Negative Group Delay Topology Research Articles

Design and Test of Innovative Three-Couplers-Based Bandpass Negative Group Delay Active Circuit

An innovative design method of bandpass (BP) negative group delay (NGD) active circuit is developed. The BP NGD topology consists originally of octopole and hexapole coupled line (CL) couplers. The NGD active circuit is validated by a prototype implemented in hybrid technology. The measured results are in good agreement with simulations. The CL-based passive circuit generates BP NGD performance with simulated and measured results showing NGD level of approximately -12 ns having 1.97 GHz center frequency with -11 dB transmission coefficient and -16 dB reflection coefficient. To compensate the loss, active circuit was fabricated by cascading the passive circuit with a microwave amplifier. Subsequently, the previous BP NGD performance is achieved with 0 dB gain. Moreover, a notable active microwave device characterization is performed with the NGD prototype via nonlinear measurements. It was found that the tested NGD prototype operates with 10-dB noise figure, 21 dBm P1dB compression, 29 dBm and 41 dBm OIP3.

Suitability of passive RC-network-based inductorless bridged-T as a bandpass NGD circuit

PurposeThe purpose of this paper is to study, a bridged-T topology with inductorless passive network used as a bandpass (BP) negative group delay (NGD) function.Design/methodology/approachThe BP NGD topology under study is composed of an inductorless passive resistive capacitive network. The circuit analysis is elaborated from the equivalent impedance matrix. Then, the analytical model of the C-shunt bridged-T topology voltage transfer function is established. The BP NGD analysis of the considered topology is developed in function of the bridged-T parameters. The NGD properties and characterizations of the proposed topology are analytically expressed. Moreover, the relevance of the BP NGD theory is verified with the design and fabrication of surface mounted device components-based proof-of-concept (PoC).FindingsFrom measurement results, the BP NGD network with −151 ns at the center frequency of 1 MHz over −6.6 dB attenuation is in very good agreement with the C-shunt bridged-T PoC.Originality/valueThis paper develops a mathematical modeling theory and measurement of a C-shunt bridged-T network circuit.

Dielectric Resonator Negative Group Delay Circuit

AbstractThis 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.

Design and Synthesis of Inductorless Passive Cell Operating as Stop-Band Negative Group Delay Function

This paper develops an original circuit theory of unfamiliar stop-band (SB) negative group delay (NGD) topology. The proposed NGD topology is implemented without inductor component. The developed theory is established with passive cell constituted by RC-network based high-pass (HP) and low-pass (LP) NGD composite circuits. The analytical investigation of the SB-NGD circuit is introduced from the elaboration of voltage transfer function (VTF). The canonical form enabling to identify SB-NGD circuit is analytically expressed. The different SB-NGD characteristics as GD value, and, center and cut-off frequencies are innovatively formulated in function of the circuit resistor and capacitor components. The existence condition of SB-NGD function is also established. The inductorless SB-NGD topology is validated by a proof-of-concept (POC) circuit implemented by surface-mounted-device (SMD) component based printed circuit board (PCB). The measured VTF magnitude and group delay (GD) are extracted from the experimented S-parameters. A good agreement between the calculated, simulated and measured results is obtained. The SB-NGD behavior has measured center frequency of about 32 MHz. The lower- and upper-NGD cut-off frequencies are about 9.15 MHz and 98.3 MHz. The optimal NGD values at low and higher frequencies are −3.25 ns and −56 ps.

O=O Shape Low-Loss Negative Group Delay Microstrip Circuit

This brief deals with an innovative design of negative group delay (NGD) topology presenting O=O geometrical shape. This fully distributed NGD topology is composed of a power divider (PWD), power combiner (PWC) and coupled line (CL) built with lossy and delayed transmission lines (TLs). The PWD and PWC are connected via the CL. By using 3-port PWD and PWC, 4-port CL S-matrices, the O=O topology model allowing to determine the group delay (GD) is established. To verify the NGD aspect of the O=O topology, parametric analyses with respect to TL characteristic impedance and delay are performed. In addition, a microstrip circuit prototype is designed, simulated and measured. A good NGD performance with NGD level of approximately −2.8 ns around the center frequencies 1.2 GHz with transmission coefficient of approximately −2.2dB and reflection coefficient better than −15dB. The measured results are in very good agreement with calculated model and simulations.

Design of Multi-Scale Negative Group Delay Circuit for Sensors Signal Time-Delay Cancellation

This paper develops an innovative method of sensors’ time-delay suppression. The proposed delay cancellation technique is highlighted with a theoretical concept and time-domain experimental demonstrations by using the negative group delay (NGD) function. The analytical investigation is elaborated with an NGD topology constituted by a simple active $RC$ network. It is established theoretically that this active cell behaves like a low-pass NGD topology. The synthesis equations enabling to calculate the NGD cell parameters as a function of the desired NGD and gain are formulated. Frequency- and time-domain analyses showing the NGD function in multi-time scale are discussed. The NGD function verification is fulfilled with the design and fabrication of a proof-of-concept prototype. Nano-, micro-, and milli-second NGD effects are numerically and experimentally proved. As expected, time-domain experimental demonstrations showing arbitrary waveform signal in outstanding time-advance are realized. Moreover, the feasibility of the signal delay cancellation with 1- and 8-m length cables is experimented. The developed NGD time-delay cancellation demonstrations open the potential applications for the sensor performance improvement.

Analysis of Interconnect Line Coupled With a Radial-Stub Terminated Negative Group Delay Circuit

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.

Time-Domain Experimentation of NGD ActiveRC-Network Cell

A theoretical and experimental investigation of low-pass negative group delay (NGD) topology is introduced. The NGD topology is composed of a low noise amplifier (LNA) and RC-parallel series mounted lumped network. The NGD cell theoretical characterization is elaborated. The NGD properties as NGD level, cut-off frequencies and central frequency are established. The synthesis formulas as function of the expected NGD level and gain are established. The NGD proof of concept using monolithic LNA LEE-9+ manufactured by mini-circuits are designed, simulated, fabricated, and measured. The simulated and measured frequency domain results are in good agreement with the circuit theory. As expected, low-pass NGD behavior is observed with −5 ns-NGD level over 32-MHz bandwidth. The low-pass NGD function meaning is illustrated by the advance of the output pulse signal leading and trailing edges compared to the input ones.

Canonical transfer function of band‐pass NGD circuit

This study introduces the generalised canonical transfer function (TF) of the band-pass negative group delay (NGD) circuit. The principle to identify the unfamiliar band-pass NGD circuits is suggested. Similar to the filter theory, the band-pass NGD TF can be established from low-pass to band-pass frequency transform. The fundamental characteristics of the NGD topology are described. The canonical TF feasibility is concretised with the second-order equivalent impedance constituted by passive elements. The synthesis formulas in function of the desired NGD level and bandwidth are analytically established. Application examples of band-pass NGD impedance synthesis, designed and fabricated are proposed as a proof of concept. Prototypes of band-pass NGD circuits with centre frequencies 1 and 1.5 MHz for the targeted group delay optimal values, respectively, −1 and −1.5 µs are designed and fabricated. As expected, band-pass NGD results in good agreement with the theoretical prediction were obtained with simple lumped circuits. In the future, thanks to theory simplicity, the NGD band-pass cell can be potentially useful for the signal delay correction.

The Design Method of the Active Negative Group Delay Circuits Based on a Microwave Amplifier and an RL-Series Network

This paper addresses a circuit theory regarding the negative group delay (NGD) principle. The methodology for characterizing this unfamiliar NGD function is described. The basic NGD topology under study is typically an active cell composed of an RF low-noise amplifier (LNA) and an RL-series passive network. It acts as a low-pass NGD topology. The family of the bandpass NGD cell is identified from the low-pass to the bandpass transform. The NGD circuit theory under study is essentially built with the S-parameter approach. The main characteristics of the proposed NGD topology and properties of the NGD level, cut-off frequencies or bandwidth, central frequency, and figure-of-merit are established. The NGD cell is synthesized using the LNA S-parameter model. A method for designing the low- and bandpass NGD cells as a function of the specified NGD values is presented. The NGD cell parameter calculations as functions of the expected NGD level, insertion loss, and reflection coefficient are introduced. Proof-of-concept NGDs are synthesized, designed, simulated, and fabricated to understand and validate the proposed NGD low-pass and bandpass functions. As expected, low-pass and bandpass NGD aspects are obtained. The low-pass NGD circuits present an NGD level of approximately −5 ns over the bandwidth fc = 25 MHz. Next, bandpass NGD circuits were synthesized to operate at approximately 0.5 GHz over the bandwidth $\Delta \text{f}\,\,=50$ MHz with an NGD level of approximately −10 ns. The measured results of the low-pass and bandpass NGD are in good agreement with the theoretical prediction obtained with simple lumped circuits. Different applications of the unfamiliar NGD function are described.

S-Parameter Model of Three Parallel Interconnect Lines Generating Negative Group-Delay Effect

This paper develops a negative group-delay (NGD) microwave circuit theory regarding topology consists of three parallel interconnect lines (3-PILs). The NGD topology under study is built using completely distributed microstrip lines. The 3-PIL NGD theory is established from the S-parameters which are determined from the general admittance matrix of the 3-PILs. The analytical expressions of reflection coefficient (S11), transmission coefficient (S21) and group-delay ( $\tau$ ) which behave as periodical functions are presented. The frequency period proper to the 3-PIL topology is established. Then, S11, S21 and $\tau $ illustrating the possibility to generate bandpass NGD function are formulated in function of the PIL parameter physical lengths and attenuation loss. Then, the NGD characterization of the 3-PIL topology is presented. The relevance of the NGD theory is verified with simulations and experimentations around the NGD center frequency of about 2.3 GHz. To do this, a 3-PIL microstrip circuit is designed and fabricated as proof-of-concept. It is shown that the simulated and measured group-delays are well-correlated. As expected theoretically, the demonstrator with identical characteristic impedance enables to generate an NGD level of approximately −2 ns at 2.3 GHz. In the future, the NGD function can be potentially used for the microwave signal integrity improvement.

Theory of Coupled Line Coupler-Based Negative Group Delay Microwave Circuit

A fundamental theory of coupled line coupler-based negative group delay (NGD) topology is established in this paper. The microwave circuit under study consists of the isolated-and coupled-accesses connected in a feedback loop through a lossy interconnect line. The NGD topology is built with fully distributed elements. The S-parameter model is formulated in order to derive the NGD optimal values, cutoff frequencies, and bandwidth. Thus, the NGD existence condition as a function of the coupling coefficient and the feedback interconnection attenuation is demonstrated and examined. Hence, the fundamental characteristics of the coupler-based NGD topology are described. In order to verify the feasibility of the theory, NGD prototypes were designed, fabricated, and measured. The implemented one- and two-stage microstrip circuits have NGDs of about −2.3 and −4 ns, respectively, at 1.26 GHz. The reflection coefficients are better than 10 dB and the insertion losses are, respectively, about 2.4 and 4.3 dB. The developed NGD topology, fully constructed with distributed elements without any lumped components, is particularly beneficial in terms of design simplicity. The proposed NGD circuit might find potential application in microwave signal delay correction.

Innovative Theory on Multiband NGD Topology Based on Feedback-Loop Power Combiner

The signal delay is one of the main issues encountered during the design and fabrication of the RF/microwave electronic circuits and systems. Therefore, the correction process is constantly needed for the signal delay cancelation. This brief introduces an innovative theory of a microwave circuit topology delay suppressor. The original circuit was originally built with a passive power combiner (PWC) in feedback with an interconnect transmission line (TL) without the use of lossy lumped elements. The theoretical formulation proves that the distributed passive circuit is capable of generating the negative group delay (NGD) phenomenon. The synthesis relations enabling us to determine the circuit parameters in function of the desired NGD value are established. The innovative NGD circuit properties are elaborated. The NGD concept validation was verified with the design of fully distributed passive NGD cell built with a Wilkinson PWC in feedback with a lossy transmission line. The influence of the feedback line attenuation on the NGD function and S-parameters is discussed. A multiband NGD of about -0.7 ns was exhibited over the frequency band of about 0.12 GHz. This distributed NGD topology can be integrated and is useful for the microwave signal delay improvements.

First‐order low‐pass negative group delay passive topology

An innovative theory on the passive circuits capable to generate low-pass negative group delay (NGD) behaviour is introduced. An identification method enabling to identify the first-order NGD simple cells built with resistor-inductor (RL)- and resistor-capacitor (RC)-networks is elaborated. The fundamental characteristics as the NGD level and cut-off frequency are formulated from the low-pass NGD circuit canonical transfer function. The NGD existence conditions are derived in function of the established topology parameters. Despite the attenuation systematically related to the passive cell nature, low-pass NGD behaviours with tens ns NGD level and tens MHz bandwidth were obtained with an example of lumped RL-network-based L-topology circuit. Transient analysis was performed to illustrate that the NGD phenomenon enables to exhibit baseband signal advance effect. The proposed NGD topology simplicity promises their potential applications especially in term of signal correction and the modern electronic system improvement.

Synthesis of RF Circuits with Negative Time Delay by Using LNA

A demonstration of the negative time-delay by using active circuit topologies with negative group delay (NGD) is described in this paper. This negative time delay is realized with two different topologies operating in base band and modulated frequencies. The first NGD topology is composed of an RL-network in feedback with an RF/microwave amplifier. Knowing the characteristics of the amplifier, a synthesis method of this circuit in function of the desired NGD values and the expected time advance is established. The feasibility of this extraordinary physical effect is illustrated with frequency- and time-domain analyses. It is shown in this paper that by considering an arbitrary waveform signal, output in advance of about 7 ns is observed compared to the corresponding input. It is stated that such an effect is not in contradiction with the causality. The other NGD topology is comprised of a microwave amplifier associated with an RLC-series resonant. The theoretical approach illustrating the functioning of this NGD circuit is established by considering the amplifier S-parameters. Then, synthesis relations enabling to choose the NGD device parameters according to the desired NGD and gain values are also established. To demonstrate the relevance of the theoretic concept, a microwave device exhibiting NGD function of about -1.5 ns at around 1.19 GHz was designed and analyzed. The NGD device investigated in this paper presents advantages on its faculty to exhibit positive transmission gain, the implementation of the bias network and matching in the considered NGD frequency band.

Methodology of elementary negative group delay active topologies identification

This work introduces a fundamental methodology enabling to identify the elementary negative group delay (NGD) topologies using transistors. These circuits are particularly beneficial compared to the other existing NGD topologies, with its flexibility to operate in ultra wideband (UWB), to compensate losses and potentially integrable. The basic families of NGD topologies obtained from the association of passive and active four-port networks are presented. The NGD existence condition is given. Based on this condition, the simplest NGD active cells are identified. After the analysis of passive networks formed by R, L and C components, first-order transfer functions of innovative elementary NGD cells are established. Then, similar to the classical circuits as the filters and amplifiers, synthesis relations for the design of integrable NGD topology with no self-element are introduced. To illustrate the relevance of the theoretic concept, a proof of concept was proposed. Finally, discussions on the applications of NGD circuits are offered in the conclusion.

Investigation on Microwave Negative Group Delay Circuit

In this article, a fundamental analytical approach and experimental verification of a radio frequency active circuit capable of exhibiting negative group delay at microwave wavelengths are presented. By using the S-parameter theory, basic properties and characteristics of the negative group delay circuit under study are established. To highlight the functionality principle of this innovative circuit, time-domain investigations based on ultra-wide-band pulse signal tests are performed. Then, the mechanism of propagating output signal envelopes in time advance compared to the input is demonstrated. To validate this concept, a prototype of a negative group delay device was designed, fabricated, and tested. Experimental results in good agreement with theory and simulation were obtained. In the frequency domain, a negative group delay of about −2.5 ns with amplification of 2 dB was measured at around 622 MHz. Due to this negative group delay effect, envelope advance of about −1.5 ns was observed by considering a pulse signal with a half-height full-width of 10 ns, which modulates a sine carrier with a frequency of 622 MHz. The negative group delay topology presented is potentially useful for the compensation of radio frequency/microwave signal delays.