Conventional Coplanar Waveguide Research Articles

Post-fabrication frequency trimming of coplanar-waveguide resonators in circuit QED quantum processors

We present the use of a set of airbridges to trim the frequency of microwave coplanar-waveguide (CPW) resonators post-fabrication. This method is compatible with the fabrication steps of conventional CPW airbridges and crossovers and increases device yield by allowing compensation of design and fabrication uncertainty with 100 MHz range and 10 MHz resolution. We showcase two applications in circuit QED. The first is the elimination of frequency collisions between resonators intended to readout different transmons by frequency-division multiplexing. The second is frequency matching of readout and Purcell-filter resonator pairs. Combining this matching with transmon frequency trimming by laser annealing reliably achieves fast and high-fidelity readout across 17-transmon quantum processors.

Periodic and Aperiodic NiFe Nanomagnet/Ferrimagnet Hybrid Structures for 2D Magnon Steering and Interferometry with High Extinction Ratio.

Magnons, quanta of spin waves, are known to enable information processing with low power consumption at the nanoscale. So far, however, experimentally realized half-adders, wave-logic and binary output operations werebased on few µm-long spin waves and restricted to one spatial direction. Here, magnons with wavelengths λ down to 50 nm in ferrimagnetic Y3 Fe5 O12 below two-dimensional lattices of periodic and aperiodic ferromagnetic nanopillars are explored. Due to their high rotational symmetries and engineered magnetic resonances, the lattices allow short-wave magnons to propagate in arbitrarily chosen on-chip directions when excited by conventional coplanar waveguides. Performing interferometry with magnons over macroscopic distances of 350 × λ without loss of coherency, unprecedentedly high extinction ratios of up to 26 (±8) dB [31 (±2) dB] for a binary 1/0 output operation at λ = 69~nm (λ = 154~nm) are achieved in this work. The reported findings and design criteria for 2D magnon interferometry are particularly important in view of the realization of complex neuronal networks recently proposed for interfering spin waves underneathnanomagnets. This article is protected by copyright. All rights reserved.

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.

Modeling and Analytical Description of Parasitic Probe Effects in Measurements of Conductor-Backed Coplanar Waveguides

Abstract. On-wafer measurements are of fundamental importance to the characterization of active and passive devices at millimetre-wave frequencies. They have been commonly known to be ambitious and challenging due to the occurrence of parasitic effects originating from probes, multimode propagation, crosstalk between adjacent structures and radiation. While a lot of investigations have been performed for conventional coplanar waveguides (CPW) measured on ceramic chucks, the parasitic effects occuring in conductor-backed CPWs (CB-CPWs) have not been fully understood yet. Therefore, this paper presents a thorough study for CB-CPWs based on electromagnetic simulations. Additionally, this paper proposes an analytical description accounting for the probe geometries to predict the occurrence of resonance effects due to the propagation of the parallel-plate-line (PPL) mode. For the first time, a new analytical description including the effects of the probe geometries is presented and validated by both measurements and simulations.

Size Reduction and Performance Enhancement of Coplanar-Waveguide Resonators for Surface Plasmonic Applications

Coplanar waveguide (CPW) is partially integrated with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> -strip TLs at critical areas with locally strong electromagnetic field confinement. The new integration is shown to impact the propagation constant of the structure.The impacts of the added <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> -strip TL are theoretically discussed on a loaded CPW using the incident-reflected wave concept. It is mathematically shown that a specific phase is added to the phase of conventional CPWs by the proposed modification. The added phase is then used for physical size reduction and performance enhancement of the structure. Considering the propagation manipulation of the CPWs, the modified structure is researched as a unit cell for spoof surface plasmon polariton (SSPP).

Implementation of Flip-Chip Microbump Bonding between InP and SiC Substrates for Millimeter-Wave Applications.

Flip-chip microbump (μ-bump) bonding technology between indium phosphide (InP) and silicon carbide (SiC) substrates for a millimeter-wave (mmW) wireless communication application is demonstrated. The proposed process of flip-chip μ-bump bonding to achieve high-yield performance utilizes a SiO2-based dielectric passivation process, a sputtering-based pad metallization process, an electroplating (EP) bump process enabling a flat-top μ-bump shape, a dicing process without the peeling of the dielectric layer, and a SnAg-to-Au solder bonding process. By using the bonding process, 10 mm long InP-to-SiC coplanar waveguide (CPW) lines with 10 daisy chains interconnected with a hundred μ-bumps are fabricated. All twelve InP-to-SiC CPW lines placed on two samples, one of which has an area of approximately 11 × 10 mm2, show uniform performance with insertion loss deviation within ±10% along with an average insertion loss of 0.25 dB/mm, while achieving return losses of more than 15 dB at a frequency of 30 GHz, which are comparable to insertion loss values of previously reported conventional CPW lines. In addition, an InP-to-SiC resonant tunneling diode device is fabricated for the first time and its DC and RF characteristics are investigated.

Human Body Specific Absorption Rate Reduction Employing a Compact Magneto-Dielectric AMC Structure for 5G Massive-MIMO Applications

A compact artificial magnetic conductor (AMC) structure for the application of specific absorption rate (SAR) reduction is presented in this paper. A magneto-dielectric (MD) structure as a host of AMC substrate is used to miniaturize the AMC size. The magneto-dielectric has been designed with a low-profile spiral loop in a way to have a high permittivity and permeability for the desired center frequency of 3.5 GHz. Simulation results confirm the zero-degree reflection phase of the proposed AMC unit cell. Moreover, a 70% reduction has been achieved in comparison to the conventional AMC. To validate the simulation results, a prototype of the board is fabricated and measured with a coplanar waveguide (CPW) antenna for the reflection coefficient. The measurement results display an excellent agreement with the simulation ones. A VOXEL model of a human body is utilized to determine the SAR value of the proposed structure. Considering the maximum SAR value for an average of 10 g human tissue, more than 70% SAR reduction is verified for the CPW antenna with the recommended MD-AMC structure compared to a conventional single CPW antenna.

Modelling Terahertz Spoof Surface Plasmon Polariton Waveguides Using a Circuit Model

The spoof surface plasmon polariton (sSPP) waveguides (WGs) are single conductor structures, which have a great potential for the demonstration of the novel and compact terahertz integrated systems. In this article, we present a circuit model for the sSPP WGs, where all the reactive circuit model elements are calculated analytically, which is demonstrated for the first-time at the terahertz band. We also employ a modified version of the proposed model to a transition circuit, which enables the integration of the sSPP WGs with the conventional coplanar waveguides. In order to verify the proposed model experimentally, sSPP WGs with different physical dimensions have been designed, fabricated, and measured for 0.25-0.3 THz band. The measurements of the fabricated sSPP WGs show that the proposed model has an average and maximum phase errors of 2.2, 1.1, and 1.6% and 3.8, 1.7, and 1.9% at 0.25, 0.275, and 0.3 THz, respectively. The proposed model will enable the time-efficient design of the sSPP WGs together with the terahertz integrated circuits in the computer-aided design environments.

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.

Advanced Electrode Design for Low-Voltage High-Speed Thin-Film Lithium Niobate Modulators

In this paper, we present a novel transmission line architecture in thin-film lithium niobate (TFLN) platforms to improve the velocity match between the microwave and the optical wave. Compared to conventional coplanar waveguide (CPW), the microwave index ( $n_m$ ) of the proposed slotted electrodes can be optimized from 2.1 to 3 while maintaining the high modulation efficiency and 50- $\Omega$ impedance match. Equivalent-circuit model analysis and finite-element simulation are performed. The simulated half-wave voltage (V $_\pi$ ) of 1.2 V and E-O modulation bandwidth greater than 80 GHz is obtained for a 2-cm-long modulator. By utilizing the slotted slow-wave electrode, TFLN Mach-Zehnder modulators with CMOS-compatible operating voltage and 3-dB modulation bandwidth greater than 100 GHz are potentialized.

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.

Spoof Surface Plasmon Polaritons Developed From Coplanar Waveguides in Microwave Frequencies

In this article, a new spoof surface plasmon polariton (SSPP) waveguide developed from traditional coplanar waveguide (CPW) is proposed. The asymptotic frequency of the SSPP unit cell can be easily manipulated by changing the meander groove dimensions of the SSPPs. A simple and efficient mode-conversion structure with gradient groove lengths is designed on the CPW’s ground to match the momentum of CPW to the proposed SSPPs smoothly. The designed SSPP waveguide has a good low-pass filtering property with cut-off frequency at 10.4 GHz. On this basis, another improved SSPP waveguide based on conventional grounded CPW (GCPW) is constructed, where a defected ground structure (DGS) is employed on the bottom layer of the circuit. Compared with the above work, this design has a lower cut-off frequency (8.9 GHz) and stronger field confinement. In order to validate the propagation performance, both SSPP waveguides are fabricated and measured. The measurements show that the GCPW based SSPP waveguide can effectively reduce the cut-off frequency. Such results are of great significance to the miniaturizations of plasmonic devices in microwave regime.

Parametrization of CPW for Photonics Application with the Use of Closed Form Formulas

In this paper parametrized analysis of CPW (Coplanar Waveguide) applied in photonics is presented. The analysis is based on analytical formulas, which were delivered and modified from conformal mapping technique, and also after review of available literature from analytical models for the conventional CPW. Adjustment of the already reported CPW formulas was performed to properly model thin films CPW structures in PIC (Photonic Integrated Circuit). Thus, a closed expressions were proposed to simulate basic parameters, like: per unit length (p.u.l.) R (resistance), L (inductance), C (capacitance), G (conductance) and propagation quantity like characteristic impedance Zo versus frequency. The CPW line dedicated for the PIC application, is based on InP (Indium Phosphide) substrate and with air or BCB (Benzocyclobutene) surroundings of the metallization on the top. The modified formulas are curve-fitting approximations, with new fitting coefficients. Essential modifications are for p.u.l. C and p.u.l. L. Usefulness and effectiveness of the modified method was verified through results comparison with simulations in full-wave Electronic Design Automation software, with the circuit simulator QUCS and with real measurements, conducted with the use of PNA (Performance Network Analyzer). The paper novelty are new coefficients for analytical formulas, implementation of modified formulas in the octave code and model parametrization for geometrical parameters.

Design of multi-band miniaturized Bagley power dividers based on non-uniform coplanar waveguide

Power dividers, in general, suffer from higher order harmonics and large occupational area, especially at low frequencies. To overcome these drawbacks, we introduce the design of a three-way Bagley power divider (BPD) using non-uniform coplanar waveguide (CPW). The compact configuration is achieved by replacing the conventional CPW with its equivalent non-uniform counterpart. An optimization process incorporating a truncated Fourier series is used to design the optimum non-uniform CPW profiles. Odd harmonics are suppressed by enforcing the divider to operate only at the design frequencies based on a predefined error function. The proposed structure is compact and easy to fabricate. To validate the design approach, different 3-way BPDs (i.e., single-, dual-, and triple-band) are designed and simulated; whereas a single-band prototype is fabricated and tested. Measured results show excellent input port matching and an insertion loss around −5 dB at the design frequency.

Spoof surface plasmonic transmission line with high isolation and low propagation loss.

A novel compact spoof surface plasmonic (SSP) transmission line (TL) consisting of a stem-shaped periodic structure is proposed to achieve high field confinement in the higher frequency range (microwave to terahertz). The dispersion characteristic of the proposed stem-shaped SSP unit cell exhibits much lower asymptotic frequency and higher field confinement than the conventional coplanar waveguide (CPW) and the rectangular SSP unit cell structure without increasing the overall transverse dimension, i.e., improved signal propagation performance with reduced cross-sectional area. The numerical study of the multi-conductor line based on the proposed stem-shaped SSP unit cell shows that it has improved propagation and isolation features in comparison to the conventional TL structures. Here, the improved isolation is characterized in terms of the mutual coupling (MC) between the two adjacent lines designed using the stem-shaped SSP unit cell, which is not found to significantly increase with an increase in the coupling length unlikely in the conventional TLs. For the proposed SSP-based multi-conductor line, the MCs for 1.6, 2.25, and 4.15λ coupling lengths with fixed separation of 0.175λ are found to be 22, -19.8, and -17.55dB, respectively.

Slot loaded EBG-based metasurface for performance improvement of circularly polarized antenna for WiMAX applications

AbstractIn this paper, an electromagnetic band gap (EBG) metasurface (MS) superstrate-based circularly polarized antenna for the WiMAX (3.5 GHz) band is proposed. The proposed structure comprises a 2 × 2 slot-loaded rectangular patch MS array that can be perceived as a polarization-dependent EBG MS superstrate. Furthermore, to achieve circular polarization, the proposed antenna has an inclined coupling slot onto the ground with a conventional coplanar waveguide feed line. The proposed antenna has a compact structure with a low profile of 0.037λ0 (λ0 stands for the free-space wavelength at 3.48 GHz) and a ground size of 30 × 30 mm2. The measured results show that the −10 dB impedance bandwidth for the proposed antenna is 34.6% and the 3-dB axial ratio (AR) bandwidth is 6.8% with a peak gain of 3.91 dBi in the desired operating band. Good agreement between the simulated and the measured results verifies the performance of the proposed antenna.

Wideband filtering power dividers using single‐ and double‐layer periodic spoof surface plasmon polaritons

In this article, four wideband power dividers (two are filtering power dividers) using single- and double-layer periodic spoof surface plasmon polaritons (SSPPs) are proposed. Double-sided parallel-strip line is used to realize the wideband and low loss for the double-layer SSPPs. T-shaped SSPPs power dividers with large bandwidth, wideband isolation, and low loss using double-layer SSPPs to single-layer SSPPs transition are realized. Conventional coplanar waveguide is used as the output ports for the single-layer SSPPs. Moreover, two new SSPPs power dividers with filtering performance are realized with adding via holes in the double-layer SSPPs. The theoretical analysis, parametric study, and design procedure for these wideband power dividers are illustrated. In addition, for validity demonstration, four wideband SSPPs power dividers are fabricated in microstrip technology and characterized. Good agreements can be observed between the measured and simulated results, indicating good potential applications in the integrated plasmonic devices.

Simple and low‐loss flip‐chip bonding based on ink‐jet printing for RF applications

In this Letter, a flip-chip bonding based on ink-jet printing technology is proposed and verified by interconnecting a separated coplanar waveguide (CPW) samples. Before the flip-chip bonding process, diameter and height of ink-jet printed silver bumps for flip-chip bonding are measured to be about 300 and 13 µm, respectively. In a frequency range from 300 kHz to 3 GHz, return loss and insertion loss of the flip-chip bonded CPW samples are measured to be higher than 20 dB and lower than 1.8 dB, respectively, where the length of the signal line is 35 mm. There are negligible discrepancies between radio frequency (RF) characteristics of the flip-chip bonded CPW and those of a conventional CPW. These results show that the proposed flip-chip bonding can be used to integrate RF components into electronic devices with low-loss using simple procedures.

Proposal and simulation of a DC–110 GHz waveguide using metal shielding and three-dimensional extension structure

In this paper, a waveguide with metal shielding and a three-dimensional extension component is proposed with frequencies up to 110 GHz. By increasing the relative area between the signal line and the ground plane vertically, the electromagnetic field is limited within the air-dielectric cavity. By embedding metal shielding strip arrays into silicon oxidation, conductor and dielectric losses can be reduced significantly. In addition, the algorithm which extracts the transmission characteristics of the waveguide based on the Z parameter matrix is implemented. Compared to the conventional coplanar waveguide (CPW) and CPW with metal shielding, the results demonstrate that the structure can achieve a large bandwidth with DC–110 GHz, while the transmission loss is 0.0765 dB mm−1 at 110 GHz, which is reduced by 19.7% and 9.9%, respectively. Moreover, the value of Q with the proposed structure can reach 37.528 at 110 GHz, which is increased by 92.7% and 37.7%, respectively.

Novel non-periodic spoof surface plasmon polaritons with H-shaped cells and its application to high selectivity wideband bandpass filter

In this paper, one kind of novel non-periodic spoof surface plasmon polaritons (SSPPs) with H-shaped cells is proposed. As we all know, the cutoff frequency exists inherently for the conventional comb-shaped SSPPs, which is a kind of periodic groove shape structures and fed by a conventional coplanar waveguide (CPW). In this work, instead of increasing the depth of all the grooves, two H-shaped cells are introduced to effectively reduce the cutoff frequency of the conventional comb-shaped SSPPs (about 12 GHz) for compact design. More importantly, the guide waves can be gradually transformed to SSPP waves with high efficiency, and better impedance matching from 50 Ω to the novel SSPP strip is achieved. Based on the proposed non-periodic SSPPs with H-shaped cells, a wideband bandpass filter (the 3-dB fractional bandwidths 68%) is realized by integrating the spiral-shaped defected ground structure (DGS) etched on CPW. Specifically, the filter shows high passband selectivity (Δf3 dB/Δf20 dB = 0.91) and wide upper stopband with −20 dB rejection. A prototype is fabricated for demonstration. Good agreements can be observed between the measured and simulated results, indicating potential applications in the integrated plasmonic devices and circuits at microwave and even THz frequencies.