Search

This paper presents, for the first time, a tunable left handed coplanar waveguide zeroth-order resonator on a ferrite substrate. Analysis and design procedures of the proposed resonator are introduced. The proposed resonator is designed to be tuned over the frequency band from 3 to 4.85 GHz with lower than 3-dB insertion loss and better than 10-dB return loss. The dimensions of the proposed resonator are 8.3 x 20 mm. The advantages of the proposed resonator are its tuning capability in addition to its compact size. Index Terms--Ferrite, left-handed media, metamaterials, resonator.

A novel coplanar waveguide ferrite-coupled line (CPW FCL) is presented and numerically verified for the first time. The proposed CPW FCL exhibits a low insertion loss for both even and odd mode excitations, equal power division for single power excitation with both isolation, and return loss better than 10 dB over the whole operating bandwidth, and 20 dB in the best cases. The coupler has a much wider operation bandwidth compared to any other configurations reported to date. In addition, the CPW FCL demonstrates better phase flatness within the operating bandwidth compared to microstrip FCL. Index Terms--Coplanar waveguide (CPW), ferrite, ferrite coupled lines (FCLs), nonreciprocal devices.

A set of novel left-handed LH) basic block monolithic-microwave integrated-circuit (MMIC) components (transmission line, open and short stubs) are presented with applications to the RF/microwave filter and power divider. These new open and short LH MMIC resonators have compact sizes of 0.11 and 0.22 [mm.sup.2], respectively. The prototypes of an LH bandpass filter and LH power divider constructed from these basic components have been designed, fabricated, and characterized. The LH filter consisting of an LH transmission line and four LH open resonators exhibits transmission zeros at both sides of the passband from 1.02 to 1.42 GHz with 33.3% fractional bandwidth. The LH power divider including two LH branches shows equal power split from 2.8 to 3.72 GHz. The filter and power divider benefit from the miniaturized LH MMIC components and have compact sizes of 2.85 and 2.3 [mm.sup.2], respectively. Loss issues of these LH structures and, more importantly, the effect of skin depth at low frequency are investigated. Full-wave simulations for conductor thicknesses of 0.2, 1.4, and 5 [micro]m are presented for the proposed LH MMIC components and circuits. There is a good agreement between the full-wave simulations, equivalent-circuit model, and measurement results with 1.4-[micro]m metal thickness demonstrating the effectiveness of the models. Index Terms--Bandpass filter, left-handed (LH) metamaterial, power divider, resonators.

A high tangential signal sensitivity (TSS) zero-bias GaAs planar doped barrier (PDB) diode for microwave and millimeter-wave power detection applications is presented. The fabricated PDB diodes have shown 4 dB better TSS at 35 GHz than that of reported devices, considerably increasing the minimum detectable power and widening the dynamic range. The high TSS was obtained by optimizing the PDB layer structures, namely, the [sigma]-doped [p.sup.++] layer and the two intrinsic layers, and by employing ion bombardment to better define the device and reduce parasitic effects. The isolation properties of ion bombarded epitaxial layers on GaAs substrates were examined and optimized to have a sheet resistivity of [l0.sup.8] [ohm]/sq. The temperature dependence of the barrier height of the PDB diode has been investigated experimentally, showing positive temperature coefficient and, hence, better thermal stability. We have also defined the critical barrier height and derived its analytical expression, which gives the theoretically lowest possible barrier height of a PDB diode. Index Terms--Ion bombardment, planar doped barrier (PDB) diodes power detectors and sensors, tangential signal sensitivity (TSS).

Current artificial magnetic conductor (AMC) designs use metallic patterns on rigid substrates and focus on shapes and sizes of AMC structures, rather than on material performance, which has hindered operation bandwidth and design flexibility. Here, we introduce printed graphene AMC-based broadband and flexible microwave radar absorbers, which not only redirect but also absorb the incident wave so to broaden the operation bandwidth. Contrasting to other reported works, the phase characteristics of the AMCs are realized through the control of the surface resistance provided by printed graphene laminates. We produced a variety of AMC structures, composed of printed graphene circular ring arrays with exactly the same shape and size, but different sheet resistances. By carefully designing the sheet resistance of printed graphene laminates, the optimized anti-phase reflection cancellation between AMCs can be achieved. With printed graphene AMCs and flexible dielectric substrate, the absorber presented in this work has a broadband effective absorption (above 90% absorptivity) from 7.58 GHz to 18, is polarization insensitive under normal incident, and can work at relatively wide incident angles. Furthermore, this absorber is capable of bending easily with notable performance, which makes it ideal for applications with irregular and uneven shapes. [ABSTRACT FROM AUTHOR]

A surface-oriented planar Schottky diode for use as a detector diode on Si monolithic microwave integrated circuits (MMIC's) was developed. The active n-on-[n.sup.+] and contact [n.sup.+] regions were doped on the high-resistivity silicon substrate using phosphorus ion implantation. The PtSi-Si barrier was formed by metallurgical interaction between pure platinum film and silicon. The process technology developed for the Schottky-detector diode fabrication is precise, simple, and cheap, and is suitable for mass production. The typical measured cutoff frequency of a zero-biased fabricated Schottky diode is 118 GHz.

A novel low RF loss trenched coplanar waveguide (CPW) transmission-line structure fabricated using evaporated aluminum tracks on a high-resistivity (10-k[Omega] [center dot] cm) silicon (HRS) substrate is reported. By assuming that Schottky contact boundaries exist at the metal silicon substrate interface in the CPW line, the finite-element analysis method is used to determine the simulated behavior of the structure. The distributed capacitance, leakage conduction current, and dynamic shunt conductance for the line are shown to be a function of dc bias applied to the line, and also to reduce as a function of trench depth in the normal bias regime. Experimental results show: 1) the reduction of RF losses in comparison with conventional aluminum conductor CPW line structures may be as much as 0.5 dB/cm at 30 GHz; 2) by proper positive dc biasing of a CPW line on a p-type HRS substrate, a further reduction (0.2 dB/cm) in RF loss at 30 GHz can be achieved; 3) predicted trends in line leakage current, capacitance, and relative characteristics impedance are experimentally verified. The proposed waveguide structure may be utilized in a special fabrication process designed for RF/microwave applications. Index Terms - Capacitance, conductance, CPW, loss, MMIC.

This paper proposes an accurate model for yarn-based embroidered coil antenna used in Near Field Communication (NFC) applications. Traditionally, the inductance of a coil-shaped antenna is calculated using the Wheeler’s equation, while accurate enough for metallic coil geometries, the results from Wheeler’s equation have more than 20% errors when being applied to yarn-based embroidered antennas. We have discovered that this discrepancy is related to the parasitic capacitance, which is caused by the subtle gaps along twisted fibers. Experiments demonstrate that the parasitic capacitance has significant impact on the overall performances of the coil antenna. In this paper, an equivalent model for yarn-based coils is proposed to take into account of the parasitic capacitance and antenna geometrical characteristics. Compared with traditional Wheeler’s equation, the inductance calculated from this proposed model is within 5% from the measured value. Additionally, the electromagnetic performance of the embroidered coil is resilient to mechanical deformation. When being used as a coupling antenna, it can harvest energy and power-up the NFC-based platform for body-area-network applications. [ABSTRACT FROM AUTHOR]

This paper proposes a signal feedback interference topology to control the characteristics of a coupled line bandpass filter. Control is carried out by varying the ratio of the transmission line parameters of the forward and the feedback couplers. The topology produces a compact filter that does not require a complicated design or fabrication. The results of the insertion and return losses show that the feedback‐controlled design has desirable features in terms of the design frequency, fractional bandwidth, stopband rejection level, roll‐off rate and insertion loss. The test results of the fabricated prototype achieved good agreement with the simulation results of the ideal transmission line design model. Several microwave, modern wireless and mobile/satellite communication systems may benefit from such a filter design due to its compactness and flexibility. [ABSTRACT FROM AUTHOR]

This paper presents high‐power broadband graphene non‐Foster circuit (NFC) enabled Class‐J GaN HEMT power amplifier (PA). A graphene resonant‐tunneling diode (RTD) NFC is proposed to provide negative differential resistance characteristics and to create an effective negative capacitance. The NFC is integrated in the input matching network of the Class‐J GaN HEMT PA to cancel out the transistor input parasitic capacitance so as to enhance PA bandwidth, efficiency, output power, and gain. The PA design is based on Cree's packaged GaN HEMT CGHV40030F biased with drain supply voltage of 50 V at quiescent drain‐to‐source current of 44 mA. The PA operates from 3.4 to 4.0 GHz with center frequency of 3.7 GHz. The effective negative capacitance of the NFC from 3.4 to 4.0 GHz stands at −3.3 to −6.0 pF. An effective capacitance of −3.7 pF has been obtained at 3.7 GHz. The PA has small signal gain of 16.1 dB at 3.7 GHz. Large signal simulation input power sweep from 1 to 33 dBm at 3.7 GHz, indicates that the PA has 57.8% drain efficiency, 54.7% power added efficiency (PAE), 44.6 dBm (28.8 W) output power and 11.6 dB transducer power gain at input power of 33 dBm. [ABSTRACT FROM AUTHOR]

This paper presents analysis and experimental measurements of CPW and microstrip compact monopole antennas loaded with resonator circuits inspired from simplified half-mode composite right / left-handed unit cell. The antennas were designed to have a typical omnidirectional radiation pattern. The CPW fed dual-band antenna resonates at 2.4 and 5.8 GHz, respectively. The antenna size is 20 × 30 mm2 and the radiator patch is only 25% at 2.4 GHz and 60% 5.8 GHz in comparison with a conventional patch antenna. The microstrip triple-band antenna covers the frequency bands from 2 to 2.4 GHz, 5.4 to 6 GHz and 6.8 to 8 GHz. The antenna size is 28 × 25 mm2 which is less than 25% at lower frequency band compared to the size of the conventional patch antenna. Detailed theoretical and full-wave analysis is presented and experimental results demonstrate a good agreement between the measured and the simulated. The suggested antennas can be employed for compact size and multi-band functionalities in wireless applications. The loading technique can be adapted for more frequency bands. [ABSTRACT FROM AUTHOR]

A quad band antenna with good gain and omni-directional pattern is proposed in this paper. The antenna design is based on loading a conventional monopole antenna by three different resonators. The resonators are inspired from the shunt branch of composite right-/left-handed cell. The resonators have a simple structure and compact size. The control of the frequency bands can be achieved arbitrarily and hence the suggested design methodology can be generalized to any required bands. The fabricated antenna prototype is operating at 2.6, 3.35, 5.15, and 6.1 GHz with bandwidth wider than 100 MHz for each band. The antenna's operating principle and design procedures with the aid of electromagnetic full wave simulation are presented. Finally, the experimental results exhibit good agreement with the simulated ones which confirm the proposed designed methodology. The proposed monopole antenna has a patch size of 13.5 mm × 6.5 mm and the whole antenna size (including the feed line) is 35 mm × 32 mm. Compared to conventional single-band microstrip patch radiator size, the proposed quad band radiator has the size of 9, 15, 37.5, and 72.5% at relevant frequency bands. [ABSTRACT FROM AUTHOR]

The design and analysis of meta-material inspired loaded monopole antenna for multiband operation are reported. The proposed antenna consists of multi resonators inspired from half mode composite right/left handed cells, which has a simple structure, compact size, and provides multiband functionalities. As a proof of concept, a triple band antenna covering all possible WiMAX operating bands, has been designed, fabricated, and characterized. The hosting monopole patch itself generates resonance for 3.3–3.8 GHz band, whereas the loaded metamaterial cells add extra resonance frequencies. The loading of two resonator cells introduces two extra resonances for 2.5–2.7 GHz and 5.3–5.9 GHz bands, respectively. The antenna's operating principle and design procedures with the aid of electromagnetic full wave simulation and experimental measurements are presented. The antenna has good omnidirectional patterns at all three bands. The monopole patch size is 13.5 × 6.5 mm2 and the whole antenna size (including the feed line) is 35 × 32 mm2. Compared with conventional single band microstrip patch radiator, the radiator size of this antenna is only 8.5% at 2.5 GHz, 17% at 3.5 GHz, and 37% at 5.5 GHz. [ABSTRACT FROM PUBLISHER]

ABSTRACT This article presents a new compact asymmetric coplanar strip -fed UWB MIMO antenna. The UWB MIMO antenna consists of two identical elements which have quarter elliptical ring radiating element with asymmetric coplanar strip-fed. By designing the antenna using asymmetric coplanar strip-fed, the antenna size can be reduced (its size is only 6 × 2.6 cm2). The distance between the two antenna elements equals 0.37 λ0-The single antenna element is operated at frequencies from 3.1 GHz to 10.6 GHz with reflection coefficient lower than −10 dB. In addition, the designed antenna elements have less than 15 dB coupling isolation between the two input ports. The diversity performance between two antenna elements such as envelope correlation coefficient and diversity gain are investigated and they are within their allowed limits. This analysis confirms that the designed antenna is suitable for portable UWB MIMO applications. The proposed antenna is designed; simulated and measured. There is a good agreement between the simulated and measured results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:31-36, 2017 [ABSTRACT FROM AUTHOR]

Covid-19 has demonstrated how vulnerable our society remains when it comes to managing a pandemic. There is an urgent need to develop and evaluate new technologies, materials, and methods for rapid measurement and continuous monitoring of body temperature, and accurate detection of elevated body temperature as a symptom of conditions which may lead to a pandemic. [ABSTRACT FROM AUTHOR]

A wideband CMOS LC tank voltage-controlled oscillator (VCO) with low phase noise variations and a linearized gain has been designed using a new binary-weighted switched-capacitor and digitally-controlled varactor bank. The novel design has the advantages of more linear VCO frequency tuning, lower phase noise and reduced gain to variations in supply voltage. The proposed VCO has been designed using UMC 90-nm, 6-metal CMOS technology and features phase noise variation of less than 4.9 dBc/Hz. The VCO operates from 3.45 to 6.55 GHz, with phase noise of -133.4 dBc/Hz at a 1 MHz offset, a figure of merit (FoM) of -203.3 dBc/Hz, less than 41 dBm spurious harmonics, and a total VCO core current consumption of 1.18 mA from a 3.3 V voltage supply. To the authors' knowledge, this is the lowest phase noise variation ever reported. [ABSTRACT FROM AUTHOR]

An enhanced heterojunction bipolar transistor small-signal extraction method is presented.

This letter presents a novel low phase noise free-running oscillator based on a high selectivity bandpass filter (BPF) using a composite right/left-handed transmission line (CRLH TL). The oscillator is designed at the spectrum-based quality factor (Qs) peak frequency to achieve low phase noise performance. Ata center frequency of 2.05 GHz, the oscillator demonstrates, experimentally, a phase noise of $-$150.4 dBc/Hz at 1 MHz frequency, offset with a figure of merit(FOM) of $-$207.2 dBc/Hz, less than $-$32 dBm spurious harmonics, and total oscillator power consumption of 6.1 mW from a 2 V supply voltage. [ABSTRACT FROM PUBLISHER]

A novel ferrite nonreciprocal left-handed (LH) transmission line is presented. The proposed structure is composed of a coplanar waveguide over a ferrite substrate, horizontally magnetized and periodically loaded with only shunt inductors. The line has a nonreciprocal LH propagation with transmission level better than -5 dB with isolation level up to 20 dB over a moderate bandwidth. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2810–2814, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22848 [ABSTRACT FROM AUTHOR]

A binomial low-pass filter provides the flattest passband response but, slow attenuation transition. This letter presents a design for improving the roll-off performance and reducing the size of the filter based on the negative-ℇ property of complementary split ring resonators (CSRRs), whilst maintaining the filter passband performance. The measured results indicate that the proposed structure achieves a flat pass-band with no ripples. Whilst also having a selectivity of 32 dB/GHz, which significantly exceeds the 17 dB/GHz selectivity of the conventional design. Furthermore, the proposed filter has reduced the filter size by 16%. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2406–2409, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22799 [ABSTRACT FROM AUTHOR]

In this letter, a microstrip Stepped Impedance Resonator (SIR) bandpass filter (BPF) based on Composite Right/Left-Handed (CRLH) transmission lines is presented for the first time. Supported by theory, full-wave simulations and measurements, operational principle of the filter is explained and results are analysed. Also, comparison is made between this filter and its conventional right-handed (RH) counterpart. For the same centre frequency, fractional bandwidth and stop-band attenuation, the CRLH SIR BPF presented here proves to surpass its conventional counterpart in terms of size, being about 80% smaller, without degradation of performance. The CRLH SIR BPF is also significantly more controllable in its dimensions and response due to the fact that more elementary parameters are available in CRLH configuration. [ABSTRACT FROM PUBLISHER]

E‐Textiles have gained increasing momentum in wearable electronics recently. Conductive‐yarn‐based embroidered devices, with the advantages of being soft, deformable, breathable, and protective for the skin, play an important role in replacing many metallic counterparts. However, embroidered devices face many new challenges in their design methodology and fabrication processes, such as high resistivity and low Q value of the conductive yarns, as well as deformation of device geometries during wearing. Herein, a strain‐free, deformation‐resilient embroidery process for near field communication (NFC) coil antennas is introduced. Coil geometry can endure extreme deformation by stretching with up to 50% elongation, bending with curvature as small as 16 mm in radius, and can still maintain a relatively small variation in its inductance, resonant frequency, Q value, as well as its energy‐harvesting capabilities. The embroidered coil antenna is used in an NFC‐based battery‐free body sensor system. Experiments demonstrate that the system can maintain a stable performance (voltage supply, temperature sensing, and reading range) under various deformation conditions. [ABSTRACT FROM AUTHOR]

In this work, we have designed, fabricated and experimentally characterized a printed graphene nano-flakes enabled flexible and conformable wideband radar absorber. The absorber covers both X (8-12 GHz) and Ku (12-18 GHz) bands and is printed on flexible substrate using graphene nano-flakes conductive ink through stencil printing method. The measured results show that an effective absorption (above 90%) bandwidth spans from 10.4 GHz to 19.7 GHz, namely a 62% fraction bandwidth, with only 2 mm thickness. The flexibility of the printed graphene nano-flakes enables the absorber conformably bending and attaching to a metal cylinder. The radar cross section (RCS) of the cylinder with and without absorber attachment has been compared and excellent absorption has been obtained. Only 3.6% bandwidth reduction has been observed comparing to that of un-bended absorber. This work has demonstrated unambiguously that printed graphene can provide flexible and conformable wideband radar absorption, which extends the graphene's application to practical RCS reductions. [ABSTRACT FROM AUTHOR]

2-Dimensional materials (2DMs) offer an attractive solution for the realization of high density and reliable memristors, compatible with printed and flexible electronics. In this work we fabricate a fully inkjet printed MoS 2 -based resistive switching memory, where graphene is used as top electrode and silver is used as bottom electrode. Memristic effects are observed only after annealing of each printed component. The printed memory on silicon shows low SET/RESET voltage, short switching times (less than 0.1 s) and resistance switching ratios of 10 3 -10 5 , comparable or superior to the performance obtained in devices with both printed silver electrodes on rigid substrates. The same device on Kapton shows resistance switching ratios of 10 2 -10 3 and remains stable at least up to 2% of strain. The memristor resistance switching is attributed to the formation of Ag conductive filaments, which can be suppressed by integrating graphene grown by chemical vapour deposition (CVD) onto the silver electrode. Temperature-dependent electrical measurements starting from 200 K show that memristic behavior appears at a temperature of ∼300 K, confirming that an energy threshold is needed to form the conductive filament. This work shows that inkjet printing is a very powerful technique for the fabrication of 2DMs-based resistive switches onto rigid and flexible substrates.

Due to the ability to tightly confine electromagnetic energy, plasmonic nanoantennas have been widely studied for surface-enhanced infrared absorption (SEIRA) spectroscopy, surface-enhanced Raman spectroscopy as well as refractive index sensing. However, most of the nanoantennas are limited by narrow resonant band and it is rather challenging to detect multiple molecular fingerprints. In this work, we report dual and triple- resonant pad-rod plasmonic nanoantennas which are nanorods with large pads at their ends placed above gold (Au) mirror separated by a spacer layer. By adjusting the geometries, the nanoantennas have demonstrated dual and triple resonant bands enabling detection of molecular fingerprints at different wavelength. The calculated maximum SEIRA enhancement factor is around 1.8 × 10 6 , which is among the highest reported so far. The pad-rod plasmonic nanoantennas have been used for the detection of molecules of polymethyl methacrylate (PMMA) by SEIRA and fingerprints of C=O and C-H bands are clearly identified. This work has shown that the multiple-resonant pad-rod plasmonic nanoantennas are promising for chemical and biomolecular sensing by the detection of vibrational fingerprints with SEIRA.

Increasing amounts of attention are being paid to the study of Soft Sensors and Soft Systems. Soft Robotic Systems require input from advances in the field of Soft Sensors. Soft sensors can help a soft robot to perceive and to act upon its immediate environment. The concept of integrating sensing capabilities into soft robotic systems is becoming increasingly important. One challenge is that most of the existing soft sensors have a requirement to be hardwired to power supplies or external data processing equipment. This requirement hinders the ability of a system designer to integrate soft sensors into soft robotic systems. In this article, we design, fabricate, and characterize a new soft sensor, which benefits from a combination of radio-frequency identification (RFID) tag design and microfluidic sensor fabrication technologies. We designed this sensor using the working principle of an RFID transporter antenna, but one whose resonant frequency changes in response to an applied strain. This new microfluidic sensor is intrinsically stretchable and can be reversibly strained. This sensor is a passive and wireless device, and as such, it does not require a power supply and is capable of transporting data without a wired connection. This strain sensor is best understood as an RFID tag antenna; it shows a resonant frequency change from approximately 860 to 800 MHz upon an applied strain change from 0% to 50%. Within the operating frequency, the sensor shows a standoff reading range of >7.5 m (at the resonant frequency). We characterize, experimentally, the electrical performance and the reliability of the fabrication process. We demonstrate a pneumatic soft robot that has four microfluidic sensors embedded in four of its legs, and we describe the implementation circuit to show that we can obtain movement information from the soft robot using our wireless soft sensors.

In this work, the relative dielectric permittivity of graphene oxide (GO), both its real and imaginary parts, have been measured under various humidity conditions at GHz. It is demonstrated that the relative dielectric permittivity increases with increasing humidity due to water uptake. This finding is very different to that at a couple of MHz or lower frequency, where the relative dielectric permittivity increases with decreasing humidity. This GO electrical property was used to create a battery-free wireless radio-frequency identification (RFID) humidity sensor by coating printed graphene antenna with the GO layer. The resonance frequency as well as the backscattering phase of such GO/graphene antenna become sensitive to the surrounding humidity and can be detected by the RFID reader. This enables battery-free wireless monitoring of the local humidity with digital identification attached to any location or item and paves the way for low-cost efficient sensors for Internet of Things (IoTs) applications.

Two-dimensional (2D) black phosphorus (BP) with direct band gap, bridges the characteristics of graphene with a zero or near-zero band gap and transition metal dichalcogenides with a wide band gap. In the infrared (IR) regime, 2D BP materials can attenuate electromagnetic energy due to losses derived from its surface conductivity. This paper proposes an IR absorber based on 2D BP metamaterials. It consists of multi-layer BP-based nano-ribbon pairs, each formed by two orthogonally stacked nano-ribbons. The multi-layer BP metamaterials and bottom gold mirror together form a Fabry-Perot resonator that could completely inhibit light transmission to create strong absorption through the BP metamaterials. Unlike previously reported BP metamaterial absorbers, this new structure can operate at two frequency bands with absorption > 90% in each owning to the first-order and second-order Fabry-Perot resonant frequencies. It is also polarization independent due to the fourfold rotational structural symmetry. To our best knowledge, this is the first report on using BP metamaterials in an absorber that operates independent of polarization and in dual bands.