Negative Group Delay Circuit Research Articles

Adaptive Multi-Band Negative-Group-Delay RF Circuits With Low Reflection

Two classes of frequency-reconfigurable multi-band negative-group-delay (NGD) circuit networks that feature low-input-power-reflection capabilities are reported. They consist of lossy-complementary-diplexer architectures, in which the NGD properties are obtained within the stopband regions of their lossy multi-band bandstop-filter (BSF) channel. Their complementary lossy multi-band bandpass-filter (BPF) branch absorbs in its terminating resistor the RF-input-signal energy that is not transmitted by the lossy multi-band BSF channel within its stopbands. In this manner, the input-reflectionless/absorptive behavior is realized. The theoretical foundations of the devised lossy-multi-band-BSF-based NGD structures using a coupling-routing-diagram formalism and single-to-multi-band admittance transformations are described. For the first-order case as illustration, guidelines for the synthesis in the bandpass frequency domain are provided. Furthermore, the extension of these multi-band NGD approaches to higher-order and in-series-cascade multi-stage realizations for more-general and wider-band NGD patterning, as well as to two-port/symmetrical designs, is shown. In addition, the conception of multi-functional passive components with NGD characteristics, such as wide-band BPFs and power directional couplers with embedded NGD regions, is also addressed. For experimental-demonstration purposes, an electronically-reconfigurable microstrip prototype of a two-stage-in-series-cascade dual-band NGD circuit is manufactured and measured.

Study and experimentation of a 6-dB attenuation low-pass NGD circuit

Because of its counterintuitive nature, the Negative Group Delay (NGD) remains as an uncommon and unfamiliar electronic function. For this reason, the design and analysis of NGD circuits are not well-known for most of electronic designers. This paper initiates a basic and easy to understand theory, in addition to a design methodology for the low-pass NGD function. The circuit theory on the low-pass NGD function is described using an NGD passive topology which is constituted by a RC-parallel network with a resistive load. The NGD analysis and synthesis equations in function of NGD specifications are provided and a proof-of-concept of 6-dB low-pass NGD circuits has been designed, simulated, fabricated and tested. Frequency and time domain analyses have been performed to validate the low-pass NGD function. Theoretical and simulated results are in very good agreement and an NGD has been obtained in measurement for the proposed structure.

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 Test of Crab-Shaped Negative Group Delay Circuit

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Editor’s notes:</i> Negative group delay (NGD) function is used to solve the delay issue of RF and microwave devices. This article presents a novel NGD circuit based on the distributed topology of a “crab-shaped” geometry structure. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">—Fei Su, Intel Corp.</i>

Negative Group Delay Circuits and Applications: Feedforward Amplifiers, Phased-Array Antennas, Constant Phase Shifters, Non-Foster Elements, Interconnection Equalization, and Power Dividers

With the rapid development of newgeneration communication technology such as multiple-input/multiple-output technology, ultrawideband communication, and 5G technology, communication systems have higher requirements for the quality of signal transmissions. Achieving this quality requires attention not only to signal amplitude characteristics but also to phase characteristics because of the long delays and signal distortion that come with positive group delay (PGD). However, negative group delay (NGD) circuits are an effective way to compensate for PGD and decrease the variability of passband group delay.

INNOVATIVE MICROWAVE DESIGN OF FREQUENCY-INDEPENDENT PASSIVE PHASE SHIFTER WITH LCL-NETWORK AND BANDPASS NGD CIRCUIT

The present paper develops an application of the bandpass (BP) negative group delay (NGD) circuit for the design of an independent frequency phase shifter (PS). The design principle of the innovative PS is constituted by an inductor-capacitor-inductor (LCL) T-shape passive cell in cascade with RLC-network series-based BP NGD circuits. The S-matrix analytical model of the LCL-NGD PS is established in function of the circuit elements. Then, the design equations of the PS elements in the function of the expected PS value and center frequency are formulated. The NGD PS topology is validated with a comparison between the calculated and simulated results of phase, transmission coefficient, and reflection coefficients. As expected, a very good correlation between the analytical model and the simulation is confirmed by the obtained results. It is found that the LCL-NGD PS presents an outstandingly flat phase shift of -120°±5° with 1.2 GHz center frequency. The LCL-NGD PS operates with about 18% relative bandwidth. The PS reflection coefficient presents a magnitude flatness around -3±1.5 dB. Moreover, the reflection coefficient is kept better than -15 dB. The sensitivity of the LCL-NGD PS performances over the NGD circuit element ±5% relative variation is studied. It is found how the PS value and center frequencychange with the R, L, and C components of the NGD circuit.

Innovative Transient Study of Tri-Bandpass Negative Group Delay Applied to Microstrip Barcode-Circuit

A transient study of bandpass (BP) negative group delay (NGD) function is devoted in this paper. The transient analysis is applied to an original topology of NGD barcode-shape microstrip circuit. The performed investigation explains how to realize the transient analysis of tri-band NGD circuit. The time-domain (TD) parametrization of the test is established from the BP-NGD specifications of the circuit under test (CUT) based on the S-parameter model. The input signal is a Gaussian pulse characterized in function of the NGD bandwidth (BW) and center frequency. The feasibility of the BP-NGD transient study is illustrated with experimentation based on ultra-wide band (UWB) pulse generator. As proof-of-concept, barcode NGD circuit exhibiting tri-band NGD value-center frequency-bandwidth, (−5.9 ns, 2.128 GHz, 20 MHz), (−7.4 ns, 2.3 GHz, 14 MHz) and (−4.8 ns, 2.42 GHz, 14 MHz) has been fabricated and tested. The transient simulations and experiences confirm that the output signal envelopes of the barcode NGD prototype present leading and tailing edges in time-advance of input ones when the carrier frequency is set equal to the NGD center frequency.

Experimental Time-Domain Study for Bandpass Negative Group Delay Analysis With Lill-Shape Microstrip Circuit

This paper focuses on the time-domain analysis of bandpass (BP) negative group delay (NGD) function. The innovative NGD investigation is based on the time-domain experimentation of an innovative topology of “lill”-shape passive microstrip circuit. The design principle of the proof of concept (POC) constituted by particular microstrip shapes is described. The NGD circuit is inspired from a recent fully distributed “li”-topology. Before the time-domain investigation, the BP NGD specifications of the circuit under study are academically defined. As practical application of the basic definition, a frequency domain validation of “lill”-circuit is presented in the first section of the paper. The POC circuit is specified by a -8 ns NGD value at 2.31 GHz NGD center frequency and a 27 MHz NGD bandwidth. The “lill”-circuit exhibits an attenuation loss of about -6.2 dB at the NGD center frequency. Then, the two-port black box model of “lill”-NGD-circuit represented by touchstone data of the measured S-parameters is exploited for the transient simulation. The measured group delay (GD) illustrates that the tested “lill”-circuit operates as a BP function regarding the NGD with NGD equal to -8.1 ns at the NGD center frequency. The time-domain demonstration of the BP NGD function was performed using a gaussian pulse modulating sine carrier. The innovative experimental setup with the possibility to plot simultaneously well synchronized input and output signals is explained. The BP NGD time-domain response is understood from commercial tool simulation using the touchstone S-parameters of the measured “lill”-circuit by using a Gaussian up-converted pulse having a 27 MHz frequency bandwidth. It was observed that the output signals are delayed when the sine carrier is out of NGD-band. However, the output signal envelope is in advanced of about -8 ns when the carrier is tuned to be approximately equal to the 2.31 GHz NGD center frequency. To confirm the time-domain typical behavior of BP NGD response, an input pulse signal having Gaussian waveform were considered during the test. However, the input signal spectrum must be determined in function of the NGD bandwidth. After tests, measured output signal envelopes presenting leading edge, trailing edge and peak in time-advance compared to the input ones are observed experimentally. The results of the present feasibility study open a potential microwave communication application of BP NGD function notably for systems operating with ISM and IEEE 802.11 standards.

STUDY OF ACTIVE NEGATIVE GROUP DELAY CIRCUIT BASED ON LNA AND RLC-PARALLEL NETWORK

STUDY OF ACTIVE NEGATIVE GROUP DELAY CIRCUIT BASED ON LNA AND RLC-PARALLEL NETWORK

A TRI-BAND NEGATIVE GROUP DELAY CIRCUIT FOR MULTIBAND WIRELESS APPLICATIONS

A TRI-BAND NEGATIVE GROUP DELAY CIRCUIT FOR MULTIBAND WIRELESS APPLICATIONS

Bandpass NGD TAN of Symmetric H-Tree With Resistorless Lumped-Network

This paper introduces an innovative passive topology of bandpass (BP) negative group delay (NGD) electrical circuit implemented with symmetric H-tree network. The multi-port topology of BP NGD circuit is originally represented by a resistorless H-tree constituted by lumped LC-passive network. Until now, the NGD electronic circuits available in the literature are implemented by two-port circuits which are using either resistive elements or distributed microstrip topologies. In the present investigation, the feasibility of the modelling, design, fabrication and test of unfamiliar BP NGD original H-tree circuits. The main objective of the study is to identify analytically the existence of the BP NGD function with the resistorless H-tree circuit. Because of its simplicity and the analytical equation compactness, the uncommon approach of tensorial analysis of networks (TAN) is used in the paper. After the branch and mesh analyses, the impedance matrix of the resistorless H-tree is elaborated. Hence, the resistorless H-tree equivalent S-matrix is established by means of impedance to scattering matrix transform. The BP NGD analysis in function of the inductance and capacitance parameters constituting the H-tree circuit is presented. Then, the main steps of the BP NGD investigation are described. The existence of BP NGD behavior in function of the adequate transmission parameters is identified by the consideration of the canonical form. To validate the BP NGD behavior, a proof of concept (POC) of LC-network based resistorless and symmetrical tree prototype is designed, fabricated and measured. Comparison results between well-correlated TAN calculation, simulation and experimentation are discussed.

Bandpass Negative Group Delay Theory of Fully Capacitive Δ-Network

A particularly original negative group delay (NGD) theory of <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> -topology is developed in the present paper. The NGD three-port topology is a passive circuit purely constituted by capacitors network. The model of the proposed <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> -topology impedance 3-D matrix is analytically established in function of the capacitor elements. Then, the S-matrix model is derived by using the Y-to-S transform. By considering the S-matrix frequency responses, a bandpass (BP) NGD analysis of the capacitive <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> -topology is originally elaborated. It is theoretically demonstrated that the passive <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> -topology is susceptible to behave as a BP NGD circuit under an analytical condition between the constituting capacitor values. The design feasibility of the BP NGD function is experimentally verified with lumped capacitor components-based <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> -circuit proof of concept. An electronic circuit board constituted by purely capacitive-network <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> -circuit is fabricated as an original <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> -circuit prototype. The tested board is constituted by arbitrary chosen capacitors, 100 nF, 10 nF and 0.1 nF. As expected, the calculation, simulation and measurement results, which are in very good agreement, confirm the BP NGD behavior. It is observed from measurement that it generates NGD of about −18.1 ns at a frequency of about 0.55 MHz and, lower and upper cut-off frequencies of about 0.33 MHz and 1.71 MHz. It is noteworthy that the transmission and reflection coefficients at very low frequency are independent of the capacitor values and analytically equal to 2/3 and 1/3, respectively.

Group delay flatness and bandwidth enhancement of wideband negative group delay microwave circuit

A wideband negative group delay (NGD) microwave circuit with group delay flatness and bandwidth enhancement is proposed. The proposed negative group delay circuit (NGDC) is composed of a resistor connected by two transmission lines and a parallel branch consisted of a resistor linking with a stepped-impedance transmission line and two open stubs. By tuning the characteristic impedance of the transmission lines, the flat-NGD bandwidth is enhanced. For verification, an NGDC with a size of 0.24λg × 0.34λg is designed, fabricated, and measured. The measurement shows that an NGD time of −0.5 ns at the center frequency of 1.0 GHz is obtained with the NGD bandwidth of 68.6% over 0.668 to 1.365 GHz. Also, the flat-NGD bandwidth reaches 46.3% or 0.776 to 1.243 GHz with ±8% group-delay fluctuation while the insertion loss is less than 18.8 dB and return loss is greater than 21 dB.

Diakoptics Modelling Applied to Flying Bird-Shape NGD Microstrip Circuit

This brief develops a diakoptics modelling of a flying bird topology constituted by interconnected piece-wises of admittance or Y-matrices. The diakoptics principle is established with passive system teared into several simplex elements as transmission and coupled lines (TLs and CLs). After introduction of subsystem Y-matrix, the global system Y- and S-matrices are established. To verify the model effectiveness, parametric analyses enabling to understand bandpass negative group delay (NGD) behavior of the flying bird topology. Furthermore, a microstrip circuit is designed, fabricated and tested. The modeled, simulated and measured NGD circuit responses are in excellent agreement. NGD value about -2.2 ns under transmission and reflection coefficients better than -2 dB and -13 dB is measured around 1.15 GHz.

Negative group delay experimentation with tee connector and cable structures

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.

Arbitrary terminated negative group delay circuit using signal interference concept

In this article, we demonstrate signal interference concept based wideband negative group delay (NGD) circuit with an arbitrary termination port impedance. The proposed circuit consists of unequal power division ratio 180° hybrid and in-phase combiner. The NGD can be generated by controlling power division ratios of 180° hybrid and combiner. For experimental verification, the circuit is designed and fabricated at a center frequency of 2 GHz. The experiment results show that the proposed NGD circuit can provide 460 MHz NGD bandwidth (bandwidth of group delay <0 ns) with group delay of −0.8 ns at 2 GHz.

Analytical modeling of H‐shape distributed topology with bandpass negative group delay behavior

This article describes an analytical modeling of a distributed negative group delay (NGD) circuit presenting a H-shape topology. It acts as an innovative typical transmission line (TL) based topology with a feedback connected with an open-stub termination. The equivalent circuit diagram is established based on TL representation of H-topology constituting elements. The S-matrix analytical model is developed. To validate the analytical model, a proof-of-concept prototype implemented in microstrip topology is designed, simulated, fabricated, and measured. The compared calculated, simulated, and measured S-parameters are in very good agreement. In addition, the microstrip prototype confirm the bandpass NGD behavior of the H-topology circuit with NGD value of approximately −2 ns around the center frequency 1.67 GHz.

Design of ₌׀₌ Shape Stub-Based Negative Group Delay Circuit

This article presents a type of negative group delay (NGD) circuit based on transmission line resonators. To obtain the circuit's S-parameters, this article uses a combination of ABCD and Z-parameters. Analytical design equations are presented, which are verified using circuit simulations.

Novel Reconfigurable Negative Group Delay Circuits With Independent Group Delay and Transmission Loss/Gain Control

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.

Radial stub based negative group delay circuit theory

This study addresses a negative group delay (NGD) circuit theory regarding a distributed passive topology consisted of an open-ended radial stub. The equivalent circuit composed of the lumped R, L and C elements is proposed. Then, the S-parameter model of the passive topology is established. The NGD analysis is described from the S-parameter model. The synthesis method enabling to determine the stub parameters as a function of the targeted NGD level, frequency centre and reflection coefficient is formulated. The radial stub topology limit is explained with an analytical condition from the synthesis relation. The developed NGD theory feasibility is validated with two cases of proof-of-concept (POC). First, ideal POC circuit with NGD value varied from −2 to −1 ns around the centre frequency 1.3 GHz is confirmed with ideal optimised circuit presenting figure-of-merit of approximately −0.27. Then, the theoretical prediction is verified numerically and experimentally by designing and fabricating an actual microstrip radial stub circuit. The calculated model, simulation and measurements are in very good correlation. The prototype test results confirm that the NGD circuit exhibits an NGD of approximately −1.2 ns level at approximately 0.85 GHz centre frequency.