Dielectric Constant Substrate Research Articles

Stable‐multiband frequency reconfigurable antenna with improved radiation efficiency and increased number of multiband operations

In this study, a multiband frequency reconfigurable antenna is presented. The proposed antenna can switch among fixed GSM850/900 MHz, LTE1600/1700/1800 MHz and ISM2400 MHz bands through switchable, single, three double, and two triple band modes. The multiband operation is obtained using a spline-based radiator and two open-ended rectangular slot-resonators (RSRs). Three series configurations of PIN diode radio-frequency (RF) switches are integrated into RSRs to activate and deactivate it. The position of RSRs and RF switches is precisely optimised to obtain the desired operating bands and the input scattering parameter ( S 11) below −10 dB. RF switches #1–3 are turned ON and OFF to transfigure the current distributions on the radiator resulting in the frequency band-switching operation. It is shown that the integration of RSRs and PIN diode RF switches into the antenna structure degrades the radiation efficiency. To improve the radiation efficiency, the antenna is fabricated on a low dielectric constant multilayered substrate built using RT/Duroid 5880 laminates and an air gap. The increased multiband operation, good radiation efficiency, omnidirectional radiation pattern, and sufficient co-cross polarisation isolation are obtained in all operating bands. The prototype of the antenna is fabricated and fairly good agreement is seen amongst simulated and measured results.

A Semianalytical Approach to Designing High-Transparency Low-Profile Circular Polarizers

This paper presents a semianalytical approach to streamline the design process of a linear-to-circular polarizer (LCP). The LCP is composed of only two identical frequency selective surfaces (FSSs) and can be based in free space or on low dielectric constant substrates. The adopted unit cell is electrically small and utilizes a modified Jerusalem cross (MJC) FSS grid. The low profile ( $0.11\lambda _{0}$ ) and compactness of the cells ( $0.17\lambda _{0}\times 0.17 \lambda _{\mathbf {0}}$ ) enhance the accuracy of the circuit-driven design approach and eases calculations associated with numerical simulations. When based in free space, the LCP offers axial ratios of less than 3 and 1 dB over 10% and 3.8% fractional bandwidths, with low insertion losses of 0.5 and 0.35 dB, respectively, making it appealing to both terrestrial and satellite applications.

Printed <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math> </inline-formula>-Band Multibeam Antenna With Luneburg Lens-Based Beamforming Network

A simple and low-cost single substrate layer Luneburg lens-based beamforming network (BFN) operating in $W$ -band is proposed. A multibeam antenna is then realized using the novel BFN and fabricated using a low-cost printed circuit board process. The Luneburg lens is realized by drilling holes in a substrate, and to extend the refractive index variation, a high dielectric constant substrate is embedded at the lens center. The lens is excited by radially placed open-ended substrate integrated waveguides (SIWs) at the lens circumference, feeding a subset of antenna ports placed on the opposite side of the lens. The proposed BFN thus provides half-power beamwidth (HPBW) and beam steering angle flexibility for multibeam antennas. An antenna generating seven beams was prototyped at 79.5 GHz to validate this BFN, providing measured beam steering of approximately ±41° with a broadside HPBW of 10°. The bandwidth of the proposed BFN is determined by the single-mode operation of the SIW. The fabricated multibeam antenna impedance bandwidth is, however, about 2% at 79.5 GHz because of the radiating elements. The radiating elements are series fed slot arrays placed on SIWs.

High space efficiency compact chipless RFID tag with equidistance resonances

Radio Frequency Identification (RFID) technology provides non line-of-sight communication between the reader and the tag. This technology is widely used for various applications such as item tracking, security, access control, health care, short and long-range applications. RFID can be used as low cost data identification technology using radio waves between the RFID transmitter and the RFID receiver. Many attempts are introduced to implement the chipless RFID tags but they suffer from non-equal spacing between resonances which makes it difficult to make the decision. In this paper, compact low cost spectral signature based chipless 8-bits RFID tag is introduced. Multi dual-band resonating circuits with different resonances are used. The operation bandwidth is limited by the second resonance of the resonator. To avoid the presence of harmonics in the operating frequency range, multiple resonators with different shapes are introduced. The proposed tag instead of encoding only one data bit it encodes two data bits providing higher bits/resonator. The proposed tag provides equidistance between resonance frequencies. The tag is implemented on FR4 substrate of dielectric constant =4.4, thickness h=1.6mm and loss tangent δ=0.0018. The scattering parameters of the fabricated tags are measured using the vector network analyzer (ROHDE&SCHWARZ ZVB 20). The designs of the tags are made using the software package CST MICROWAVE STUDIO.

Substrate integrated non-radiative dielectric waveguide and its applications

In this article a Substrate Integrated Non Radiative Dielectric Guide (SINRD) has been realized with the concept of substrate integration circuits. In SINRD, a specific pattern of air holes have been used grooved in a dielectric substrate to reduce the effective dielectric constant of a particular region. Accordingly, design and implementation of SINRD guides and its applications in millimeter wave subsystems have been investigated by using published literatures. Thereby the concept has been utilized to develop an optimized design flow of SINRD transmission line. Design has been carried out at W band (85–110 GHz) on a high dielectric constant substrate and subsequently dispersion characteristics has been studied subject to transmitted and radiated field configuration.

Shared radiator MIMO antenna for broadband applications

In this study, a new compact broadband two-port multiple-input–multiple-output (MIMO) antenna using shared radiator is proposed. The radiator making an angle of 135° from X-axis is symmetrically shared by two tapered microstrip feed lines in orthogonal polarisations. The shared radiator MIMO antenna is more compact as compared with conventional MIMO antenna which uses separate radiator for each port. The proposed antenna is designed on low-cost FR4 substrate (dielectric constant = 4.4, and loss tangent = 0.02) of size 39 × 39 mm2 and provides a bandwidth of 136.63% (2.4–12.75 GHz) with reflection coefficients, S11/S22 less than or equal to −10 dB and values of mutual coupling between antenna ports S21/S12 less than or equal to −15 dB. Through the utilisation of end-loaded meandered line stub attached to modified curved ground plane, low mutual coupling between antenna ports is achieved. The simulated results for input and radiation characteristics of the proposed MIMO antenna are compared with corresponding experimental results.

Modeling and Design Empirical Formulas of Microstrip Ridge Gap Waveguide

Recently, interest in the microstrip ridge gap waveguide (MRGW) has increased due to the need for a self-packaged and low-loss structures for millimeter-wave applications. The MRGW consists of a grounded textured surface, which is artificially representing a perfect magnetic conductor surface loaded with a thin low dielectric constant substrate with a printed strip. This is topped with another dielectric substrate covered with a conducting plate at the top as a ground plane. Currently, the full-wave and optimization tools are used to design the MRGW structure. Consequently, an efficient modeling and design tool for the MRGW is proposed in this paper via curve fitting. Closed form empirical expressions for the effective dielectric constant, characteristic impedance, and the dispersion effect are provided. The developed expressions are generalized for arbitrarily chosen MRGW parameters. The expressions are verified with the full-wave solution. The results show the potential of the proposed approach in modeling the MRGW structure

Analysis of Substrate Effect in Field Effect Transistor Terahertz Detectors

The development of terahertz (THz) detectors based on field effect transistors (FETs) with planar antennas requires improving the detector responsivity, thus it needs higher coupling efficiency between the antenna and THz radiation. Substrate effect and its impact on the detector responsivity have been investigated for the case of semiinfinite substrate, and four different types of planar dipole antennas are compared. The ratio ( R ) of the power radiated into the air to the total power radiated by planar antenna shows several peaks when the substrate thickness increases. Independent of antenna structure and source impedance, the ratio R would only depend on the substrate thickness, the dielectric constant of substrate, and the operation frequency. Furthermore, the simulation result shows that the radiation power ratio R is correlated with the detector responsivity. This correlation is independent of FET input impedance and antenna structure. It indicates that the ratio R can be used as a reference to choose proper substrate parameters. All the results above can be extended to common materials and broad range of frequency. The comparison of four antennas shows that besides substrate effect, the antenna design would also have a significant impact on the detector responsivity.

An Electrical Model to U-Slot Patch Antenna with Circular Polarization

The microstrip antenna is one of the best antenna structures, due to its low cost and compact design. In this paper, a coaxial feed circularly polarized square patch antenna is designed using the U-slot. The proposed antenna is suited for the RFID readers in the SHF band. This structure of antenna of FR-4 substrate (dielectric constant = 3.5), is capable to cover the range of frequency of 2.4 to 2.5GHz. The size of patch is 25*25 mm2. An equivalent electrical model of this antenna was proposed and simulated by the ADS software. The simulated gain is 4.189 dBi and S11 bandwidth is about 100 MHz. Analysis and modeling of the proposed antenna was carried out using the CST and HFSS simulator based on the finite element method. The simulation results obtained are presented and discussed.

Diced and grounded broadband bow‐tie antenna with tuning stub for resonant tunnelling diode terahertz oscillators

Radiation from antennas integrated with indium phosphide (InP)-based resonant tunnelling diode (RTD) oscillators is mainly through the substrate because of the effects of the large dielectric constant. Therefore, hemispherical lenses are used to extract the signal from the backside of the substrate. In this study the authors present a broadband bow-tie slot antenna with a tuning stub which is diced and mounted on a ground plane to alleviate the substrate effects. Here, the large dielectric constant substrate around the antenna conductor is removed. In addition, the ground plane underneath the diced substrate acts as a reflector and, ultimately, the antenna radiates to the air-side direction. Antenna integration with RTD oscillators is described in this study as well. Two-port bow-tie slot antennas were designed and characterised and showed the suitability of integration with power combining RTD oscillator circuits which are based on mutual coupling. The antennas were fabricated using electron beam lithography on a semi-insulating InP substrate. Simulated and measured bandwidth almost extends the entire frequency range 230–325 GHz. Simulations shows air-side radiation pattern and antenna gain of around 11 dB at 280 GHz. Simulations also show that the antenna may be fed with a 50-Ω or 30-Ω feed line, i.e. suitable feed lines, without compromising its performance which may prove beneficial for optimum loading of RTD oscillators.

Coupled C-band stacked antenna using different dielectric constant substrates for communication systems

This paper proposed a coupled C-band stacked dual resonant antenna using different dielectric constant substrates for communication systems. The antenna operates in C-band resonating at two different frequencies. Two different substrates FR4 and Mica are used in this antenna structure. The stacked antenna design is fed coaxially at the central patch keeping the other three patches as parasitic patches. The antenna is optimized to obtain an impedance bandwidth of about 8% and 7% in the two bands respectively with a peak gain of 9.5dBi and side lobe level of −12.2dB at the resonant frequency. The antenna has obtained very good cross-polarization of about −28dB in YZ-plane and even less than −40dB at XZ-plane. The efficiencies at both the resonances are very good and the other simulated results are in good agreement with the measured results.

SERS-Active Ag Nanoparticles on Porous Silicon and PDMS Substrates: A Comparative Study of Uniformity and Raman Efficiency

Silver-coated porous silicon and polydimethylsiloxane (PDMS) are systematically analyzed as substrates for surface-enhanced Raman scattering (SERS). They were selected as representative metal–dielectric nanostructures characterized by different morphology and substrate dielectric constant which is reflected in the electromagnetic near-field intensity spectra. The study is conducted using 4-mercaptobenzoic acid as probe molecule with the aim to compare the scattering efficiency and the homogeneity of the Raman signal on the selected substrates. A larger SERS enhancement is evidenced for the silicon-based plasmonic nanostructures (>106, despite the electronic off-resonant excitation of the analyte). On the other hand, the silvered elastomeric substrates, characterized by a good Raman efficiency, show good repeatability featured by a low inter- and intrasubstrate standard deviation of the SERS signal intensity, which make them suitable for quantitative analysis. The influence of the excitation wavelength on such properties is deeply discussed taking into account experimental results and 3D modeling.

A High-Gain Single-Feed Dual-Mode Microstrip Disc Radiator

A novel high-gain circular microstrip radiator is proposed. The antenna consists of two circular discs, in a stacked configuration, designed to operate in ${\rm TM}_{11}$ and ${\rm TM}_{13}$ modes. The patches are designed, so that the resonant frequencies for both modes converge into a single frequency. It is found that by simultaneous excitation of both resonant modes, high gain and low sidelobe level (SLL) can be obtained in the radiation patterns. Excitation is done using a single coaxial feed. The fundamental working principle of the antenna is based on the superposition of radiated far fields of the ${\rm TM}_{11}$ and ${\rm TM}_{13}$ modes. At first, through a pattern synthesis, using different far field mode amplitude ratios, it is shown that the substrate dielectric constants can be selected for both layers such that it leads to low SLL. Next, for practical antenna design, the mode excitation, input impedance, and radiation properties of the ${\rm TM}_{13}$ mode are studied. For sound understanding and explanation, the edge voltage ratio at the aperture and mode amplitude ratio in the far field are calculated and their effects on SLL and peak directivity are discussed. Finally, the measurements results are provided in support of simulations.

1.8GHz 대역용 CPWG 안테나 연구

본 논문에서는 코프래너 그라운드 도파관(CPWG)에 의해 급전되는 패치 안테나의 설계 방법 및 안테나 특성을 연구하였다. 안테나의 패치 길이, 폭, 위치를 조절하여 안테나와 CPWG 급전선이 임피던스 정합 되도록 하였다. 또한 안테나의 특성을 향상시키기 위해 CPWG 안테나의 설계 변수인 패치 길이. 패치 넓이, 패치 위치 및 그라운드 포지션에 따른 안테나 특성 변화를 HFSS 프로그램을 사용하여 안테나의 주파수 특성을 시뮬레이션 하였다. 이 결과를 바탕으로 1.8GHz LTE 대역에서 사용 가능한 CPWG 안테나를 설계하고, 설계 된 안테나를 유전율 4.4, 두께 0.8mm인 FR4-epoxy 기판을 사용 하여 포토리소그래피 방법으로 안테나를 제작하였다. 제작된 안테나는 최종적으로 회로망 분석기(Network Analyzer)를 통해 안테나 특성을 분석하였다. 측정된 안테나의 주파수 특성은 시뮬레이션 결과와 잘 일치하여 본 연구의 타당성을 확인 할 수 있었다. 제작된 CPWG 안테나는 중심주파수 1.80 GHz, 입력반사손실 -32.1 dB, 대역폭 22 MHz, 임피던스 $50.2{\Omega}$ 의 결과 값을 보였다. 본 연구에서 제안된 안테나는 LTE 대역에 응용이 가능할 것으로 기대된다. 【In this study, the properties of a patch antenna fed by a coplanar waveguide with ground (CPWG) and design method were studied. The antenna was impedance-matched to the CPWG feedline by adjusting the width, length, and position of the patch. To improve the frequency properties of the CPWG type antenna, patch length, patch width, patch position, and ground distance were simulated using HFSS (High Frequency Structure Simulator) simulation program. A CPWG antenna of 1.8 GHz for LTE band was designed and fabricated by photolithography on an FR4 substrate (dielectric constant of 4.4 and thickness of 0.8 mm). The fabricated antenna was analyzed using a network analyzer. The measured results agree well with the simulations, which confirmed the validity of this study. The fabricated CPWG antenna showed a center frequency, minimum return loss and -10dB bandwidth of 1.8GHz, -32.1dB, 22MHz and $50.2{\Omega}$ respectively. The proposed antenna is expected to be applicable to the LTE band.】

Bandwidth Improvement of Microstrip Crossed Monopole Antenna

compact size low profile microstrip-fed crossed monopole antenna for ultra wideband communication is presented. The impedance bandwidth of a microstrip crossed monopole antenna has increased with a suitable dimension of ground plane and rectangular patch. The aim of this paper is to improved bandwidth and return loss of a Crossed Monopole Microstrip patch antenna and study the effect of antenna and ground dimension length (L), width (W) and substrate parameters relative dielectric constant, substrate thickness on radiation parameters of bandwidth. Low dielectric constant substrates are generally preferred for maximum radiation. The crossed monopole shows the return loss of -10dB over ultra wideband frequency range (3.3 - 13.6 GHz) while maintain the stability in radiation pattern. The simulation software (CST) obtains the effect of the parameter on the performance of the antenna.

A Novel High-Gain Printed Antenna Configuration Based on $\text{T}{\text{M}_{12}}$ Mode of Circular Disc

The fundamental (TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) mode of a circular patch antenna is generally used for broadside gain applications. However, other TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1m</sub> modes (m = 2,3⋯) also radiate in the broadside direction with high directivities, but are avoided due to the occurrence of sidelobes in the radiation pattern. Here, a simple high-gain disc antenna configuration, using high dielectric constant substrates, operating in the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> mode, is presented. At first, through an analytical study, it is shown that by selecting an appropriate value of the dielectric constant, both high directivity and low sidelobe level (SLL) can be attained. Next, it is demonstrated that the excitation of adjacent modes can be reduced significantly by a proper selection of feed location. For a practical antenna design, it is also shown that the SLL can be further reduced using a finite ground plane size.

A Defected Structure Shaped CPW-Fed Wideband Microstrip Antenna for Wireless Applications

A coplanar waveguide (CPW) fed compact wideband defected structure shaped micro-strip antenna is proposed for wireless applications. Defected structure is produced by cutting the shape antenna in the form of two-sided T shape. The proposed antenna consists of two-sided shape strip as compared to usual monopole patch antenna for minimizing the height of the antenna. The large space around the radiator is fully utilized as the ground is on the same plane as of radiator. Micro-strip line feed is used to excite the proposed antenna placed on an FR4 substrate (dielectric constant). The antenna is practically fabricated and simulated. Simulated results of the proposed antenna have been obtained by using High-Frequency Structure Simulator (HFSS) software. These results are compared with measured results by using network analyzer. Measured result shows good agreement with the simulated results. It is observed that the proposed antenna shows a wideband from 2.96 GHz to 7.95 GHz with three bands.

Thin PCB-Type Metamaterials for Improved Efficiency and Reduced EMF Leakage in Wireless Power Transfer Systems

Current wireless power transfer (WPT) technology can only allow power transfer over a limited distance because, as the distance between the transmitter (Tx) and receiver (Rx) coils increases, the power transfer efficiency (PTE) decreases with a steep slope, while the electromagnetic field (EMF) leakage increases. In order to increase the PTE and decrease the EMF leakage simultaneously, we need to develop a method to concentrate the magnetic fields between the Tx and Rx coils. In this paper, we proposed a novel metamaterial structure to realize high efficiency and low EMF leakage. Metamaterials can confine the magnetic fields between the Tx and Rx coils by negative relative permeability. We designed and fabricated a thin metamaterial using a 1.6-mm dual layer printed circuit board (PCB) with a high dielectric constant substrate and a fine pattern to achieve a negative relative permeability with low loss at 6.78 MHz. The thin PCB-type metamaterial has a wide range of applications with low fabrication cost, light weight, and a simple fabrication process. We demonstrated a 44.2% improvement in the PTE and 3.49-dBm reduction in the EMF leakage around the WPT system at 20-cm distance. Furthermore, we first analyzed metamaterials from an EMF point of view using the 3-D magnetic field scanner. Finally, we discussed a combination of metamaterials and ferrites to further improve the PTE and reduce the EMF leakage for long-distance mobile WPT systems.

Study on the interfacial adhesion property of low-k thin film by the surface acoustic waves with cohesive zone model

The cohesive zone model being increasingly used in discrete fracture processes simulation is adopted to study the interfacial adhesion property of low dielectric constant film deposited on the silicon substrate in this work. The two parameters, maximum normal traction and normal interface characteristic length in cohesive zone model, are taken into account to calculate the theoretical surface acoustic wave dispersion curves. Broadband surface acoustic wave signals with effective frequency up to 200MHz are generated by short pulse ultraviolet laser source and detected by a piezoelectric transducer. The interfacial adhesion properties of dense and porous films determined accurately by matching the experimental dispersion curves with the calculated theoretical dispersion curves are 10.7PPa/m and 2.8PPa/m, respectively. The results show that the adhesion quality of dense low dielectric constant film is better than that of the porous. The study exhibits that the adhesion properties determined by improved laser-generated surface acoustic wave technique have the same trends with the test results of the nanoscratch technique, which indicates that the surface acoustic wave technique with cohesive zone model is a promising and nondestructive method for determining interfacial adhesion properties between low dielectric constant film and substrate.

New compact printed leaky-wave antenna with beam steering

A new printed compact structure constructed of six E-shaped arms arranged in three columns and two rows is proposed and demonstrated as a novel leaky-wave antenna beam steering from −30° to +15° with respect to broadside direction. This antenna covers the measured frequency bandwidth from 0.93 GHz to 3.65 GHz (approximately 119%, S11 less than10 dB) and the scanned angle moves from backward to forward radiation as the frequency increases. The antenna with overall size of 19.2 mm by 15.2 mm by 1.6 mm (0.059 lambda by 0.047 lambda by 0.004 lambda, where lambda is free space wavelength at 930 MHz), is fabricated on Rogers_RT_Duroid5880 substrate (dielectric constant of 2.2, loss tangent of 0.0009, height of 1.6 mm). The maximum measured gain and efficiency are observed at broadside direction with 8 dBi gain and 90% radiation efficiency. This low-profile antenna can be flush-mounted on various structures including vehicles, cellular base stations, or mobile devices. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:215–217, 2016