Waveguide Transmission Line Research Articles

Dual‐Wideband Slot Antenna With Simple Structure

ABSTRACTA compact dual‐wideband slot antenna with a simple structure is presented. A wide slot etched in a rectangular ground plane is fed by a T‐shaped strip and a coplanar waveguide (CPW) transmission line for generating an ultrawide lower operating band. Then a narrow slot, which is embedded in the T‐shaped strip, is fed by a microstrip line for introducing a wide higher operating band. It is worth noting that the loading of the narrow slot and microstrip line does not enlarge the antenna size, but introduce an extra higher operating band. By using this method, a dual‐wideband antenna is designed. It achieves dual wide bandwidths of 117.8% and 58.1%, which covers 0.698–2.7 and 3.3–6 GHz for the lower and higher bands, respectively. The isolation between the ports can exceed 30 dB. Additionally, the overall size of our antenna is only 0.30λ0 × 0.24λ0 × 0.002λ0 (λ0 is the free‐space wavelength at the lowest frequency).

Achieving desired characteristic impedances in customized coplanar waveguide transmission line design

Coplanar waveguide (CPW) transmission lines are valued for their planar design, low radiation, and minimized signal loss, but controlling their characteristic impedance remains a challenge. This study employs the Taguchi method, a statistical approach, to optimize the characteristic impedance by adjusting eight control factors: track width, track thickness, gap width, dielectric height, backplane thickness, conductor material conductivity, dielectric conductivity, and operational frequency. The analysis evaluates these factors across three levels to find optimal conditions, with dielectric height and track width identified as most influential. Additional assessments using main effect screening, Analysis of Variance (ANOVA), and multivariable linear regression validate the Taguchi method's effectiveness. The results of this effort encompass a distributed resistance of 133.69 Ω/m, a distributed inductance of 2.6676E-7H/m, a shunt conductance of 2.8880E-16 S/m, a capacitance of 7.4103E-11 F/m, a propagation constant of (1.1141 + 279.36i) m-1, and a characteristic impedance of (59.999 - 0.23928i) Ω. A CPW transmission line with a characteristic impedance of 60 Ω was successfully designed and simulated using COMSOL Multiphysics, showing promising results for efficient CPW designs tailored to specific applications. The paper describes•Applied the Taguchi method to assess control factors that affect the Characteristic Impedances of the coplanar waveguide Transmission Lines.•Conducted additional validations with ANOVA and regression analysis.•Simulated designs based on optimized parameters using COMSOL Multiphysics.

A microwave permittivity sensor on a Mach–Zehnder Interferometer of: Spoof surface plasmon polariton waveguides

A microwave Mach–Zehnder Interferometer (MZI) sensor for the permittivity characterization of liquids is presented in this paper. Two spoof surface plasmon polariton (SSPP) waveguide transmission lines (TLs) composed of compact spiral units is utilized in a differential architecture. Loading a dielectric material on the sensing arm induces a phase difference between the two arms, leading to periodic interference dips on the transmission curve. The spectral positions and magnitudes of these dips change with different dielectric materials. Due to the nonlinear dispersion characteristics of the SSPP TL, the proposed SSPP-based MZI sensor achieves improved sensitivity compared with microstrip-based MZI sensor. To validate the sensor’s performance, six different oil samples and a set of adulterated oils were measured, incorporating a polydimethylsiloxane (PDMS) channel on the sensing arm. The variations in the spectral position and magnitude of the interference dip centered at 3.2 GHz are employed to determine the dielectric constants and loss tangents of the tested oils. The sensitivity in measuring the dielectric constant is 3.61 %. The maximum errors for measuring the dielectric constant and the loss tangent are 4.3 % and 6.7 %, respectively. Compared to other sensors for liquid oil detection, the proposed sensor provides a relatively high sensitivity while maintaining a low liquid volume, making it a promising candidate for permittivity measurements of liquid analytes and solid materials with similar dielectric constants.

Quantum computation with electrons trapped on liquid Helium by using the centimeter-wave manipulating techniques

Surface-state electrons floating on liquid Helium have been served as one of the great potential experimental platforms to implement quantum computation, wherein the qubits are usually encoded by either the lowest two levels of the vertical vibrations (i.e., Hydrogen-like atoms) or the electronic spins. Given the relevant operations require additional techniques, such as the corresponding millimeter-wave or magnetic field manipulations, here we investigate how to implement the scalable quantum computation with a trapped electron array by alternatively using the usual centimeter-wave manipulating techniques. This is because the eigenfrequency of the present qubit, encoded by the two lowest levels of the lateral vibration of the trapped electron, is limited in the centimeter-wave band. We show that, by biasing the electrodes properly and driving the coplanar waveguide transmission line resonator, the electrons can be individually trapped in a series of anharmonic potentials on liquid Helium. Therefore, the well-developed circuit quantum electrodynamics technique for the implementation of superconducting quantum computation can be conveniently utilized here in the present quantum computing platform (proposed firstly in Phys Rev Lett 105:040503, 2010, to implement the fundamental logic gates, typically such as the single-qubit rotations of the individually addressable trapped electrons, the switchable two-qubit manipulations between the electrons trapped in the distant traps, and also the high-fidelity readouts of the target qubits. The feasibility of the proposal is also discussed by numerical simulations.

A method for extracting the 1-60 GHz dielectric spectrum of trace liquids using standard design coplanar waveguide sensing devices

Abstract This paper introduces a sensor designed for measuring the dielectric constant of small amounts of liquid. The sensor consists of a coplanar waveguide transmission line and an open container for the liquid, enabling broadband dielectric spectroscopy measurements for milliliter-scale liquids in the 1-60 GHz range. To improve the accuracy of dielectric spectroscopy testing, the sensor is calibrated using air and deionized water to obtain a coefficient matrix relating the sensor’s distributed parameters to the sample’s dielectric constant. This matrix is then used to calculate the dielectric spectroscopy of subsequent test samples. Tests on the dielectric spectroscopy of deionized water with this sensor and algorithm indicate that over the 1-60 GHz band, the error compared to previous literature results is within 5%, demonstrating the reliability of the proposed sensor and dielectric spectroscopy extraction algorithm.

High Frequency Mid-Infrared Quantum Cascade Laser Integrated With Grounded Coplanar Waveguide Transmission Line

High Frequency Mid-Infrared Quantum Cascade Laser Integrated With Grounded Coplanar Waveguide Transmission Line

Dual-Band Large-Frequency Ratio Power Divider Using Mode Composite Transmission Line for 5G Communication Systems

In this paper, a novel kind of mode composite transmission line (MC-TL) is proposed, and a dual-band power divider with a large frequency ratio using this novel MC-TL for 5G communication systems was developed. The proposed MC-TL was developed using spoof surface plasmon polaritons (SSPPs) and a corrugated substrate-integrated waveguide (CSIW) transmission line, which supports both a surface plasmon mode and TE10 mode, independently. The surface plasmon mode operates in the grooves of the surface metal layer, while the TE10 mode works in the substrate between two metal layers. These two parts can transmit different modes at independent frequencies. This structure can be used in dual-band transmission lines with a high frequency ratio. The characteristics and design of the MC-TL (SSPPs and CSIW) are analyzed and illustrated. The MC-TL was fabricated and measured to demonstrate its performance. Moreover, based on the proposed MC-TL, a dual-band power divider with a large frequency ratio (operating at 3 GHz and 28 GHz simultaneously) was also designed and fabricated. It can cover the frequency of a fifth-generation communication system perfectly. The measured outcomes align closely with the simulated results, demonstrating robust agreement and showcasing excellent transmission capabilities.

Field Analysis for Superconducting Grounded Coplanar Waveguide Transmission Lines

Field Analysis for Superconducting Grounded Coplanar Waveguide Transmission Lines

Optimize Purcell filter design for reducing influence of fabrication variation

To protect superconducting qubits and enable rapid readout, optimally designed Purcell filters are essential. To suppress the off-resonant driving of untargeted readout resonators, individual Purcell filters are used for each readout resonator. However, achieving consistent frequency between a readout resonator and a Purcell filter is a significant challenge. A systematic computational analysis is conducted to investigate how fabrication variation affects filter performance, through focusing on the coupling capacitor structure and coplanar waveguide (CPW) transmission line specifications. The results indicate that the T-type enclosing capacitor (EC), which exhibits lower structural sensitivity, is more advantageous for achieving target capacitance than the C-type EC and the interdigital capacitor (IDC). By utilizing a large-sized CPW with the T-type EC structure, fluctuations in the effective coupling strength can be reduced to 10%, given typical micro-nanofabrication variances. The numerical simulations presented in this work minimize the influence of fabrication deviations, thereby significantly improving the reliability of Purcell filter designs.

Characterization of Embedded and Thinned RF Chips

This work studies the effect of thinning down chips with transmission line structures for flexible embedding technology. Test chips with 90 Ω grounded coplanar waveguide (GCPW) transmission lines have been designed and manufactured to characterize the high-frequency performance before and after embedding in sheet molding compound (SMC), and thinning down from 300 μm to 20 μm. Molding first technology enables single-die or multiple-die thinning with the embedding material while being held in the exact position, where the subsequent fanout copper (Cu) redistribution layer (RDL) structuring realizes the direct contacts to the embedded chip, followed by semiadditive manufacturing of traces. The embedded and thinned chips are characterized by S-parameter measurements in the frequency range from 20 MHz to 65 GHz using a vector network analyzer (VNA). The results show the feasibility of the examined embedding and thinning processes which are suitable for millimeter wave (mmWave) components as shown by the example of a G-CPW transmission line without degrading its RF performance in terms of characteristic impedance and attenuation.

Broadband Balanced-to-Balanced Filtering Power Divider Using HMSIW-SSPP Transmission Line.

In this paper, a novel broadband balanced-to-balanced (BTB) filtering power divider (FPD) utilizing the half-mode substrate-integrated waveguide and spoof surface plasmon polariton (HMSIW-SSPP) hybrid transmission line is introduced. Initially, a new HMSIW-SSPP unit cell is proposed, demonstrating a lower upper cut-off frequency compared to the classical HMSIW-SSPP unit cell. Building upon this unit cell, a bandpass BTB FPD is devised employing dual-layer stacked substrates, enabling independent control over the passband's lower and upper cut-off frequencies through specific physical dimensions. Additionally, the incorporation of isolation resistors and defected ground structures in the BTB FPD enhances differential-mode isolation and common-mode (CM) suppression between output ports. A manufactured and tested BTB FPD prototype validates this design method, showcasing a broad fractional bandwidth of 52.31% (6.72-11.48 GHz), output port isolation surpassing 14.25 dB, and transmitted CM suppression exceeding 34.05 dB.

Broadband coplanar-waveguide-based impedance-transformed Josephson parametric amplifier

Quantum-limited Josephson parametric amplifiers play a pivotal role in advancing the field of circuit quantum electrodynamics by enabling the fast and high-fidelity measurement of weak microwave signals. Therefore, it is necessary to develop robust parametric amplifiers with low noise, broad bandwidth, and reduced design complexity for microwave detection. However, current broadband parametric amplifiers either have degraded noise performance or rely on complex designs. Here, we present a device based on the broadband impedance-transformed Josephson parametric amplifier that integrates a hornlike coplanar waveguide transmission line, which significantly decreases the design and fabrication complexity while keeping comparable performance. The device shows an instantaneous bandwidth of 700 (200) MHz for 15 (20) dB gain with an average input saturation power of −110 dBm and near quantum-limited added noise. The operating frequency can be tuned over 1.4 GHz using an external flux bias. We further demonstrate the negligible backaction from our device on a transmon qubit. The amplification performance and simplicity of our device promise its wide adaptation in quantum metrology, quantum communication, and quantum information processing. Published by the American Physical Society 2024

A study into strain sensor of cement-based material using CPW transmission lines

Abstract Based on the theory of coplanar waveguide (CPW) transmission line, a novel microwave non-destructive strain monitoring sensor specifically designed for cement-based material structures is presented in this study. The aim is to establish the relationship between the variation of the S11 phase parameter of the CPW strain sensor and the structural strain, utilizing a linear analysis. The feasibility of the strain monitoring by the CPW sensor is validated through simulations and experiments. The obtained results demonstrate a strong linear correlation between the phase change of the S11 parameter and the strain, with a goodness of fit of 0.987. The simulated strain sensor exhibits a sensitivity of 48.83 ppm/με, while the experimental measurement sensor shows a sensitivity of 65.82 ppm/με. These findings highlight the potential significance of the proposed method, offering a new approach that is characterized by high sensitivity, low cost, and simplicity for strain monitoring in concrete structures. Among them, the sensor cement mortar matrix made in this study was mixed with the recycled material made of waste glass steel FRP after a certain treatment process. The development of this method holds promise for the advancement of health monitoring in concrete structures.

Measuring the permittivity of fused silica with planar on-wafer structures up to 325 GHz.

Fused silica has become an interesting alternative to silicon for millimeter-wave (mmWave) applications. Unfortunately, there are a few reports on the measurement of fused silica's permittivity above 110 GHz that use electrical rather than optical methods. Given that mmWave applications use electrical circuits, additional electrical data would be useful to industry. To test the feasibility of electrical methods, we applied on-wafer techniques based on coplanar waveguide transmission lines to measure the complex permittivity of fused silica to 325 GHz. Our approach used the multiline thru-reflect-line algorithm on the scattering parameter measurements of transmission lines. Our method combined these results with dc measurements of the resistivity of the metals, simulations of the coplanar waveguide cross section, and dimensional metrology. In short, our measurements do not show significant dielectric dispersion for fused silica up to 325 GHz. The resulting complex permittivity was and a loss tangent from 320 MHz to 325 GHz. To support our conclusions, we performed an uncertainty analysis considering relevant sources of uncertainty. In the broader context, these results show that fused silica is a suitable substrate for mmWave electronics where the loss tangent must be less than 0.005 up to 325 GHz.

In-situ Low Power Tests of the ASDEX Upgrade ECRH Transmission Lines

An Electron Cyclotron Resonance Heating (ECRH) system employing 8 gyrotrons is in routine operation at the ASDEX Upgrade tokamak at IPP Garching. The gyrotrons are of two-frequency type operating at 105 and 140 GHz with a maximum output power of up to 1 MW and 10 s pulse length. The gyrotron output beams are coupled to 8 waveguide transmission lines via quasi-optical Matching Optics Units (MOUs). The oversized corrugated HE11 waveguides with a diameter of 87 mm are operated at atmospheric pressure with overall lengths between 65 and 103 meters. The number of quasi-optical miter bends per line is between 6 and 8. High mode purity in the transmission lines is critical with respect to both, losses and atmospheric breakdowns in the waveguides. Beam measurements at low power have been performed along the transmission lines and are compared to high power measurements. Near-field calculations and measurements of mm-wave beams radiated from open-ended HE11 waveguides show, that varying intensity patterns determine the distribution of Ohmic loading in compact mm-wave beam launching antennas, where the first mirror is located in the reactive near-field or close to the Fresnel maximum.

Above 20 GHz high frequency operation of mid-infrared doughnut-shaped microcavity quantum cascade lasers

Microresonator-based high-speed single-mode quantum cascade lasers are ideal candidates for on-chip optical data interconnection and high sensitivity gas sensing in the mid-infrared spectral range. In this paper, we propose a high frequency operation of single-mode doughnut-shaped microcavity quantum cascade laser at ∼4.6 µm. By leveraging compact micro-ring resonators and integrating with grounded coplanar waveguide transmission lines, we have greatly reduced the parasitics originating from both the device and wire bonding. In addition, a selective heat dissipation scheme was introduced to improve the thermal characteristics of the device by semi-insulating InP infill regrowth. The highest continuous wave operating temperature of the device reaches 288 K. A maximum −3 dB bandwidth of 11 GHz and a cut-off frequency exceeding 20 GHz in a microwave rectification technique are obtained. Benefiting from the notch at the short axis of the microcavity resonator, a highly customized far-field profile with an in-plane beam divergence angle of 2.4° is achieved.

A novel method for the measurement of superconducting transmission lines at terahertz frequencies.

Characterizing the properties (e.g., effective dielectric constant εeff, attenuation constant α, and characteristic impedance Z0) of terahertz (THz) superconducting transmission lines is of particular interest in designing on-chip integrated THz bandpass filters, which are a critical component for THz astronomical instruments, such as multi-color camera and broadband imaging spectrometers. Here, we propose a novel method for the characterization of three parameters (εeff, α, and Z0) of THz superconducting transmission lines. This method measures the ratio of the THz signal powers through two different-length branches of the superconducting transmission line to be measured. In addition, only one measurement is required for an all-in-one device chip, including an antenna, a half-power divider, the superconducting transmission line to be measured, and two detectors. The key point is that the superconducting transmission line to be measured is impedance-mismatched with the two integrated detectors. The method is validated through simulation and measurement for superconducting coplanar waveguide transmission lines around 400GHz.

Interconnect for Dense Electronically Scanned Antenna Array Using High-Speed Vertical Connector.

We present the design and the performance evaluation of a new interconnect for large-scale densely packed electronically scanned antenna arrays that utilize a high-speed digital board-to-board vertical connector. The application targets microwave tissue, imaging in the frequency range from 3 GHz to 8 GHz. The tissue-imaging arrays consist of hundreds of active antenna elements, which require low-reflection, low-loss, and low-crosstalk connections to their respective receiving and transmitting circuits. The small antenna size and the high array density preclude the use of coaxial connectors, which are also expensive and mechanically unreliable. Modern board-to-board high-speed connectors promise bandwidths as high as 12 GHz, along with high pin density, mechanical robustness, and low cost. However, their compatibility with the various transmission lines leading to/from the miniature printed antenna elements and microwave circuitry is not well studied. Here, we focus on the design of the transitions from coplanar waveguide transmission lines to/from a high-speed vertical connector. The performance of the interconnect is examined through electromagnetic simulations and measurements. Comparison is carried out with the expensive sub-miniature push-on sub-micro coaxial connectors commonly used in miniature radio-frequency electronics. The results demonstrate that high-speed vertical connectors can provide comparable performance in the UWB frequency range.

Differential magnetic field probe calibration based on symmetric de‐embedding technology

AbstractThe de‐embedding calibration method has been proposed to achieve high‐precision calibration for a single port electric field or magnetic field probe, which can effectively eliminate the calibration ripple. However, the method's effectiveness for a four‐port calibration system has not been verified yet. In this paper, a four‐port de‐embedding calibration method with a differential magnetic field probe is proposed, and its effectiveness is proved. Two symmetric grounded coplanar waveguide transmission lines are applied in the proposed method to solve the ABCD‐matrix of the embedded part of the calibrator. The de‐embedded S‐parameter model of the four‐port calibration system for differential magnetic field probe can be obtained. The calibration results indicate that the proposed method can also reduce the calibration ripple and compensate for the attenuation caused by the calibrator. Compared with the traditional calibration method using a microstrip line calibrator, the ripples of the proposed method can be reduced by 34%. The analysis results of the frequency interval of the ripple (FIR) in different methods show that the de‐embedding method can reduce the FIRs (except around 1.2 GHz) caused by the reflection of the calibrator and retain the FIR (about 1.2 GHz) caused by the reflection of the probe itself.

High-frequency signal transmission in a coplanar waveguide structure with different surface finishes

Continuous pursuits for higher data rate, larger network capacity, low-latency communication, and better energy efficiency have motivated the development of the fifth generation (5 G) mobile communication technologies in recent years. Under a high-frequency transmission, the alternating electric current (AC) tends to distribute to the outer of a conductor due to the so-called “skin effect”; therefore, the surface coatings of Cu interconnect becomes an indispensable factor of the signal transmission characteristics. The focus of this study is to deeply probe into the effect of surface coatings on the high-frequency signal transmission (1–100 GHz) of Cu interconnects. We investigated six different surface finishes over a coplanar waveguide (CPW) transmission line structure, including immersion tin (ImSn), immersion silver (ImAg), immersion gold (IG), electroless palladium/immersion gold (EPIG), immersion gold/electroless palladium/immersion gold (IGEPIG), and ultrathin-Ni(P)-type ENEPIG. The high-frequency signal performance of the CPW transmission line was analyzed through the finite element analysis (FEA) method by using a 3D electromagnetic simulation software. Furthermore, experimental measurements were conducted by using a vector network analyzer (VNA) to characterize the signal loss arising from different surface finishes, so as to validate the numerical simulation results. The FEA and VNA results showed that a noticeable current redistribution might be induced by a high conductivity/permeability of surface coating(s), i.e., ImSn and ultrathin-Ni(P)-type ENEPIG, which significantly increases the signal insertion loss at high frequencies. Thus, an appropriate surface coating over Cu interconnects was necessary for enhancing the high-frequency signal transmission performance.