Coplanar Waveguide Transmission Line Research Articles

Design of a 1×2 CPW Fractal Antenna Array on Plexiglas Substrate with Defected Ground Plane for Telecommunication Applications

In this paper, a fractal antenna array for telecommunication applications is presented. The proposed antenna array is realized on a Plexiglas substrate, has 1×2 radiating elements, and dimensions of 170mm×105mm. The antenna array is composed of two Koch Snowflake patches and is fed by a Coplanar Waveguide (CPW) transmission line. Radiating elements and the ground plane are printed on the top side of the substrate. Defected Ground Structure (DGS) technique is employed to enhance the bandwidth and improve the impedance matching. The proposed antenna array operates at two frequency bands, 1.08-1.32GHz covering the GPS band and 1.7-3.7GHz covering the GSM 1800/1900, UTMS, Bluetooth, LTE, and WiMAX bands. In addition, the antenna has a good performance with efficiency and peak gain of 82% and 6.3dB respectively. These characteristics allow the antenna to be an attractive candidate for telecommunication systems. Design and analysis of different structures were carried out with Ansys HFSS.

A Microwave Quantum-Defined Millivolt Source

We demonstrate a tenfold increase in the amplitude of microwave-frequency waveforms generated by a quantum-defined superconducting voltage source, with an open-circuit signal of 17.56 mV rms at 1.005 GHz. The voltage source is an RF Josephson arbitrary waveform synthesizer (RF-JAWS) that utilizes a circuit that is cooled to 4 K and is composed of an array of 4500 Josephson junctions. These junctions are connected in series along the center conductor of a 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> superconducting coplanar waveguide transmission line. We introduce a new zero-forcing equalization technique for reducing distortion in drive current pulse patterns. This technique allows an increase in the amplitude of the quantum-based voltage waveforms while suppressing parasitic feedthrough signals to −75 dBc. Synthesizing a two-tone delta–sigma waveform, we monitor an audio-frequency 10-kHz tone of less than 100- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{V}$ </tex-math></inline-formula> rms amplitude while simultaneously measuring the 1.005-GHz tone of −28.12-dBm power in a 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> environment. The two-tone synthesis allows simultaneous verification of correct operation of the voltage source using time-efficient low-frequency measurement techniques as well as slower microwave measurements.

Novel Calibration Method for the Asymmetric Probing in the Near-Field Measurement With a Dual Probe

Dual probe is capable of simultaneously measuring electric and magnetic fields in the same position, given that perfectly symmetric design is realized on the transmission paths connecting the detection loop and the probe outputs. For general application, a calibration method for the asymmetric probing in near-field measurement with the dual probe is presented, in order to deal with the failure of the traditional calibration due to the asymmetric transmissions in both paths. The asymmetric probing measurement is modeled, and then the proposed calibration to eliminate the asymmetry is further derived based on two independent measurements at two directions (0° and 90°) between the probe and the microstrip line providing a known electromagnetic field at the surface. The calibration method is demonstrated with two kinds of dual probes of different coupling structure. The proposed calibration is validated by introducing the asymmetry to the probing process in the measurement of the standing wave along a conductor-backed coplanar waveguide transmission line.

A Transmission Line Sensor With Sensitivity Improved for Detection of Ionic Concentration in Microfluidic Channel

Microwave measurements of minute dielectric property variations have many advantages such as noninvasive test, rapid sensing capability, and being label-free. Several researches including concentration detection are promoted by measuring the minute dielectric property variations of samples. Highly sensitive and accurate device is required for measurement of electrolyte concentration in biological fluids, especially when measuring samples in nanoliter or less scale. In this paper, a miniaturized broadband coplanar waveguide (CPW) transmission-line (TL) sensor with enhanced sensitivity is proposed. The sensitive device is realized by introducing interdigital capacitance (IDC) at the central conduction band of the CPW TL. The sensor is fabricated using print circuit board (PCB) technology with a microfluidic channel designed on it. A calibration based on microwave network theory is used to obtain the characteristic impedance and propagation constant of the sensing part. And accordingly, variations in magnitude and phase of S-parameters are employed to express the changes in concentration of the sample. Furthermore, an extracted equation between S-parameters and electrolyte concentration of the sample is first proposed. Experiments show the proposed sensor can detect the minimum concentration of 0.05 g/l for the three electrolytes (NaCl, KCl, and GaCl2 in deionized (DI) water)). Compared with a corrugator coplanar transmission line and a split ring resonator senor, the proposed sensor has a much higher sensitivity. Moreover, the device is robust in front of cross sensitivity caused by external factors (such as temperature variations, moisture, etc.). Thus, the proposed sensor is well suited for low-cost, real-tine, and CMOS compatibles sensing technologies.

Performance Enhancement of mm-Wave Phased Arrays for Mobile Terminals Through Grounded Coplanar Waveguide Feeding Networks With via Fences

This paper presents a design methodology focused on feeding networks that can improve the insertion loss and coverage efficiencies of millimeter-wave (mm-Wave) phased arrays in mobile terminals. This enhancement is accomplished by using a grounded coplanar waveguide (GCPW) transmission line (TL) withviafences fabricated on single-layer FR-4 PCB. The exemplified 8-element phased arrays incorporating a compact one-dimensional electromagnetic bandgap (1-D EBG) antenna are fed through a 1 × 8 T-junction power divider, which includes the predetermined phased delay lines. To achieve high radiation performance with minimum leakage power or spurious waves in the T-junction power divider, an island-shape GCPW TL topology withviafences featuring high-impedance surfaces (HIS) is devised and fabricated. For further investigation on the radiation performance and spherical coverage of the mm-Wave mobile antenna, a mobile device prototype equipped with two sets of the 8-element phased arrays is prepared and studied. Through extensive simulation and experimental studies, it can be ascertained that the proposed GCPW TL topology withviafences can improve the realized gain at a coverage efficiency of 50% by more than 3 dB, between 26 and 36 GHz.

Dual-Band Antenna With Large Frequency Ratio Based on Dual-Mode Transmission Line

A dual-band antenna with large frequency ratio for microwave and millimeter-wave applications based on the dual-mode coplanar waveguide (CPW) transmission line is investigated in this letter. The dual-mode operation of the transmission line is obtained by introducing a rectangular stub to traditional CPW, which can provide different phase shift in different frequency bands. In the millimeter-wave band, the dual-mode transmission line can support odd mode while it supports even mode in the microwave band. Based on this, the dual-band antenna which operates as monopole antenna in the microwave band and Vivaldi antenna in the millimeter-wave band is realized using the same aperture. Moreover, the radiation structure for monopole in the microwave band is designed to enhance the radiation performance of the antenna in the millimeter-wave band. For verifying, the prototype of the antenna is fabricated on a Rogers 4003 substrate with an overall size of 45 × 20 × 0.508 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and the measured results agree well with the simulated ones.

Coherent GHz lattice and magnetization excitations in thin epitaxial Ag/Fe/Cr/Fe films

We excited an epitaxial magnetic Ag/Fe/Cr/Fe multilayer nonthermally and nonoptically with very short (1 ps) electromagnetic pulses. We detected the synchronous phononic-magnetic response by time-resolved magneto-optical Kerr effect measurements. The Ag/Fe/Cr/Fe multilayer was patterned into a coplanar waveguide transmission line, and the electromagnetic pulses were generated by pulsed-laser illumination of an integrated GaAs photoconductive switch (PCS). The detected magnetic excitations comprise up to four narrow-band high-order modes with the highest frequency reaching 30 GHz. The mode frequencies are independent of both temperature in the range from 16 to 300 K and the applied external magnetic field up to 120 mT. Our analysis shows that the origin of the rigidity of these high-frequency modes is the strong coupling of the magnetic subsystem with the lattice of the Ag/Fe/Cr/Fe multilayer. The exciting electromagnetic pulse generated by the PCS induces, via magnetoelastic coupling, long-lived (ns) standing GHz acoustic waves normal to the Ag/Fe/Cr/Fe film plane. These lattice oscillations in turn couple back and drive the magnetization oscillations via the magnetoelastic coupling. The temperature and field dependence of the damping of the oscillations can be described by inelastic phonon-phonon and phonon-magnon scattering. Our study opens up a possibility of using coherent lattice and magnetization dynamics in ferromagnetic films for spintronic devices at GHz clock rates.

Graphene-based terahertz closed-stopband tunable composite right/left-handed leaky-wave antennas

A simple scheme for the realization of the terahertz (THz) fundamental-mode tunable closed-stopband composite right/left-handed leaky-wave antennas (CRLH LWAs) is presented. The proposed CRLH LWAs are reconstructed by graphene-based coplanar waveguide (CPW) transmission line supercells. Their shunt inductances achieved by narrow graphene strips of two unit cell structures are halved. The CRLH LWAs are designed and confirmed by numerical simulations. They also exhibit frequency-scanning behaviors at THz with narrower bandwidth than that of the conventional graphene-based fundamental-mode CPW unit cell CRLH LWAs at THz. Besides, the LWAs also exhibit strong tunable characteristics and achieve the closed-stopband condition more effectively. Therefore, the proposed supercell CRLH LWAs could further improve the performance of the beam-steering antennas at THz.

Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba0.5Sr0.5TiO3 Films

Ba0.5Sr0.5TiO3 (BST-0.5) thin films (600 nm) were deposited on single crystal MgO, SrTiO3 (STO), and LaAlO3 (LAO) substrates by pulsed laser deposition at an oxygen partial pressure of 80 mTorr and temperature of 720 °C. X-ray diffraction and in situ reflection high-energy electron diffraction routinely ascertained the epitaxial quality of the (100)-oriented nanocrystalline films. The broadband microwave (1–40 GHz) dielectric properties were measured using coplanar waveguide transmission line test structures. The out-of-plane relative permittivity (ε⏊/) exhibited strong substrate-dependent dielectric (relaxation) dispersions with their attendant peaks in loss tangent (tanδ), with the former dropping sharply from tens of thousands to ~1000 by 10 GHz. Although homogeneous in-plane strain (ϵǁ), enhances ε⏊/ with εMgOBST−0.5⏊/&gt;εSTOBST−0.5⏊/&gt;εLAOBST−0.5⏊/ at lower frequencies, two crossover points at 8.6 GHz and 18 GHz eventually change the trend to: εSTOBST−0.5⏊/&gt;εLAOBST−0.5⏊/&gt;εMgOBST−0.5⏊/. The dispersions are qualitatively interpreted using (a) theoretically calculated (T)−(ϵǁ) phase diagram for single crystal and single domain BST-0.5 film, (b) theoretically predicted ϵǁ-dependent, ε⏊/ anomaly that does not account for frequency dependence, and (c) literature reports on intrinsic and extrinsic microstructural effects, including defects-induced inhomogeneous strain and strain gradients. From the Vendik and Zubko model, the defect parameter metric, ξs, was estimated to be 0.51 at 40 GHz for BST-0.5 film on STO.

Characterization and role of deep traps on the radio frequency performances of high resistivity substrates

In this study, high-resistivity gold-implanted silicon substrates developed for radio frequency (RF) applications were characterized. By varying PICTS (Photo-Induced Current Transient Spectroscopy) measurement conditions such as the illumination wavelength, we identified the signature and the nature of four dominant traps. Two were electron traps and the others were hole traps. All of the related defects involved gold atoms. RF simulations of coplanar waveguide transmission lines integrated on these substrates were carried out, based on the trap properties extracted from PICTS results. A good agreement between RF experimental data and simulations was achieved by tuning the trap concentrations. Finally, the gold density extracted from the fit was successfully compared with the secondary ion mass spectrometry profile and an explanation of the role of the traps in RF behavior of the substrate was given.

Asymmetric Metaconductors Featuring Wideband Skin Effect Suppression

Metaconductors with near-zero permeability is an incentive for the development of high-frequency passive components due to effective suppression of skin effect. In this work, an asymmetric multilayered structure is proposed to broaden the bandwidth of skin effect suppression while preserving a sufficient lower frequency limit of permeability compensation. Coplanar waveguide (CPW) transmission lines consisting of two ferromagnetic layers alternatively stacking with Cu layers were designed and fabricated. Near-zero permeability is obtained at two separated frequencies, which enables broadband eddy current canceling and resistance reduction. The measured results manifest a resistance reduction up to 46% at 11.1 GHz, compared to a Cu transmission line with the same dimensions, and a broad skin effect suppression band between 7.5 and 30.0 GHz, which is sufficient to cover the important 5G applications.

RF Small and large signal characterization of a 3D integrated GaN/RF-SOI SPST switch

AbstractThis paper presents the radio frequency (RF) measurements of an SPST switch realized in gallium nitride (GaN)/RF-SOI technology compared to its GaN/silicon (Si) equivalent. The samples are built with an innovative 3D heterogeneous integration technique. The RF switch transistors are GaN-based and the substrate is RF-SOI. The insertion loss obtained is below 0.4 dB up to 30 GHz while being 1 dB lower than its GaN/Si equivalent. This difference comes from the vertical capacitive coupling reduction of the transistor to the substrate. This reduction is estimated to 59% based on a RC network model fitted to S-parameters measurements. In large signal, the linearity study of the substrate through coplanar waveguide transmission line characterization shows the reduction of the average power level of H2 and H3 of 30 dB up to 38 dBm of input power. The large signal characterization of the SPST shows no compression up to 38 dBm and the H2 and H3 rejection levels at 38 dBm are respectively, 68 and 75 dBc.

Terahertz Quasi-TEM Mode Tunable Composite Right/Left-Handed Leaky-Wave Antennas Using Graphene-Based Coplanar Waveguides

A novel and simple scheme for the realization of the terahertz (THz) fundamental-mode composite right/left-handed leaky-wave antennas (CRLH LWAs) is proposed. The CRLH LWAs are reconstructed by graphene-based coplanar waveguide transmission line (CPW TL) unit cells. Their signal lines are grounded by narrow graphene strips to achieve the shunt inductances, and parallel-plates are periodically added along the signal line to obtain the series capacitances. The propagation properties of the LWAs are detailed. The LWAs have both left-handed (LH) and right-handed (RH) regions by varying frequency. By numerical simulations, the LWAs are verified. Their backfire-to-endfire beam-steering capabilities through frequency scanning are confirmed. Compared with the CRLH LWAs at THz proposed in previous literature, the graphene-based CRLH LWAs operate in the Quasi-TEM mode. They possess low fabrication, excitation, and impedance matching difficulty. They also show the possibility of integration with other micro-devices. With the application of graphene, the LWAs exhibit strong tunable characteristics that conventional CRLH LWAs are absent. Therefore, the proposed CRLH LWAs have great potential applications for the development of beam-steering antennas at THz.

Low-loss through silicon Vias (TSVs) and transmission lines for 3D optoelectronic integration

The optoelectronic hybrid integration based on co-package has attracted much attention to meet the requirements of high-performance chip development and functional integration. TSVs and redistribution layers (RDLs) are of great importance for both the packaging process and the system design of 3D integration. This paper presents the measurements and analysis of TSV and RDL test structures, from DC to high frequency up to 67 GHz. TSVs and RDLs with low insertion loss up to 67 GHz are demonstrated and the impact of TSV arrangements on the transmission performance are analysed. The insertion loss of a 500 μm long coplanar waveguide (CPW) transmission line of frontside RDL (FSRDL) is 0.75 dB at 67 GHz. The insertion loss is less than 1 dB at 67 GHz for a TSV-RDL signal path with the length of 500 μm.

Design of a flexible waterproof antenna for Internet of Things applications

We propose a new broadband flexible waterproof antenna suitable for Internet of Things applications. The antenna is comprised of three components: radiating elements fed by a 50-Ω coplanar waveguide transmission line and two layers from an elastomer composite (used as a substrate and top encapsulation) which completely covers the antenna's radiating elements to provide water and dust resistance. An antenna prototype is fabricated and tested. Experimental and numerical results show that the proposed antenna has broad bandwidth (|S11| ≤ −10 dB) over the frequency range of 0.83–2.52 GHz, high radiation efficiency of about 92% and good radiation patterns. The antenna was also immersed into water for 10 s, 10, 30 and 60 min, respectively and reflection coefficient magnitudes were measured, to verify its waterproof capability. The durability and flexibility tests were performed on the antenna prototype. Results show that there is no significant degradation in the antenna performance.

Ultrawideband Characterization of Complex Dielectric Constant of Planar Materials for 5G Applications

A broadband (1–35 GHz) time-/frequency-domain reflection technique for measuring the complex dielectric constant of low-loss dielectric slabs is presented. The technique uses a coplanar waveguide (CPW) transmission line sample holder for measurements. In addition to the standard substrate materials, the technique is suitable for the characterization of materials, such as glass, as it does not require complicated sample machining and preparation. The procedure is based on comparing the measured effective dielectric constant and the attenuation constants for both the loaded and unloaded CPW line sample holder. The effective dielectric constant and the attenuation constant are first modeled as a function of the real and imaginary parts of the superstrate’s dielectric constant using a 2-D numerical line calculator. Samples under test are assumed to be nonmagnetic and have their material resonances at frequencies substantially above 35 GHz. The technique is validated through measurements of known Rogers RT/duroid samples. Measured complex dielectric constants of different materials are in very good agreement with data reported in materials’ datasheets.

Highly Sensitive Reflective-Mode Phase-Variation Permittivity Sensor Based on a Coplanar Waveguide Terminated With an Open Complementary Split Ring Resonator (OCSRR)

This paper presents a one-port reflective-mode phase-variation microwave sensor consisting of a coplanar waveguide (CPW) transmission line terminated with a grounded open complementary split ring resonator (OCSRR). The sensor is useful for measuring the dielectric constant of the so-called material under test (MUT), which should be placed in contact with the OCSRR, the sensitive element. The output variable is the phase of the reflection coefficient. Design guidelines for the implementation of highly sensitive sensors are derived in the paper, and validated through simulation and experiment. As compared to other reflective-mode phase-variation sensors based on open-ended sensing lines, the designed and fabricated devices exhibit a very small sensitive region by virtue of the use of an electrically small resonant element, the OCSRR. The relevant figure of merit, defined as the ratio between the maximum sensitivity and the size of the sensing area (expressed in terms of the squared wavelength), is as high as FoM $= 5643^{\circ }/\lambda ^{2}$ in one of the reported prototypes. Moreover, the paper analyzes the effects of losses. From this study, it is concluded that MUT losses do not significantly affect the output variable, provided losses are small. It is also demonstrated that the sensor is useful to estimate the loss tangent of the considered MUT samples.

Graphene-based Terahertz closed-stopband composite right/left-handed leaky-wave antennas

A simple scheme for the realization of the terahertz (THz) fundamental-mode closed-stopband composite right/left-handed leaky-wave antennas (CRLH LWAs) is presented. The proposed CRLH LWAs are reconstructed by graphene-based coplanar waveguide (CPW) transmission line supercells. Their shunt inductances achieved by narrow graphene strips of two unit cell structures are halved. The CRLH LWAs are designed and confirmed by numerical simulations. They also exhibit frequency-scannable behaviors at THz with narrower bandwidth than that of the conventional graphene-based fundamental-mode CPW unit cell CRLH LWAs at THz without stopbands. Therefore, the proposed supercell CRLH LWAs could further improve the performance of the beam-steering antennas at THz.

Preliminary study on the new wound monitoring technology using co-planar waveguide sensor: Modeling and simulation.

BACKGROUND:Wound monitoring is very meaningful for the clinical research, diagnosis and treatment. But the existing wound monitoring technology is hard to meet the needs of modern medical care in terms of real-time, non-invasive and anti-interference.OBJECTIVE: To solve this problem, this paper proposed a new kind of monitoring technology based on the co-planar waveguide transmission line theory and assessed the application value of this method as a wound monitoring technology.METHODS: The simplified wound model included the skin, fat, muscle, tissue fluid and bandage and a new co-planar waveguide sensor were designed and established. All of the simulation was achieved in the electromagnetic special software. The data processing method was based on the transmission line theory.RESULTS: Detailed analyses of the results from the simulation were conducted. The sensor has a good monitoring effect in the low frequency band. The monitoring results could be influenced by the thickness of the bandage outside the wound. The thickness of the bandage should not be larger than 10 mm. The effective monitoring area of the sensor is 30 20 mm. CONCLUSIONS: The proposed sensor based on the CPW transmission principle in this paper has good wound monitoring potential.

Microwave transmission characteristics of carbon nanofiber films with different micrometer-scale thickness

In this study, the microwave, i.e. 0.5–10 GHz, transmission characteristics of carbon nanofiber (CNF) with three different micrometer-scale thicknesses were experimentally investigated using a coplanar waveguide transmission line. In the experimental results, when the film of CNF was thick, the signal transmission level (S21-magnitude) was significantly lower and its phase (S21-phase) was shifted toward the low-frequency region. Based on the obtained S21-parameter (S21-magnitude and S21-phase), the electric permittivity (ε) of CNF was extracted and showed clear differences depending on the thickness, i.e., εthin = 1.20 (0.28), εmiddle = 1.84 (0.60), εthick = 6.30 (1.15) at 0.5 GHz (7.8 GHz). From the analysis of electromagnetic fields, the microwave conductivity (σmw) of CNF linearly increased with the increasing thickness, i.e., σmw/thin = 0.35 (S/m), σmw/middle = 0.58 (S/m), σmw/thick = 0.75 (S/m), due to enhanced electromagnetic field coupling between the film of CNF and the CPW line. As a result, we demonstrated that the film of CNF has a significant attenuation effect on signal transmission in the microwave regime, depending on micrometer-scale changes in film thickness.