Dielectric Loading Research Articles

In-Band Mutual Coupling Suppression in Dual-Band Shared-Aperture Base Station Arrays Using Dielectric Block Loading

Dual-band base station antenna (BSA) arrays with shared aperture have attracted considerable attention for the fifth-generation (5G) communication. The focus is mainly on decoupling between lower band (LB) and higher band (HB) antennas (i.e., cross-band decoupling). The in-band BSA decoupling techniques are usually not applicable to broadband dual-band shared-aperture BSA arrays. HB BSAs’ elements usually are separated by more than half-wavelength to reduce the in-band mutual coupling, which increases the array aperture and causes grating lobes for beam steering. Here, a novel decoupling technique of dielectric blocks is proposed to suppress the in-band couplings in dual-band shared-aperture BSA arrays. The dielectric blocks are placed above the HB elements to neutralize the original coupling by creating partially reflected waves (an addition wave path). A compact interleaved dual-band BSA array with dielectric blocks is designed and manufactured. The LB operates between 1.9 and 2.5 GHz, and the HB covers the 5G band from 3.3 to 3.9 GHz. The HB coupling is effectively reduced below −25 dB, while the impedance matching and radiation performance of the HB and LB elements are maintained. Moreover, the dielectric blocks are implemented for stacked and interleaved dual-band BSA arrays with suppressed cross-band interference. The proposed decoupling method has simple structures, easy to design and fabricate, and is compatible with the existing cross-band decoupling techniques for different dual-band BSA array configurations.

A Sensitivity-Enhanced Sensor Based on Zeroth-Order Resonance for Liquid Characterization

A high-sensitivity planar microfluidic sensor is proposed in this paper based on composite left/right-handed transmission line (CRLH TL). By employing the series zeroth-order resonance (ZOR), the resonance of proposed sensor is only determined by surface capacitance and inductance. The short-circuit structure reduces the energy loss due to edge radiation and generates a highly concentrated electric field on the top surface of the substrate, which can be used to detect the dielectric loading samples. The presented sensor has been simulated, fabricated and tested. The sensor on the printed circuit board (PCB) is integrated with the fluidic container made of polydimethylsiloxane (PDMS) to form the test device. The water-ethanol binary mixture and sucrose solution are used to proof the concept. Finally, the prediction model for the water-ethanol mixture based on measured parameters has been established and the analysis of prediction error has been carried out. The sensor works around 4 GHz, and the maximum sensitivity reaches 1.04. Due to the high sensitivity and simple structure, the proposed structure is a competitive candidate for the applications including bio-sensing and portable biomedical device.

Low-Profile High-Gain Endfire Antenna With Circular Polarization

A circularly-polarized (CP) traveling-wave endfire antenna featuring low profile, high gain, and simple feeding structure is presented in this communication. Offset parallel strips with proper dielectric loading are employed in a low-profile substrate to achieve two orthogonal electric field components with equal magnitude and 90° phase difference for CP endfire radiation. Meanwhile, periodic phase-loading technique is used to achieve a proper phase constant for high endfire gain. A prototype is designed and fabricated to verify the proposed method. Experimental results demonstrate CP endfire radiation within a frequency band of 9.78–10.09 GHz. The average endfire gain is 10.3 dBic with an average efficiency of 62.5%.

A Deionized Water-Infilled Dual-Layer Insulator-Applied Brain-Implanted UWB Antenna for Wireless Biotelemetry Applications

We propose a novel double-layered insulator configuration for a human-brain-implanted impulse radio ultra-wideband (IR-UWB) antenna. The dimension of the antenna is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10.0\times 11.0\times0.954$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , including the dual-layer insulator. The insulator provides a dielectric loading effect of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r}~\approx ~50$ </tex-math></inline-formula> (lossless) for obtaining an improved radiating power and the broadband-impedance-matching characteristic in brain tissues. The outer layer is made of biocompatible 3-D printing material, and the inner insulator is filled with deionized water with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r}~\approx ~80$ </tex-math></inline-formula> and loss tangent (tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta$ </tex-math></inline-formula> ) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx ~0.25$ </tex-math></inline-formula> at 4 GHz. A slotted UWB antenna with the proposed insulator is located between the emulated dura and CSF tissues inside the skull for brain signal detection. The design uses a multilayer phantom, mimicking the seven tissue layers of the brain. The impedance and radiation performance of the proposed antenna configuration are also discussed using the commercial high-precision human phantom model. The designed IR-UWB antenna shows a boresight radiation characteristic toward the top of the head with a proper high gain in the target frequency of 3–5 GHz. The computed expectations are verified experimentally. Furthermore, it is demonstrated that the UWB spectrum generated from a UWB radio-frequency (RF) transmitter can be transmitted stably using the proposed antenna as a transmitting antenna. In addition, the link budget of the system setup is analyzed. The improved gain characteristic of the antenna from the proposed dual-layer insulator can be utilized to retain the link margins while satisfying the UWB communication regulation and average specific absorption rate (SAR) limitation.

Design of a Split Ring Resonator Integrated with On‐Chip Terahertz Waveguides for Colon Cancer Detection

AbstractFinite element method (FEM) simulations (employing ANSYS High Frequency Structure Simulator, HFSS) are used to investigate the response of terahertz (THz) frequency range split‐ring resonators (SRRs) integrated with on‐chip THz waveguides to cancerous tissues. Two‐port S‐parameter simulations are performed to obtain the transmission spectra (S21) of a planar Goubau line (PGL) integrated with an SRR. Permittivity and loss tangent of the colonic tissues are both taken into account in the numerical simulation. The transmission spectra of the SRR integrated PGL are obtained for cancerous and healthy tissues in close proximity to the SRR, and it is found that they can be distinguished by the resonant frequency shift of the SRR induced by dielectric loading. The electric field distribution and magnitude near the SRR for various capacitive gap widths of SRR are investigated to understand how the gap width affects the maximum electric field magnitude and the vertical extent of the electric field in the gap area. The simulated imaging of colonic tissue consisting of healthy and cancerous tissues using the SRR integrated PGL device with a protective layer on it is performed, showing how the technique could in principle be used to distinguish tumor margins with realistic THz dielectric parameters.

High Average Power Investigation of Dielectric Dissipation in the W-Band Gyro-TWT

The dielectric load gyro-traveling wave tube (gyro-TWT) is a primary high-power millimeter source, and its power capacity is limited by the thermal capacity of the attenuated dielectric. The heavy outgassing was observed when the gyro-TWT operated in a long pulse duration in the experiment. The heat dissipated on the dielectric, and its distribution is analyzed. Then the thermal performance for different pulse duration is investigated. The dielectric temperature reaches 390 °C and 214 °C for the pulse duration of 2 ms and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200 ~\mu \text{s}$ </tex-math></inline-formula> with a duty cycle of 10%, respectively. It indicates the thermal resistance of the dielectric limits the power capacity. The average power capacity in different pulse duration is evaluated. Then a high average power experiment is realized. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band gyro-TWT is operated at 60.5 kV–9.4 A, with a pulse duration of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200 ~\mu \text{s}$ </tex-math></inline-formula> and a duty cycle of 16%. A peak power of 126.1 kW and an average power of 20.2 kW are obtained at 94 GHz.

Folded circulator with shorted Y‐junction for high power applications

AbstractIn this letter, a compact suspended‐stripline circulator with high power‐handling capability has been proposed. The presented double‐knotted circulator is constructed by folding the structure through an air‐filled micro‐coaxial line. Power‐handling capability is increased using a single‐sided ferrite disc and dielectric loading at the central junction. Moreover, another Y‐junction shorted to the ground is coupled on the other side of the substrate to improve the circuit impedance matching. The equivalent circuit model and high power characteristics of the suspended‐stripline circulator are proposed and analyzed. An X‐band double‐knotted circulator has been designed, simulated, fabricated, and measured. The measured results show a reasonable agreement with the simulated ones.

Bidirectional CPW Fed Quad-Band DRA for WLAN/WiMAX Applications

Due to the size constraint, antennas with compact size are required that can support multibands with single radiating element. Dielectric resonator antenna (DRA) can support multiple modes with good efficiency and gain using single radiating element. In this paper, a quad-band DRA is proposed for WLAN/WiMAX bands using a single CPW feed. Out of four bands, WLAN (2.37-2.55) GHz, (5.15-5.35) GHz, and (5.6-5.83) GHz are achieved by the excitation of fundamental and higher-order modes whereas WiMAX (3.58-3.72) GHz band is achieved by dielectric loading of the DR. Dielectric loading makes it possible to operate the antenna at desired frequency band. Due to the partial ground plane and single coplanar waveguide (CPW) feed radiation pattern of the proposed antenna is bidirectional. The design is efficient in terms of radiation efficiency. Simulated and measured results show that it can be a suitable candidate for WLAN and WiMAX applications.

Robust and Broadband Graphene Surface Plasmon Waveguide Coupler via Quantum Control

In this article, a novel graphene subwavelength waveguide coupler is designed based on the quantum control theory. Compared with metal surface plasmon polaritons (SPPs), graphene surface plasmon polaritons (GSPPs) have a smaller SPP wavelength and tunable properties. The dielectric load graphene plasmon waveguide (DLGPW) is used for designing to avoid the influence of the edge shape of the graphene nanoribbons on the waveguide mode. The coupling coefficient between the waveguides is calculated by using the coupled-mode theory (CMT). Due to the subwavelength properties of the graphene surface plasmons (GSP) and the robustness of the quantum control technique, our device is more compact and robust against perturbations of geometrical parameters under the premise of high transmission efficiency. The device we designed also has broadband characteristics, ranging from 30 THz to 40 THz, with high transmission efficiency when considering the transmission loss. We believe that our device will significantly contribute to integrated optics and photo-communication.

Reconfigurable Dual-Band Capsule-Conformal Antenna Array for In-Body Bioelectronics

Wireless in-body bioelectronics offer powerful biosensing and therapeutic capabilities. Efficient and robust in-body antenna designs are required to ensure a reliable through-body link, increase data rates, and reduce power budgets. This study proposes and demonstrates a pattern- and frequency-reconfigurable capsule-conformal antenna array that responds to the challenges of next-generation in-body bioelectronics. The array comprises two mirrored dual-band elements operating at 434 MHz and 2.45 GHz ISM bands. Tissue-matched dielectric loading of the array improves the radiation efficiency and ensures quasi tissue-independent operation for both bands. Due to the full ground plane, the antenna is shielded from the capsule payload. The achieved efficiencies are compared to the fundamental limitations and closely approach them. The realized gains are −28.9 and −18.6 dBi at 434 MHz and 2.45 GHz, respectively, when the array is placed in the center of a ø100-mm diameter spherical phantom with muscle-equivalent properties. Using a single switch, the array can be reconfigured to adjust the angular position of the nulls in the radiation pattern in both bands thereby enabling synthesis of an effectively null-free omnidirectional pattern. The array prototypes are fabricated, and the impedance and far-field radiation patterns are characterized to validate the design in tissue-equivalent liquid phantoms.

Novel electromagnetic-black-hole-based high-efficiency single-mode microwave liquid-phase food heating system

Microwave heating exhibits a high potential for usage in liquid food processing. Current microwave heating systems are designed for a specific load. However, when the permittivity of the load changes dynamically, the heating efficiency of these systems fluctuates considerably. We proposed a novel high-efficiency microwave liquid heating system for dynamic dielectric loads to address this limitation. In this system, an electromagnetic black hole efficiently absorbs electromagnetic waves in all directions. First, an electromagnetic black hole was realized using metamaterials (which means artificially structured dielectric materials with extraordinary physical properties) with a radially continuous refractive index distribution. Next, an electromagnetic field simulation model was established to calculate the microwave absorption of various load permittivity. To discretize and simplify the parameters of the continuous distribution in an electromagnetic black hole, a concentric layered structure and a punched structure composed of uniform isotropic dielectric materials were designed. Finally, the experimental samples were processed based on the two discrete structures. The microwave system developed for experimental verification confirmed the high efficiency of the heating system; the system is simple and usable in numerous applications. Thus, the proposed method can realize high-efficiency heating of loads over large dielectric dynamic ranges. When the dielectric constant of the load changed dynamically from 10 to 80, the microwave energy utilization rate can increase by up to 90%.

Dielectric loading method for doubly resonant enhancement of third-harmonic generation from complementary split-ring resonators

Nonlinear optical response could be greatly enhanced when metasurfaces support plasmonic resonances at both fundamental and harmonic wavelengths. However, it is still challenging to fulfill the doubly resonant condition. Here, we propose a dielectric-loading method, which simply coats a conformal thin dielectric layer onto the plasmonic metasurfaces, to introduce an additional degree of freedom and make the doubly resonant condition easily fulfilled. We demonstrate that by simultaneously tuning the thickness of the coated dielectric layer and the geometrical parameters of the gold complementary split-ring resonators (CSRRs), the doubly resonant enhancement of third harmonic generation (THG) could be achieved for any given fundamental wavelengths. We also experimentally verify this concept and show that the THG intensity in the dielectric-loaded CSRRs under the doubly resonant condition could be further increased about 3 times as compared with the case of the conventional CSRRs.

Asymmetric carbon nanotube dimers embedded in a dielectric slab: new plasmonic resonance behavior

All prior work on modeling the full-wave electromagnetic response of carbon nanotubes (CNTs) have focused on CNTs in free-space, whereas in most practical applications, CNTs are embedded in a dielectric substrate. In this work, we use full-wave simulations to study the plasmonic resonances of CNT dimers embedded in a lossy dielectric slab with a finite thickness. The numerical results show that the finite thickness dielectric slab leads to the emergence of new CNT resonance behavior that is not present in a homogeneous environment. As a single CNT approaches the dielectric slab interfaces, the resonance frequency of the CNT increases due to reduced dielectric loading. The resonance behavior changes completely when two CNTs in proximity form a dimer near the slab interface. The bonding and antibonding resonances of CNT dimers and the absorbed power vary significantly with the distance between the slab interface and the CNT dimer. Using this phenomenon, we show that symmetric CNT dimers can behave like asymmetric CNT dimers. Also, the antibonding resonance of an asymmetric CNT dimer can be suppressed by adjusting the length and depth of the CNT dimer inside the slab. This work can guide future sensing modalities based on CNT dimer as well as can provide an accurate assessment of the proximity of a CNT network to the interface of the embedding substrate.

Refractive Index-Based Terahertz Sensor Using Graphene for Material Characterization.

In this paper, a graphene-based THz metamaterial has been designed and characterized for use in sensing various refractive index profiles. The proposed single-band THz sensor was constructed using a graphene-metal hybridized periodic metamaterial wherein the unit cell had a footprint of 1.395λeff × 1.395λeff and resonated at 4.4754 THz. The realized peak absorption was 98.88% at 4.4754 THz. The sensitivity of the proposed metamaterial sensor was estimated using the absorption characteristics of the unit cell. The performance of the sensor was analyzed under two different categories, viz. the random dielectric loading and chemical analytes, based on the refractive index. The proposed THz sensor offered a peak sensitivity of 22.75 GHz/Refractive Index Unit (RIU) for the various sample loadings. In addition, the effect of the sample thickness on the sensor performance was analyzed and the results were presented. From the results, it can be inferred that the proposed metamaterial THz sensor that was based on a refractive index is suitable for THz sensing applications.

Dual Band, Miniaturized Permittivity Measurement Sensor With Negative-Order SIW Resonator

A novel dual band, highly sensitive Substrate Integrated Waveguide (SIW) sensor for permittivity measurements is presented. A pair of modified Complementary Split Ring Resonators (CSRRs) is etched on SIW surface. CSRRs are located in the center of SIW, where the electric field distribution is high so that the coupling be maximized. The coupling between the SIW and the CSRRs as well as the adjacent CSRRs results in two notches in transmission coefficient. These notches vary with the dielectric loading on the sensor. The ratio of a notch variation to the load permittivity variation determines the sensitivity of proposed sensor. Two sensitivities proportional to two notches are provided. Normalized sensitivities from both notches show identical values. Therefore, any environmental effect have the same variation on the TZs. This demonstrates the potential of the proposed sensor for differential operation that can mitigate the effect of environmental condition. The size of the proposed sensor is small as the inductive and the capacitive effects of CSRRs forced the SIW to operate below the cut off frequency at negative-order-resonance mode. All design steps including SIW design, CSRRs design and modified CSRRs effects are presented in details. The sensor operation principle is described through an equivalent circuit model as well as simulation results. The experimental results indicates that the normalized sensitivity is 3.4% which is much higher than similar sensors. The prototype sensor size ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$27.8\times 18.4\times 0.508$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) is smaller than those reported in the literature.

A Compact Wideband Vertically Polarized End-Fire Millimeter-Wave Antenna Utilizing Slot, Dielectric, and Cavity Resonators

A compact wideband vertically polarized endfire antenna operating at millimeter-wave (mmWave) is proposed. The wideband characteristic is achieved by combining three resonances which are, respectively, formulated using slot, dielectric, and cavity resonators. The compact topology is realized through the employment of dielectric loading technique. The proposed via-structured antenna element is designed to operate from 25.8 to 40.1 GHz, which represents a bandwidth of 43.4%. The antenna features a compact size of 0.37×0.45×0.17 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ( 4.3×5.2×2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ), where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> is the free-space wavelength at the lowest frequency. The element realized gain varies from 3.5 to 7.6 dBi. A detailed performance analysis is provided, which helps to understand the principle of operation of the proposed antenna. The dielectric situated in the frontside of the cavity features a dual-function: 1) a resonator to generate the second resonance and 2) an impedance matching layer for the entire operating band. Two antenna array models are fabricated and examined for in-depth investigation. The first model contains a power divider for fixed beam analysis, and the second model is connected to the mmWave beamforming module to investigate the beam scanning capability of the proposed antenna. The simulated impedance bandwidth (reflection coefficient <; -10 dB) of the four-element array equals 47.1% from 24.75 to 40 GHz and the realized gain varies from 6 to 11.4 dBi. The studies collectively ascertain that the proposed antenna features one of the most compact volumes while exhibiting one of the widest bandwidths to be reported in the literature.

Single-step etched grating couplers for silicon nitride loaded lithium niobate on insulator platform

Dielectrically loaded thin-film lithium niobate (LiNbO3) on insulator (LNOI) platforms have enabled a range of photonic integrated circuit components, such as high-speed optical modulators, switches, and nonlinear devices, while avoiding the direct etching of the LiNbO3 thin film. Silicon nitride (Si3N4) is one of the most attractive dielectric loading materials as it has a similar refractive index and transparency window to LiNbO3 and can be deposited and patterned by mature fabrication processes. The patterning of Si3N4 opens the opportunity to fabricate grating couplers in the same fabrication step, providing efficient optical interfaces for wafer-scale testing. In this paper, we investigate and demonstrate single-step etched grating couplers on a Si3N4-LNOI (X-cut) platform. The grating couplers (straight and curved) are designed and fabricated for TE-polarized modes along the Y and Z crystallographic directions, considering the LiNbO3 crystal’s birefringence. The experimentally demonstrated coupling losses are as low as 4.02 and 4.24 dB along the crystallographic Y and Z directions, respectively. The corresponding peak wavelengths are 1609 and 1615 nm, respectively. The measured 3-dB bandwidths are wider than 70 nm for both crystallographic directions. We also numerically investigated the influence of fabrication variations and the fiber angle on the transmission. To the best of our knowledge, this work is the first demonstration of grating couplers with different light propagation directions on the Si3N4 loaded LNOI platform.

Estimation of Glucose Levels in Blood Sample using A Biosensor

This paper discusses about estimation of glucose concentration in blood using a Triple pole Complementary split ring resonator (TP-CSRR) antenna. Glucose concentration in blood is the direct indicator of Diabetes disease. The designed microstrip antenna operates in range of 2-5 Ghz and has a resonance frequency of 3.35 Ghz when simulated. When the antenna is excited, blood acts as dielectric load to it. Hence the glucose concentration of blood affects the resonant frequency and amplitude at resonant frequency of the s21 parameter of the antenna. Using this information, we can estimate the glucose concentration of blood sample. Debye model was used to model the blood. It is effective in detecting glucose concentration of Type-2 diabetes (70-120 mg/dL). The amplitude sensitivity is 0.58 dB(mg/ml) and frequency sensitivity is 583 Mhz/(mg/ml).

A Novel Coplanar Slow-Wave Structure for Millimeter-Wave BWO Applications

A novel coplanar slow-wave structure (SWS) for application in millimeter-wave backward-wave oscillator (BWO) is proposed in this article. Unlike the traditional microstrip meander-line SWS with metal layers on both top and bottom surfaces of the substrate, the proposed SWS has a metal layer only on the top surface of the substrate. This significantly reduces the dielectric loading effect. The SWS is quite suitable for fabrication using PCB or microfabrication techniques and can be directly fed with coplanar waveguide (CPW), which has a lower loss than microstrip line. A design of the SWS presented here covers a -15-dB S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> frequency range from 13.7 to 120 GHz. Simulation results for a BWO based on the proposed SWS show a tunable frequency range of 32.7 GHz and a maximum output power of 22.7 W at 114 GHz. To verify the proposed concept, a scaled version of the SWS is fabricated and measured S-parameters are presented. With a good potential for fabrication using microfabrication techniques, this structure can be a good candidate for millimeter-wave BWO applications.

A Coupled-Cavity Resonator Technique for Simultaneous Sensing of Dielectric Load and Position of Continuous Material Streams

An electromagnetic coupled-cavity resonator equipped with permanent insertion holes and designed to sense continuous dielectric material streams through the resonator is presented. The resonating structure comprises a pair of pill-box-shaped cylindrical cavities mutually coupled to each other through an aperture-loaded metal sheet of finite thickness. The input and output insertion holes in the top and bottom lids of the cavity structure form a channel for the flow of dielectric samples under test. The arrangement of aperture-coupled cavity sections results in antisymmetric and symmetric field distributions with split resonances. The resonating antisymmetric field is primarily utilized to detect dielectric load variations of the sample stream, similar to the commonly practiced permittivity based measurements in TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">010</sub> cavities. The additional resonance mode with the symmetric field distribution is more sensitive to position offsets of the sample in its concentric flow along the axis. Due to the added resonance, the arrangement provides for 2-D sensing of dielectric specimens under test (dielectric load variation and position offset) and improved accuracy can, thus, be achieved. The working principle of the coupled-cavity technique is analyzed qualitatively by numerical computations. The technique is validated by measuring samples of commercially available cotton fibers with a realized prototype.