefficient which is less than 0.001, and suitable mean effective gain is also in the defined range. The suggested parasitic element UWB – MIMO antenna thus supports its suitability for use in UWB communication networks.

The Gap Waveguide technology utilizes an Artificial Magnetic Conductor (AMC) to prevent the propagation of electromagnetic (EM) waves under certain conditions, resulting in various gap waveguide configurations. In this study, a novel combination of Gap Waveguide technology and the traditional coplanar waveguide (CPW) transmission line is introduced, analyzed, and demonstrated experimentally for the first time. This new line is referred to as GapCPW. Closed-form expressions for its characteristic impedance and effective permittivity are derived using traditional conformal mapping techniques. Eigenmode simulations using finite-element analysis are then performed to assess its low dispersion and loss characteristics. The proposed line demonstrates an effective suppression of the substrate modes in fractional bandwidths up to 90%. In addition, simulations show that a reduction of up to 20% of the dielectric loss can be achieved with respect to the traditional CPW. These features depend on the dimensions of the line. The paper concludes with the fabrication of a prototype and validation of the simulation results in the W band (75–110 GHz). [ABSTRACT FROM AUTHOR]

This paper presents a broadband miniaturized Fabry–Perot cavity resonator antenna (CRA) made of novel electromagnetic bandgap (EBG) superstrate as partially reflecting surface (PRS) and reactive impedance surface (RIS) backed rectangular patch antenna. To the best of the authors' knowledge, the proposed EBG exhibits the highest stopband bandwidth (BW) with a bandgap existing between 7.37 and 12.4 GHz (50.9%). Frequency-selective property of the EBG is utilized under plane wave incidence to demonstrate it as PRS superstrate in CRA antenna. The cavity is excited with a rectangular microstrip antenna which is made of two dielectric substrates with an additional RIS layer sandwiched between them. The RIS provides wideband impedance matching of the primary feed antenna. A 7 × 7 array of the EBG superstrate is loaded over the patch antenna having an overall lateral dimension of only 45 × 45 mm2 or 1.62 λ 0 × 1.62 λ 0 where λ 0 is the free space wavelength at the center frequency of 10.8 GHz. The proposed Fabry–Perot CRA (FP-CRA) achieves gain enhancement of 6.59 dB as compared with the reference antenna and has a 10 dB return loss BW of 23.79% from 10.07 to 12.79 GHz. A prototype of the FP-CRA is fabricated and experimentally tested with single and dual layers of EBG superstrate. Measured results show BWs of 21.5 and 24.8% for the two cases with peak realized gain of 12.05 and 14.3 dBi, respectively. Later a four-element antenna array with corporate feeding is designed as the primary feed of the CRA. The simulation result shows a flat gain of >13 dBi with gain variation <1.2 dB over the impedance BW of 13.2%. [ABSTRACT FROM AUTHOR]

Wearable electronics have gained opportunities in recent years, and the last decade has been evidence of this growth in Wireless Body Area Networks (WBAN). They meet the criteria for personalizing healthcare, communication, patient monitoring, tracking, and rescue operations. The main challenge for the WBAN is to handle the radiator's coupling with the human body. An artificially generated Electromagnetic Band Gap (EBG) structure was designed and used in this work to improve the performance of a microstrip patch antenna. A jeans-based microstrip patch antenna with an EBG surface demonstrated to enhance the performance for 5.5 GHz WiMAX application. The use of an EBG surface increases return loss by 20%, with a reasonable bandwidth of 0.528 GHz (5.271 GHz to 5.749 GHz) at the resonance frequency of 5.5 GHz. The EBG surface improved the Voltage Standing Wave Ratio (VSWR) by 60%. A three-layered human body tissue model is also used for on-body measurements to determine the performance of an EBG-based antenna. The presence of human tissues generally reduces performance and shifts the resonance, but the shifting in this work with the simplified EBG structure and adequate gain and VSWR is only 2.6 percent. [ABSTRACT FROM AUTHOR]

High isolation between massive MIMO antenna elements is one of the important parameters that improves antenna performance, especially for 5G communication applications. In this study, we propose a design to improve isolation between elements to enhance the antenna performance. The proposed solution to improve the performance of massive MIMO antennas is to use a combination of dielectric resonator, electromagnetic bandgap (EBG) and defected ground structure (DGS) techniques at the frequency band 3.5 GHz as the 5G frequency band under 6 GHz. The material used is FR-4 which has a dielectric constant ( ε r ) of 4.3. Simulation results and measurements between antenna elements show an improvement in mutual coupling, widening the bandwidth and increasing the gain of the antenna. The proposed design using the dielectric resonator antenna (DRA) by MIMO 8 × 8 16 port—64 elements and the addition of EBG and DGS structures on the ground plane—has shown to suppress mutual coupling parameter lower than without using DRA-EBG-DGS design by 15 dB, increase bandwidth to 246 MHz, increase gain to 24.7 dB and improve the overall envelope correlation coefficient (ECC) parameter. [ABSTRACT FROM AUTHOR]

This paper investigates a trapezoidal Monopole Patch Antenna (MPA) with an Ultra-Wideband (UWB) characteristic and a dual-stage notched band at fifth generation (5G) and Wireless Local-Area Network (WLAN) bands. The 5G band is notched by inserting a U-shaped slot on the trapezoidal UWB MPA. The WLAN band is notched using five-square metallicconductor Electromagnetic Bandgap (EBG) patches that are installed on the surface of the backside of the radiating patch and attached to the ground plane via a shorting pin. The small, proposed antenna is built upon an FR4 substrate substance, having dielectric comparative permittivity εr= 4.7, and fed by a 50O coplanar waveguide. The antenna's size is 32×42.90×0.8 mm3. The simulated results show that the antenna has an operating frequency range of 2.39-14.72 GHz for |S11|<-10 rejecting WLAN (5.15-5.825 GHz), as well as sub-6 GHz 5G (3.4-3.9 GHz) great-selectivity signals. A higher gain obtained by the UWB antenna is 6.4 dBi, while a sharp decrease occurs in the rejected bands, reaching -8.29 dBi. This study also employs the Orbital Angular Momentum (OAM) technique. However, OAM waves are generated using eight trapezoidal UWB MPAs. Creating notches reduces the interference problem in UWB frequencies, and merging the UWB with the OAM technique allows the OAM to operate on many frequencies. Moreover, notches can be generated for specific frequencies inside the UWB bands. These techniques, trapezoidal UWB MPA and OAM wave generation, can significantly increase the spectrum range and improve the spectrum efficiency in wireless communications. [ABSTRACT FROM AUTHOR]

This article proposes a method to engineer degenerate band-edge conditions in periodic substrate-integrated waveguides (SIWs). A degenerate band edge (DBE) is a fourth-order exceptional point originating from the coupling of four Floquet–Bloch modes; it leads to a dispersion relation flatter than a regular band edge (RBE) and is suitable to design slow wave structures and high $Q$ -factor resonators. Design guidelines to achieve a DBE point are given based on Bloch analyses of unit cells. An oblique line of vias in SIW is proposed to form a suitable modal coupling between adjacent waveguides enabling a degenerate band-edge condition. The effect of losses and the robustness to parameter variations are discussed by means of rigorous Bloch analyses. A unit cell showing the best behavior concerning the losses and geometric tolerances is selected and prototypes of finite-length resonators are realized. Measurements validate simulated results and confirm the typical $N^{5}$ scaling of the loaded $Q$ -factor to the number of cells $N$ of the resonator. [ABSTRACT FROM AUTHOR]

We present a transmission line theory of exceptional points of degeneracy (EPD) in coupled-mode guiding structures, i.e., a theory that illustrates the characteristics of coupled electromagnetic modes under a special dispersion degeneracy condition, yet unexplored in the contest of gain and loss. We show that coupled transmission lines (CTLs) at radio frequencies having gain (active devices) and loss (e.g., material, radiation) balance exhibit EPDs. We demonstrate the concept of parity-time (PT)-symmetry in uniform CTLs that involve symmetric gain and loss and how this condition is associated with a second-order EPD. Furthermore, we also demonstrate that $\mathcal {PT}$-symmetry is not a necessary condition for realizing EPDs, and indeed, we show that EPD is also obtained with asymmetric distributions of gain and loss in uniform CTLs. We further propose potential applications of the EPDs in designing leaky-wave antennas with the capability of beam and directivity control as well as enhanced sensitivity. Operating near such special degeneracy conditions leads to potential performance enhancement in a variety of microwave and optical resonators, antennas, and devices such as distributed oscillators, including lasers, amplifiers, radiating oscillators, pulse compressors, and Q-switching sensors.

In this study, we propose a segment substitution method (SSM) for the fast analysis of a non-periodic electromagnetic bandgap power distribution network (NP-EBG PDN) in high-speed packages and printed circuit boards (PCBs). The proposed SSM is based on a hybrid of the desegmentation and segmentation methods, and the analytical equations for an EBG structure that are derived herein. The proposed SSM is verified using full-wave simulations and measurements. The proposed SSM achieves a 97.4 % reduction in the computation time of the NP-EBG PDN as compared to that of the commercial field solver. Thus, the SSM can be adopted for the fast analysis and optimization of the NP-EBG PDN. [ABSTRACT FROM AUTHOR]

Stretchable materials are widely used for the realization of various sensors, but their radio frequency behavior has not been fully characterized so far. Here, an innovative method is proposed for deriving the surface impedance of this kind of materials. The material characterization represents a fundamental step for exploiting the material as a sensing element within a radio frequency device. Indeed, the proposed method is capable of retrieving the surface impedance of the material while it is being stretched, thus deriving a correspondent calibration curve. The characterization approach is based on a contactless measurement of the scattering parameters using waveguides. By exploiting the measured scattering parameters, the variation in the surface impedance as a function of both frequency and strain is recovered through an analytical inversion procedure. Numerical simulations were initially performed trough a numerical electromagnetic simulator, and subsequently, experimental validation was carried out using a dedicated test bench designed to ensure a contactless measurement of the stretchable material. [ABSTRACT FROM AUTHOR]

We present the theory of a new amplification regime in traveling wave tubes (TWTs) composed of a slow wave periodic structure that supports multiple electromagnetic modes that can all be synchronized with the electron beam. The interaction between the multimodal slow wave structure and the electron beam is quantified using a multi-transmission line (MTL) approach based on a generalized Pierce model and transfer matrix analysis, leading to the identification of modes with complex Bloch wavenumber. In particular, we address a new possible operation condition for TWTs based on the supersynchronism between an electron beam and four modes exhibiting a degeneracy condition near a band edge of the periodic slow wave MTL. We show a phenomenological change in the band structure of a periodic MTL, where we observe at least two growing modal cooperating solutions as opposed to a uniform MTL, interacting with an electron beam where there is rigorously only one growing modal solution. We discuss the advantage of using such a degeneracy condition in TWTs that leads to larger gain conditions in amplifier regimes and also to very low starting beam current in high-power oscillators.

A broadband coplanar‐to‐rectangular waveguide transition using contactless electromagnetic bandgap (EBG) structure in the form of interdigital‐pin bed of nails has been introduced in this paper. The electromagnetic (EM) wave propagates from the CPW, and then radiates from the probe into the WR4. The rectangular patch is adopted as the probe to accomplish a broadband performance without an impedance transformer. At the same time, CPW to rectangular waveguide (RW) directly transition without EBG unit also has been designed and the simulated results show the transmission performance has low tolerance to air gap. The interdigital‐pin EBG structure is added to the machining splitter of the RW which is no need for strict electrical contact and is not harmful for transition performance. The greatest advantage of the interdigital‐pin lattice has a significant pin gap increase and is easy to fabricate for millimeter‐wave (mm‐Wave) and terahertz (THz) applications. The back‐to‐back prototype is designed, fabricated and measured. The measured |S11| is better than −10 dB over 170–260 GHz, covering a bandwidth of 41.8%. [ABSTRACT FROM AUTHOR]

Signal line transition with layer transition via is inevitable in multi-layer PCB. The return current can generate voltage noise between the cavities due to the discontinuity of the return current path. Other layer transition vias passing through the cavity can pick up the voltage noise and result in problems of signal integrity. In this paper, an electromagnetic bandgap (EBG) structure is proposed for suppression of the broadband cavity noise. The impedance discontinuity between layers of interleaved EBG cell enhances the efficiency of noise suppression, and the slots embedded in the EBG cell excite multi-mode resonances for extending the bandwidth of noise suppression. The dispersion diagram is utilized to preliminarily analyze the characteristic of the proposed EBG cell, and a 5χ5 cells EBG board is further analyzed for characterizing the efficiency of noise suppression. Both simulation and measurement results prove the proposed structure can effectively suppress the cavity noise under --35 dB over the frequency range from 0.56 GHz to the highest measurement frequency, 20 GHz. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a microstrip phased array using High Impedance Surface - Electromagnetic Bandgap (HIS-EBG) in order to minimize the effects of mutual coupling among the antenna elements. Each element of the array is fed by a coaxial cable allowing the beam steering by controlling the signal of the input port of each element. This phased array operates at X Band as well as the bandgap of the HIS-EBG structure. Its main applications are satellite communication and broadcasting systems. Results show reductions in the mutual coupling up to 12 dB, and improvements in the return loss and gain.

In this paper, an eight-shaped polarization-dependent electromagnetic bandgap (ES-PDEBG) structure is proposed. The unit cell of ES-PDEBG structure consists of an outer eight-shaped EBG patch with two inner square patches and three vias. Surface wave bandgap and reflection phase characteristics have been studied for the proposed structure. From the measurement results, two surface wave bandgaps with center frequencies 3.42 and 5.88 GHz are observed along the X-direction, and one surface wave bandgap with center frequency 3.69 GHz is observed along the Y-direction. The refection phase bandgap of the proposed structure is centered at 5.61 and 3.31 GHz for x- and y-polarized incident plane waves, respectively. Furthermore, the application of the proposed structure as polarization reflector is presented. The study demonstrates that the structure can act as dual-band in-polarization reflector for circularly polarized waves. In addition, incident linearly polarized waves are reflected as circularly polarized waves in four operating bands. [ABSTRACT FROM AUTHOR]

With the popularization of electronic products, more and more people have cervical spine troubles. This paper proposed an antenna sensor for detecting the bending state of the neck in people’s daily life. The antenna works in the 2.45 GHz industrial, scientific, and medical (ISM) band. When the cervical spine drives the antenna sensor to bend, the resonance frequency of the antenna sensor shifts. Based on this characteristic, the antenna sensor can monitor the bending angle of the cervical spine wirelessly. Placing a ${2}\times {2}$ electromagnetic bandgap (EBG) array between the antenna sensor and the neck reduces the specific absorption rate (SAR) of the human body by about 90% and increases the peak gain from 2.46 dBi to 6.75 dBi. Even if the antenna sensor is bent and deformed greatly, the gain of the antenna sensor remains good. The efficiency of the antenna sensor loaded with the EBG array keep at 65%, and the sensitivity to the bending angle reaches 7.5 MHz/1°. The measured results of the fabricated antenna sensor are in good agreement with the simulated ones. The experimental results show that the proposed antenna sensor is suitable for cervical curvature monitoring. [ABSTRACT FROM AUTHOR]

We demonstrate the existence of a special degeneracy condition, called degenerate band edge (DBE), between two Bloch modes in periodically-loaded circular all-metallic waveguides at microwave frequencies. The DBE condition has been associated with a dramatic reduction in group velocity and with some unique resonance properties, but it has not been shown in hollow waveguide structures yet. Hence, we show here its existence in two periodic waveguide examples. The unit cell of the first structure is composed of a circular waveguide loaded with two inner cylinders with elliptical irises with misaligned angles. The second structure is composed by loading the waveguide with elliptical rings. The demonstration of DBE in those waveguide is explained through a simple multi-transmission line approach where the conditions to obtain DBE are clarified, and suggests that the DBE can occur in several other analogous periodic waveguides. These structures can be potentially used to investigate unconventional gain schemes in traveling wave tubes or other kinds of distributed amplifiers, oscillators and novel pulse compressors.

A 1-D finite electromagnetic bandgap (EBG) periodic structure is studied. In the structure, EBG behaviour arises from a unit cell comprised of a metallic patch sandwiched between microstrip line and ground plane. Reactive loading offered by patch size determines the bandgap position. A detailed parametric study of various physical structure parameters is presented as a basis to develop a interrelation between physical parameters of the structure and cutoff frequencies. Closed-form synthesis equations are then formulated using curve fitting techniques. Subsequently, a step-by-step design methodology is presented to get a close first pass approximation of structure dimensions for a given specification. This design method reduces the effort required for a designer to perform extensive electromagnetic simulations at early stages of the design. The proposed synthesis method is tested for a variety of commercially available substrates and different frequency ranges for validation. Comparison with electromagnetic (EM) simulations and measurement show that the proposed synthesis method provides first pass approximation of the physical structure dimensions with 94% accuracy.

A planar electromagnetic bandgap (EBG) structure designed for broadband common-mode suppression is proposed. A uniplanar compact photonic-bandgap (UC-PBG) structure with periodic center slots is etched on the ground plane to obtain broadband common mode suppression while minimally disturbing the differential signal within the designed bandwidth. Dispersion analysis has been conducted for both common (even) and differential (odd) mode signals. Good signal integrity is observed in both simulated and measured results. The fractional bandwidth of the proposed EBG ground plane is around 70% with common-mode suppression below - 20 dB. The proposed EBG ground planes may be applicable for systems requiring low-cost and simple solutions in designing high-speed differential interlinks operating above 5 Gbps.

This article presents a novel dual‐band and dual‐polarization Fabry‐Pérot resonator antenna (FPRA). The proposed FPRA consists of a partially reflective surface (PRS), an electromagnetic bandgap (EBG) structure, and a dual‐band and dual‐polarization planar patch antenna. The novel PRS with a large positive reflection phase gradient (PRPG) is etched on a single‐layer superstrate. The EBG structure is adopted as the reflection plane to reduce the profile of FPRA. A rectangular microstrip patch antenna integrated into the center of the EBG structure is used as a dual‐band and dual‐polarization feed for FPRA. A dual‐band and dual‐polarization FPRA is proposed, fabricated and measured. The measurement results demonstrate that the proposed FPRA has peak gains of 14.3 dBi with the horizontal polarization (H‐pol) at 12.4 GHz and 16.8 dBi with vertical polarization (V‐pol) at 14.1 GHz. Moreover, the measured 3‐dB gain bandwidths in the lower and higher bands are 7.3% and 3.6%, respectively, which cover receiving (Rx) and transmitting (Tx) bands of satellite communication in the Ku band. [ABSTRACT FROM AUTHOR]

This article presents a high gain cavity‐backed slot antenna using a perfect magnetic conductor (PMC) ground plane and multilayered superstrates. A textured surface of periodic pins is applied to realize a high impedance surface (HIS), which simulates a PMC ground plane. The main advantage of using this structure is to suppress the surface wave propagation, improve the input impedance matching, increase the bandwidth, control the side‐lobe levels, and also provide higher gain. Moreover, the multilayered superstrates has been used to enhance the antenna gain. The simulations and measurements for the S‐parameter, gain, and radiation patterns of the antenna are presented. The proposed cavity‐backed slot antenna offers a maximum gain of 18 dBi and an impedance bandwidth of 16.5% at 11.5 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a unique technique to enhance isolation between transmit/receive radiating elements in densely packed array antenna by embedding a metamaterial (MTM) electromagnetic bandgap (EMBG) structure in the space between the radiating elements to suppress surface currents that would otherwise contribute towards mutual coupling between the array elements. The proposed MTM-EMBG structure is a cross-shaped microstrip transmission line on which are imprinted two outward facing E-shaped slits. Unlike other MTM structures, there is no short-circuit grounding using via-holes. With this approach, the maximum measured mutual coupling achieved is -60 dB @ 9.18 GHz between the transmit patches (#1 & #2) and receive patches (#3 & #4) in a four-element array antenna. Across the antenna's measured operating frequency range of 9.12-9.96 GHz, the minimum measured isolation between each element of the array is 34.2 dB @ 9.48 GHz, and there is no degradation in radiation patterns. The average measured isolation over this frequency range is 47 dB. The results presented confirm the proposed technique is suitable in applications such as synthetic aperture radar and multiple-input multiple-output systems.

A wearable planar inverted‐F antenna (PIFA) fed by the coplanar waveguide (CPW) and backed with an optimized electromagnetic bandgap (EBG) structure is presented. The antenna is made of conductive textile and polydimethylsiloxane (PDMS), which is a conformal and robust solution to wearable applications. The EBG unit cell is miniaturized according to the equivalent circuit model, and the cross‐polarization is suppressed due to its approximate 180° reflection phase in the orthogonal direction. The measured impedance bandwidth ranges from 2.30 to 2.65 GHz, which covers the 2.4 GHz Industrial Scientific Medical (ISM) band. The antenna keeps a high gain and efficiency above 70% under different conditions including being flat, bent, and close to the human body. The maximum SAR value is limited to 0.612 and 0.330 W/kg under 1 and 10 g standard, respectively. Therefore, the antenna is a promising candidate for wearable applications in various domains. [ABSTRACT FROM AUTHOR]

This paper presents a microstrip phased array using High Impedance Surface - Electromagnetic Bandgap (HIS-EBG) in order to minimize the effects of mutual coupling among the antenna elements. Each element of the array is fed by a coaxial cable allowing the beam steering by controlling the signal of the input port of each element. This phased array operates at X Band as well as the bandgap of the HIS-EBG structure. Its main applications are satellite communication and broadcasting systems. Results show reductions in the mutual coupling up to 12 dB, and improvements in the return loss and gain. [ABSTRACT FROM AUTHOR]

This letter is concerned with a comparative study of the electromagnetic properties of two-dimensional, finite-size, aperiodically ordered "quasi-crystal" dielectric structures based on representative categories of "aperiodic-tiling" geometries. In this framework, a rigorous full-wave solver is used to explore the electromagnetic bandgap and directive radiation properties of potential interest in antenna applications. © 2006 IEEE.

This letter is concerned with a comparative study of the electromagnetic properties of two-dimensional, finite-size, aperiodically ordered "quasi-crystal" dielectric structures based on representative categories of "aperiodic-tiling" geometries. In this framework, a rigorous full-wave solver is used to explore the electromagnetic bandgap and directive radiation properties of potential interest in antenna applications. © 2006 IEEE.

An efficient algorithm based on a moment-method formulation is presented for the evaluation of the field produced by a line source at the interface between an air superstrate and a one-dimensional-periodic artificial-material slab. The formulation provides physical insight into the nature of the fields via path deformation in the complex wavenumber plane. From an asymptotic analysis in the complex wavenumber plane it is found that the space wave produced by a line source consists of an infinite number of space harmonics that decay algebraically as x-3/2. Guided modes may also exist and be excited, including leaky modes. © 2005 IEEE.

A compact and cost effective multislot type electromagnetic bandgap (EBG) structure for high noise isolation in ultra‐wideband applications is proposed. The proposed multislot type structure is a hybrid EBG structure with multislot in an alternating impedance EBG unit cell to achieve both the excellent noise isolation and the bandwidth improvement of the noise suppression. This type of the hybrid structure shows a high noise suppression ability of above −40 dB in an ultra‐wideband stop frequency range from 3 to 20 GHz. The performance of the proposed multislot type EBG structure is evaluated and verified by comparing the simulated and measured results. [ABSTRACT FROM AUTHOR]

In this paper, we propose a method for designing checkerboard surfaces using strategically placed artificial magnetic conductors (AMCs) for wideband radar cross section (RCS) reduction. The theoretical analysis shows that the reflection phases of the two AMCs should be linear. The cancelation conditions of checkerboard structure are analytically derived using an equivalent transmission line model, and the ideal impedance conditions of the two AMCs are obtained, which serve as guidance to select patterns of two AMCs unit. A planar checkerboard surface with two kinds of AMC elements is designed for wideband RCS reduction. A 10 dB RCS reduction is observed for approximately 91.5% of the relative bandwidth (3.77–10.14 GHz) under normal incidence. A prototype of the proposed checkerboard surface is fabricated, and the measurements results show good coincidence with the synthetic studies. The bistatic RCS of the checkerboard surface is considered for both transverse electric and transverse magnetic polarizations under oblique incidence. [ABSTRACT FROM AUTHOR]

An equivalent circuit is developed for an electromagnetic bandgap (EBG) antenna that can provide a mathematically simple means for calculating the antenna's input impedance. The model predicts a −10 dB impedance bandwidth of 0.42 GHz which is validated against simulated and measured values of 0.50 GHz and 0.51 GHz, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the design of the electromagnetic soft surfaces realized by metal strips loaded with C-shaped slots is demonstrated having good suppression of electromagnetic coupling in between two patch antennas. Electromagnetic bandgap properties of the as-prepared electromagnetic soft surfaces with C-shaped slots loading is proposed for normal incidence, and compared with that from the one of the same size but none C-shaped slots on the patches. The proposed structure possesses excellent miniaturization properties with working frequency of bandgap toward lower frequency but keeping the filtering level unchangeable. Then, the proposed structure is loaded in two patch antennas for decoupling in between them. Experimental results are presented and compared to numerical simulations, and they demonstrated that the proposed electromagnetic soft surfaces loading advances excellent suppression of electromagnetic coupling and the coupling decrease about 17 dB near the working frequency band. [ABSTRACT FROM AUTHOR]

This paper presents a microwave angular displacement sensor that consists of a curved two-metal-layer coplanar waveguide (TML CPW) loaded by an electromagnetic bandgap structure (two semi-cylindrical periodic air-gap structures of dielectrics, allocated at the top and bottom of the curved TML CPW). Rotating one of the dielectrics against the other one, produces a variation in the depth of the stopband at the central frequency. The magnitude change is proportional to the angle of the rotation. The curved TML CPW line with the length of 140 mm is fabricated on a 254~\mu \textm thick RO3010 Rogers substrate ( \varepsilon r = 10.2 and \tan \delta = 0.0022 ), which is arched in a semi-cylindrical shape with a radius of 50 mm. The periodic air-gap structures, in order to create the electromagnetic bandgap, are manufactured by laser cutting of an optically transparent polycarbonate ( \varepsilon _{r} = 2.8 and \tan \delta =0.01$ ) in semi-cylindrical shapes. The analysis, finite element method simulation, realization, and measurements have been performed for the sensor with 15 unit cells. An average sensitivity and a dynamic range of about 3 dB/deg and 5° degrees, respectively, have been obtained at 10.2 GHz. The fixed operating frequency and the wide bandwidth of the sensor (>1 GHz) will simplify the design and fabrication of the data readout circuit. The impact of the structure curvature on the sensor response is also investigated as an important practical issue. [ABSTRACT FROM PUBLISHER]

In this paper, an electromagnetic bandgap inspired scanning-probe sensor and its measurement platform is presented for the characterization of high-frequency dielectric laminates. In the proposed sensing technique, the material under test (MUT) is placed between the electromagnetic bandgap structure and a substrate comprising of 50- \Omega microstrip lines. Transverse electric excitation is given from the microstrip line to the suspended electromagnetic bandgap structure via MUT, which allows the characterization of different types of damage and defect severities in the MUT. By tapping the material surface with the proposed sensor, a shift in the effective relative permittivity is calculated. The sensor structure consists of 1 \times 3 unit-cell elements. Each of the unit-cell structure has two asymmetrical H-shaped slots and a metal via. The sensor system is modeled and fabricated using Rogers isotropic thermoset microwave material of relative permittivity \varepsilon r = 12.85 , and loss tangent \tan \delta = 0.0018 . The dispersion analysis of the electromagnetic bandgap structure shows frequency bandgap between 1.93 to 3.18 GHz, which defines the operating range of the sensor. The fit effective permittivity values obtained from simulation and measured results for nondefective samples are in close agreement with the literature. A deviation in the effective permittivity is obtained for the defective material which indicates the severity of the defect. The proposed method can be effectively utilized for fault monitoring and testing of larger dielectric laminates. [ABSTRACT FROM PUBLISHER]