Dielectric Loading Research Articles

Microwave reflective biosensor for glucose level detection in aqueous solutions

This article presents the design and analysis of a real-time non-invasive microwave microfluidic sensor for measuring glucose concentration in aqueous solutions. The sensor is made of an open-ended microstrip transmission line loaded with a complementary split-ring resonator (CSRR). The CSRR shows a very intense electric field concentration at resonance, which is highly sensitive to the dielectric sample loading. A microfluidic channel is designed to deliver the glucose solutions to the sensitive area of the device. By applying liquid samples to the channel, a resonance frequency shift is detectable in the reflection coefficient (S11) of the device. This in turn leads to a change in the |S11|. Both of the frequency shift and Δ|S11| can be used to measure the glucose level in the solution. Mathematical models are developed based on the measurement results of the glucose-water solutions using the resonance frequency shift and Δ|S11|. The developed sensing models are then used for detecting the glucose levels down to physiological values using the designed biosensor. The results prove the potential compatibility of the proposed biosensor for human glycaemia monitoring.

Dielectric-Loaded Ultrawideband RCS Reduction Structures

A novel yet geometrically simple radar cross section suppression structure is proposed. Unlike designs fostered in prior works, which contain multiple elevated metal layers, the proposed configuration is only accomplished with a dielectric superstrate. Dielectric loadings of different properties such as permittivity, loss tangent, and thickness are applied to form phase cancellation structures. Contrary to structures based on resonant elements, the proposed constructs are electrically large and are made of homogeneous loadings. A high-frequency method is developed to explain how the ultrawideband backscattering suppressing feature is accomplished. Since it assesses structure reflection properties in a timely fashion with the results comparable to the ones acquired from full-wavelength tools, design optimization can be carried out via grid search. One design exhibits a 4.09:1 bandwidth ratio of 10 dB backscattering reduction for normal incidence, while another achieves a 70% bandwidth of 20 dB reduction. Angular domain performances were also researched. By adopting either the conventional checkerboard pattern or our previously developed random patch pattern, strong backscattering lobes can be avoided near the boresight region. Performance verification via measurements on prototypes is also provided.

Frequency and impedance reconfigurable antenna using magnetically-actuated low-loss Ferrofluid loads

ABSTRACTWith space and spectrum at a premium, antennas must be capable of operating well across a variety of frequencies and environments. This work presents a novel method of frequency and impedance reconfiguration through the actuation of a ferrofluid load with a permanent magnetic bias field, while still achieving up to 85% efficiency. Under a sufficiently strong bias field, the ferrofluid load behaves as a low-loss movable dielectric load, and the actuation method avoids the complexity associated with microfluidic pumps and DC bias networks. This work opens a new field of reconfiguration mechanisms for antennas through magnetic repositioning of low-loss ferrofluid loads.

Ultrahigh-Sensitivity Microwave Sensor for Microfluidic Complex Permittivity Measurement

The conventional resonant-type microwave microfluidic sensors made of planar resonators suffer from limited sensitivities. This is due to the existence of several distributed capacitors in their structure, where just one of them acts as a sensing element. This article proposes a very high-sensitivity microwave sensor made of a microstrip transmission line loaded with a shunt-connected series LC resonator. A large sensitivity for dielectric loadings is achieved by incorporating just one capacitor in the resonator structure. Applying sample liquids to the microfluidic channel implemented in the capacitive gap area of the sensor modifies the capacitor value. This is translated to a resonance frequency shift from which the liquid sample is characterized. The sensor performance and working principle are described through a circuit model analysis. Finally, a device prototype is fabricated, and experimental measurements using water/ethanol solutions are presented for verification of the sensing principle.

3-D Printed Monolithic GRIN Dielectric-Loaded Double-Ridged Horn Antennas

Monolithic integration of 3-D printed gradient index (GRIN) dielectric loading with a double-ridged rectangular horn standard gain horn (SGH) and its impact on antenna performance are demonstrated. Results show that the GRIN loaded horns improve sidelobe levels (SLLs) and beam symmetry, while maintaining good impedance match and relatively high radiation efficiency over more than an octave bandwidth from 7.5 to 18 GHz. Moreover, they have low weight and show good robustness to fabrication imperfections. This work paves the way for seamless integration of complex wideband antennas in 3-D printed systems such as unmanned aerial vehicles (UAVs).

Integration of $S$ /Ka/$D$ -Band Antennas in LTCC With a Cylindrical Radome for Triband Applications

This paper presents the integration of S /Ka/D -band antennas in a low-temperature cofired ceramic (LTCC) package. Three types of antennas, microstrip patch, grid array, and step-profiled horn, operating at different bands are compactly assembled in the same substrate. For electromagnetic isolation, a specific layout and extra-shielding structures, such as fences of metallic vias and air cavities, are designed to reduce the unwanted coupling between antennas. In addition to the antennas, a cylindrical radome is introduced closely attached to the surface of the LTCC substrate. Since radome acts as a dielectric superstrate, its influence on radiation performance is also taken into consideration, especially for D -band operation, where a ring-shaped cavity is introduced to suppress the detrimental propagation of surface waves inside radome and enhance the gain as a consequence of dielectric loading effect. Measured results agree well with simulation. Proposed triband antennas, working at three frequencies 3, 30.5, and 120 GHz, achieve broadside gains of 6.51, 9.74, and 13.36 dBi with -10 dB fractional impedance bandwidths of 15.3%, 6.1%, and 6.5%, respectively.

Compensation of Dispersion in Sinuous Antennas for Polarimetric Ground Penetrating Radar Applications

In order to improve the accuracy of subsurface target classification with ground penetrating radar (GPR) systems, it is desired to transmit and receive ultra-wide band pulses with varying combinations of polarization (a technique referred to as polarimetry). The sinuous antenna exhibits such desirable properties as ultra-wide bandwidth, polarization diversity, and low-profile form factor, making it an excellent candidate for the radiating element of such systems. However, sinuous antennas are dispersive since the active region moves with frequency along the structure, resulting in the distortion of radiated pulses. This distortion may be compensated in signal processing with accurately simulated or measured antenna phase information. However, in a practical GPR, the antenna performance may deviate from that simulated, accurate measurements may be impractical, and/or the dielectric loading of the environment may cause deviations. In such cases, it may be desirable to employ a simple dispersion model based on antenna design parameters which may be optimized in situ. This paper explores the dispersive properties of the sinuous antenna and presents a simple, adjustable, model that may be used to correct dispersed pulses. The dispersion model is successfully applied to both simulated and measured scenarios, thereby enabling the use of sinuous antennas in polarimetric GPR applications.

The Evolution From Metal Horns to Metahorns: The development of EM horns from their inception to the present day

The development of horn antennas is described from their inception in the 1890s to the present. Our main objective is to describe the advancement of their fundamental features, which are often driven by applications. The horn antennas discussed here were selected based on their significant concept advancements and are listed in chronological order within each class based on their first publication. Until the 1960s, only metal horns were used. In the 1970s, horns with dielectric loading were developed and resulted in several new and advanced horn designs. The latest renaissance in horn technology was fueled by the advent of metamaterials over the last 15 years, enabling horns with metasurfaces (metahorns) and horns with metalenses in particular. We now have air-filled, dielectric-loaded, and metamaterial-loaded horns; from inception, we have seen the transformation from metal horns to metahorns. More details will be supplied in the following sections.

Differential Microfluidic Sensors Based on Dumbbell-Shaped Defect Ground Structures in Microstrip Technology: Analysis, Optimization, and Applications.

A microstrip defect ground structure (DGS) based on a pair of dumbbell-shaped slots is used for sensing. The device is a differential sensor consisting of a pair of mirrored lines loaded with a dumbbell-shaped DGS, and the output variable is the cross-mode transmission coefficient. Such a variable is very sensitive to asymmetries in the line pair, e.g., caused by an asymmetric dielectric load in the dumbbell-shaped DGSs. Therefore, the sensor is of special interest for the dielectric characterization of solids and liquids, or for the measurement of variables related to complex permittivity changes. It is shown in this work that by adding fluidic channels on top of the dumbbell-shaped DGSs, the device is useful for liquid characterization, particularly for the measurement of solute concentration in very diluted solutions. A sensitivity analysis useful for sensor design is carried out in this paper.

Gain and Bandwidth Improvement of Empty Substrate Integrated Waveguide H-plane Horn Antenna at W-band

A high-gain broadband empty substrate integrated waveguide (ESIW) H-plane horn antenna constructed by four low-cost printed circuit board (PCB) layers is proposed in this paper. The empty structure is fabricated by using high-precision laser engraving technology. A slotted rectangular dielectric load (SRDL) is introduced by simply extending the substrates, resulting a 4-dB gain enhancement and a 31% bandwidth improvement. The proposed antenna gives a measured realized gain at 14.5-dBi level with a relative impedance bandwidth larger than 19.6% (|S11| ≤ − 10 dB). The proposed antenna features the merits of low cost, high gain, and broad bandwidth.

A Superwide Bandwidth Low-Profile Monocone Antenna With Dielectric Loading

A dielectric-loaded low-profile monocone antenna with vertical polarization and omnidirectional radiation is proposed to cover a superwide frequency bandwidth for some emerging wireless communication applications. The extended bandwidth is achieved by using four quasi-TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0N</sub> modes (N from 1 to 4) and introducing the dielectric loading (DL) with optimal design. The DL can effectively change the impedance response of the monocone antenna and provide additional degree of freedom for increasing the bandwidth. The proposed antenna is designed, fabricated, and tested to verify the antenna's performance. The designed and fabricated antenna with a thickness of only 0.057 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">low</sub> can achieve a superwide impedance bandwidth of 7.3:1 (from 1.6 to 11.7 GHz).

Strip-loaded nano-photonics on horizontal slot waveguide

BackgroundA strip-loaded slot waveguide is a waveguide platform allowing a large amount of degrees of freedom in terms of fabrication. Contrary to other waveguide types where the guiding layer has to be patterned, only the shape of the top layer, usually a polymer, dictates the response of this platform.MethodsWe use the Finite Difference Time Domain method to study the field distribution and the modal behavior of light inside such a waveguide when the loading strip is patterned.ResultsWe present an overview of several photonic-crystal-based structures on a strip-loaded slot waveguide platform. This theoretical study shows how the fundamental mode confined in the horizontal slab slot waveguide interacts with the dielectric loading structures. By investigating the field confinement, one determines the importance of the longitudinal shape over the lateral shape of the loading structure. Through the examples of sidewall corrugation, row of cylindrical or elliptical holes, and random shapes, we show how such a platform can help integration of complex functions in waveguides.ConclusionsAlthough the spectral features depend strongly on the period and fill factor of the Bragg gratings studied in our case, the material distribution plays a key-role in the mode behavior. This impacts directly on the applications of such a platform for further modulators and sensors, for instance.

Millimeter-Wave ATS Antenna With Wideband-Enhanced Endfire Gain Based on Coplanar Plasmonic Structures

Coplanar plasmonic structures are proposed to converge the beam of electromagnetic (EM) wave and to enhance the gain of an antenna. While propagating along the plasmonic structures, EM wave shows a larger propagation constant than that in free space due to the slow wave feature of spoof surface plasmon polaritons (SPPs) SPPs; i.e., it sees a higher equivalent refractive index. Therefore, a dielectric substrate sandwiched by plasmonic structures can be equivalently taken as a refractive index graded lens. To validate this concept, a millimeter-wave antipodal tapered slot (ATS) antenna loaded with the plasmonic structures is designed. The antenna shows merits of beam convergence both in the E-plane and in the H-plane, although the plasmonic structures are coplanar with the E-plane, and also a wide frequency band of gain enhancement due to the nonresonant characteristic of the SPPs. Compared with the reference ATS antenna with dielectric loading, the proposed one shows an additional gain enhancement of 2 dBi in the band of interest (22–27.5 GHz) and the peak gain of 15.5 dBi. The measured and simulated results agree well with each other, which effectively validates the convergence effect of the plasmonic structures in the antenna.

Pattern diversity of path loss compensated antennas for 5G base stations

In this article, a tapered slot antenna (TSA) operating from 27 to 29.8 GHz with an endfire gain of 9 dBi and high pattern integrity is presented. The gain specifications for path loss compensation on ground for a ceiling mounted millimeter wave base station is computed and the gain of the antenna elements with beam angled at ±45° was found to be 12 dBi. To enhance gain with minimal physical footprint, a combination of dielectric loading and electrical resonator metamaterial unit cells were integrated to the proposed TSA to achieve the expected gain enhancement of 3 dB across the band, operating in the same frequency band with aperture efficiency greater than 73% and a 1 dB gain bandwidth of 20.7%. A compact stacking topology for pattern diversity of all three antenna elements for path loss compensation is also investigated. The base station has a coverage of ±60° with uniform illumination and mutual coupling lesser than 35 dB. The detailed simulated and measured results are presented.

A Novel Passive Cost-Effective Technique to Improve Radiated Immunity on PCBs

This paper proposes a novel simple cost-effective technique to improve the potential immunity of integrated circuits (ICs) to radiated electromagnetic (EM) disturbances. It is based on dielectric loading which lessens the susceptibility of ICs independently of frequency by confining the reactive fields inside the dielectric load. This has no side effects on the IC performance. To highlight the importance of the proposed technique, immunity testing was performed numerically both in near and far fields. A loaded IC (a microcontroller) was compared to an unloaded one through far-field measurements inside a transverse EM cell to indirectly assess the suitability of the proposed approach. Results show that loading the IC with non-ferromagnetic dielectric material not only effectively decreases its susceptibility to electric field, but also to magnetic field. Moreover, a significant difference of $\sim$ 48% less failure rate was achieved for the loaded compared to the unloaded IC demonstrating the usefulness of this technique as a potential solution for radiated immunity improvement.

Design of Microwave-Based Angular Displacement Sensor

This letter presents a novel microwave-based rotation sensor having a wide dynamic range to detect and measure the angular displacement in terms of the change in resonant frequency. The proposed sensor is based on the microstrip technology, where a rotor comprised of a complementary split-ring resonator (CSRR) placed on the ground plane of the microstrip line is free to rotate around its axis. The mechanical rotation of CSRR determines a change in the cross coupling between the microstrip line and the CSRR, thus changing the overall inductance. The proposed planar unloaded microwave sensor, working around ISM band of 5.8 GHz, is quite sensitive to detect angular rotation in the wide dynamic range of 0°–90°. The linearity in dynamic range is achieved in the range of 30°–60°. Operating frequency and bandwidth can be adjusted by loading the rotor with dielectric. Depending on the type of dielectric loading of CSRR, it is possible to select the center frequency from a wide range of 4.67–5.94 GHz, with the bandwidth ranging from 116 to 250 MHz. Due to its features, the proposed sensor can be useful for various industrial applications.

Cutoff Frequencies of a Dielectric-Loaded Rectangular Waveguide With Arbitrary Anisotropic Surface Impedance

The coupled transcendental equations describing cutoff frequencies of TE and TM modes are deduced for a rectangular waveguide with arbitrary wall impedance. In the case of TE modes, their generalization is made to a rectangular guiding structure, which possesses both distributed wall impedance and inhomogeneous dielectric loading. Effective impedance is obtained for imperfectly conducting surface incorporating periodic rectangular corrugations along the direction of mode propagation. Circular waveguide bounded by such corrugated surface and rectangular impedance waveguide are considered as numerical examples. For these waveguides, the computations performed to determine the cutoff frequencies of TE guiding modes are validated against the results of the perturbation theory and the finite-element method.

Low Phase Noise Feedback Oscillators Utilizing High-Q SIW Filter with Dielectric Loading

Abstract High-Q substrate integrated waveguide (SIW) resonator and its application to low phase noise oscillators are focused in this paper. By drilling air holes in the substrate, SIW bandpass filters (BPFs) with high Q factor could be achieved. This SIW filter is embedded into the feedback loop to be treated as a frequency stabilization element in designing the oscillator. The complex quality factor (Qsc)-peak frequency of the filter is chosen as the final oscillation frequency to obtain low phase noise performance. Moreover, air boxes are utilized instead of the air holes in the substrate to design another oscillator with lower phase noise performance and good harmonic suppression. Two low phase noise oscillators based on fourth-order SIW BPFs with dielectric loading have been studied, demonstrated and fabricated to verify the design concept.

Dual-Band Spiral Printed Quadrifilar Helical Antenna Miniaturized by Surface and Inner Dielectric Loading

The design and implementation of a spiral-folded printed quadrifilar helical antenna (FPQHA) is presented for a global positioning system (GPS) $L1$ -/ $L2$ -band application. The proposed FPQHA can be miniaturized by inserting dielectric loading inside the helix, covering the radiation elements by the dielectric sealant and turning the radiation elements into the form of parallelogram spirals. The manufactured antenna’s radiation elements are printed on a hollow rod ceramic substrate with a diameter of 12 mm and a height of 24.7 mm. The measurement results of the proposed FPQHA mounting on unmanned platform fit very well with the simulations, which validates the design methods and suggests that the proposed FPQHA is suitable for GPS $L1$ -/ $L2$ -band applications.

A high gain 60 GHz antipodal Fermi‐tapered slot antenna based on robust synthesized dielectric

AbstractA high performance antipodal Fermi taper slot antenna based on unique synthesized dielectric is presented for ultra‐wideband radar applications at 60 GHz band. Specifically, the synthesized dielectric is implemented based on machined holes concentrates only at aperture area to improve its mechanical robustness for lengthy antenna. Further, it is able to suppress back lobe level by 2.5 dB through curving tapered end of the antenna. Concurrently, sine corrugations and dielectric loading are adopted to improve radiation pattern and gain of the antenna for over 20 dB.