Coplanar Waveguide Research Articles

English

An ultra-wideband (UWB) antenna is designed, which is fed by a coplanar waveguide along with Dielectric ResonatorAntenna (DRA) is discussed. The patch of ultra-high-frequency antenna structure comprises many full circles and half circles, rearranging the two focal point orientation and dimension of radius such that the antenna works in ultra-wideband frequency range and a rectangular slot in the middle of the antenna patch to change the orientation of current distribution. The antenna is resonating at 8.9GHz with a reflection coefficient (S11) of -15.39dB, Gain is negative at resonating frequency, and Polarization at resonating frequency is linear. The proposed antenna is designed by mounting Cylindrical Dielectric Resonating Antenna (CDRA) on the rectangular slot made on the patch. By mounting a cylindrical DRA structure on the patch, the antenna is resonating at 3.6 GHz with a reflection coefficient (S11) value - 22.54dB, achieving a Gain of 3.44dB at resonating frequency. The Polarization achieved by placing cylindrical DRA is circular Polarization which is more useful in Ground Penetrating Radar (GPR) applications. The proposed antenna is practically designed, and performance characteristics are measured and verified with simulation results.

Flexible and frequency reconfigurable CPW-fed monopole antenna with frequency selective surface for IoT applications

This paper proposes a flexible, frequency-reconfigurable monopole antenna design with frequency selective surface (FSS) for Internet of Things (IoT) applications. The proposed antenna operates at three of the IoT frequency bands. This antenna is a coplanar waveguide (CPW)-fed monopole with two balanced arms printed on a thin ROGERS 3003 flexible substrate. The length of the right-hand arm of the antenna is used to achieve frequency reconfiguration by using PIN diodes. Three frequency modes of operation have been obtained; the 2.4 GHz frequency band with the right-hand arm is fully truncated, the 3.5 GHz frequency band with the two arms is completely maintained, and the 4 GHz frequency band with the right-hand arm is partially truncated. To improve the gain of the antenna, a simple FSS surface is designed to be placed under the antenna at a distance of 15 mm. The FSS operates efficiently from 2 to 4.5 GHz and has improved the gain of the antenna. A maximum gain of 6.5 dBi, 7.52 dBi, and 7.91 dBi has been achieved at the three frequency bands respectively. The behavior of the flexible antenna has been evaluated in both the flat and bent states, and stable performance has been observed in both cases.

Reflection-enhanced gain in traveling-wave parametric amplifiers

The operating principle of traveling-wave parametric amplifiers is typically understood in terms of the standard coupled mode theory, which describes the evolution of forward propagating waves without any reflections, i.e. for perfect impedance matching. However, in practice, superconducting microwave amplifiers are unmatched nonlinear finite-length devices, where the reflecting waves undergo complex parametric processes, not described by the standard coupled mode theory. Here, we present an analytical solution for the TWPA gain, which includes the interaction of reflected waves. These reflections result in corrections to the well-known results of the standard coupled mode theory, which are obtained for both 3-wave and 4-wave mixing processes. Due to these reflections, gain is enhanced and unwanted nonlinear phase modulations are suppressed. Predictions of the model are experimentally demonstrated on two types of unmatched TWPA, based on coplanar waveguides with a central wire consisting of i) a high kinetic inductance superconductor, and ii) an array of 2000 Josephson junctions.

Millimeter-wave to near-terahertz sensors based on reversible insulator-to-metal transition in VO2

In the quest for low power bio-inspired spiking sensors, functional oxides like vanadium dioxide are expected to enable future energy efficient sensing. Here, we report uncooled millimeter-wave spiking detectors based on the sensitivity of insulator-to-metal transition threshold voltage to the incident wave. The detection concept is demonstrated through actuation of biased VO2 switches encapsulated in a pair of coupled antennas by interrupting coplanar waveguides for broadband measurements, on silicon substrates. Ultimately, we propose an electromagnetic-wave-sensitive voltage-controlled spike generator based on VO2 switches in an astable spiking circuit. The fabricated sensors show responsivities of around 66.3 MHz.W−1 at 1 μW, with a low noise equivalent power of 5 nW.Hz−0.5 at room temperature, for a footprint of 2.5 × 10−5 mm2. The responsivity in static characterizations is 76 kV.W−1. Based on experimental statistical data measured on robust fabricated devices, we discuss stochastic behavior and noise limits of VO2 -based spiking sensors applicable for wave power sensing in mm-wave and sub-terahertz range.

A tri-band flexible antenna based on tri-band AMC reflector for gain enhancement and SAR reduction

A tri-band wearable antenna fed by coplanar waveguide (CWP) with an artificial magnetic conductor (AMC) reflector is presented in this paper. The radiation patch consists of three open inverted triangles for multiband, and the ground is defected for better impedance matching The AMC unit is composed of three concentric nested regular octagonal rings. And to improve the performance of gain, the unit achieves three reflection zero phases at 1.8, 2.45 and 3.5 GHz corresponding to the three bands of the antenna. The proposed antenna based on AMC has been fabricated and measured. The working frequency bands are 1.34–1.67 GHz, 2.33–2.47 GHz and 3.55–3.7 GHz. The measured gain has increased by 3.4, 1.8, 4 dBi at 1.8, 2.45 and 3.5 GHz, respectively. The scenario that the antenna is placed on the human arm is also considered and experimented for wearable applications. The results are in good agreement with the simulation data and verify that the antenna has good robustness. When the antenna is conformal with the human tissue, the specific absorption rate (SAR) is calculated and reduced by about 99.8% after adding AMC reflector. Hence the proposed antenna has excellent wearable safety and is compatible with LTE 1800, WLAN, WiMAX communication systems.

Spin Defects in hBN assisted by Metallic Nanotrenches for Quantum Sensing.

The omnipresence of hexagonal boron nitride (hBN) in devices embedding two-dimensional materials has prompted it as the most sought after platform to implement quantum sensing due to its testing while operating capability. The negatively charged boron vacancy (VB-) in hBN plays a prominent role, as it can be easily generated while its spin population can be initialized and read out by optical means at room-temperature. But the lower quantum yield hinders its widespread use as an integrated quantum sensor. Here, we demonstrate an emission enhancement amounting to 400 by nanotrench arrays compatible with coplanar waveguide (CPW) electrodes employed for spin-state detection. By monitoring the reflectance spectrum of the resonators as additional layers of hBN are transferred, we have optimized the overall hBN/nanotrench optical response, maximizing thereby the luminescence enhancement. Based on these finely tuned heterostructures, we achieved an enhanced DC magnetic field sensitivity as high as 6 × 10-5 T/Hz1/2.

Low-cost thin film patch antennas and antenna arrays with various background wall materials for indoor wireless communications

The present study introduces an inkjet-printed flexible coplanar waveguide patch antenna array concept. Single antenna and four-element antenna arrays were characterized, which were attached to a subminiature version A connector via an innovative solderless, 3D-printed ‘plug-and-play-type’ tightener. Furthermore, indoor wireless communication and Internet of Things scenarios with commonly used wall materials including gypsum and plywood boards, on which patch antennas and antenna arrays can be attached, were also presented. In order to validate the concept, design and fabrication iterations in parallel with numerical and experimental investigations were executed. To elaborate, single antenna and antenna array configurations without and with wall materials were characterized to see their functionality at 2.4 GHz resonance frequency and beyond 300 MHz bandwidth, respectively. The results demonstrate that the investigated configurations fulfill short-range radio transmission and can be utilized, e.g., for indoor backscattering-type communications and wireless sensing applications, as an affordable and versatile alternative to their conventional counterparts. Being attached to their corresponding background materials, single-antenna specimens were measured to have return losses beyond 18 dB and peak gains around 1 dBi, while higher peak gains above 6 dBi were detected for antenna arrays. Moreover, the antenna arrays can enable multiple-input and multiple-output communication. The proposed arrays had diversity performance in terms of return losses higher than 15 dB, isolation of more than 20 dB, envelope correlation coefficient , diversity gain dB, mean effective gain dB, power ratio factor dB, and channel capacity loss bits/s/Hz.

Pure spin squeezing of h -BN spins coupled to superconducting resonator

The negatively charged boron vacancy (${\text{VB}}^{\ensuremath{-}}$) spin defect in two-dimensional (2D) hexagonal boron nitride ($h$-BN) has attracted much attention for potential applications in quantum photonics recently. Its inherent van der Waals force mechanism guarantees convenient heterostructures for quantum sensing. By virtue of such materials, researchers not only can fabricate enough thin spin film naturally close to the sensing target but also can prepare an almost perfect spin ensemble with a uniform orientation. We here propose a setup with an ensemble of ${\text{VB}}^{\ensuremath{-}}$ spins strongly coupled to the superconducting coplanar waveguide resonator through the magnetic-dipolar interaction. The collective coupling strength is predicted to be $G/2\ensuremath{\pi}\ensuremath{\sim}15$ MHz, which corresponds to the strong coupling region. This collective spin-photon interaction can mimic the one-axis twisting Lipkin-Meshkov-Glick model effectively and therefore guarantee the dynamic generation of the spin-squeezed state. In addition, we show the influence of inhomogeneous coupling caused by sample thickness on squeezing, which proves the validity of the homogeneity assumption in our scheme. This attempt not only explores the possibility and superiority of 2D ${\text{VB}}^{\ensuremath{-}}$ spins but also opens another avenue for quantum hybridization.

A quadband polarization insensitive and angularly steady frequency Selective surface for gain enlargement of multiband antenna

A simply constructed bi-layered compact Frequency Selective Surface (FSS) is reported in this article to attain four distinct stop bands for multiband wireless applications. The compact FSS consists of complimentary oriented repeated cells in top and bottom layers with cell size of 0.135λL × 0.135λL and 0.12λL × 0.12λL respectively where λL refers the lower band edge wavelength. The FSS exhibits bi-polarized characteristic with angular steadiness till 450 in TE and 300 in TM polarization. The FSS, act as a sub-reflector to broaden the antenna gain, is placed beneath a simple co-planar waveguide (CPW) fed quadband antenna having three triangular patches with rectangular slots stacked together. This united ‘antenna-FSS’ structure attained S11 < -10 dB spectrums at 3.1–3.7 GHz (17.65 %), 5.3–6 GHz (12.34 %), 9.7–11.72 GHz (18.86 %) and 17.4–19.15 GHz (9.57 %) as per experimental evaluation. The ‘antenna-FSS’ offers maximum gain value 9.56 dBi with an enlargement of 4.9 dBi, 3.7 dBi, 4.3 dBi and 5 dBi in its four bands. Adequate radiation efficiency, linear transfer function response and smooth group delay contour are also conquered from ‘antenna-FSS’ in its four bands. The reported ‘antenna-FSS’ is appropriate for multiband wireless technologies as it covers WiMAX, WLAN, ISM, terrestrial and satellite spectrums.

CPW fed shovel shaped super wideband MIMO antenna for 5G applications

A shovel shaped antenna operating from 4.1 to >60 GHz to cover C/X/Ku/K/Ka/Q/U bands along with 5G bands n257/n258/n259/n260/n261/n79/60 GHz is presented in this paper. It consists of a modified square patch, tapered feed line and modified defected coplanar waveguide ground planes. A half-wavelength split ring resonator (SRR) is used to achieve X-band satellite downlink (6.8–7.8) GHz band notch. It has dimensions of 20 × 14 mm2, quasi-stable radiation patterns, a maximum peak realized gain of 9 dBi, fidelity factor > 50%, |S21| > 32 dB and linear S21 phase response. It’s two element spatial diversity configuration has footprint of 20 × 36 mm2, operating bandwidth of 4.3 to >60 GHz with notch band characteristics and isolation >15 dB due to hybrid decoupling structure. The pattern diversity configuration has footprint of 20 × 41.5 mm2, impedance bandwidth of 4.3 to >60 GHz for Port 1 & 3.9 to >60 for Port 2 and isolation >21 dB due to hybrid decoupling structure. Both MIMO antennas have ECC≤0.01, DG≅10, TARC < -10 dB, ηmux > -3.5 dB and CCL≤0.3 b/sec/Hz and channel capacity of ∼11.34b/sec/Hz. The proposed antenna geometries are dominating previously reported structures in terms of superwide bandwidth, compact dimensions, high BDR ∼3335, high peak gain and good diversity performance with less intra element spacing.

RF sensor dedicated to the dielectric characterization of spheroids between 500 MHz and 20 GHz

AbstractTo achieve better accuracy in their investigations, biologists have recently been using three-dimensional models as intermediates between two-dimensional cell culture and the in vivo study of tissues. Some of these models are based on spheroids, which are cellular aggregates retaining many characteristics of in vivo behaviors while being still easy to use and implement in labs. To study such objects, multiple observation techniques can be used according to the objective of the study, including those using electromagnetic waves as nondestructive, noninvasive, and label-free analysis. Low-frequency (&lt;1 MHz) ones are currently under investigation as electrochemical impedance spectroscopy. However, unlike microwaves (from 300 MHz to 60 GHz), they cannot penetrate the cell. Furthermore, most of the devices dedicated to microwave dielectric characterization are only focusing on cellular scales lower than spheroids (single cell, cell mats, or suspensions) or on tissues and organs. In this article, a microwave spectroscopy device using a coplanar waveguide adapted to the study of spheroids is presented with the dielectric characterization of fixed spheroids, with capacitance and conductance measurements from 0.5 to 20 GHz, aiming at filling the scale gap in the state of the art.

Microwave coplanar band-stop filters based on electric-LC resonators: systematic numerical approach and experimental validation

In this paper, we propose a comparative method to analyze a complex microwave structure consisting of a silicon-based coplanar waveguide line and four electric-LC resonators, thus forming a wideband microwave band-stop filter that can be easily integrated at the wafer level together with other devices and sub-systems for large-scale production of high-frequency electronics. A rigorous and careful approach is needed when choosing the proper simulation settings and, as a good rule of thumb, both time and frequency domains should provide the same results. Furthermore, the experimental validation requires supplementary components (like connectors), often ignored when designing an electromagnetic structure highly impacting on the overall performance. In this work, we go in depth into all these issues and show how the right choices in terms of computational parameters can lead to a good agreement with the measurements of the proposed CMOS-compatible band-stop filter in the band 2–18 GHz, with a relative bandwidth of almost 30% around the band-stop frequency of 13.2 GHz and a rejection level of − 40 dB.

Capacitor-Loaded Coplanar Waveguide Spoof Surface Plasmon Polariton With Reduced Transversal Width

To reduce transversal width, a new spoof surface plasmon polariton (SSPP) based on coplanar waveguide (CPW) is proposed. By using capacitor loading technique to control the dispersion characteristics and electromagnetic field, the proposed capacitor-loaded CPW SSPP exhibit a similar transmission performance to conventional unloaded CPW SSPP TL, but with a transversal width reduction up to 64%. On this basis, another modified capacitor-loaded CPW SSPP is presented by changing the groove shape from strip-shape to T-shape. Results validate that the transversal width of the T-shape CPW SSPP is only 24% to that of conventional unloaded CPW SSPP. Besides, much more tighter field confinement is achieved for both the two proposed CPW SSPPs. Such results are of great significance to reduce the size of plasmon devices in microwave regime.

Asymmetric Calibration and Characterization for Diff-Port Magnetic Field Probing System

Strict symmetry limits the application of the differential port magnetic field probing system (DMPS). Asymmetric calibration is very meaningful for DMPS. Ultrawindband asymmetric calibration theory was first proposed and applied to the electromagnetic field measurement system. However, the asymmetric calibration theory is not clear for the DMPS because only magnetic field is concerned. This paper proposes an ultrawideband asymmetric calibration method (UACM) for the DMPS. The output voltage and asymmetric factor of the DMPS are redefined using the UACM. Compared with the previous asymmetric calibration method, the proposed method is based on a symmetry calibrator with grounded coplanar waveguide structure. The proposed method is validated by eliminating a severe asymmetry in the DMPS, whose severe asymmetry is achieved by introducing a connector intentionally. The proposed method has been verified with the frequency of up to 20 GHz by measuring a standing wave magnetic field on an open-terminated transmission line. The key parameters of the DMPS, including unwanted field suppression, spatial resolution, and sensitivity, are also estimated.

A 3.7 GHz CPW Filtering Antenna with a Pair of Gain Zeros

In recent years, there has been a development of multifunctional components, including filtering antennas. Co-designing the filter and antenna can effectively reduce the overall size and thus realize high integration. A new coplanar waveguide (CPW) omnidirectional filtering antenna with a pair of gain zeros is presented using separation electric/magnetic coupling (SEMC) paths that greatly enhance frequency selectivity and effectively suppress the spurious responses of the circular patch radiator. The impedance bandwidth of the filtering antenna can also be controlled/adjusted through electric/magnetic coupling. The design results demonstrate that the filtering antenna achieves an omnidirectional pattern with a center frequency of 3.7 GHz, an impedance bandwidth of about 3%, a gain of 2.7 dBi, and a pair of gain zeros.

Plasmonic-Enhanced Bright Single Spin Defects in Silicon Carbide Membranes.

Optically addressable spin defects in silicon carbide (SiC) have emerged as attractable platforms for various quantum technologies. However, the low photon count rate significantly limits their applications. We strongly enhanced the brightness by 7 times and spin-control strength by 14 times of single divacancy defects in 4H-SiC membranes using a surface plasmon generated by gold film coplanar waveguides. The mechanism of the plasmonic-enhanced effect is further studied by tuning the distance between single defects and the surface of the gold film. A three-energy-level model is used to determine the corresponding transition rates consistent with the enhanced brightness of single defects. Lifetime measurements also verified the coupling between defects and surface plasmons. Our scheme is low-cost, without complicated microfabrication and delicate structures, which is applicable for other spin defects in different materials. This work would promote developing spin-defect-based quantum applications in mature SiC materials.

A monopole antenna with cotton fabric material for wearable applications

A monopole antenna operated at 2.45 GHz and embedded with artificial magnetic conductor (AMC) for wearable communication systems is investigated in this article. The proposed antenna is composed of a metalized loop radiator with a coplanar waveguide microstrip feedline which is affixed on a cotton fabric material substrate. As well, a cotton-based AMC surface is utilized to eliminate the body’s absorbed radiation and enhance the gain of the antenna. It is composed of 5 × 5 array unit cells etched with I-shaped slots. Using this configuration, simulations show that the specific absorption rate (SAR) level was significantly reduced. Considering flat and rounded body parts, it was found that the SAR values averaged over 10 g at a distance of 1 mm away from the tissues model were only 0.18 W/kg and 0.371 W/kg, respectively. Additionally, the antenna gain was improved up to 7.2 dBi with an average radiation efficiency of 72%. Detailed analysis with experimental measurements of the cotton-based antenna for different operation scenarios is introduced. The measured data show a good correlation with the electromagnetic simulation results.

A novel filtering monopole antenna for 5G communications

PurposeThis study aims to design a compact filtering monopole antenna for 5G communication. The design is most suited for various applications within the frequency range of 2.2–3.8 GHz. It offers enhanced bandwidth and reasonable gain with wide-stopband performance.Design/methodology/approachA low-pass filter (LPF) of complementary split ring resonator (CSRR) with short-circuited stub lines is integrated with a compact defected coplanar waveguide fed truncated circular monopole ultrawideband (UWB) antenna. The reference UWB antenna etched on an FR4 substrate was coupled to the designed LPF to transform the UWB antenna into a wideband antenna. The effect of coupling is analyzed based on the real and imaginary responses of the terminal impedance (ZT) curve. Three short-circuited stub lines of asymmetric lengths are added to the CSRR LPF to suppress harmonics, thereby enhancing the stopband performance and impedance matching between the elements. The proposed filtering antenna is fabricated using a photolithography process, and the corresponding results are measured using a network analyzer (N9951A). The radiation parameters of the proposed filtering monopole antenna are tested in the anechoic chamber. The simulated/measured results are compared and are found in agreement with each other.FindingsThe proposed design suppresses 6.5f0 harmonics, resulting in wide stopband performance and increased gain selectivity at the transition edge. A peak suppression of −41 dB and an average suppression of −18 dB were attained throughout the stopband. An operating fractional bandwidth of 54.5%/143% with a peak gain of 3 dBi/5 dBi was obtained. The proposed filtering antenna supports 5G applications such as WiMAX, WLAN, n7, n38 IMT-E, n30 WCS, n40 TDD, n41 TDD, n48 TDD, n78 TDD and n90 TDD.Originality/valueThe proposed design is novel and compact and has a wide application in 5G communication. With the filter, the antenna operates in wideband, and without the filter, it operates in UWB. Besides, it offers enhanced stopband performance with high gain selectivity at the transition edge. Comparatively, a 50% improvement in bandwidth, 52% improvement in size reduction and 33% improvement in harmonic suppression are attained.

A Transparent Antenna Using Metal Mesh for UWB MIMO Applications

This paper presents a transparent ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna based on a wired metal mesh (MM) structure. Transparent antennas (TAs) can be integrated on various building materials with little visual impact to facilitate flexible massive indoor wireless device deployment. The proposed antenna achieves 77% transparency by hollowing out both metal and substrate into a mesh shape, while maintaining more than 83% radiation efficiency. The MIMO antenna consists of 4 elements, each being a co-planar waveguide (CPW) fed UWB monopole and adjacent elements being placed orthogonally to produce dual polarisation. The operating band of the MIMO antenna spans over 3.2-11.2 GHz. A parasitic decoupling structure aligned with the mesh grid is designed to enhance the isolation between MIMO elements without degrading the transparency. Within the entire operating band, the isolation between any two elements is more than 20 dB. The peak gain varies from 3.3 dBi to 7.2 dBi within the bandwidth. The envelop correlation coefficient (ECC) is less than 0.004. The channel capacity and time domain response are analysed. The antenna can be easily fabricated by conventional PCB and laser cutting techniques with a low cost.

Ultrawideband De-Embedding Calibration for Magnetic Field Probes by Using Symmetric GCPW Calibrators

Microstrip line is commonly used as a calibrator for probe calibration. However, some issues need to be addressed for high frequency application, such as ripple and attenuation caused by the embedded part of the calibrator. In this paper, an ultra-wideband de-embedding calibration method (DCM) for magnetic field probe is proposed. Two symmetric non-soldering grounded coplanar waveguide (GCPW) calibrators, including Through and Line standards, are used to solve the de-embedded <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameter matrix of a 3-port calibration system. Compared with the traditional calibration method (TCM), the proposed method can reduce the influence of the reflection and attenuation caused by the embedded part and preserve the intrinsic properties of the probe itself. By using the DCM with a symmetric and good matched GCPW calibrator, the ripples of the DCM decreases by 6.57 dB, which is 82 % of the TCM with a microstrip line, and the attenuation has been compensated by about 0.7 dB at 10 GHz. In addition, a new characterization method of common mode suppression ratio for H-field probe is also presented, and it is applicable to conducted emissions measurement in which a probe can detect signals without 90° rotation.