Coupled Transmission Lines Research Articles

Transmission Line Coupler: High-Speed Interface for Non-Contact Connecter

Transmission Line Coupler: High-Speed Interface for Non-Contact Connecter

Continuous True-Time Delay Phase Shifter Using Distributed Inductive and Capacitive Miller Effect

A new true-time delay phase shifter concept is proposed exploiting the distributed Miller effect in coupled transmission lines. Simultaneous change in Miller capacitance and inductance controlled by a single analog voltage changes the propagation delay of a transmission line with constant input impedance and insertion loss. The true-time delay line feature of the proposed architecture accommodates a wide bandwidth signal without group delay distortion. A theoretical framework for understanding Miller inductance from voltage and current duality and the distributed Miller effect using coupled wave equations is presented. As a proof of concept, a four-stage tunable delay line with a high-speed phase modulation capability was fabricated in a 45-nm RF SOI CMOS process and occupies an active area of 0.28 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The measured IC demonstrates a broadband tunable true-time delay with a measured group delay tuning range of 18 ± 1 ps from 11 to 24 GHz. The measured phase shift ranges are 173° and 182° with insertion losses of 10.6 ± 0.7 dB and 11.6 ± 1 dB at 28 and 30 GHz, respectively. The measured dc power consumption is 22 mW from a 1.2-V supply.

Study on Reactive Power Imbalance and Its solution of Parallel Coupled Transmission Lines

In view of the imbalance and even the abnormal phenomenon of reactive circulation of parallel high voltage transmission lines with similar measured parameters in actual operation, combined with field investigation and test, theoretical analysis and simulation demonstration, it is clear that this phenomenon is caused by the use of unconventional phase sequence and unreasonable transposition of the two-circuit lines when erecting the same tower. Based on the PSCAD simulation, the corresponding improvement measures are put forward from two aspects of optimizing the arrangement of phases and transposition. The results show that in order to solve the power imbalance problem of parallel coupled transmission lines, it is recommended to optimize the phase sequence of conductors in consideration of economy and operability.

Super rogue waves in coupled electric transmission lines

Coupled electric transmission lines (CETLs), which consist of a great number of identical sections, have been studied theoretically in the present paper. The super rogue wave (SRW) in CETLs is analyzed using the nonlinear Schrodinger equation. The dependence of the characteristics of the SRW parameters on CETLs is displayed in this paper. The results may be useful for exploiting or avoiding SRWs in CETLs.

Crosstalk modeling in high-speed transmission lines by multilayer perceptron neural networks

Signal degradation due to crosstalk-related issues has become increasingly important particularly in high-speed signal transmissions. Conventional analysis of crosstalk requires a full electromagnetic modeling of the signal transmission path along with a time-domain transient simulation which is computationally demanding. In this work, we apply a multilayer perceptron neural network for crosstalk prediction in coupled transmission lines. The well-trained neural networks can be used to predict the time-domain crosstalk directly, thereby replacing complex circuit simulations. Numerical results show a high degree of generalization of the neural networks, which are able to produce accurate results and can be trained to include effects such as reflections and input mismatches.

A G-Band Wideband Bidirectional Transceiver Front-End in 40-nm CMOS

A G-band wideband bidirectional transceiver front-end is proposed. Coupled transmission line (CTL) and the staggered inter-stage wideband matching technique are exploited to extend the bandwidth of low noise amplifier (LNA) and power amplifier (PA). The transmit/receive (T/R) switch is realized as a single-pole-double-throw (SPDT) switch to connect the LNA and PA with good matching performance, low insertion loss, and high isolation simultaneously. The proposed G-band bidirectional transceiver front-end is implemented in 40-nm CMOS and occupies $ {870}\,\, {\mu } \textrm {m} {\times } {910}\,\, {\mu } \text{m}$ die area including the pads. The front-end in the transmitter (TX) mode achieves a measured 3-dB bandwidth of 32.8 GHz with a peak gain of 9.6 dB and a simulated saturated output power of 3.0 dBm, while the receiver (RX) mode features a measured 3-dB bandwidth of 34.8 GHz with a maximum gain of 10.5 dB and a simulated minimum noise figure (NF) of 10.8 dB. The implementation of the bidirectional transceiver front-end demonstrates the feasibility to integrate the TX and RX with a single on-chip antenna in G-band.

Synthetic spin\u2013orbit coupling and topological polaritons in Janeys\u2013Cummings lattices

The interaction between a photon and a qubit in the Janeys–Cummings (JC) model generates a kind of quasiparticle called polariton. While they are widely used in quantum optics, difficulties in engineering-controllable coupling of them severely limit their applications to simulate spinful quantum systems. Here we show that, in the superconducting quantum circuit context, polariton states in the single-excitation manifold of a JC lattice can be used to simulate a spin-1/2 system, based on which tunable synthetic spin–orbit coupling and novel topological polaritons can be generated and explored. The lattice is formed by a sequence of coupled transmission line resonators, each of which is connected to a transmon qubit. Synthetic spin–orbit coupling and the effective Zeeman field of the polariton can both be tuned by modulating the coupling strength between neighboring resonators, allowing for the realization of a large variety of polaritonic topological semimetal bands. Methods for detecting the polaritonic topological edge states and topological invariants are also proposed. Therefore, our work suggests that the JC lattice is a versatile platform for exploring spinful topological states of matter, which may inspire developments of topologically protected quantum optical and information-processing devices.

Calculation of Distance Protection Settings in Mutually Coupled Transmission Lines: A Comparative Analysis

Protection of mutually coupled transmission lines poses special challenges to protection engineers, since the general principles outlining the expected performance of the protection elements are based on simplified versions of the issues affecting them. Distance protection elements are among the most commonly accepted methods for protecting mutually coupled transmission lines, however, the calculation of settings and the validation of their performance is a complex task, involving lots of simulations and analysis of results to come up with an acceptable solution. Though various methods have been proposed to deal with the problem of calculating the optimal settings of distance protection elements, there is still room for improvement, since these methods have been formulated for the general case considering simple transmission lines. In this paper, a variation of one of these methods is introduced to enhance the computing times and reliability of the solutions for the specific application of quadrilateral distance protection to mutually coupled transmission lines, through the characterization of the expected performance of the operating characteristic, and the formulation of the optimization problem and the solution method. The obtained results show the improvements in computing times and quality of the solution provided by the proposed algorithm.

Exceptional Points of Degeneracy and Branch Points for Coupled Transmission Lines—Linear-Algebra and Bifurcation Theory Perspectives

We provide a new angle to investigate exceptional points of degeneracy (EPD) relating the current linear-algebra point of view to bifurcation theory. We apply these concepts to EPDs related to propagation in waveguides supporting two modes (in each direction), described as a coupled transmission line. We show that EPDs are singular points of the dispersion function associated with the fold bifurcation connecting multiple branches of dispersion spectra. This provides an important connection between various modal interaction phenomena known in guided-wave structures with recent interesting effects observed in quantum mechanics, photonics, and metamaterials systems described in terms of the algebraic EPD formalism. Since bifurcation theory involves only eigenvalues, we also establish the connection to the linear-algebra point of view by casting the system eigenvectors in terms of eigenvalues, analytically showing that the coalescence of two eigenvalues results automatically in the coalescence of the two respective eigenvectors. Therefore, for the studied two-coupled transmission-line problem, the eigenvalue degeneracy explicitly implies an EPD. Furthermore, we discuss in some detail the fact that EPDs define branch points in the complex frequency plane, we provide simple formulas for these points, and we show that parity-time (PT) symmetry leads to real-valued EPDs occurring on the real-frequency axis.

Unconditionally Stable Multiple One-Dimensional ADI-FDTD Method for Coupled Transmission Lines

The unconditionally stable multiple one-dimensional alternating direction implicit finite-difference time-domain (M1-D ADI-FDTD) method for coupled transmission lines is presented. The differential equations for coupled transmission lines are formulated in compact matrix form. Proper $4 \times 4$ split matrices are introduced, which feature unconditional stability for the ADI procedures. These matrices also lead to update equations with the left-hand sides involving tridiagonal matrices that can be solved efficiently. The update equations of the M1-D ADI-FDTD method are given, which comprise one implicit and three explicit updates in each procedure. The analytical proof of unconditional stability is also provided based on the von Neumann method. The M1-D ADI-FDTD method allows quick simulation and visualization of electromagnetic fields everywhere along the coupled transmission lines. To demonstrate the usefulness of the M1-D ADI-FDTD method, various coupled line structures for filter and filtering antenna are analyzed using the method.

On the Radiated Susceptibility of a Two-Wire Transmission Line Under Near- and Far-Field Conditions

An analytical transmission line (TL) coupling model is presented for evaluating the deviation between the susceptibility of a DUT in the near- and far-field of a noise source. Appropriate field solutions of elementary antennas are used in combination with coupling equations of an electrically short two-wire TL. A normalized coupling is defined to quantify the difference between the near- and far-field disturbances. It is found that the field coverage and the wave impedance of the radiating source are the dominant factors. The evaluation of the normalized coupling voltage results in potential deviations up to an order of magnitude. Therefore, it is concluded that standard EMC-test in the far-field may not always reflect the coupling level under different realistic circumstances appropriately. The analytical model is validated by accurate three dimensional field simulations and experiments.

Design of dual wideband bandpass filter using stub loaded multi‐mode resonators

AbstractIn this paper, a novel dual wideband microstrip bandpass filter is proposed. The designed filter is constructed by two different stub loaded resonators located at the upper and bottom sides of the coupling line. The coupling transmission line is also connected to input and output (IO) ports. The upper resonator creates a wide passband, whereas the bottom resonator is used to create two transmission zeros in the passband. Thus, a wide passband can be divided into dual wide passbands. The bottom resonator is also utilized to improve the insertion and return losses in the passband. The designed filter is fabricated and tested in a very good agreement with the simulated results. The measured fractional bandwidths (FBWs) of the passbands are 44.6% and 24.2% at the center frequencies of 3.4 GHz and 5.51 GHz, respectively. The measured insertion losses in the passbands are 0.51 dB and 1.13 dB.

185–220 GHz wideband amplifier in 40 nm CMOS

A 185–220 GHz four-stage differential wideband amplifier is presented. The bandwidth (BW) is significantly expended by using the coupled transmission line (CTL) technique and the staggered inter-stage wideband matching technique. CTL is adopted due to its high self-resonant frequency, high simulation accuracy, compact layout and wide BW characteristics. The amplifier achieves a peak gain of 10.1 and 3 dB BW of 35 GHz ranging from 185 to 220 GHz. With a supply voltage of 0.9 V, the amplifier consumes a DC power of 54.5 mW. The amplifier occupies a core area of 500 × 250 μm2 in 40 nm CMOS.

$\mathcal {H}$-Matrix Accelerated Contour Integral Method for Modeling Multiconductor Transmission Lines

An efficient algorithm based on the contour integral method (CIM) is presented in this letter for the modeling of lossy multiconductor transmission lines. Different from the volume integral equation, the CIM only discretizes the contour of the cross section of each conductor, which significantly reduces the number of unknowns in the resultant system equations. The solution of the CIM is accelerated by the hierarchical-matrix ( $\mathcal {H}$ -matrix) algorithm for the extraction of the per-unit-length resistance and inductance parameters of massively coupled transmission lines. The procedures for the $\mathcal {H}$ -matrix-based solution are optimized to keep its optimal computational complexity. The numerical results from the proposed method agree well with those from the commercial software. The complexities of CPU time and memory cost for the construction of the $\mathcal {H}$ -matrices are both $O(N\log {}N)$ , and the complexity of the solution for parameter extraction is $O(N\log ^2{}N)$ .

Compact spiral band pass filter with low group delay

AbstractA complementary coupled spiral transmission line with center via is proposed to design band pass filter with compact and simple profile, low group delay, and low insertion loss. A compact wideband band pass filter is designed and fabricated for demonstration which has 26% bandwidth, 0.3 dB insertion loss, and compact size as 0.41 × 0.23 λg with very low group delay, 0.28 ns. These good specifications prove the capability of the proposed approach to design of band pass filter compared with the literatures.

Dual-band transmission polarization converter based on planar-dipole pair frequency selective surface

A novel linear polarization converter operating in C- and X-bands with high polarization conversion ratio is described and demonstrated based on frequency selective surface. The building element is a planar-dipole pair, which is orthogonally printed on a double-layer substrate and vertically connected by a pair of through-via holes functioning as a quasi-two-wire transmission line coupler. A perforated metal shielding layer is sandwiched between the double-layer structure to only support a transverse electric and magnetic (TEM) mode coupling between the top and bottom dipolar components. The front dipole responds to the incident transverse electric (TE) wave, and sends the induced current into the two-wire transmission line to feed the bottom dipole. The bottom dipole is orthogonal or oriented at an arbitrary angle with respect to the top one, and a resultant outgoing transverse magnetic (TM) wave or arbitrary orientation polarized wave can be achieved. In addition, a bidirectional orthogonal polarization converter is realized by using double orthogonally arranged planar-dipole pairs, which are also printed on the same double-layer substrate.

A ku‐band distributed SPDT switch in 0.5 μm AlGaN/GaN HEMT technology

AbstractIn this paper, a wideband single‐pole double‐throw (SPDT) switch using the traveling‐wave concept was demonstrated. Realized in 0.5 μm AlGaN/GaN HEMT process, it achieves good performance at Ku‐band despite the process being intended for low‐frequency applications. This type of switch combined the off‐state shunt transistors and series coplanar waveguide (CPW) lines to form an artificial transmission line. CPW is also used to eliminate parasitics associated with through‐substrate microstrip vias and coupling of adjacent transmission lines. An accurate switch HEMT model was extracted and used in the design. A 9–25 GHz single‐pole double‐throw (SPDT) switch in conjunction with quarter‐wavelength impedance transformers demonstrates an insertion loss of less than 6 dB, return loss better than 10 dB and an isolation of better than 25 dB.

Circuit Breaker Rate-of-Rise Recovery Voltage in Ultra-High Voltage Lines with Hybrid Reactive Power Compensation

With the development of ultra-high voltage (UHV) technology, hybrid reactive power compensation (HRPC) will be widely applied in the future. To study the mechanism by which HRPC influences the characteristics of circuit breakers in UHV transmission lines, this paper establishes an improved electromagnetic coupling transmission line model for out-of-phase and short-line faults. Based on the HRPC equivalent model, a simulation analysis was performed on the characteristics of the circuit breaker when a fault occurs. Using an equivalent lumped parameter circuit, the rate-of-rise of recovery voltage (RRRV) computational formula was deduced and computed. The RRRV variation in the circuit breakers in the system, with and without HRPC, was obtained. Given the circuit breaker interruption characteristics, the research results provide an analysis foundation and a theoretical basis for optimizing the HRPC parameters and selecting the arrangements of circuit breakers in an UHV transmission line.

A New Amplification Regime for Traveling Wave Tubes With Third-Order Modal Degeneracy

Engineering of the eigenmode dispersion of slow-wave structures (SWSs) to achieve desired modal characteristics, is an effective approach to enhance the performance of high power traveling wave tube (TWT) amplifiers or oscillators. We investigate here for the first time a new synchronization regime in TWTs based on SWSs operating near a third order degeneracy condition in their dispersion. This special three-eigenmode synchronization is associated with a stationary inflection point (SIP) that is manifested by the coalescence of three Floquet-Bloch eigenmodes in the SWS. We demonstrate the special features of "cold" (without electron beam) periodic SWSs with SIP modeled as coupled transmission lines (CTLs) and investigate resonances of SWSs of finite length. We also show that by tuning parameters of a periodic SWS one can achieve an SIP with nearly ideal flat dispersion relationship with zero group velocity or a slightly slanted one with a very small (positive or negative) group velocity leading to different operating schemes. When the SIP structure is synchronized with the electron beam potential benefits for amplification include (i) gain enhancement, (ii) gain-bandwidth product improvement, and (iii) higher power efficiency, when compared to conventional Pierce-like TWTs. The proposed theory paves the way for a new approach for potential improvements in gain, power efficiency and gain-bandwidth product in high power microwave amplifiers.

Tunable Constant-Bandwidth Substrate-Integrated Bandstop Filters

A new method for designing tunable bandstop filters with constant fractional and absolute bandwidths (ABWs) is presented. The constant bandwidth is achieved through a new coupling structure, which is passive and consists only of coupling elements and transmission lines. Its theory of operation is presented, and design principles and tradeoffs are examined in detail. Several prototype filters are fabricated and measured to demonstrate the performance and versatility of this method. An octave-tunable filter with less than 12% fractional bandwidth variation is demonstrated, along with an octave-tunable filter with 12.3% variation in ABW variation, a filter with a 50% tuning range and less than 4% variation in ABW, and a four-pole octave-tunable filter with less than 4% variation in its 10-dB ABW. These results represent state-of-the-art performance when compared to other constant-bandwidth bandstop filters at frequencies higher than those compatible with lumped-element filters.