Stop-band type NGD RLC-resonant circuit sensitivity analysis

This article introduces a negative group delay (NGD) analysis of interconnect line coupled with a radial stub terminated line. The NGD topology equivalent model is established by considering the microstrip interconnect line and radial stub circuits. The S-parameter and the group delay are expressed as a function of NGD fully distributed topology parameters. The NGD optimal frequencies and existence condition are originally established as a function of the coupler and the associated RLC -network parameters. It was innovatively shown that the proposed NGD circuit presents a property to generate double NGD center frequency. A proof-of-concept designed and implemented in the microstrip technology was simulated and fabricated to validate the NGD concept. Simulated and measured results are in good correlation with the NGD theoretical prediction. The prototype test results confirm the NGD characteristics as −2.1 ns NGD level at the 1.34-GHz center frequency over 56-MHz bandwidth.

This paper investigates on the theorization, design, fabrication and measurement of original phase shifter (PS) operating with two-step stair phase behavior. The innovative stair PS is designed with unfamiliar stop-band (SB) negative group delay (NGD) passive circuit. The elementary unfamiliar SB-NGD topology constituted by resistive, inductive, and capacitive lumped network is described. Acting as an RF and microwave circuit, the S-matrix model is expressed in function the RLC-network parameters. Thus, the canonical form of unfamiliar SB-NGD transfer function (TF) represented by the transmission coefficient is established. The unfamiliar SB-NGD circuit equations in terms of the NGD parameters are formulated. The established theory is validated comparing the calculated, simulated, and measured S-parameters and group delays (GDs). Results with a very good agreement showing unfamiliar SB-NGD behavior are observed around the central frequency 2.45 GHz and bandwidth of 100 MHz. An innovative application of unfamiliar SB-NGD function for the communication system front-end is developed. The developed application concept of unfamiliar SB-NGD circuit is illustrated by designing a microwave device operating as a PS presenting a two-step stair response completely original behavior. The basic theory, design and implementation of the two-step stair PS concept are introduced. To validate the two-step stair PS principle, a proof of concept (PoC) is designed based distributed element based inductive and capacitive microstrip elements. The simulated and measured results of the PS PoC are in good agreement. The experimental results confirm the feasibility of two-step stair PS with phase jumping from −70°±4° (from 2 GHz to 2.3 GHz) to −104°±2° (from 2.6 GHz to 3.0 GHz). The investigated unfamiliar SB-NGD function-based stair PS is promising for future development 5G and 6G communication system.

This study investigates an innovative theory on design of dielectric resonator (DR) based negative group delay (NGD) microwave circuit. The NGD circuit is mainly constituted by a cylindrical bulk of DR as a coupling element with a microstrip line. The developed theory is analytically established from the S‐parameters modeling of this innovative DR NGD topology. The NGD analysis and synthesis equations are formulated by considering the key parameters of the DR NGD cell. The NGD existence condition as a function of the DR and microstrip line parameters is also introduced. The behavioral response of the bandpass NGD function is verified with different designed proof‐of‐concepts (POCs). The developed NGD DR topology was validated with original circuit design by commercial simulations and experimentations with insertion and reflection losses lower than 4 and 10 dB, respectively. The POC prototypes operate with low attenuation losses in mono band and dual bands up to 10 GHz. Single NGD cells with DR coupled with “I” and “U” shape microstrip lines operating at different central frequencies were designed and implemented. Then, dual‐band NGD circuits operating at approximately 2.5 and 5 GHz were also tested. The possibility to widen the NGD bandwidth with double DR NGD circuits was investigated.

This work reports a half-mode substrate integrated waveguide (HMSIW) negative group delay (NGD) compensating circuit based on the equivalent left-handed material coupling mechanism. The proposed microwave NGD compensating circuit mainly consists of a HMSIW section, a split-ring resonator (SRR) and two coupling capacitors between them, as well as a pair of grounded metal sheets on the two sides of SRR for impedance matching enhancement. In specific certain frequency band, SRR is able to generate magnetic plasma effect and exhibit negative permeability. Simultaneously, negative permittivity can be produced by the negative capacitance, which is created by the J-inverter between the HMSIW section and the SRR. Thus, the proposed circuit will behave as an equivalent left-handed material to realize bandpass negative group delay function. Then, the analytical model allowing to determine the group delay is established from equivalent circuit approach. Later, to validate the proposed NGD function, a prototyped circuit is designed, simulated and fabricated. Bandpass NGD operation was realized, with a center frequency of 11.2 GHz, an effective bandwidth of 110 MHz, and a maximum NGD of -1.58 ns.

In this paper the transients in gain compensated negative group delay (NGD) circuits are investigated. The study is conducted on an active unity gain NGD circuit with an RLC resonator integrated in the feedback loop of an operational amplifier. The circuit operates at a center frequency of 454MHz, and it is cascadable. The single stage circuit exhibits a NGD of 1.52ns and a gain of 0.69dB, with a fractional bandwidth of 23%. The circuit transient response to a step-modulated sinusoidal input is measured for a single-stage and two-stage circuits, showing a good agreement with analytical results. The analytical study is extended to general NGD multi-stage circuits based on RLC resonators and shows an exponential relationship between the transient level and the square of achieved NGD. We show that when considering information transfer applications, there is a limit on achievable NGD.

A novel reconfigurable negative group delay (NGD) circuit based on branch-line coupler is proposed in this article. It consists of two branch-line couplers that are connected by two varactors with different capacitance values. By simply adjusting the capacitance values, both the transmission gain/loss and group delay (GD) values of the proposed circuit can be independently adjusted as desired. Full theoretical analysis has been given to verify the reconfigurable NGD responses. To compensate for the transmission loss, an active NGD circuit is also proposed by inserting two simple amplifiers in the transmission paths. The active circuit can also achieve independent transmission gain/loss and GD by tuning the amplifiers’ gain with fixed capacitance value. Passive and active prototypes were designed, fabricated, and tested to demonstrate the proposed techniques. The experimental results show that NGD of the proposed passive circuit can be adjusted from 0 to −90 ns, while the gain varies from −14 to −53 dB. The GD of active circuit can also be adjusted from 0 to −80 ns, while the gain varies from 17 to −18 dB. These experimental results agree well with simulations.

Design of multi-band circuit with negative group delay and lower insertion loss characteristics

In this study, a power dividing network with negative group delay (NGD) and balanced‐to‐single‐ended topology is proposed. The resistors connected with coupled lines achieve both the functions of NGD and isolation. Therefore, the approach is much simpler than the one for single‐ended power divider with NGD function. Furthermore, the insertion loss of the proposed design is lower than those of the power dividers with a similar level of NGD. Theoretic and experimental investigations of the proposed design are given to guide the design. One prototype working at 1.8 GHz is designed and fabricated. The measured results show that the group delay, return loss, insertion loss, common‐mode suppression, and isolation at the centre frequency are −1.1 ns, 20, 2.4, 15, and 17 dB, respectively. The measured results agree well with the analytical and simulated ones.

This paper presents a design of power divider with tunable positive and negative group delays. The positive group delay can be obtained between paths 2 and 1 whereas negative group delay (NGD) between paths 3 and 1. The NGD is controlled by varying bias voltage of parasitic compensated PIN diodes. For experimental verification, power divider was designed and fabricated at center frequency of 2.14 GHz. Measurement results had a good agreement with simulation results.

A simple topology of negative group delay (NGD) distributed active circuit (NGDDAC) is analyzed in this paper. The NGD cell is composed of a field effect transistor (FET) associated with a series resistance in cascade with short-circuited stub line. The theoretical approach illustrating the determination of the proposed NGD circuit S-parameter modelling is presented. Then, the synthesis formulas enabling to determine the NGDDAC parameters in function of the expected NGD specifications are established. In difference with the lumped NGD circuits, the distributed proposed NGDDAC operates without need of lossy lumped inductance. To illustrate the NGD concept feasibility, a cell of NGDDAC integrating 16mm length microstrip stub using the pHEMT EC2612 is synthesized and simulated. It was found that the circuits generate 5GHz periodical multiband NGD with extremal peak of about −0.5ns over the bandwidth more than 1GHz.

ABSTRACTThis paper deals with the similitude between the behaviours of linear filter gain and negative group delay (NGD) function. The transposition method of low‐pass/high‐pass, low‐pass/band‐pass and low‐pass/band‐stop NGD circuits is established. To the best of the author knowledge, it acts as the first paper devoted on the NGD function generalized theory. The introduced transform relationships simplify the synthesis of any NGD circuits from simple elementary low‐pass NGD topologies. Families of innovative NGD topologies are identified. To verify the relevance of the concept proposed, frequency‐ and time‐domain analysis results from realistic proofs of concept demonstrating the feasibility of developed NGD transforms were performed. Thanks to the NGD phenomenon, the possibility of the ultra‐wideband pulse signals propagating in time‐advance is verified. Finally, potential applications of NGD circuits are discussed. Copyright © 2013 John Wiley & Sons, Ltd.

Negative group delay is one of the anomalous characteristics of the metamaterial, and can be used to compensate the group delay of systems and is applicable to signal processing devices. In this paper, to achieve negative group delay with not only wide-band characteristics but also low-insertion loss, we newly propose the embedded transmission line with half-wavelength type folded-stepped impedance resonator (F-SIR) structure which has the symmetrical electric-wall at the guide center driven by differential-mode. The characteristics are discussed with numerical simulation. The concept of the proposed TL is based on the combination of resonance and anti-resonance due to open-stub resonator and F-SIR. The negative group delay and slope characteristics are achieved around anti-resonance. The insertion loss is dramatically improved compared with our previous results, which is constructed by gap and F-SIR structure. This study is a successful report that the validity of the proposed embedded TL structure is demonstrated.

The unfamiliar negative group-delay (NGD) phenomenon is experimented with structure constituted by tee-connectors and coaxial cables. The topology of the NGD generator is described. It consists of two parallel 50-Ω characteristic impedance cables. The S-parameter model in function of the cable physical lengths is established. The existence condition enabling to understand the NGD phenomenon is defined. A proof of concept simply is constituted by two three-port SMA connectors, three SMA transitions and 13-cm length cables. The NGD experimentation is performed from 1.5 GHz to 3.5 GHz. Tri-band NGD aspects in good agreement with the theory and simulation is observed experimentally. Particularly, high figure-of-merit NGD circuit with −3 ns NGD level, less than 2 dB insertion loss and 12 dB return loss around 3 GHz centre frequency is measured.

A dispersion-engineered artificial transmission line (TL) enabled by negative group delay (NGD) is proposed to exhibit squint-free dominant mode leaky-wave radiation. The unit cell of the proposed artificial TL is based on a multi-section directional coupler, which is used to generate the desired NGD, followed by a composite right/left-handed transmission line (CRLH-TL) structure. An amplifier is incorporated within each unit cell to compensate for the power loss from the NGD coupler. By incorporating the NGD response, the resulting artificial TL can demonstrate a dispersionless fast wave characteristic within the NGD frequency band. For proof-of-concept, prototypes of a single unit cell and a three-unit cell NGD artificial TL are fabricated and tested to verify the dispersion and radiation characteristics. The measured radiation patterns of the proposed NGD artificial TL indicate that the main beam angle is located at -35 degrees in the backward direction, with a squint-free bandwidth from 2.55 GHz to 2.75 GHz.

Controllable negative and positive group delay in transmission through a single quantum well at finite magnetic fields