Low-loss Dielectric Substrate Research Articles

A Substrate Integrated Waveguide Based Filtenna for X and Ku Band Application

In this paper Substrate Integrated Waveguide-based filtenna operating at Ku band is proposed. The model is designed on a low loss dielectric substrate having a thickness of 0.508 mm and comprises of shorting vias along two edges of the substrate walls. To realize a bandpass filter, secondary shorting vias are placed close to primary shorting vias. The dimension and position of the vias are carefully analyzed for Ku band frequencies. The model is fabricated on Roger RT/duroid 5880 and the performance characteristics are measured. The proposed model achieves significant impedance characteristics with wider bandwidth in the Ku band. The model also achieves a maximum gain of 7.46 dBi in the operating band thus making it suitable for Ku-band applications. Substrate Integrated Waveguide (SIW) Structures possess most of the advantages over conventional radiofrequency waveguides since they have high power management capacity with self-consistent electrical shielding. The most noteworthy advantage of SIW, it can able to integrate all the components on the same substrate, both passive and active components.

Design and Development of Substrate Integrated Waveguide Based Filtenna for X Band Application

In this paper, substrate integrated waveguide based filtenna operating at X band is proposed. The model is designed on a low-loss dielectric substrate having a thickness of 1.6 mm and comprises shorting vias along two edges of the substrate walls. To realize a bandpass filter, secondary shorting vias are placed close to primary shorting vias. The dimension and position of the vias are carefully analyzed for X band frequencies. The model is fabricated on Roger RT/duroid 5880 and the performance characteristics are measured. The proposed model achieves significant impedance characteristics with wider bandwidth in the X band. The model also achieves a maximum gain of 7.46 dBi in the operating band, thus making it suitable for X band applications.

위성 Synthetic-Aperture Radar (SAR) 시스템용 X-밴드 이중 편파 마이크로스트립 패치 부배열 안테나

In this study, a high-performance, dual linearly polarized patch array antenna is presented for satellite synthetic aperture radar (SAR) applications. The antenna features an aperture-fed stacked patch as the radiation element and a stripline feeding network. A high-performance and low-loss dielectric substrate RF-35 by Taconic, and a honeycomb substrate is used. The honeycomb substrate is used to maximize the impedance bandwidth and decrease the insertion loss of the antenna. The proposed antenna offers exceptional isolation between the antenna’s ports in excess of 55 dB owing to its stripline feeding network. The via stitching technique is utilized to suppress the parallel-plate mode excited by the discontinuities in the stripline. The antenna is designed to possess a wide impedance bandwidth. A prototype antenna of size 2×4 elements, which operates in the X-band, is fabricated. Its impedance and radiation performance are experimentally verified, and the results are presented. The antenna exhibits a 15.7 dB peak gain and more than 40 dB of cross-polarization discrimination. In addition, a wide bandwidth of 19.4 % at a −10 dB return loss (RL) level is obtained.

Monopulse Radial Line Slot Array Antenna Fed by a 3-D-Printed Cavity-Ended Modified Butler Matrix Based on Gap Waveguide at 94 GHz

This article presents the design and fabrication of a monopulse radial line slot array (RLSA) antenna excited with a circular cavity connected to a modified Butler matrix at 94 GHz. The antenna consists of two pieces: the RLSA antenna implemented over a low loss dielectric substrate and a 3-D-printed Butler matrix based on gap waveguide. The interface between both parts is a circular cavity that couples two different modes into the RLSA through a coupling slot in the dielectric substrate. The coupled mode depends on the input excitation of the Butler matrix for the generation of simultaneous sum and difference radiation patterns. This interface is deeply detailed in this article, together with the design of the RLSA antenna and the integration of the full monopulse antenna. The measured S-parameters fit very well with simulations. The operation is inherently narrowband with a realized gain of 27.8 dBi at 94 GHz, a radiation efficiency of 70%, 0.3 dB axial ratio, and a maximum null relation between sum and difference patterns higher than 50 dB.

A tightly coupled dipole array used for radiation power improvement on finite radiation aperture

Radiation power of an electromagnetic wave plays a decisive role in its transmission distance. Traditionally, the radiation power can be improved by expanding the radiation aperture size of the antenna array or increasing input power of the unit cell. However, the radiation aperture size is always restricted by assembly space. The input power improvement of the unit cell is always limited by the signal source. It is difficult to improve radiation power on a finite radiation aperture. However, the radiation power on a finite radiation aperture is related closely to the number of antenna elements and the radiation efficiency of the antenna array. It is useful to arrange more elements and improve radiation efficiency of the antenna array to improve the radiation power on a finite radiation aperture. Wideband wide-angle scanning phased array is able to make full use of a finite radiation aperture. The wide-angle scanning properties make it possible for the radiated power to cover a wide area. In this paper, a compact wideband wide-angle scanning tightly coupled dipole array (TCDA) is proposed. A high permittivity substrate and compact wideband balun are used for miniaturizing the antenna array. The period of the unit cell is only 0.144<i>λ</i><sub>high</sub> × 0.144<i>λ</i><sub>high</sub> (<i>λ</i><sub>high</sub> is the wavelength at the highest operation frequency in free space). Parameters of the balun are optimized to improve impedance matching between the balun and the antenna array. Two bilateral frequency selective surfaces (FSSs) are used to replace traditional dielectric superstrate to improve the impedance matching between the antenna array and free space. A low-loss dielectric substrate is used to reduce dielectric loss of the antenna array. In these ways, the radiation efficiency is greatly improved. The simulation results show that the proposed antenna array operates at 1.7–5.4 GHz (3.2:1) while scanning up to 65° in the E plane, 45° in the H plane and 60° in the D plane with following a rigorous impedance matching criterion (active VSWR < 2). A 16 × 16 prototype array is fabricated and measured. Good agreement is achieved between the simulation results and the measurement results. Compared with the designs in the literature, the proposed antenna array has an excellent performance in radiation power on a finite radiation aperture.

H-Band Substrate-Integrated Discrete-Lens Antenna for High Data Rate Communication Systems

A substrate-integrated discrete-lens antenna manufactured in standard printed-circuit-board (PCB) technology is demonstrated in H-band (225-325 GHz). The arrays composed of phase-shifting unit cells and a waveguide-fed planar focal source are designed on a single PCB stack with five metal layers and multiple low-loss dielectric substrates in a monolithic module of 20×20×4.52 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The linearly polarized unit cells are based on arc-shaped resonators placed between two perpendicular polarizing grids. They achieve eight transmission phase states with less than 1 dB average insertion loss and 27% 1 dB bandwidth. Two antenna prototypes with radiating apertures of 6.6×6.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 10.56×10.56 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are designed, fabricated, and measured. They demonstrate linearly polarized pencil-beam radiation patterns with low sidelobes, low cross-polarization, an experimental gain of 20.6/23.1 dBi at 327/332 GHz, and 3 dB gain bandwidth of 26.3%/17.2%. The impact of manufacturing tolerances is detailed both at unit-cell level and antenna level.

Design, Simulation and Experimental Analysis of Square Microstrip Patch Antenna with Superstrates at 2.4GHz

Microstrip antenna is used in wide area of applications such as high speed vehicles, missiles, tanks and satellite communications. In these applications dielectric superstrate (or cover) is used above the square patch antenna for providing the protections from severe environmental conditions such as rain, snow, heat, and damage etc. The proposed square microstrip patch antenna is designed using coaxial probe feed technique and transmission line model and operated at center frequency of 2.40 GHz, which is lying in the S-band region. The proposed model is used in linear polarization applications. The square patch is fabricated on low loss dielectric substrate material having dielectric constant is 2.2 and loss tangent of the substrate material is 0.0009. Ansoft electromagnetic simulator software such as HFSS is used for simulating proposed model and studied the effect cover or superstrate on different parameters of square patch antenna. This paper mainly focuses on the performance of square patch antenna without superstrate, and with superstrate at different height of dielectric superstrate above the patch antenna. The result found of patch antenna without superstrate the bandwidth is 0.04GHz and gain is obtained 8.9 dB and 7.51 dB in azimuth and elevation respectively. The result observed of patch antenna with dielectric cover (or superstrate) at height H =0, the antenna performance characteristics are slightly degraded and also comparing the antenna with the bandwidth is decreased to 0.02GHz from 0.04 GHz and gain is decreases to 6.44 dB and 6.6 dB from 8.9 dB and 7.51 dB in both azimuth and elevation plane respectively. The decreased performance characteristics of antenna will be improved by varying height of the superstrate above the patch antenna.. At particular optimum height, the performance characteristics patch antenna will be almost same as the patch antenna without superstrates. The obtained simulated results good match with measurement results.

Parametric study of metamaterial-inspired resonator for wireless power transfer

A metamaterial-inspired resonator for free-positioning wireless charging of several devices is proposed and numerically studied. The resonator is based on orthogonal metallic wires arrays deposited on a high permittivity low loss dielectric substrate. Given a fixed area of 50 × 50 cm, its resonant frequency can be tuned in a wide frequency band from 5 MHz to 45 MHz. A parametric study is performed to reveal the influence of resonant frequency, dielectric permittivity and number of wires on Q-factor.

Low-Cost Air Gap Metasurface Structure for High Absorption Efficiency Energy Harvesting

This manuscript deals with the design of a metamaterial-based surface structure for high efficiency wireless power harvesting or collection. Differently from the previously presented structures which require the use of thicker and low-loss (and for this reason high cost) dielectric substrates, the presented work employs a dual-layer structure with a thin low-loss material and an air gap; they allow for the design of very high absorption efficiency metamaterial-based surfaces, with noticeably reduced costs. Furthermore, the air gap thickness can be used as a new degree-of-freedom (more easily adjustable than the thickness of a single-layer structure) for the optimization of other design requirements such as bandwidth or structure sizes. In comparison with other existing designs, the proposed metasurface shows a comparable absorption efficiency of 84.4% but with a larger power collection surface and lower costs.

Dielectrics for Terahertz Metasurfaces: Material Selection and Fabrication Techniques

AbstractManipulation of terahertz radiation opens new opportunities that underpin application areas in communication, security, material sensing, and characterization. Metasurfaces employed for terahertz manipulation of phase, amplitude, or polarization of terahertz waves have limitations in radiation efficiency which is attributed to losses in the materials constituting the devices. Metallic resonators‐based terahertz devices suffer from high ohmic losses, while dielectric substrates and spacers with high relative permittivity and loss tangent also reduce bandwidth and efficiency. To overcome these issues, a proper choice of low loss and low relative permittivity dielectric layers and substrates can improve field confinement and reduce dissipation. Alternatively, replacing metallic resonators with a moderate relative permittivity dielectric material that supports cavity mode resonances also reduces dissipation due to the absence of conduction current. Herein, an overview of dielectric materials employed as spacers and dielectric resonators is provided, and the fabrication methods employed to realize these devices at the terahertz frequency range are also presented. Material selection guidelines, material‐specific and application‐specific fabrication quality metrics are outlined, and new techniques are proposed.

Control of the magnetic near-field pattern inside MRI machine with tunable metasurface

The metasurfaces concept allows developing and advancing the methods to control the near electromagnetic field pattern in almost arbitrary ways. This property, among other things, is making them an essential platform for useful applications, for example, to improve magnetic resonance imaging (MRI) characteristics through local enhancement of the transmit efficiency as well as the increase in the sensitivity of the radio frequency coils. In this letter, we investigate a compact metasurface-based resonator formed as an array of parallel copper wires with capacitive loads printed on the low-loss dielectric substrate. We demonstrate how to tailor the spectral characteristics of the metasurface eigenmode as well as to control precisely the homogeneity of the near-field pattern by changing the effective capacitance of the structure. We experimentally verify that by tuning the metasurface characteristics, it is possible to decrease the excitation power needed to provide the optimal transmit efficiency of the body coil, thus making the MRI procedure safer. Our approach offers a practical method to control the electromagnetic near-field pattern and has potential in various applications, such as MRI and wireless power transfer.

Design of Broadband W-Band Waveguide Package and Application to Low Noise Amplifier Module

In this paper, the broadband millimeter-wave waveguide package, which can cover the entire W-band (75–110 GHz) is presented and applied to build a low noise amplifier module. For this purpose, a broadband waveguide-to-microstrip transition was designed using an extended E-plane probe in a low-loss and thin dielectric substrate. The end of the probe substrate was firmly fixed on to the waveguide wall in order to minimize the performance degradation caused by the probable bending of the substrate. In addition, we predicted and analyzed in-band resonances by the simulations that are caused by the empty spaces in the waveguide package to accommodate integrated circuits (ICs) and external bias circuits. These resonances are removed by designing an asymmetrical bias space structure with a radiation boundary at an external bias connection plane. The bond-wires, which are used to connect the ICs with the transition, can generate impedance mismatches and limit the bandwidth performance of the waveguide package. Their effect is carefully compensated for by designing the broadband two-section matching circuits in the transition substrate. Finally, the broadband waveguide package is designed using a commercial three-dimensional electromagnetic structure simulator and applied to build a W-band low noise amplifier module. The measurement of the back-to-back connected waveguide-to-microstrip transition including the empty spaces for the ICs and bias circuits showed the insertion loss less than 3.5 dB and return loss higher than 13.3 dB across the entire W-band without any in-band resonances. The measured insertion loss includes the losses of 8.7 mm-long microstrip line and 41.8 mm-long waveguide section. The designed waveguide package was utilized to build the low noise amplifier module that had a measured gain greater than 14.9 dB from 75 GHz to 105 GHz (&gt;12.9 dB at the entire W-band) and noise figure less than 4.4 dB from 93.5 GHz to 94.5 GHz.

Numerical and Experimental Time-Domain Characterization of Terahertz Conducting Polymers

A comprehensive framework for the theoretical and experimental investigation of thin conducting films for terahertz applications is presented. The electromagnetic properties of conducting polymers spin-coated on low-loss dielectric substrates are characterized by means of terahertz time-domain spectroscopy and interpreted through the Drude-Smith model. The analysis is complemented by an advanced finite-difference time-domain algorithm, which rigorously deals with both the dispersive nature of the involved materials and the extremely subwavelength thickness of the conducting films. Significant agreement is observed among experimental measurements, numerical simulations, and theoretical results. The proposed approach provides a complete toolbox for the engineering of terahertz optoelectronic devices.

Surface conductance of graphene from non-contact resonant cavity

A method is established to reliably determine surface conductance of single-layer or multi-layer atomically thin nano-carbon graphene structures. The measurements are made in an air filled standard R100 rectangular waveguide configuration at one of the resonant frequency modes, typically at TE103 mode of 7.4543GHz. Surface conductance measurement involves monitoring a change in the quality factor of the cavity as the specimen is progressively inserted into the cavity in quantitative correlation with the specimen surface area. The specimen consists of a nano-carbon-layer supported on a low loss dielectric substrate. The thickness of the conducting nano-carbon layer does not need to be explicitly known, but it is assumed that the lateral dimension is uniform over the specimen area. The non-contact surface conductance measurements are illustrated for a typical graphene grown by chemical vapor deposition process, and for a high quality monolayer epitaxial graphene grown on silicon carbide wafers for which we performed non-gated quantum Hall resistance measurements. The sequence of quantized transverse Hall resistance at the Landau filling factors ν=±6 and ±2, and the absence of the Hall plateau at ν=4 indicate that the epitaxially grown graphene is a high quality mono-layer. The resonant microwave cavity measurement is sensitive to the surface and bulk conductivity, and since no additional processing is required, it preserves the integrity of the conductive graphene layer. It allows characterization with high speed, precision and efficiency, compared to transport measurements where sample contacts must be defined and applied in multiple processing steps.

Highly linear dual capacitive feedback LNA for L-band atmospheric radars

This paper presents the design of ultra-low noise amplifier (LNA) with dual capacitive shunt feedback in conjunction with source degenerated inductance methodology to simultaneously improve gain, noise figure (NF), and linearity. Addition of two feedback capacitors from drain to gate of the two transistors will relieve the trade-off between NF and linearity and the cascode design will increase the gain. To demonstrate this methodology, a single stage LNA is designed for UHF atmospheric radar application at 1.3 GHz and pHEMT technology is used for the design of LNA and fabricated on low-loss dielectric substrate. Measured results show that LNA has a gain of 24.1 dB and a very low NF of 0.38 dB. The input and output return losses are less than 11 dB and the third-order input intercept point is 48 dBm.

Measuring low loss dielectric substrates with scanning probe microscopes

This letter presents an algorithm for measuring the relative permittivity of thick dielectric substrates with scanning probe microscopy. Our technique does not rely on a specific type of microscopy setup and does not require expensive numerical field simulations. To demonstrate the versatility of our method, we perform measurements at high frequencies (18 GHz) with a scanning microwave microscope and at low frequencies (2 kHz) with electrostatic force microscopy. In our experiments, we study dielectric materials with epsilon values ranging from 4 (SiO2) to 300 (SrTiO3). For low epsilon values, the accuracy of the algorithm is better than 2% for tips with less than 80 nm tip radius.

Hybrid-shaped single-loop resonator: a four-band metamaterial structure

The aim of this reported work is to demonstrate the feasibility of a miniaturised four-band metamaterial resonator which has potential use in the design of multiband microwave devices such as four-band mobile phone patch antennas. The suggested resonator topology is called the hybrid-shaped single-loop resonator (HSLR) as its unit cell is formed by the combination of square-shaped and triangular-shaped sections of a single piece metal loop printed on a planar low-loss dielectric substrate. The performance of this novel four-band HSLR structure is investigated in comparison to the circular, triangular and square-shaped structures, which are recently reported double or triple band single-loop resonators. Simulations are performed using two different full wave electromagnetic solvers, HFSS and CST Microwave Studio, with excellent numerical agreement.

Complex permittivity measurements of RF plasma polymerized polyterpenol organic thin films employing split post dielectric resonator

Abstract In the fields of organic electronics and biotechnology, applications for organic polymer thin films fabricated using low-temperature non-equilibrium plasma techniques are gaining significant attention because of the physical and chemical stability of thin films and the low cost of production. Polymer thin films were fabricated from non-synthetic terpinen-4-ol using radiofrequency polymerization (13.56 MHz) on low loss dielectric substrates and their permittivity properties were ascertained to determine potential applications for these organic films. Real and imaginary parts of permittivity as a function of frequency were measured using the variable angle spectroscopic ellipsometer. The real part of permittivity (k) was found to be between 2.34 and 2.65 in the wavelength region of 400–1100 nm, indicating a potential low-k material. These permittivity values were confirmed at microwave frequencies. Dielectric properties of polyterpenol films were measured by means of split post dielectric resonators (SPDRs) operating at frequencies of 10 GHz and 20 GHz. Permittivity increased for samples deposited at higher RF energy – from 2.65 (25 W) to 2.83 (75 W) measured by a 20-GHz SPDR and from 2.32 (25 W) to 2.53 (100 W) obtained using a 10-GHz SPDR. The error in permittivity measurement was predominantly attributed to the uncertainty in film thickness measurement.

Microwave Conductivity of Very Thin Graphene and Metal Films

The surface resistance of Ag, Au and A1 thin conducting films deposited on low loss dielectric substrates at microwave frequencies using TE011 mode single post-dielectric resonator (10-13.22 GHz) was measured to calculate their conductivity in relation to layers thickness. This method enabling measurements near metal-insulator percolation transition was also applied for epitaxial graphene deposited on semi-insulating SiC. Moreover, effective microwave conductivity has been determined for intentionally made aluminum island structure where the DC conductivity is equal to zero. Special attention was paid to films thickness measurements which is critical for accuracy of sheet resistance calculation. Conductivity of thin metal layers and very thin graphene was compared.

An electrode-free method of characterizing the microwave dielectric properties of high-permittivity thin films

A thin dielectric resonator consisting of a dielectric substrate and the thin film deposited upon it is shown to suffice for microwave characterization and dielectric parameter measurement of high-permittivity thin films without electrodes. The TE01δ resonance mode was excited and measured in thin (down to 0.1 mm) rectangular- or disk-shaped low-loss dielectric substrates (D∼10 mm) with permittivity ε′≥10 inserted into a cylindrical shielding cavity or rectangular waveguide. The in-plane dielectric permittivity and losses of alumina, DyScO3, SmScO3, and (LaAlO3)0.29(SrAl1/2Ta1/2O3)0.71 (LSAT) substrates were measured from 10 to 18 GHz. The substrate thickness optimal for characterization of the overlying thin film was determined as a function of the substrate permittivity. The high sensitivity and efficiency of the method, i.e., of a thin dielectric resonator to the dielectric parameters of an overlying film, was demonstrated by characterizing ultrathin strained EuTiO3 films. A 22 nm thick EuTiO3 film grown on a (100) LSAT substrate and strained in biaxial compression by 0.9% exhibited an increase in microwave permittivity at low temperatures consistent with it being an incipient ferroelectric; no strain-induced ferroelectric phase transition was seen. In contrast, a 100 nm thick EuTiO3 film grown on a (110) DyScO3 substrate and strained in biaxial tension by 1% showed two peaks as a function of temperature in microwave permittivity and loss. These peaks correspond to a strain-induced ferroelectric phase transition near 250 K and to domain wall motion.