Two-port Device Research Articles

Quasi-bound states in the continuum for electromagnetic induced transparency and strong excitonic coupling

Advancing on previous reports, we utilize quasi-bound states in the continuum (q-BICs) supported by a metasurface of TiO2 meta-atoms with broken inversion symmetry on an SiO2 substrate, for two possible applications. Firstly, we demonstrate that by tuning the metasurface's asymmetric parameter, a spectral overlap between a broad q-BIC and a narrow magnetic dipole resonance is achieved, yielding an electromagnetic induced transparency analogue with a 50 μs group delay. Secondly, we have found that, due to the strong coupling between the q-BIC and WS2 exciton at room temperature and normal incidence, by integrating a single layer of WS2 to the metasurface, a 37.9 meV Rabi splitting in the absorptance spectrum with 50% absorption efficiency is obtained. These findings promise feasible two-port devices for visible range slow-light characteristics or nanoscale excitonic coupling.

A novel design methodology for asymmetric coupled line passive devices and its application in impedance transformers

ABSTRACT This article presents a novel design methodology for asymmetric coupled line passive devices. Based on the extraction of distributed parameters of coupled lines from S-parameters, we re-derived modal characteristic parameters and Z matrix of four-port asymmetric coupled lines in inhomogeneous mediums. Then, Z matrices of ten two-port asymmetric coupled line circuits are derived and their frequency responses are analyzed. Inspired by the image parameter method, image impedances are adopted for two-port device designs. Data diagrams which connect geometric parameters with impedances are provided to simplify design processes. Two impedance transformers utilizing the open-ended and short-ended coupled line circuits, respectively, producing high transforming ratios of 100 (50 Ω to 0.5 Ω) and 40 (50 Ω to 2000 Ω) are fabricated to verify the proposed analysis and design method. Excellent agreement between the simulation and measurement result proves the unique superiorities of asymmetric coupled lines with better initial values.

Wideband frequency reconfigurable plasma antenna launched by surface wave coupler

A wideband reconfigurable plasma antenna excited by a surface wave coupler (SWC) operating at 13.56 MHz is presented in this study. The plasma antenna and SWC are designed and modeled in CST Studio. A detailed analysis of the SWC is carried out using CST Studio, and experimental measurements supplement the performance. This work explores the signal transmission capabilities of a plasma antenna excited at 13.56 MHz for the first time. A SWC is a two-port device that is modified for radiating electromagnetic waves through a plasma column produced at a frequency of 13.56 MHz with a coupling efficiency of 99%. The power port and signal port of the SWC are isolated for better coupling efficiency and to reduce interference. The return loss and isolation between the ports of the SWC at 13.56 MHz are −22 dB and −46.81 dB, respectively. The plasma antenna excited by a surface wave has a wider bandwidth than its metallic counterpart. It varies from 280 to 540 MHz for input plasma power ranging from 2 W to 10 W. In addition, a reconfigurability frequency span of 240 MHz for power ranging from 2 to 10 W is achieved experimentally. Moreover, we attained an enhanced peak gain of -5 dBi. The radiation efficiency of the plasma antenna is around 20%. The experimental results of the SWC and plasma antenna are in coherence with its simulations.

Dynamically manipulation of anisotropic coherent perfect absorption in borophene metasurface

This paper proposed a borophene-based metamaterial device to achieve the anisotropic coherent perfect absorption (CPA) effect in the two-port device. By simply adjusting the polarization angle of the incident light, the dynamic switching of the CPA resonance peak wavelength can be achieved. Besides, by simultaneously modulating the electron doping concentration of borophene and the relative phase of the incident light, the coherent absorption efficiency of borophene can be continuous modulated for both polarization directions. Furthermore, the theorem of scattering matrix is utilized to elucidate the physical mechanism of CPA, and the analytical results demonstrate remarkable accordance with the numerical computations. Owing to the flexible continuous tunability, the proposed borophene CPA device is expected to open up new opportunities for optical modulators and all-optical logic chips.

De-embedding technique relying on a new formalism for two-port network characterization using raw S-parameter measurements

A de-embedding technique based on a new formalism is proposed for determining all scattering (S-) parameters of a two-port network (or sensing area) using raw (uncalibrated) measurements at microwave frequencies. It uses raw S-parameter measurements of a reflecting line, (direct and reversed configurations) a non-reflecting line, and (direct and reversed configurations) a device (e.g., only three different topologies). In addition to its unique advantage that it fully and uniquely determines S-parameters of a two-port network, it also has the capability of determining terms of error networks, as a byproduct, up to two multiplicative constant terms. The formalism was tested for evaluating S-parameters of a sensing area of a microstrip line sensor, as a two-port device, involving double SRRs next to a microstrip line. Root-mean-square-error analysis was implemented to examine the accuracy of our extracted S-parameters in comparison with those of similar de-embedding techniques in the literature.

Graphical Approach to Optimization of Maximally Efficient-Gain-Boosted Feedback Amplifiers

It is challenging to design high-gain amplifiers near the maximum oscillation frequency (fmax) of the transistors. This paper presents a comprehensive graphical approach to maximize the gain of feedback amplifiers with maximally efficient gain (GME) conception at near-fmax frequency. The complex gain-plane and the reflection-coefficient-plane are utilized to provide clear insights into both the gain and stability states of the two-port device while boosting GME. An efficient flowchart to synthesize feedback amplifiers is given, which optimizes the GME of a two-port device while ensuring the stability. A 210 GHz power amplifier in 40 nm CMOS was designed and optimized based on the proposed approach. The feedback circuit of the transistor pushes it to become potentially unstable and boosts GME. The measured peak small-signal gain was 10.48 dB at 195.33 GHz. The measured saturation output power and large-signal gain at 210 GHz were 3.04 dBm and 7.08 dB, respectively. The presented method could facilitate terahertz amplifier design.

Super-High-Frequency Low-Loss Sezawa Mode SAW Devices in a GaN/SiC Platform.

This paper presents a comprehensive study of the performance of Sezawa surface acoustic wave (SAW) devices in SweGaN QuanFINE® ultrathin GaN/SiC platform, reaching frequencies above 14 GHz for the first time. Sezawa mode frequency scaling is achieved due to the elimination of the thick buffer layer typically present in epitaxial GaN technology. Finite element analysis (FEA) is first performed to find the range of frequencies over which the Sezawa mode is supported in the grown structure. Transmission lines and resonance cavities driven with Interdigital Transducers (IDTs) are designed, fabricated, and characterized. Modified Mason circuit models are developed for each class of devices to extract critical performance metrics. We observe a strong correlation between measured and simulated dispersion of the phase velocity (vp) and piezoelectric coupling coefficient (k2). Maximum k2 of 0.61% and frequency-quality factor product (f.Qm) of 6×1012 s-1 are achieved for Sezawa resonators at 11 GHz, with a minimum propagation loss of 0.26 dB/λ for the two-port devices. Sezawa modes are observed at frequencies spanning up to 14.3 GHz, achieving a record high in GaN microelectromechanical systems (MEMS) to the best of the authors' knowledge.

Port reconfigurable phase-change resonator

Active control and manipulation of electromagnetic waves are highly desirable for advanced photonic device technology such as optical cloaking, active camouflage, and information processing. Designing a resonator with high ease-of-control and reconfigurability remains an open challenge thus far. Here, we propose a mechanism to continuously reconfigure a resonator between one-port and two-port configurations via a phase-change material for efficient spectra modulation. By incorporating a phase-change material VO2 substrate into a photonic crystal, we computationally show that the system behaves as a one-port device with near-perfect absorption and two-port device with high transmission up to 92% when VO2 is in the metallic rutile phase and insulating monoclinic phase, respectively. The optical response can be continuously and reversibly modulated between various intermediate states. More importantly, the proposed device is compatible with wide-angle operation and is robust against structural distortion. The switching operation of the proposed device can be further expanded into the mid-infrared regime. These findings reveal a device architecture of a port reconfigurable resonator uniquely enabled by the switchable optical properties of phase change materials.

Surface Acoustic Wave (SAW) Sensors for Hip Implant: A Numerical and Computational Feasibility Investigation Using Finite Element Methods

In this paper, a surface acoustic wave (SAW) sensor for hip implant geometry was proposed for the application of total hip replacement. A two-port SAW device was numerically investigated for implementation with an operating frequency of 872 MHz that can be used in more common radio frequency interrogator units. A finite element analysis of the device was developed for a lithium niobate (LiNBO3) substrate with a Rayleigh velocity of 3488 m/s on COMSOL Multiphysics. The Multiphysics loading and frequency results highlighted a good uniformity with numerical results. Afterwards, a hip implant geometry was developed. The SAW sensor was mounted at two locations on the implant corresponding to two regions along the shaft of the femur bone. Three discrete conditions were studied for the feasibility of the implant with upper- and lower-body loading. The loading simulations highlighted that the stresses experienced do not exceed the yield strengths. The voltage output results indicated that the SAW sensor can be implanted in the hip implant for hip implant-loosening detection applications.

Effect of Scattering Parameter on Small Signal analysis in Direct Modulated Dynamic Semiconductor Lasers

Effect of scattering parameter is that the effect which it is effected on the operating characteristics of direct modulated semiconductor lasers by small signal analysis for injection current density , where this parameter is effected on amount of quantum confinement carriers density where the part of this carriers density is lost in the active region. The scattering parameter leads to appear the nonlinear gain effects which they are reduced the response frequency of the direct modulation process. We use the rate equations of the single-mode semiconductor lasers and that they have characteristics are used to continuous-wave small-signal modulation. We can presented this effect and discussion it by the simple two-port device.

Quantifying Receiver Nonlinearities in VNA Measurements for the WR-15 Waveguide Band

Scattering (<inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula>)-parameters are fundamental to numerous microwave quantities, including antenna factors, microwave power, and phase. The uncertainty in <inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula>-parameter measurements is influenced by the test setup, including instrument noise, drift, and position of the cables. In this article, we present a model to assess the uncertainty in <inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula>-parameter measurements due to nonlinearity in the receivers of a vector network analyzer (VNA). We developed a model that describes the nonlinearity of raw wave parameters and can be propagated through the corrected <inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula>-parameters. We designed an experiment to extract the parameters of our model for a test setup from measurements of a series of devices under test and demonstrated our model for the WR-15 rectangular waveguide band. This model can correct for or assess uncertainties due to receiver nonlinearity on <inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula>-parameter measurements and is agnostic to the calibration method used. Using our model, we assess the effects of receiver nonlinearity on calibration error coefficients and the corrected <inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula>-parameters of one- and two-port devices under test (DUTs).

Microwave Detection Using Two-Atom-Thick Self-Switching Diodes Based on Quantum Simulations and Advanced Circuit Models

In this article, a two-atom-thick diode based on 2-D materials is presented for microwave detection. The diode consists of a molybdenum disulfide monolayer/graphene monolayer heterojunction transferred onto a silicon/silicon dioxide substrate and patterned by means of nanolithography techniques to obtain a geometrical self-switching diode. The interaction between the two monolayers gives rise to a double-stage device, which behaves as a back-to-back diode in the [−3, +3] V voltage range, and as a tunnel diode when exceeding +10 V. The heterojunction can be reproduced at the wafer scale, thanks to its CMOS compatibility and ease of fabrication, and it can be used efficiently as a microwave detector up to 10 GHz, with the best performance around the ISM 2.45-GHz band. Starting from advanced quantum simulations to predict the dc behavior of the single heterojunction-based channel, the diode was fabricated and fully characterized experimentally. Lastly, a rigorous equivalent circuit model is provided, which relies on the measured scattering parameters at high frequencies and allows treating the diode embedded into a coplanar waveguide line as a two-port lossy device. This way, the device can be exploited in circuit-based numerical tools for the design of complex microwave front ends.

Determination of error-corrected full scattering parameters of a two-port device from uncalibrated measurements

A methodology relying on relating terms of a two-port error network to the scattering (S-) parameters of a two-port network or device is applied to extract its full S-parameters. The new methodology has only one sign ambiguity problem (two solutions) in evaluation of S11 (and thus S22) while the similar methodology in the literature has two sign ambiguity problems (4 solutions). This ambiguity problem of our method is shown to be eliminated by applying an approach based on continuity of the argument of S11 in the frequency domain. On the other hand, our methodology, as compared with the thru-reflect-line calibration technique, does not necessitate usage of any reflection standard in determining full S-parameters of a two-port network or device. Finally, it gives information about error networks. For its validation, S-parameters of a microwave phase shifter and a polyethylene sample flushed with the left/bottom terminal of the coaxial cell were extracted.

Highly Sensitive Defect Detectors and Comparators Exploiting Port Imbalance in Rat-Race Couplers Loaded With Step-Impedance Open-Ended Transmission Lines

Defect detectors and comparators, able to detect tiny differences between a reference (REF) sample and a material under test (MUT), are presented in this paper. In one version, the comparator is implemented by means of a rat-race hybrid coupler and a single step-impedance open-ended transmission line connected to one of the ports of the coupler. The comparator exploits the imbalance generated in one of the two pairs of isolated ports of the coupler when the MUT sample differs from the REF sample. The other pair of isolated ports is used for comparator feeding ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula> -port) and for recording the output signal ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Sigma $ </tex-math></inline-formula> -port), and feeding is achieved by means of a harmonic signal tuned to the operating frequency of the coupler. The resulting device is therefore a two-port structure, and the considered output variable is the magnitude of the transmission coefficient, an easily measurable quantity. By virtue of the step-impedance transmission line, used as the sensitive element of the comparator, the device exhibits very high sensitivity to variations in the dielectric constant between the REF and MUT samples, this being the input variable. A prototype device example, with a maximum sensitivity of 0.72 is reported, and applied to the detection of defects in the REF sample, a dielectric slab, generated by drilling holes of different densities across it. In the second prototype, a true differential-mode sensor, two identical sensing elements (step impedance lines) are connected to one of the pairs of isolated ports of the coupler, and roughly perfect balance is obtained when the MUT is identical to the reference sample. The maximum sensitivity in this case is 1.20, and the device discriminates also small perturbations generated in the REF material. The main relevant aspect of the reported prototypes, phase-variation sensing devices by nature, is the phase-to-magnitude conversion achieved by means of the hybrid coupler. This transforms the reflective-mode phase-variation sensing element to a two-port transmission-mode device where the output variable is the magnitude of the transmission coefficient, an easily measurable quantity.

First-principles based simulations of electronic transmission in ReS2/WSe2 and ReS2/MoSe2 type-II vdW heterointerfaces

Electronic transmission in monolayer ReS_{2} and ReS_{2} based van der Waals (vdW) heterointerfaces are studied here. Since ReS_{2}/WSe_{2} and ReS_{2}/MoSe_{2} type-II vdW heterostructures are suitable for near infrared (NIR)/short-wave infrared (SWIR) photodetection, the role of interlayer coupling at the heterointerfaces is examined in this work. Besides, a detailed theoretical study is presented employing density functional theory (DFT) and nonequilibrium Green’s function (NEGF) combination to analyse the transmission spectra of the two-port devices with ReS_{2}/WSe_{2} and ReS_{2}/MoSe_{2} channels and compare the near-equilibrium conductance values. Single layer distorted 1T ReS_{2} exhibits formation of parallel chains of ‘Re’-‘Re’ bonds, leading to in-plane anisotropy. Owing to this structural anisotropy, the charge carrier transport is very much orientation dependent in ReS_{2}. Therefore, this work is further extended to investigate the role of clusterized ‘Re’ atoms in electronic transmission.

Passive High Power RF Comb Filters Using Epitaxial GaN/NbN/SiC HBARs.

This report presents the first demonstration of passive RF comb filters made using epitaxial GaN/NbN/SiC high overtone bulk acoustic resonators (epi-HBARs). The two-port device is fabricated on electronic-grade GaN, electrically transduced, and acoustically coupled. The multi-mode epi-HBAR comb filter demonstrated here has 158 sharp filter passbands periodically distributed between 1 and 4 GHz (L-S-bands) with a free spectral range (FSR) of 17 MHz. The individual passbands of the epi-HBAR comb filter demonstrate transmission bandwidths (BWs) up to 800 kHz, f × Q values of up to 7×1014 Hz, and an average [Formula: see text] figure of merit of 41.2 at room temperature. The GaN/NbN/SiC epi-HBAR comb filter is capable of operating at high RF power levels, with linear and distortion-free performance seen up to at least 1 W of continuous wave (CW) power and up to at least 10 W of pulsed power. The compact epi-HBAR comb filters can be co-fabricated with GaN-based electronics and could potentially replace larger, off-chip or discrete-component comb filters. They can be used for spectrum sensing and as signal processing elements for remote sensing and pulsed radar.

An Efficient Full-Wave Method for Analyzing the Radiation Pattern of an Antenna Enclosed by an Axisymmetric Radome

This article proposes an efficient full-wave method to analyze the radiation pattern of an antenna in the presence of a multilayer axisymmetric radome. In this method, first, the field distribution on the antenna aperture is replaced with the respective equivalent currents to compute the incident electromagnetic field on the inner surface of the radome. The radome is then modeled with a cascaded network of two-port devices and generalized transmission lines based on the theory of surface equivalence and the method of moments. The cascaded network is used to relate the tangential components of the electromagnetic field at the inner surface of the radome to their counterparts at the outer surface of the radome which, in turn, are used to obtain the respective equivalent currents. Finally, these currents are used to determine the radiation pattern of the antenna in the presence of the radome. The efficiency of the proposed method is demonstrated by comparing the simulation results of several case studies with those obtained by the rival theoretical models in the literature or computed by commercial numerical codes.

Pade-Approximation Based Behavioral Modeling for RF Power Amplifier Design

Radio frequency (RF) power amplifier (PA) design using Gallium Nitride (GaN) transistor technology requires accurate device models in order to maximise performance and reduce development time. The current state-of-the-art frequency-domain behavioural models focus on linear and quadratic approximations to the polyharmonic distortion (PHD) formalism. However, the linear approximation suffers from poor accuracy under load mismatch conditions, while the quadratic approximation suffers from poor extrapolation beyond the measured range, leading to erroneous predictions of the optimum load impedances for maximum output power and maximum drain efficiency. In this work, a rational Padé-based approximation is proposed as the model core, and it is shown, through experimental validation, that the Padé approximation-based model can provide superior results in a more scalable format. It can mitigate problems found in the existing PHD models when applied to the matching problem. Specifically, the proposed model produces fewer erroneous solutions for the optimum load points, due to the well-behaved nature of Padé approximants. In addition, for the first time, results are reported on using the behavioural model to determine the optimum impedance for maximum transducer gain in a two-port device model. All results show the Padé model has high potential when compared to the established PHD-derived models in RF PA design.

Terahertz Spoof Surface Plasmonic Logic Gates.

SummaryLogic gates are important components in integrated photonic circuitry. Here, a series of logic gates to achieve fundamental logic operations based on linear interference in spoof surface plasmon polariton waveguides are demonstrated at terahertz frequencies. A metasurface-based plasmonic source is adopted to couple free-space terahertz radiation into surface waves, followed by a funnel-shaped metasurface to efficiently couple the surface waves to the waveguides built on a domino structure. A single Mach-Zehnder waveguide interferometer can work as logic gates for four logic functions: AND, NOT, OR, and XOR. By cascading two such interferometers, NAND and NOR operations can also be achieved. Experimental investigations are supported by numerical simulations, and good agreement is obtained. The logic gates have compact sizes and high intensity contrasts for the output “1” and “0” states. More complicated functions can be envisioned and will be of great value for future terahertz integrated computing.

Wide-band high dynamic range variable passive intermodulation generator using fabric-over-foam gasket

Accurate measurement of Radio Frequency (RF) component’s passive intermodulation (PIM) and systematic evaluation of PIM’s effect on mobile communication require flexible PIM generator. This work presents a wide-band high dynamic-range PIM generator using a fabric-over-foam (also known as RF Interference Shielding Gasket) as superstrate of low-PIM microstrip line (MS-line). An air gap of 1 mm introduced between the foam and the MS-line to ensure long-term repeatability by avoiding the nonlinearity that can be generated by the metal-to-metal contact. To make the PIM generator adjustable, the foam moved transversely over the MS-line. The size of the gasket selected in such a way that it slightly changes the S-parameters of the MS-line. Due to the variation of the exposure area of the foam (which is an electromagnetic magnetic material) to the electromagnetic (EM) field generated by the MS-line; the PIM level of the MS-line changes with the foam’s location. The minimum PIM level of the proposed generator determined by the PIM level of the MS-line, which is no more than -125dBm @2×43dBm. However, the maximum PIM level can be as high as -48dBm @2×43dBm, achieved by placing a gasket piece on the top of the MS-line. The proposed generator verified from 700MHz to 2.7GHz and all of the measurement results show its feasibility. Moreover, presented PIM generator can be used a single-port or two-port calibration device.