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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.

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]

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]

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.

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.

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. [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]

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]

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 ( \mathcal 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. [ABSTRACT FROM PUBLISHER]

The detection of a drug having a weak basic dissociation constant (pKa) in bio-fluids requires a complex organic framework, time-consuming assay, and costly characterization techniques. To overcome this, a novel metallic photonic bandgap-inspired probe that as a sensor device is proposed for the microwave spectroscopy of gold nanoparticles. Minoxidil drug with dissociation constant 4.61 was detected using gold nanoparticles as a colorimetric probe and the sensor device as a microwave signal detection probe. In this method, the aggregation of gold nanoparticles is induced with the drug and then shift in the probe resonant frequency through in situ analysis was calibrated. The induced aggregation between gold nanoparticles and the drug was confirmed by dynamic light scattering and Fourier transform infrared measurements. This method was tested and validated in human urine samples, which provided an acceptable linear relationship between the resonant frequencies over 100–500 and 0.1– 10~\mu \textM concentration of the drug. The present analytical technique can be effectively used for detecting drugs having low pKa value in the real biological samples. [ABSTRACT FROM PUBLISHER]

This paper is focused on the synthesis of capacitively loaded coupled lines for the design of bandpass filters with compact size and spurious suppression. The filters consist of cascaded pairs of coupled lines periodically loaded with patch capacitors. The loading capacitances provide a slow-wave effect to the coupled lines useful for filter miniaturization, whereas periodicity introduces bandgaps that can be controlled in order to achieve spurious suppression. Filter design is achieved following an automated process based on aggressive space mapping (ASM) optimization. The two reported examples, a third-order filter with central frequency f0 = 1.0 GHz, 8% fractional bandwidth, and 0.1-dB ripple level and a fifth-order filter with central frequency f0 = 1.8 GHz, 8% fractional bandwidth, and 0.1-dB ripple level, demonstrate the potential of the proposed ASM-based design approach, as well as the effectiveness of the loading capacitances to reduce filter size and reject the spurious bands. Significant size reduction in both filters is achieved, whereas the out-of-band rejection is better than 30 and 45 dB in the third-order and fifth-order filters, respectively, up to at least 4f0 . [ABSTRACT FROM PUBLISHER]

A novel fixed-frequency electronically steerable Fabry–Pérot Antenna (FPA) with electronic two-dimensional (2-D) (azimuth and elevation) steering capability is presented. The configuration is based on a centrally fed Fabry–Pérot cavity (FPC) loaded with a tunable high impedance surface (HIS). Varactor diodes are used to electronically tune the HIS reflection coefficient, forming four azimuthal sectors that are independently controlled by four control signals, respectively. It is demonstrated that this simple configuration generates a pencil beam that can be pointed to eight discrete azimuthal directions, whereas continuous elevation scanning is also attained simultaneously for each azimuthal direction by controlling the leaky-wave propagation constant. The theory, simulation analysis, and experimental results obtained from a prototype operating at 5.5 GHz are presented to validate the antenna design. [ABSTRACT FROM AUTHOR]

This paper deals with the filters based on EBG cavities employed for reducing common-mode currents along differential stripline traces. The crosstalk among differential interconnects routed in close proximity to EBG-based filters, and next to filtered pairs, is accurately quantified. The comparison between the experimental and simulation frequency-domain results validate the proposed filter's effectiveness and make the simulation model reliable for investigating the complex multichannel crosstalk problem. This paper focuses on the stripline environment, where crosstalk occurs among traces routed on adjacent layers, with the EBG cavity acting as a coupling path. Multichannel time-domain simulations complete the characterization of the filter, showing the limited effects of the filter on the intentional differential signal, and the beneficial impact on reducing the potentially radiating common-mode harmonics. The quantification of the common-mode spectrum shows that the filtered harmonics are reduced by 10–15 dB; thus, minimizing the corresponding electromagnetic interference. Design guidelines are defined for the filter layout according to the relative position of unfiltered differential traces, when constraints force them to be placed in close proximity to EBG cavities and filtered pairs. In particular, the best layout for unfiltered traces on adjacent layers is orthogonal with respect to the filtered pair, whereas the parallel routing should be carefully used taking into account the signal bandwidth on the victim pairs. [ABSTRACT FROM AUTHOR]

The aim of this study is to analyze from a modeling and experimental point of view the filter effectiveness and the crosstalk among signal traces crossing the same common-mode filter based on electromagnetic bandgap structures in a modern server design configurations. Both microstrips and striplines are considered in the study, detailing the differences among them in the design step as well as in filter geometry and response. Simulation models and experimental setups are carefully described, and the numerical and measurement results are compared and discussed. [ABSTRACT FROM AUTHOR]

A method is proposed to decrease the matching frequency of the recently introduced self-excited electromagnetic bandgap (EBG) resonator antenna (SE-EBG-RA). The method is based on the application of a metal shorting plate at the open end of the antenna which reduces the resonance. EBG unit cells are comprised of thick metal patches on top of a PEC-backed substrate, which are separated by tiny high aspect ratio (HAR) gaps. Two to six cells, each electrically much smaller than wavelength, are deployed in one-dimensional (1-D) as a fragment of EBG microstripline with high radiation properties. Both open-circuit (OC) and short-circuit (SC) versions are presented, the SC version being electrically smaller. The miniaturization effect of dielectric loading of HAR gaps is also examined. The characteristics of proposed structures as improved radiators in terms of bandwidth (BW), size, gain, and efficiency are demonstrated through parametric and comparative analyses and also prototyping. The efficiency, BW, and footprint of the smallest dielectric-loaded version, a two-cell SC SE-EBG-RA, are 96%, 3.5%, and $0.22\lambda \times 0.28\lambda $, respectively. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a compact and wideband electromagnetic bandgap (EBG) structure using a defected ground structure (DGS) to significantly enhance the wideband suppression of power/ground noise coupling in multilayer packages and printed circuit boards. The proposed EBG structure is implemented simply by adding a rectangular-shaped DGS which is etched periodically onto the ground plane without changing any other geometrical parameter from a mushroom-type EBG structure. The DGS effects on the f _L and f _U are thoroughly analyzed using the dispersion characteristics. We experimentally verified that the proposed EBG structure achieved the wideband power/ground noise suppression (below −40 dB) between 2.5 and 16.2 GHz. In addition, we demonstrated the considerable reduction in f_L from 3.4 to 2.5 GHz and a significant increase in f_U from 9.1 to 16.2 GHz when compared with the mushroom-type EBG structure. [ABSTRACT FROM PUBLISHER]

in this communication a high directive electromagnetic bandgap (EBG) antenna operating in wide frequency band for both return loss (RL) and directivity is examined. In this EBG antenna an aperture coupled microstrip antenna (ACMA) is used as a feeding source and a frequency selective surface (FSS) is used as a superstrate layer. Suitable use of the superstrate layer, microstrip patch and coupling aperture simultaneously, leads to produce separate resonance frequencies and therefore the wide frequency band for RL. Also, high directivity is achieved only by using the superstrate layer that has been made by the FSS layer with square loop elements. At first, a wideband ACMA is designed to operate in x-band. In this step appropriate design of coupling aperture is of a great importance. Secondly, after the design of optimum superstrate layer by the FSS structure, it is added to the ACMA in order to increase both bandwidth and directivity. [ABSTRACT FROM AUTHOR]

A compact reduced unit cell size electromagnetic bandgap (EBG) power plane, realized with a combination of alternating impedance EBG and multiple narrow slits, is presented. By concatenating 2 × 2 high-frequency unit cells, a virtual low-frequency EBG unit cell is synthesized without changing the overall dimensions. In this configuration, the basic slit in the high-frequency unit cell remained same, and an additional slit with longer dimensions is added in parallel to the basic slit by synthesizing a larger low-frequency unit cell. EBG is characterized for its dispersion diagram, noise suppression, signal integrity, and electromagnetic radiation. Fabricated EBG exhibits a bandgap from 0.9 to 3.5 GHz with isolation better than −40 dB over the band. Radiated emission of the new EBG is small with an average value of 35 dB·uV/m. Compact EBG also exhibits low impedance, which is less than 1 Ω over the stopband. Eye patterns are generated to analyze signal integrity issues when the data lines are referenced over the solid ground plane and EBG plane. The degradation of the maximum eye opening and the maximum eye width for the proposed EBG power plane at 2 Gb/s data rate is about 17.8% and 1%, respectively, with reference to the equivalent board with solid power plane. [ABSTRACT FROM AUTHOR]

In this paper, an embedded electromagnetic bandgap structure is proposed for harmonic filtering of differential signal's undesired common mode components. Rather than use lumped circuit components and likely causing some degradation to the intended high speed differential signal, the embedded planar common mode filter causes no degradation to the intended signal, and enhances the signal integrity and electromagnetic compatibility performance of the system. Single ended and differential traces are considered and the impact of the common mode filtering is measured in terms of mixed mode scattering parameters and eye diagram metrics. The systematic procedure to design such a structure is outlined, and its design robustness is also verified. [ABSTRACT FROM AUTHOR]

In this paper, a novel full-wave method for the modal characterization of closed metallic periodic structures based on arbitrarily shaped waveguides is presented. This method relies on an integral equation formulation solved via the method of moments, which finally leads to the solution of a standard eigenvalue problem. The required modal spectrum of waveguides with arbitrary cross section is determined through the boundary integral-resonant mode expansion technique. For validation purposes, the proposed analysis method is first successfully applied to standard waveguide periodic geometries already considered in the technical literature. Our new algorithm is then used to identify the higher order Floquet modes, as well as to compute the related Brillouin diagrams, of complex closed metallic periodic structures loaded with arbitrarily shaped waveguides. [ABSTRACT FROM AUTHOR]

One of the known advantages of an electromagnetic bandgap (EBG) ground plane is the fact that a straight-wire dipole can be located parallel and in very close proximity to the ground plane. For such a structure and geometry, a reasonable impedance match to 50 Ω can be achieved with more bandwidth than when the dipole is located in close proximity to a PEC ground plane. However, in addition to impedance, radiation-pattern properties must be considered when evaluating the antenna's overall performance and usable bandwidth. Here, we consider the performance properties of a folded bowtie dipole element in close proximity to an EBG ground plane, with emphasis on examining the bandwidth and pattern characteristics. We demonstrate that a dipole element can be designed to exhibit a matched input impedance over approximately a 1.4:1 bandwidth with respect to a 50 Ω characteristic impedance, when located in close proximity to the EBG ground plane. While the shape of the radiation pattern of the antenna remains relatively unchanged over much of this operating bandwidth, we show that the usable bandwidth of the antenna-EBG combination is limited to approximately 1.5:1, due to pattern degradation at both the lower and upper frequencies. Details of the design approach and feed structure used to match the impedance of the dipole to 50 Ω are discussed. Finally, we show that with this element design, the reflection phase bandwidth of the EBG ground plane does not limit the matched impedance bandwidth of the antenna. Aportion of the work detailed here was presented at the 2005 Antenna Applications Symposium. [ABSTRACT FROM AUTHOR]

A novel implementation of periodic boundary conditions in the finite-element method is presented that is applicable to complex eigen-mode analysis of the electromagnetic waves in infinite periodic media. A weighted residual finite-element (FE) model is employed to obtain the attenuation constant of evanescent/complex modes within bandgaps by analyzing only one unit cell of the structure. Plots of the imaginary and the real parts of the propagation constants versus frequency are shown which confirms the capability of the developed FE code in capturing complex modes. [ABSTRACT FROM AUTHOR]

An alternative signal guiding structure, which can be integrated within the printed circuit substrates, is investigated in this paper. The structure is realized by forming a rectangular waveguide in a 2-D electromagnetic bandgap (EBG) substrate. In this manner, a bandpass interconnect is provided that proves to be a promising technology for the high-speed/high-frequency system design. A systematic approach to the design and optimization of this interconnect is presented here followed by investigation of various bend geometries. The studied structures exhibit very low levels of loss and leakage when inspected at tens of gigahertz frequency range. Moreover, the near-end and the far-end crosstalks are monitored in multiple interconnects proving the high efficiency of this alternative routing structure in dense layouts. Nonetheless, the crosstalk performance is degraded as the coplanar microstrip-to-waveguide transitions are added. These transitions are essentially tapered microstrip lines that are connected to other circuitries. Continuous via fences are inserted in the transition sections of multiple structures demonstrating significant improvement in the crosstalk performance. [ABSTRACT FROM AUTHOR]

Due to their unique properties, electromagnetic bandgap (EBG) materials are of high interest for applications in communication technology for many frequency bands from microwave up to optical frequencies. We have investigated in both simulation and experiment a two dimensionally periodic EBG structure made by reactive ion etching of silicon with a bandgap for transverse magnetic waves in the millimeter wave range around 100 GHz. The structure comprises both a large bandgap and a high mechanical stability due to interconnecting dielectric bridges. [ABSTRACT FROM AUTHOR]